Today_s Technician_ Automotive Heating & Air Conditioning Classroom Manual and Shop Manual [6 ed.] 2015956682, 9781305497603, 9781305497627

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Classroom Manual for Automotive Heating & Air Conditioning

Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Classroom Manual for Automotive Heating & Air Conditioning Mark Schnubel Naugatuck Valley Community College Waterbury, Connecticut

Sixth Edition

Australia • Canada • Mexico • Singapore • Spain • United Kingdom • United States

Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

This is an electronic version of the print textbook. Due to electronic rights restrictions, some third party content may be suppressed. Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. The publisher reserves the right to remove content from this title at any time if subsequent rights restrictions require it. For valuable information on pricing, previous editions, changes to current editions, and alternate formats, please visit www.cengage.com/highered to search by ISBN#, author, title, or keyword for materials in your areas of interest. Important Notice: Media content referenced within the product description or the product text may not be available in the eBook version.

Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Today’s Technician™: Classroom Manual for Automotive Heating & Air Conditioning, Sixth Edition Mark Schnubel SVP, GM Skills & Global Product Management: Dawn Gerrain Product Director: Matthew Seeley Product Team Manager: Erin Brennan Senior Director, Development: Marah Bellegarde Senior Product Development Manager: Larry Main Senior Content Developer: Meaghan Tomaso Product Assistant: Maria Garguilo Vice President, Marketing Services: Jennifer Ann Baker Production Service/Compositor: SPi Global Marketing Manager: Jonathon Sheehan Senior Production Director: Wendy Troeger Production Director: Andrew Crouth Senior Content Project Manager: Cheri Plasse Senior Art Director: Benjamin Gleeksman Cover image(s): © cla78/Shutterstock

© 2017, 2013 Cengage Learning WCN: 02-200-203

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Library of Congress Control Number: 2015956682 Book Only ISBN: 978-1-305-49760-3 Package ISBN: 978-1-305-49762-7 Cengage Learning 20 Channel Center Street Boston, MA 02210 USA Cengage Learning is a leading provider of customized learning solutions with office locations around the globe, including Singapore, the United Kingdom, Australia, Mexico, Brazil, and Japan. Locate your local office at: www.cengage.com/global Cengage Learning products are represented in Canada by Nelson Education, Ltd. To learn more about Cengage Learning, visit www.cengage.com Purchase any of our products at your local college store or at our preferred online store www.cengagebrain.com

Notice to Reader Publisher does not warrant or guarantee any of the products described herein or perform any independent analysis in connection with any of the product information contained herein. Publisher does not assume, and expressly disclaims, any obligation to obtain and include information other than that provided to it by the manufacturer. The reader is expressly warned to consider and adopt all safety precautions that might be indicated by the activities described herein and to avoid all potential hazards. By following the instructions contained herein, the reader willingly assumes all risks in connection with such instructions. The publisher makes no representations or warranties of any kind, including but not limited to, the warranties of fitness for particular purpose or merchantability, nor are any such representations implied with respect to the material set forth herein, and the publisher takes no responsibility with respect to such material. The publisher shall not be liable for any special, consequential, or exemplary damages resulting, in whole or part, from the readers’ use of, or reliance upon, this material.

Printed in the United States of America Print Number: 01  Print Year: 2016

Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Contents Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii Chapter 1  Heating and Air Conditioning—History and the ­Environment ����� 1 • Introduction 1 • Air Conditioning Defined 2 • Refrigeration 2 • Historical Development of Refrigeration 2 • Refrigerant and the Environment 4 • The Ozone Hole 7 • Effects of Loss of Ozone on Human Health 9 • Climate Change and the Greenhouse Effect 11 • The Clean Air Act 15 • Stratospheric Ozone Protection—Title VI 16 • Ozone Protection Regulations 16 • Refrigerant HFO-1234yf (R-1234yf ) 17 • Technician Certification 20 • Injuries as a Result of High Pressure 20 • Special Safety Precautions 21 • Antifreeze/Coolant 23 • Hazardous Materials 24 • Breathing Toxic Gases 26 • The Industry 27 • ASE Certification 28 • EPA Certification 30 • Cost of Operation 31 • Summary 31 • Terms to Know 31 • Review Questions 32

Chapter 2  Temperature and Pressure Fundamentals . . . . . . . . . . . . . . . . 33 • Introduction 33 • Elements and Matter 33 • The Atom 34 • The Molecule 35 • Chemical Compounds 35 • Heat and Cold 37 • Sensible Heat of a Solid 38 • Melting or Fusion 38 • Sensible Heat of a Liquid 39 • Evaporation 39 • Specific Heat 42 • Latent Heat of Fusion 43 • Latent Heat of Vaporization 43 • Heat Flow 44 • Radiation 44 • Conduction 45 • Convection 46 • Personal Comfort and Convenience 46 • Specific Gravity 52 • Gas Laws 52 • Summary 55 • Terms to Know 55 • Review Questions 55

Chapter 3  Electricity and Electronic Fundamentals . . . . . . . . . . . . . . . . . . 57 • Introduction 57 • Electrical Principles 57 • Fuses and Circuit Breakers 67 • Circuit Resistance 68 • Diodes 70 • Relays 71 • Blower Motor 73 • Electromagnetic Clutch 78 • Summary 80 • Terms to Know 80 • Review Questions 80

Chapter 4  Engine Cooling and Comfort Heating Systems . . . . . . . . . . . . 82 • Introduction 82 • The Cooling System 82 • Heat Measurement 84 • Radiator 85 • Pressure Cap 89 • Coolant Recovery System 91 • Engine Block and Cylinder Head Coolant Passages 95 • Coolant Pump 95 • Fan Shrouds, Air Baffles, and Seals 100 • Thermostat 101 • Pulley and Belt 109 • Fans 112 • Hoses and Clamps 120 • Heater System 121 • Additives 124 • Antifreeze 125 • Preventive Maintenance 129 • Summary 130 • Terms to Know 130 • Review Questions 131

Chapter 5  Air-Conditioning System Operating Principles . . . . . . . . . . . . 133 • Introduction 133 • Heat Transfer in the Refrigerant System 134 • Air Conditioning and Humidity 136 • The Relationship of Pressure and Vacuum in the Air-Conditioning System 138 • Air Conditioning 101 140 • Compressor 141 • Condenser 144 • Receiver-Drier Accumulator 144 • Metering Devices 146 • Evaporator 148 • Hoses and Lines 149 • Refrigerant 150 • Refrigerant R-134a (Hfc-134a) 153 • Refrigerant HFO-1234yf (R-1234yf) 155 • R-1234yf Refrigerant System Design 157 • Pressure versus Temperature Relationship 158 • Handling Refrigerant 160 • Air-Conditioning Circuit 161 • Summary 165 • Terms to Know 165 • Review Questions 165

Chapter 6  Refrigerant System Components . . . . . . . . . . . . . . . . . . . . . . . 167 • Introduction 167 • The Refrigeration Cycle 167 • Compressor 170 • Hoses And Lines 172 • Discharge Line 175 • Condenser 176 • Receiver-Drier 180 • Liquid Line 183 • Thermostatic Expansion Valve 183 • H-Valve 188 • The Orifice Tube 190 • Evaporator 193 • Internal Heat Exchanger (IHX) 197 • Accumulator 198 • What Type System 199 • Summary 200 • Terms to Know 200 • Review Questions 200

v Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Contents Chapter 7  Refrigerant System Servicing and Testing . . . . . . . . . . . 203 • Introduction 203 • Performance Testing 203 • Refrigerant Analyzer 205 • Noncondensable Gas 207 • Moisture and Moisture Removal 209 • Prevention 212 • Evacuating the Refrigeration System (Moisture Removal) 212 • Moisture Removal at High Altitudes 214 • Mixed Refrigerant Types 215 • Hazardous Refrigerant 216 • Leak Detectors 216 • Leak Detection Using a Soap Solution 216 • Leak Detection Using Visible Dye 217 • Fluorescent Leak Detectors 217 • Electronic (Halogen) Leak Detectors 218 • Other Types 220 • Recovery/Recycling/Recharging Systems 221 • Record Keeping Requirements 225 • PDA Diagnostics 225 • Charging the System with Refrigerant 226 • Diagnosis 227 • Refrigeration Oil 232 • Summary 238 • Terms to Know 238 • Review Questions 239

Chapter 8  Diagnosis of the Refrigeration System . . . . . . . . . . . . . . 241

• Introduction 241 • System Diagnosis 241 • Temperature and Pressure Relationships of R-12 (CFC-12) 244 • Temperature and Pressure Relationships of R-134a (HFC-134a) 246 • Temperature and Pressure Relationships of R-1234yf (HFO-1234yf ) 246 • Moisture Contamination 265 • Restriction Diagnosis 265 • Preventive Maintenance 267 • Advanced Diagnostic Tools 268 • High Pressure 272 • Connections 273 • Restrictions 273 • Contamination 274 • Summary 275 • Terms to Know 275 • Review Questions 275

Chapter 9  Compressors and Clutches . . . . . . . . . . . . . . . . . . . . . . . 278 • Introduction 278 • Function 278 • Design 279 • Clutch 281 • Types of Compressors 286 • Reciprocating (Piston-Type) Compressors 286 • Rotary Vane Compressors 290 • Scroll Compressors 291 • Scotch Yoke Compressors 293 • Variable Displacement Compressors 294 • Diagnosing Problems and Making Repairs 300 • Electric Motor–Driven Compressors 301 • Stretch to Fit Belts 303 • Summary 304 • Terms to Know 304 • Review Questions 304

Chapter 10  Case and Duct Systems . . . . . . . . . . . . . . . . . . . . . . . . . 306

• Introduction 306 • Air Intake 310 • Core Section 310 • Distribution Section 311 • Combined Case 311 • Air Delivery 312 • Dual-Zone Duct System 319 • Rear Heat/Cool System 320 • Evaporator Drain 323 • Odor Control 323 • Cabin Air Filters 325 • The Air Door Control System 329 • Control System Faults 333 • Visual Inspection 334 • Mode Door Adjustment 334 • Summary 335 • Terms to Know 335 • Review Questions 336

Chapter 11  System Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 • Introduction 338 • Manual Master Control 340 • Thermostat 344 • Pressure Cutoff Switch 347 • Factory-Installed Wiring 349 • Coolant Temperature Warning System 350 • Control Devices 352 • Vacuum System Diagrams 355 • Automatic Temperature Controls 356 • Electronic Temperature Control Systems 360 • Scan Tool 375 • Controller Area Network 379 • Heated and Climate Controlled Seating 385 • Summary 388 • Terms to Know 388 • Review Questions 388

Chapter 12  Retrofit and Future Trends (R-12 TO R-134a) . . . . . . . . 392 • Introduction 392 • New Refrigerant Systems on the Horizon 393 • The Replacement Refrigerant of Choice 397 • Other Refrigerants 399 • Substitute Refrigerants 399 • The Do-It-Yourselfer 402 • Contaminated Refrigerant 403 • Purity Test 405 • Disposal of Contaminated Refrigerant 405 • Use of Alternate Refrigerants 405 • Retrofit Components 407 • System Flushing 413 • An Industry Study 413 • Summary 415 • Terms to Know 415 • Review Questions 415

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433 vi Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Preface Thanks to the support the Today’s Technician™ series has received from those who teach automotive technology. Cengage Learning, the leader in automotive-related textbooks, is able to live up to its promise to provide new editions regularly. We have listened and responded to our critics and our fans and present this new updated and revised sixth edition. By revising our series regularly, we can and will respond to changes in the industry, changes in technology, changes in the certification process, and to the ever-changing needs of those who teach automotive technology. The Today’s Technician™ series features textbooks that cover all mechanical and electrical systems of automobiles and light trucks (while the heavy-duty trucks portion of the series does the same for heavy-duty vehicles). Principally, the individual titles correspond to the main areas of ASE (National Institute for Automotive Service Excellence) certification. Additional titles include remedial skills and theories common to all of the certification areas and advanced or specific subject areas that reflect the latest technological trends. Each text is divided into two volumes: a Classroom Manual and a Shop Manual. Unlike yesterday’s mechanic, the technician of today and for the future must know the underlying theory of all automotive systems and be able to service and maintain those systems. Dividing the material into two volumes provides the reader with the information needed to begin a successful career as an automotive technician without interrupting the learning process by mixing cognitive and performance learning objectives in one volume. The design of Cengage’s Today’s Technician™ series was based on features that are known to promote improved student learning. The design was further enhanced by a careful study of survey results in which the respondents were asked to value particular features. Some of these features can be found in other textbooks, whereas others are unique to this series. Each Classroom Manual contains the principles of operation for each system and subsystem. The Classroom Manual also contains discussions on design variations of key components used by the different vehicle manufacturers. This volume is organized to build upon basic facts and theories. The primary objective of this volume is to allow the reader to gain an understanding of how each system and subsystem operates. This understanding is necessary to diagnose the complex automobiles of today and tomorrow. Although the basics contained in the Classroom Manual provide the knowledge needed for diagnostics, diagnostic procedures appear only in the Shop Manual. An understanding of the basics is also a requirement for competence in the skill areas covered in the Shop Manual. A spiral-bound Shop Manual covers the “how-to’s.” This volume includes step-by-step instructions for diagnostic and repair procedures. Photo Sequences are used to illustrate some of the common service procedures. Other common procedures are listed and are accompanied with fine-line drawings and photos that allow the reader to visualize and conceptualize the finest details of the procedure. This volume also contains the reasons for performing the procedures, as well as information on when that particular service is appropriate. The two volumes are designed to be used together and are arranged in corresponding chapters. Not only are the chapters in the volumes linked together, but the contents of the chapters are also linked. This linking of content is evidenced by marginal callouts that refer the reader to the chapter and page where the same topic is addressed in the other volume. This feature is valuable to instructors. Without this feature, users of other two-volume textbooks must search the index or table of contents to locate supporting information in the other volume. This is not only cumbersome but also creates additional work for an instructor when vii Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Preface planning the presentation of material and making reading assignments. This linking feature is also valuable to students; with page references they also know exactly where to look for supportive information. The art is a vital part of each textbook. Both volumes contain clear and thoughtfully selected illustrations, many of which are original drawings or photos specially prepared for inclusion in this series. The page layout used in the series is designed to include information that would otherwise break up the flow of information presented to the reader. The main body of the text includes all the “need-to-know” information and illustrations. In the wide side margins of each page are many of the special features of the series: simple examples of concepts just introduced in the text, explanations or definitions of terms that will not be defined in the glossary, examples of common trade jargon used to describe a part or operation, and exceptions to the norm explained in the text. Many textbooks attempt to include this type of information by inserting it in the main body of text; this tends to interrupt the thought process and cannot be pedagogically justified. By placing this information off to the side of the main text, the reader can choose when to refer to it. Jack Erjavec Series Advisor

Highlights of this Edition—Classroom Manual The Classroom Manual of this edition has been updated to include new technology used in the automotive heating and air-conditioning systems of today’s vehicles while still retaining information on systems used in older vehicles that are still in use. In addition, an emphasis has been placed on updating images throughout the text with full-color photos. Charts, graphs, and line drawings are now also in full color to be more visually appealing and improve the content comprehension by the reader. Coverage of R-1234yf has been added throughout the text. Chapter 2 covers the basic theories required to fully understand the operation and diagnosis of the complete HVAC system. A chapter on electricity and electronic fundamentals has been added covering the application and use of digital multimeters for those readers that have a limited background in electrical applications. This is intended to improve their understanding of electrical applications material covered in later chapters and prepare them with the electrical knowledge needed to complete future job sheets. Chapter 4 covers the automotive heating system and engine cooling system, including systems used on today’s hybrid electric vehicles. The electronic thermostat used on some of today’s vehicles is thoroughly explained along with the rationale behind its use. The rest of the text is laid out in a logical order, beginning with basic air-conditioning system operating principles and progressing to diagnosis of the refrigerant system. The end-of-chapter questions in all chapters have been revised and updated. Updated coverage on advanced electronics has been included, from the operation of electronic variable compressors and electric motor–driven compressors to advanced sensors such as the airborne pollutants sensor. Chapter 11 on HVAC system controls has been updated to include more information on advanced climate control systems while still including a thorough description of CAN system operation.

viii Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Preface Highlights of this Edition—Shop Manual Safety information remains the first chapter of the Shop Manual and covers general safety issues as well as topics specific to automotive HVAC service. This chapter includes an in-depth discussion on high-voltage safety on today’s hybrid and electric vehicles and the equipment necessary to service these vehicles. As with the Classroom Manual, an emphasis has been placed on updating Shop Manual images and photo sequences throughout the text with full-color photos and line art. Chapter 3, “Electricity and Electronic Fundamentals,” has been added. This chapter contains detailed information on digital multimeter usage for electrical system diagnosis and troubleshooting. Chapter 4 and later chapters cover service information related to the system information covered in the corresponding Classroom Manual chapters. Many new job sheets have been added and existing job sheets have been updated with 100 percent of the NATEF tasks covered. The latest use of tools and technology has been integrated into the text, including hybrid electric compressors and the operation and use of SAE standard J2788 refrigerant recovery/recycling/recharging equipment needed to service today’s small-capacity refrigerant systems. Added coverage of today’s automatic climate control system service and diagnosis has been updated and includes specific examples. This edition of the Shop Manual will guide the student/technician through all the basic tasks related to automive heating and air-conditioning service and repair.

ix Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Classroom Manual

Chapter 4

Engine Co o and Comf ling ort Heating S ystems

Features of this manual include:

Upon Comp letion an d Review of this Ch apter, yo Explain the eng u should ine cooling sys be able to tem and its com ■■ Recogn ponents. : ize the various

COGNITIVE OBJECTIVES

■■

components of cooling system the automotive . Identify the diff erent types of radiators. ■■ Explain the operation and function of (water) pump. the coolant

These objectives outline the contents of the chapter and define what the student should have learned upon completion of the chapter.

Introduc

Each topic is divided into small units to promote easier understanding and learning.

tion

Normal ope ration of the automobile excessive eng engine produc ine heat, wh es heat that ich is a produc then dissipate must be car t of d ried away. Th as conduction in the radiator. This is acc combustion, is transf is erred to the omplished by and convention coolant and operational two heat tra . The cooling design temper sys tem , when operati nsfer principles known ature for the The cooling ng eng pro ine sys perly, mainta and automatic tem functio radiator. Eng ins ns tra by an nsm circ ine heat is pic ula ission. ked up by the ting a liquid coolant thr hot outside air passing thr ough the eng coolant by con ine and the ough the rad the heater cor duction and iator by convec Shop Manua e, l tion. Coolant is given up to the less compartment which also uses the con vection proces is also circula Chapter 4, pag . e 101 ted through s to supply hea ted air to the passenger The Coolin g System The purpos e of engine during the automotive cooling system is to the combustion carry the hea constant eng process away t that is ine operatingBypass from the eng temperatureHousing tions. Due to ine (Figure 4-1 generated by the during var yin inefficiencie ) to maintain A defective cool s of the inte g engine spe Ser pentine energy fro a near ing rna m eds and ope gas l combustion oline is con system may imp rating condipulley hub internal com engine, as mu verted into air bustion tem heat. The coo ch as 70 per air conditioning peratures, wh cent of the the engine’s ling system has ich may exc heat is sent out a performance. diff icu eed lt the exhaust walls, heads, task with 4,5008F (2, 482 system elleris and pistons 8C). Actually, Impand absorbed and into remove abo most of ut 35 percen Seal the ambient air. The dis cooling system sipated by the cylinder t of the total Another imp heat produc is designed, ortant functio ed by the eng the temperatures refo n re, to of the cooling sys ine. as tem is to allo emissions are quickly as possible. Wh w the engine ft en engSha increased, inte ines are bel to reach ope rnal compon rating ents wear fast ow operating temperatu re, exhaust er, and operati 82 on is less effi cient.

MARGINAL NOTES These notes add “nice-toknow” information to the discussion. They may include examples or exceptions, or may give the common trade jargon for a component.

Discuss the req uirements for a closed cooling Explain the pur system. pose, advanta ge, and operati thermostat. on of a ■■ Recogn ize the safety hazards associa system service. ted with a coo ling ■■ Explain the operation of various type s of cooling fans . ■■

■■

■■

97603_ch04_h

r_082-132. indd 82

Bearings Drain 11/18/15 4:48 PM

Inlet from radiator Parts of a wat FIGURE 4-18

er pump.

eable de, nonservic an impeller bla p that moves t and outlet, part of the pum ies of flat or g with an inle rnal rotating s of a housin a ser inte h sist wit the con is te p r pla elle The pum sists of a flat ls. The imp casting. This g(s), and sea impeller con h the pump system. The sealed bearin more sealed t passes throug h the cooling to a shaft tha is equipped with one or impeller coolant throug vanes and is mounted shaft. As the or prevent rust, to the des t el g bla ste por ss ved sup cur passage enterin al seal to erally stainle ern the gen to ext is rd ich and wa l shaft, wh forced out opposite the an interna is end and s ft and sha blie ter are bearing assem is drawn in from the cen pulley is mounted on the fan is also attached. Coolant pumps to , the belt lant generally referred rotates, coo ugal force. A ted cooling fan uired and is ck by centrif ps. engine-moun e of the special tools req as water pum the engine blo icles equipped with an aus veh lly rebuilt bec 9). impeller. On p is not genera t (Figure 4-1 pum bel t lan ing coo tim ven by the A defective ven-tative p that is dri assembly. viced as pre l replaced as an s may have a coolant pum en the timing belt is ser viced at 90,000 miles Shop Manua Some vehicle is generally replaced wh belts are ser e 105 Chapter 4, pag e most timing 0). t pump repair becaus ns (Figure 4-2 of the radiator with a This coolan avoid a future e for millions of rotatio tom intenance to maBattery ser vic ted to the bot it generally in nec n con bee is t has engine, and lant the pump Battery r and model lant pump inle and yea coo lar the s, ion of the coo es ticu ine fit a par tionFuelact The bypass pump sag On most eng preformed to collapsing due to the suc letrelay is through pas has This hose is redirects coolant out m e. p fro hos it t t pum ber t ven rub er the coolan g The coolan wire to pre Aft up. away from the Ign. ral ck. spi ved blo a rev s ine back ine is contain at housin ough the eng thermostat and r when the eng hesIgn. h the thermost Restrictthe coolant thr p iator throug pump impelle to the water pum ment pump. eller, which pus it is returned to the rad ant iable-displace tricting behind the imp Potentio meter ine block, to enable cool pump is a var thermostat is closed, res ough the eng l waterIgn. at thr the uga in sed trif ion the pas cen ulat circ the thermost When iator hose. A Flap ng m the pump. passage below coolant flow and upper rad engine block duri switch via a bypass n, t does not har ine lan ope is eng coo at e. of the ost cycl h p flow Power the warm-u tes throug ing the en the therm ula Wh circ t p. lan supply pum , coo t flowThermos to the water result of coolan relay tat ine block are often the the eng . leading from is leaks, which failures to improper The thermostat cooling system coolant pump failure bearing andDiagnos is through the t cause of tic these leaks uen outlet hosing is ed freq st link e mo connection rred The dies hav sometimes refe Air mass . Industry stu ABS gooseneck. meter bearing failure

CROSS-REFERENCES TO THE SHOP MANUAL Reference to the appropriate page in the Shop Manual is given whenever necessary. Although the chapters of the two manuals are synchronized, material covered in other chapters of the Shop Manual may be fundamental to the topic discussed in the Classroom Manual.

TERMS TO KNOW DEFINITIONS Many of the new terms are pulled out into the margins and defined.

to as the

PM 11/18/15 4:48

96 Electronic control module

97603_ch04_h

indd 96 r_082-132.

Control unit for radiator fan

Radiator fan M

Radiator fan 2 M

Engine speed sender

Positive

Output signal

Ground

FIGURE 4-36 An exampl e of a typical

Coolant temperature sender

Input signal

electronic thermostat

AUTHOR’S NOTES

Radiator outlet sender

wiring diagram.

Bidirectional

Author’s Note: If a vehicle comes into your shop overheatin coolant or water to the g, do not add system until it has comp letely cooled down. The process is necessary to cool-down avoid thermal shock to the engine and coolin components. Thermal g system shock could cause comp onents to crack and gaske making a bad situation ts to fail, worse. 108

97603_ch04_hr_082-132.indd

This feature includes simple explanations, stories, or examples of complex topics. These are included to help students understand difficult concepts.

108

11/18/15 4:49 PM

x Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

ol Ethylene glyc FIGURE 4-66

A BIT OF HISTORY This feature gives the student a sense of the evolution of the automobile. It not only contains nice-to-know information, but should also spark some interest in the subject matter.

antifreeze.

glycol antifree

ze.

FIGURE 4-68

Distilled wat

REVIEW QUESTIONS

er.

Short-answer essay, fill-inthe-blank, and multiple-choice questions are found at the end of each chapter. These questions are designed to accurately assess the student’s competence in the stated objectives at the beginning of the chapter.

temperature increase the ___ perature and of the coolan boiling point ____________ ______ the freezing t in an autom temperature system? ___ the boiling of the coolan otive cooling t. 10. A typical 4. Describe cooling syst the operation em 4:49 PM of /15 con a ___ thermostat. typical cooling 11/18 tain ____________ s a mix system ant ifre eze and ______ ture of water which 5. What are _________ offe the adv ____________ rs an excellent balance of both being adjusted antages of engine tem ___ freeze poi per boiling point nt and ______ protection. electronically to current operating dem ature _________ ands on the controlled coo ling system? 6. Describe Multiple Ch an advantage oice of a declutchin cooling fan. g engine-driven 1. All of the follow are tru 7. Describe e about engine except: an advantage thermostats of an electric cooling fan. A. A stuck -motor-driv open thermo en stat will cause overcooling. 8. Briefly, wh engine at is the pur pos B. A stuck e of the coolan recovery tank closed thermo ? t stat will cause overheating. 9. What is a engine PTC C. A faulty can it be foun heater and on what veh thermostat will icles d? effect vehicle D. A thermo emissions. stat may be rem 10. What are ove the advantage running hot d from a syst . s of a 50/50 em if it is and water? mix of antifre 2. Engine coo eze lant is design ed to provid ing except: Fill in the Bl e all of the foll anks owA. Provide water pump 1. Radiators lubrication. B. Inhibit rus are constructed t and corros of _________ ____________ ion. ______, C. Lower the ___, and/or plastic. boiling point 2. A frequen of the solution D. Lower the t coo . freezing tem by worn ___ lant pump failure is due perature of the ____________ to often cau 3. If a thermo solution. sed . stat 3. If the gasket lowing will occ fails in the open positio or sealing sur n, all of the folur, except: faces of a pre cap are dam A. A vehicle aged, the coo ssure may fail emissi ling system Swollen ____________ ons test. cannot be B. A loss of ___. engine coolant 4. A thermo . C. Poor hea stat failing in ter performanc the ___ will result in e. D. A longer engine ______ ____________ positio than normal n _________. warm-up per 5. Engine-dr 4. All of the iod. iven fans are following stat balanced to ____________ ements about systems are preven ___ engine cooling true EXCEPT ____________ , _______________, coo t : A. Extended lant pump ___ failure, and life coolant and /or seal dam Chafed 6. Many elec age stan bot . dard life coo h ethylene glyc tric cooling lant are ol based. fans are trolled by the B. It is ok for ____________ ultimately cona tech ____________ ___, _________ with a low tem nician to install a thermo ___. ______, stat perature rati ng than the orig thermostat. 7. Electric coo inal ling fans ma C. Extended y ___ warning, eve life coolant is n with the ign ____________ without rated to last 100k miles. the position. ition ______ in excess of _________ in D. Electric cooling fans Soft may turn on even engine is not when an running.

12 6

indd 126 r_082-132.

97603_ch04_h

A list of new terms appears after the Summary.

Propylene

re, heric pressu -level atmosp psi cap will at ambient sea 15 iator with a as a coolant, ine because ature of water 8F (1008C). Water in a rad eng per an tem in g t lan The freezin point is 212 ight as a coo itives that are and the boiling er be used stra or other necessary add is 328F (08C) ter should nev properties, (1208C). Wa a), , lubricating boil at 2508F be red (Toyot ion protection also ros can cor but no in color it offers and water en or yellow ylene glycol antifreezes. 8C) in is generally gre of 50/50 percent eth 9.4 available in col (12 F 8 gly ne 265 OF yle ture point of A BIT Standard eth mende d mix and a boiling ter is increased k. The recom nt of 2348F (236.78C) to distilled wa ling point is HISTORY blue, or pin poi ylene glycol boi has a freeze methyl centage of eth 48C) and the 70 (Figure 4-69) Prior to 1930, cap. If the per 2848F (264. sed beyond to psi rea t 15 inc sed a mos be h rea e the centalcohol was a radiator wit t, the freeze point is dec mended that the mixtur ses as the per engine n ay heat decrea dow commonly used ired is not recom 70/30 percen aw It to ry tion C). 8 car tec 5.6 to requ coolant 2768F (13 es freeze pro ne antifreeze and increased to e ability of the ylene glycol only provid ance ture of ethyle ne glycol. Th constant mainten ze A straight mix than water at . Straight eth percent ethyle 8F (135.68C). er free cient col increases 276 of gly effi e nt less to ensure prop t ylen poi age of eth a boiling is 15 percen lene glydamage. 98C) but has ylene glycol protection. Ethy severe engine In warmer duced to 228F (218. d because eth resulting in ed col was first intro never be use ts to develop, ature expect uired for 1927, but glycol should cause hot spo be to the lowest temper by Prestone in tection is req t and could pro uld hea a, ng sho stan rni a d ovi lifo cte rem any climate level sele it did not become ory Southern Ca protection. In tion. The fact The protection as southern Florida and anti-boiling rica for as dard year-round lub ll h p we suc as pum , t es, y 1960s. ll as coolan climate zon sion inhibitors protection to fill until the earl tection, as we and anticorro will provide the antirust ial for this pro cent antifreeze, which eze is essent ene than 30 per zone, antifre d with propyl l contain no less late uld mu for sho t eze ifre coolan r for anima coolant is ant toxic and safe ol ognized 258F (2158C). rnative to ethylene glycol entially non Rec Propylene glyc ess ally is ner col gly “Ge A safer alte is safe col, propylene pylene glycol is classified (C 3H8O2 ) is the mean that it ethylene gly for pro icity does not base stock used glycol. Unlike the environment. Also, ation. Low tox REVIEW QU ive and ill g Administr most automot life, children, d as factor y-f uced. TI . Food and DruES red use ON U.S tly and atly ren zes the gre S a by free anti glycol as Safe” soning is and not cur rra®. Propylene and aftermarket the risk of poi is a colorless, e Brands Sie col Saf ilable on the to drink, butShorcol gly ava and ene is ® in pyl t-A d Tox pro nswer Pre viscous liqui Essay stone Propylene gly s Lowe glycol. A 50/50 mixture Fof(124.48C) in a radiator nds are has its pure form, 1. ula Whratbra is the teripos stices as ethylen a boiling point of 2568 8. Hea antifreeze. Pop 78C) and a and 256. cor of the C) and 708F (ter rmal characpur a low toxicity, otive cooaling ze point of 2 _________ e leaks are detected by a loss 2. What are 268F (232.28automtur has similar the freesyst an of 2 has nt e poi the ______ and em is considered of ze two ? mix t free typper es cen a wet ______ of radiator cor a 15 psi cap. ____________ llywater has a in the a 100 aut as _________ om ere h e otiv environmenta wh tha ___. wit , t are found e cooling cap a radiator ive to with a 15 psi 9. An antifre 3. Wh (187.88C) in system? friendly alternat 8Ftho at me eze solution nt of 370 d(s poi ) ol. is ling use glyc boi ___ d lene to ___ tem ethy

TERMS TO KNOW LIST

FIGURE 4-67

Hardened

97603_ch04_h

r_082-132.

Terms to Know

13 1

indd 131

Antifreeze Bypass Centrifugal impeller Control valve Distilled water Electrolysis Ethylene glycol Expansion tank Heater core Hybrid organic acid technology (HOAT) Organic acid technology (OAT) Overcooling Overflow tank Pitch Power train control module (PCM) Pressure cap Propylene glycol Radiator Ram air Recovery tank Reverse flow Thermostat

al hose defec FIGURE 4-70 Typic

ts.

road a minimum sustained ther m is to provide for 1258F (528C). Ano tion of a cooling syste ient temperature of The design considera ient temperature .8 km/h) at an amb amb (144 an in c mph 90 traffi of ested stop-and-go speed operation iderations cong cons n in ng desig e drivi of . Thes tes criteria is for 30 minu experiencing any overheating problems ng. out lar day-to-day drivi engine of 1158F (468C) with to encounter in regu cted. The life of an s that one is likely it be found and corre exceed the condition ced. The high-lim the problem should redu s, tly heat grea over is ne If the engi formulated allowed to overheat erve y pres tuall to habi val is that proper heat remo and or a transmission uate adeq ire cating oil requ properties of lubri istics. lubricating character

11/18/15 4:49 PM

SUMMARIES Each chapter concludes with a summary of key points from the chapter. These are designed to help the reader review the contents.

SUMMARY

es: following procedur should include the tenance program The preventive main thermostat. Test or replace the pressure cap. Test or replace the the radiator hose(s). Inspect or replace heater hoses. the ce repla or ■■ Inspect the cooling system. ■■ Pressure test antifreeze solution. the ce repla , and belt(s). or ■■ Test p, heater, control valve ect the coolant pum ■■ Visually insp

■■

■■

■■

130 11/18/15 4:49 PM

32.indd 130 97603_ch04_hr_082-1

xi Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Shop Manual To stress the importance of safe work habits, the Shop Manual also dedicates one full chapter to safety. Other important features of this manual include: Chapter 4

PERFORMANCE OBJECTIVES

Diagnosis and Service of Engine Cooling and Comfor t Heating Systems

These objectives outline the contents of the chapter and identify what the student should have learned upon completion of the chapter. These objectives also correspond to the list of required tasks for NATEF certification.

Each chapter begins with a list of the Basic Tools needed to perform the tasks included in the chapter. Whenever a Special Tool is required to complete a task, it is listed in the margin next to the procedure.

Upon Completion and Review of this Chapter, you shou ld be able to: Identify

the major components of the automotive engine cooling and comfort heating system. Compare the different types of radiators. ■■ Discuss the function of the coolant pump. ■■ Explain the need for a pressurized cooling system. ■■ Describe the advantage of a thermostat in the cooling system. ■■

■■

■■

Although this textbook is not designed to simply prepare someone for the certification exams, it is organized around the NATEF task list. These tasks are defined generically when the procedure is commonly followed and specifically when the procedure is unique for specific vehicle models. Imported and domestic model automobiles and light trucks are included in the procedures.

■■

■■

Understand the procedures used for testing the various cooling system components. Recognize the hazards associ ated with cooling system service. Understand troubleshooting procedures for determining the malfunction of cooling system components.

A typical gasoline engine is only about 15 percent efficient; is used to move the vehicl e. That means that 85 percen only about 15 percent of the energy t of all energy developed is wasted in friction and by the engine heat—heat that must be removed. While the heat of combu stion may reach as high as 4,0008F (2,2008C), most when the exhaust valve of it is expelled opens. This results in an actual net engine tempe about 7508F (4108C) to rature range from about 1,5008F (8158C). This is still a great deal be removed. The coolan of heat, tempe t, a mixture of water (H and rature must O) and ethylene glycol, Checkthermit transfer this heat from the ostat iswhen the liquid used engine to the radiator.2 to opens

The Cooling System

Classroom Manual Chapter 4, page 82

The cooling system (Figur A common leak point e 4-1) is made up of severa l components, all of which to its proper operation. is due to loose hose They are the radiator, pump are essential , pressure cap, thermostat, heater core, hoses and clamp clamps. cooling fan, s, and coolant. oomcomm Classr The most on cooling system proble ms are a result of a leakin Manualpresents a tem seldom g system. A sound sysproblem. Leaks are genera Ambien t 101 lly page easy 4, ble. types are to find using a pressure tester. Chapter availa The following is a typica temperature is the Heat Several l procedure for pressu re testing operation. 1. Allow the engine and stat coolin temperature of the thermo ng a g system : coolant to cool to ambie FIGURE 4-17 Checki nt temp 2. Remove the pressure eratu surrounding air. re. cap. Note the pressure range pulley is acoolan indicated on the cap (Figur r and turn on the burner. 3. Adjus An idler t the t e 4-2). ts on a stove burne below the bottom or level to a point just and conten tension 4. Attach used tothe to open at its rated temof the fill neck valve Place the container pressure tester 6. the should radiator.begin The fillvalue, (Figur neck isreplace e 4-3). r. The thermostat of the direction reroute rated 5. While its F 8 3 6 obser Obser ve the thermomete than ving the gauge7., pump the part of the begins to open more the tester until ea 4-17). of a belt. pressuIfreitequal achiev ed. If the pressure can be perature value (Figur to the cap rating is radiator on which If yes, achieved, proceed with step 6. If the rated value? achieved, make a visual thermostat. 8C) abovetheitspressur pressu 258F (11 ely e cap is re canno inspecthe ximat t be appro tion for leaks. at d opene 8. Is the thermostat fully ostat. A drive pulley attached. If not, replace the therm the thermostat is all right. transmits or inputs power into a component.

97610_ch04_hr_101-156.indd

Replace any belt that appears to be worn, frayed, or damaged.

CUSTOMER CARE

replacement interval stated for the ostat is generally no service maintenance item, therm Customer Care: There ostat. But, as a preventive nt is changed. 101 of the cooling system therm coola e engin the suggested when replacement should be

This feature highlights those little things a technician can do or say to enhance customer relations.

101

A serpentine belt is a flat or multi V-grooved belt that winds through all of the engine accessories to drive them off the crankshaft pulley with both sides of the belt being drive surfaces.

TERMS TO KNOW DEFINITIONS

11/16/15 7:04 PM

Pulleys

e due to colms that may occur are damag tforward; inspection. Pulley proble Pulleys require periodic . In all cases, repair is straigh gs in an idler or drive pulley tine belt systems will wear serpen on lision or defective bearin used s pulley g or pulley. Plastic necessary. replace the faulty bearin t and replace them when cracks over time; inspec and develop grooves and

r Belts and Tensione

air-conditioning otive engine cooling and belts used in the autom Photo Sequence 1 There are two types of the V-belt (Figure 4-19). belt (Figure 4-18) and belt. drive system: the serpentine tine serpen the Replacing l procedure for servicing typicaione m similar to the one shown a Belt ates aTens illustr r belt locate the routing diagra on the A V-belt is a belt removal of the serpentine The following proced in the engine bay, often Prior to ure is typical for m located under the hood in is often replac designed to runthe ing an e service information. automatic 4-18. This diagra particular the vehicl Figurefactur belt tensio d in ner. in manu locate be Alway also d er’s may s follow recom V-shape m single mend a ed procedures for each al. to remov support cover. The diagra prior or g vehicl radiat routin e. 1. belt Attach the of drive a a socket wrench to a sketch groove of s with to draw the emoun icians choos ting bolt of the autom tensioning for those system r belt propeatic 4-20). techn tensio or idler pulley with (Figure Some ner pulley be used to ensure bolt ner, a springatic belt tensio A belt tension gauge may 2. Rotate the tensio only the tapered be odel vehicles have an autom ner assemblyMany clockwlate-m ise (cw) sted that a new belt again al adjustment. until the 3. Remove manu it isn sugge belted, tensio surface being the adjust the belt has ally been frompulley ing. manu is relieve the stretch belt idler d. g and pulley first, then remove . If the MostDisconnect for initial seatin loaded time the theallow drive surface. 4. belt from and idler remove and other pulley of operation to set15 minut aside anyescompo or so.s. after about eters) ned nents kilom 5. Remove the tensio hinder systems require (8,000 ing tensioner removal. tensioner assembly from every 5,000 miles check theedmoun ting bracket. several V belts The belt should then be

Many of the new terms are pulled out into the margin and defined.

to drive all of the engine accessories.WARNAuto matic ING: Becau

Belt Tensioner -loaded automatic se of high spring pressu are equipped with a spring engin late-model re, does not disassemble ns, such as with tensioner. uratio theconfig autom The drive belts on most atic used with all belt atic belt tensioner may be autom tensioner. An g. tionin 6. Remove the condi air and g pulley steerin and remov ut power e the pulley from the tensio or withobolt 7. Install the pulley ner. and pulley bolt in the tensio ner. Tighten the bolt to An indexing 8. Install the tensioner 45 ft.-lb (61 N ⋅ m). assembly to the mounting tab is a mark or 110 bracket. An indexing tab is generally located on the (Figure 4-21) back of the tensioner to protrusion on mating align with the slot in the bracket. Tighten the nut mounting to 50 ft.-lb (67 N ⋅ m). components to 9. Replace any components removed in step 4. ensure that they will 10. Position the drive belt over all pulleys, except the be assembled in 110 1-156.indd idler 11. pulley. 04_hr_10 Using a socket wrench on their proper97610_ch the pulley mounting bolt position. of the automatic tensioner, tensioner cw. rotate the 12. Place the belt over the idler pulley and allow the tensioner to rotate back should spring back smoot into position. It hly and with adequate tensio n pressure on the belt.

CAUTIONS AND WARNINGS Throughout the text, cautions are given to alert the reader to potentially hazardous materials or unsafe conditions. Warnings are also given to advise the student of what can go wrong if instructions are not followed or if a nonacceptable part or tool is used.

TOOLS LISTS

BASIC TOOLS Basic mechanic’s tool set

CAUTION:

When installing the serpentine accessory drive belt, the belt must be routed correctly. If not, the water pump may rotate in the wrong direction (Figure 4-22), causing the engine to overheat.

11/16/15 7:05 PM

Belt Failure Troublesh

ooting

A variety of critical engine components stop worki ng when a serpentine belt components may includ e the water pump, altern fails. These ator, air conditioning compr steering pump to name essor, and power some of the more comm on belt-driven accessories. It is important Turn clockwise to remove belt

Tensioner

Socket wrench Idler pulley

Fan blade

FIGURE 4-20 Rotate the tensioner clockw ise (cw) to loosen the belt.

114

xii

97610_ch04_hr_101-156.indd

114

12/28/15 9:27 PM

Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

PHOTO SEQUENCES

PHOTO PHO SEQTO UEN SEQ CEUEN 1

Many procedures are illustrated in detailed Photo Sequences. These detailed photographs show the students what to expect when they perform particular procedures. They can also provide a student a familiarity with a system or type of equipment that the school may not have.

P2-1 Ensure that the engine is cold, and slowly remove the radiato r cap. CAUTION: If the radiato r cap is removed from a hot cooling system , serious personal injury may result.

CE 2

(continued)

Draining and Refi lling the Cooling System

P2-2 Place a drain pan of adequate size under the radiator drain cock.

CROSS-REFERENCES TO THE CLASSROOM MANUAL

P2-3 Install one end of a tube or hose on the draincock and position the other end in the drain pan.

Reference to the appropriate page in the Classroom Manual is given whenever necessary. Although the chapters of the two manuals are synchronized, material covered in other chapters of the Classroom Manual may be fundamental to the topic discussed in the Shop Manual.

Fuse

P2-4 Open the radiato r draincock and allow the radiator to t drain V Bat until 12the flow stops.

t*

Thermosta

F/L

P2-5 Place a drain pan of adequate size under the engine.

P2-6 Remove the drain plug from the engine block and allow motorthe engine block to drain until Fan the flow stops. NOTE: There may be more drainag e from the radiator at this time.

12-V Ign Fuse

Fan relay Selector switch

Norm Max Off

t) engine *(Thermosta perature coolant tem switch FIGURE 4-37

fused jum Connect a

per wire from

the battery

Bi-level Vent Heat Def

positive (1)

the cooling

fan connec

for poo P2-8 Remove the pans t. Check righ dispose alland of the 9. fan isconsist coolant a manner yesin, the h step and must witlocal entdwith t and run? If tor is shorted If no, procee Did the fan star if necessary.regulations. ? If yes, the mo

Chapter 4, pag

air them Is it blown motor and rep fuse in the jumper wire. replaced. ck the and must be 9. Again che If no, the motor is open be replaced.

97610_ch04_hr_101-156.indd

CASE STUDIES

131

Hoses

131 This should ry few years. re ps replaced eve schedule, mo and Clam ps should be on a periodic ly to occur. clam e don and If es m. ce progra system hos not as like

s if Replace all hose to be any are found defective.

A customer brin gs temperature gaug his car into the shop because e does not oper the ate. It remains all of the time , regardless of on engine heat cond cold The lead wire itions. to the sending nected, and a unit is disconindd 123 test -156. light r_101 is 04_h used to probe 0_ch The 9761test light comes on for voltage. when the igni placed in the ON tion switch position. When the lead is conn is ected

to ground (−) through a 10 0 resistor, the needle moves dash unit to the full hot position. This operation acco is a normal rding to the serv ice manual. The diagnosis is that the sending unit is tive. It is replaced defecafter approval the temperature by the custome r and gauge system is returned to operation. normal

Terms to Know

Ambient tempera ture Constant tens ion hose clamp Dissipate Drive pulley Fan relay Fill neck Heat exchang er Idler Indexing tab Serpentine belt

ASE-STYL E REVIEW QUESTION

V-belt

S 1. Engine ove rcooling is bei ng discussed: Technician A says that a the be the cause rmostat stuc 5. Technician of this conditi k open could A says that as on. a neoprene Technician B ages and wea serpentine belt says that a mis rs cracks will the cause of that if there form on the this condition. sing thermostat could be are belt ribs and span, the belt more than three cracks Who is correc in a 4-inch should be rep t? lace Tec d. hnician B say A. A only resist crackin s that serpentine belts C. Both A B. B only made of EPD g and instead and B M similar to tire exhibit wear D. Neither to wea the belt ribs r, 2. Technician and A nor B tha used to asse A say ss belt wear. t a depth gauge should system, it sho s that when pressure test be Who is correc uld hold pre t? ssure for 5 min ing a cooling Technician B utes. A. A only says that a wet heater core carpet may leak . C. Both A indicate a B. B only and B Who is correc D. Neither t? 6. Technician A nor B A. A only A say every 2 years. s that antifreeze should C. Both A B. B only be changed and B Technician B D. Neither say s tha 3. All of the t extended-life A nor B up to 5 years. follow coolant may serpentine belt ing may cause the back last Who is correc side of a to separate exc t? ept : A. Contact A. A only ing stationary object B. Excessive C. Both A B. B only heat and B C. Fractured D. Neither splice 7. An overhe A nor B ating conditi D. Pulley mis on is being disc alignment Technician A ussed: says that rep 4. Coolant loss lacing the the one of a low is being disc er rmo tem stat wit per uss ature rating ed: Technician A coolant tem will reduce the h perature. says that a mis the problem sing thermo Technician B . stat could be says that rep Technician B lacing the pre with one of a lower rating say ssu may be the pro s a heater control valv will reduce the re cap temperature. e stuck open blem. coolant Who is correc Who is correc t? t? A. A only A. A only C. Both A B. B only C. Both A B. B only and B and B D. Neither D. Neither A nor B A nor B

97610_ch04_h

r_101-156.

indd 137

SERVICE TIPS

nan , are Engine cooling good preventive mainte ating engine of a by an overhe 11/16/15 7:05 PM become part : those caused airs, such as SERVICE TIP a expensive rep have e following is Some engines ser viced. Th ng s such bei is additional hose when a vehicle ss es Hoses bypa hos ll sma tem sys as a the leak . ck all cooling the the point of hose between Carefully che for this ser vice: rust color at re. and ist ite, green, or coolant pump rating pressu simple checkl noted by a wh ine is at ope k, leaks, usually the engine bloc s when the eng nearby component. iou obv 1. Check for ally carry ration. swelling, usu caused by a belt or other hoses used to mical deterio 2. Check for , usually lant pump. indicate che ant to heat the fing coo cool uld cha the wo r t for nea tha fuel 3. Check ngy hose ting, usually throttle body on hose. a soft or spo repeated hea and y, replace the 4. Check for or corroe indicating injected engines, ts or flakes awa e is missing (due to rust a brittle hos to 5. Check for hose. If its outer layer spli ing wir short hoses used the the reinforc If ant e. cool hos ect r 6. Squeeze conn iato inter if any the lower rad es nts e hos eez pone ter com Squ 7. carrying iator and hea the hose. this rad t lace nes the tha rep engi of er ), all tom sion on certain e to replace vince the cus Do not good practic possible to con (Figure 4-38). Hose. It is a is not always hoses Replacing a defective. It overlook these found to be n checking the 4-40). of them are and whe ure p (Fig pum e t e. ing system. ends of the hos it loose from the coolan oval. cool h should be don bot at k bac hose to break ilitate its rem hose clamp 1. Slide the e will help fac st and turn the carefully twi ough the hos ter to slice thr 2. Firmly but ng a box cut 12 3 radiator. Usi 4-41). ure (Fig e the hos 3. Remove

case stud y

Case Studies concentrate on the ability to properly diagnose the systems. Beginning with Chapter 3, each chapter ends with a case study in which a vehicle has a problem, and the logic used by a technician to solve the problem is explained.

tor.

Classroom Manual e 120

s at the fan r connection

P2-7 Close the radiato r draincock and replace the engine block drain plug.

8.

terminal to

PM 11/16/15 7:05

Whenever a shortcut or special procedure is appropriate, it is described in the text. These tips are generally those things commonly done by experienced technicians.

TERMS TO KNOW LIST A list of new terms appears after the case study.

ASE-STYLE REVIEW QUESTIONS Each chapter contains ASE-style review questions that reflect the performance objectives listed at the beginning of the chapter. These questions can be used to review the chapter as well as to prepare for the ASE certification exam.

13 7

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xiii Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

JOB SHEETS Located at the end of each chapter, the Job Sheets provide a format for students to perform procedures covered in the chapter. A reference to the NATEF Task addressed by the procedure is referenced on the Job Sheet.

ASE PRACTICE EXAMINATION An ASE practice exam, located in the Appendix, is included to test students on the content of the complete Shop Manual.

JOB SHEE T Name ______ ____________ ____________ ________

Drain and Fill

Coolant

Upon comple tion of this job coolant. sheet, you sho uld

10 Date ______ ____________ ______

be able to rem ove and replace NATEF Corre cooling system lation NATEF AST and MAST Correlations Diagnosis and : EN Repair; GINE REPA IR: Lubrication Task #4. Ins and Cooling pect Systems with recomme and test coolant; drain and recover nded coolan coolant; flus t; bleed air as h and refill coo req uired. (P-1) Tools and Ma ling system terials Late-model vehicle Shop manua l Two pans Safety glasse s or goggles Hazardous wa ste container Funnel Rubber hose Hand tools, as required Describe the Vehicle being Worked on. Year ______ ____________ __ Make ___ VIN ______ ____________ ____________ ______ Model ___________ ____________ Engine type __________ Procedure and size ___ ____________ ____________ Follow the pro _ cedure outline a guide where d ver applicable in the ser vice manual. Photo Sequen . ce 2 may also 1. Ensure tha be use N d IO as t the engine AT EXAMIN is cold, and slowly remove E PR ACTICE ASthe radiator cap . WA RN A IN G: If the rad iator cap is APPENDIX personal inj removed fro ury may res below is 0. The m a hot ult. illustra thecoo lingtion sys t the,: seriou ter reading in thatem s 7. The voltme cause of this problem is 2. Place a dra A7 le ng in oniade pan ditiof most probab Con Air qua rted and sho te of size under the tinga tube or hos dings are Winrad omotive Hea e A. on Aut em iato the m syst r Exa dra nock and radiato incock . Positio oning inc ope Final diti rcon gs aredra dra airdin inc ins or? the Win n ock of tall vap the t a B. and one other end in ed id to allow the rad end ponent par the drain pan nge from a liqu iator toRel is not energiz 1. What com chace 3.toPla ayin dra . Open the C. igerant until the flow a drain pan causes the refr of adequate stops. tor is seized engine block r and allow the size underD.theMo A. Evaporato engine. Rem engine block ove r sso the pre drain plug fro to drain unt B. Com m the il the flow sto ser ps. C. Conden Voltmeter device D. Metering ove excess rem oning system compartment? the air-conditi the passenger 2. How does the air entering duct walls. humidity from collects on the re istu ser. Mo den A. the con condenses on r. B.9761Moisture the evaporato 0_ch04_hr_101condenses on C. Moisture -156.indd 139ted by the blower motor. is separa re istu Mo ditioning D. of the air-con test e anc system perform high-side and low-side r 3. During a on both the the compresso rati and e ope sam em syst ut the most dings are abo owing is the pressure rea ich of the foll Wh d. age clutch is eng pressure line likely cause? ion in the low A. A restrict valve plate compressor B. A faulty the system tamination of con re istu C. Mo valve ed expansion ch of D. A restrict ant tank, whi osable refriger formed? arding a disp 4. Before disc procedures should be per prevent closed to is e the following valv k e the tan A. Make sur atmosphere. g agent. venting to the igerant flushin tank. tank with refr ant left in the B. Flush the aining refriger rem any the pressure. C. Recover te ina elim valve to the tify D. Open the l must iden retrofit labe A says that a ant oil. 5. Technician the ount of refriger l must identify labe type and am ofit says that a retr alled. Technician B refrigerant inst new of t amoun t? and B Who is correc C. Both A A nor B A. A only D. Neither y onl B B. ssor clutch to se a compre owing may cau foll the of 6. All slip, except : ant ge of refriger A. Overchar e belt B. Loose driv air gap C. Improper age D. Low volt

13 9 Blower motor relay

11/16/15 7:05 PM

Blower motor Blower motor relay

Ammeter

Blower motor 20 A fuse

54 9

PM 11/20/15 1:09

indd 549

A_hr_549-554.

97610_em_app

xiv Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Supplements Instructor Resources The Instructor Resources, now available both online and on DVD, are a robust ancillary product that contains all preparation tools to meet any instructor’s classroom needs. It includes chapter outlines in PowerPoint with images, video clips, and animations that ­coincide with each chapter’s content coverage, chapter tests powered by Cognero with hundreds of test questions, an Image Gallery with all photos and illustrations from the text, theory-based Worksheets in Word that provide homework or in-class assignments, the Job Sheets from the Shop Manual in Word, a NATEF correlation chart, and an Instructor’s Guide in electronic format. To access these Instructor Resources online, go to login.cengagebrain.com, and create an account or log into your existing account.

MindTap MindTap for Today’s Technician: Automotive Heating & Air Conditioning, 6th edition, is a personalized teaching experience with relevant assignments that guide students to analyze, apply, and improve thinking, allowing you to measure skills and outcomes with ease. ■■

Relevant readings, multimedia, and activities are designed to guide students through progressive levels of learning, from basic knowledge to analysis and application.

■■

Personalized teaching becomes yours through a Learning Path built with key student ­objectives and your syllabus in mind. Control what students see and when they see it.

■■

Analytics and reports provide a snapshot of class progress, time in course, ­engagement, and completion rates.

MindTap for Today’s Technician: Automotive Heating & Air Conditioning, 6th edition, meets the needs of today’s automotive classroom, shop, and student. Within the MindTap faculty and students will find editable and submittable job sheets, based on NATEF tasks. MindTap also offers students engaging activities that include videos, matching exercises, and assessments.

xv Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Reviewers The author and publisher wish to thank the instructors who reviewed this text and offered their invaluable feedback: Dan Cifalia Mesa Community College Mesa, AZ

William McGrath Moraine Valley Community College Palos Hills, IL

Lance David College of Lake County Grayslake, IL

Rouzbeh “Ross” Oskui Monroe County Community College ­Monroe, MI

Randy Howarth Hudson Valley Community College Troy, NY

Christopher Parrot Vatterott College Wichita, KS

Shannon Kies University of Northwestern Ohio Lima, OH

Mike Shoebroek Austin Community College Austin, TX

John Koehn Pueblo Community College Pueblo, CO

Ira Siegel Moraine Valley Community College Palos Hills, IL

Christopher J. Marker University of Northwestern Ohio Lima, OH

Stephen Skroch Mesa Community College Mesa, AZ

Gary McDaniel Metropolitan Community College–Longview Longview, MO

Christopher C. Woods University of Northwestern Ohio Lima, OH

xvi Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Chapter 1

Heating and Air Conditioning— History and the Environment Upon Completion and Review of this Chapter, you should be able to: ■■

Define the term air conditioning.

■■

Discuss the Clean Air Act.

■■

Discuss the historic developments of modern refrigeration.

■■

Discuss ozone protection regulations.

Discuss the advantages of air conditioning in the automotive industry.

■■

■■

■■ ■■

■■

Explain the importance of the ozone layer.

Discuss CFC-12 (R-12), HFC-134a (R-134a), and the introduction of HFO-1234yf (R-1234yf) as an automotive refrigerant.

Discuss what industry is doing about the ozone depletion problem.

■■

Describe technician certification.

■■

Explain special safety precautions.

Discuss what government is doing about the ozone depletion problem.

■■

Discuss the types of antifreeze/coolant used.

■■

Discuss the hazardous materials used.

■■

Describe toxic gases.

■■

Describe how ozone is created.

■■

Describe how ozone is destroyed.

Introduction Since the dawn of time, humans have been trying to control their environment. It was natural that after the automobile became popular, a passenger comfort heating and cooling system would be required. And so began the quest for vehicle passenger compartment temperature control. The first year that automotive air conditioning was offered on a production vehicle was 1940, by the Packard Motor Car Company. Cadillac soon followed in 1941. After its initial introduction in the early 1940s, it did not become a popular option until the early 1960s. Since then the popularity of air conditioning has increased annually. In 1962, just over 11 percent of all cars sold were equipped with air conditioners. This accounted for 756,781 units, including both factory-installed systems and those with addon systems installed after the purchase, which are referred to as “aftermarket” systems. Just five years later, in 1967, the total number had increased an astounding 469 percent—to 3,546,255 units. Air conditioning is now one of the most popular selections in the entire list of ­automotive accessories and is often standard equipment on many vehicle models today. At the present time, over 93 percent of all automobiles sold in the United States are equipped with air conditioning units. It is expected that this percentage will remain at approximately 93 percent into the future.

1 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Air conditioning is the process of adjusting and regulating by heating or refrigerating; the quality, quantity, temperature, humidity, and circulation of air in a space or enclosure; to condition the air.

Temperature and humidity refer to the quality of the conditioned air.

Volume refers to the quantity of the conditioned air.

Artificial ice, usually cut from frozen ponds, contained many impurities, dirt, and debris.

When mobile air conditioning was first introduced, it was considered a luxury. Its ­ sefulness, however, has made it a necessity. As a matter of fact, if a vehicle is not equipped u with air conditioning, its value is dramatically reduced on the resale market. This text concentrates on the heating and air-conditioning system’s function and o ­ peration as employed by various automotive manufacturers and the methods they use to improve passenger comfort levels.

Air Conditioning Defined The definition of air conditioning should be reviewed before tracing its history and its application to the automobile. Air conditioning, by definition, is the process by which air is: ■■ Cooled ■■ Heated ■■ Cleaned or filtered ■■ Humidified or dehumidified ■■ Circulated or recirculated In addition, the quantity and quality of the conditioned air are controlled. This means that the temperature, humidity, and volume of air can be controlled at any time in any given situation. Under ideal situations, air conditioning can be expected to accomplish all of these tasks at the same time. It is important to recognize that the air conditioning process includes the process of refrigeration (cooling by removing heat).

Refrigeration Refrigeration is the term given to a process by which heat is removed from matter—solid, liquid, or vapor. It is the process of lowering the temperature of an enclosure or area by natural, chemical, electrical, or mechanical means. The fluid that circulates through an air-conditioning system is referred to generically as refrigerant. The refrigerants used in automotive air conditioning systems are commonly referred to as R12 and R134a. These refrigerants will be discussed further in this chapter and in Chapter 5.

Historical Development of Refrigeration Refrigeration, as we know it today, is less than one hundred years old. Some of its principles, however, were known as long ago as 10,000 bc. The Egyptians developed a method for cooling water. They found that water could be cooled by placing it in porous jugs on the rooftop at sundown. The night breeze evaporated the moisture seeping through the jugs and, in turn, cooled the contents. The Greeks and Romans had snow brought down from mountaintops. They preserved it by placing it in cone-shaped pits lined with straw and covered with a thatched roof. Even earlier, the Chinese learned that ice improved the taste of drinks. They cut it from frozen ponds and lakes in the winter, preserved it in straw, and sold it in the summer.

Domestic Refrigeration

Dr. John Gorrie (1803–1855) of Abbeville, South Carolina, was issued the first U.S. patent for a mechanical refrigeration system in 1851. Gorrie correctly theorized that if air were highly compressed, it would be heated by the energy of compression. If this compressed air were then run through metal pipes that were cooled with water, the air could be cooled to the water temperature. If this air were then expanded back to atmospheric pressure, low temperatures of about 268F (—338C—low enough to freeze water in pans in a refrigerator box—could be obtained. The compressor of this system could be powered by horse, water, wind, or steam. Gorrie’s original system was installed in the U.S. Marine Hospital in Apalachicola, Florida, where he used it to treat patients suffering from yellow fever. A replica of his system is on display at the John Gorrie State Museum in Apalachicola. 2 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

While Dr. Gorrie’s mechanism produced ice in quantities, leakage and irregular performance often impaired its operation. Gorrie’s basic principle, however, is the one most often used in today’s modern refrigeration: cooling caused by the rapid expansion of gases. Domestic refrigeration systems first appeared in 1910, although in 1896 the Sears, ­Roebuck and Company catalog offered several refrigerators. Refrigeration, however, was provided by ice. The refrigerator held 25 pounds (11.34 kilograms) of ice and was useful only for short-term storage for the preservation of foods. In 1899, the first household refrigeration patent was awarded to Albert T. Marshall of Brockton, Massachusetts. A manually-operated refrigerator was produced by J. L. Larsen in 1913. The Kelvinator Company produced the first automatic refrigerator in 1918. The acceptance of this new technology was slow. By 1920, only about 200 refrigerators had been sold. In 1926, the first hermetic (sealed) refrigerator was introduced by General Electric. The following year, Electrolux introduced an automatic absorption unit. A 4-cubic-foot refrigerator was introduced by Sears, Roebuck, and Company in 1931. The refrigerator cabinet and the refrigeration unit were shipped separately and required assembly. In terms of the cost per cubic foot of refrigeration, the early refrigerator compares favorably to today’s modern machines. In terms of the economy, one worked about four times longer to pay for the 4-cubic-foot refrigerator than one works for today’s 16-cubic-foot refrigerator, which is four times larger. Shortly after the beginning of the twentieth century, T. C. Northcott of Luray, Virginia, became the first person known in history to have a home with central heating and air conditioning. A heating and ventilating engineer, Northcott built his house on a hill above the famous Caverns of Luray. Because of his work, he knew that air filtered through limestone was free of dust and pollen. This fact was important because Northcott and his family suffered from hay fever. Some distance behind his house he drilled a shaft through the ceiling of the cavern and installed a fan to pull cavern air through the shaft. He then constructed a shed over the shaft and a duct system to the house. The duct system was divided into two chambers, one above the other. The upper duct, which carried air from the cavern, was heated by the sun, providing air to warm the house on cool days. The lower duct, which was unheated, carried air from the cavern to cool the house on warm days. The moisture content (humidity) of the air was controlled in a chamber in Northcott’s basement. Here, air from both ducts could be mixed. Because it is known that warm air contains more moisture than cool air, Northcott was able to direct conditioned air from the mixing chamber to any or all of the rooms in his house through a network of smaller ducts. During the winter season, auxiliary heat was provided by steam coils located in the base of each of the branch ducts.

Cooling accomplished by humidification is only effective in arid (dry) areas of the country.

Mobile Air Conditioning

The first automotive air conditioning unit appeared on the market in 1927. True air conditioning was not to appear in cars for another 13 years. However, air conditioning was advertised as an option in some cars in 1927. At that time, air conditioning meant only that the car could be equipped with a heater, a ventilation system, and a means of filtering the air. In 1938, Nash introduced “air conditioning” heating and ventilation. Fresh outside air was heated and filtered, then circulated around inside the car by fan. By 1940, heaters and defrosters were standard equipment on many models. That year Packard offered the first method of cooling a car by means of refrigeration. Actually, these first units were belt-driven commercial air conditioners that were adapted for automotive use and the evaporators were usually located in the trunk. Two years earlier, a few passenger buses had been air conditioned by the same method. Accurate records were not kept in the early days of automotive air conditioning. However, it is known that before World War II between 3,000 and 4,000 units were installed in

Humidity refers to the amount of moisture in the air.

Early studies of the effectiveness of vehicles equipped with automotive air conditioning proved that sales and production increased significantly.

3 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Ozone (O3 ) is a form of oxygen.

Ozone (O 3 ) is an unstable, pale blue gas with a penetrating odor; it is an allotropic form of oxygen (O) that is usually formed by electrical discharge in the air.

Oxygen (O) is an odorless, colorless, tasteless element that forms 21 percent of our atmosphere. It is an essential element for plant and animal life.

Allotropes are structurally different from elements. For example, though different in structure, the properties of charcoal and diamond are the same as the element carbon; they are both made up of the same element in differing combinations.

Atmosphere is a general term used to describe the gaseous envelope surrounding the earth to a height of 621 miles (1,000 km); it is 21 percent oxygen, 78 percent nitrogen, and 1 percent other gases.

Packards. Defense priorities for materials and manufacturing prevented the improvement of automotive air conditioning until the early 1950s. At that time, the demand for air conditioned vehicles began in the Southwest. The first of today’s modern automotive air-conditioning systems was introduced by ­Cadillac in 1960. Their bi-level system could cool the top level of the car while heating the lower level. This method provided a means of controlling the in-vehicle humidity. Many large firms reported increased sales after air conditioning was installed in the cars of their salespeople. Most commercial passenger-carrying vehicles are now air conditioned. Truck lines realize larger profits because drivers who have air conditioned cabs average more miles per day than those who do not. In 1967, all of the state police cars on the Florida Turnpike were air conditioned. Since that time, most governmental and law enforcement agencies across the nation have added air conditioning to their vehicles.

Other Applications

Mobile air conditioning is not only found in cars, trucks, and buses. In recent years, mobile air conditioning application has been expanded for use in farm equipment such as tractors, harvesters, and thrashers. Additionally, mobile air-conditioning systems have been developed for use in other off-road equipment, such as backhoes, bulldozers, and graders. Air conditioning may be found in almost any kind of domestic, farm, or commercial equipment that has an enclosed cab and requires an onboard operator.

Refrigerant and the Environment Since the discovery of the hole in the ozone layer over Antarctica, there has been widespread concern about the consequences for human health and for the environment. Ozone depletion, together with global warming resulting from the greenhouse effect, has attracted widespread media attention and well-founded concern around the world. This chapter will explain: ■■ The importance of the ozone layer ■■ How the ozone layer is formed ■■ How the ozone layer is being depleted ■■ What is causing ozone depletion ■■ What industry is doing to correct the damage ■■ What government is doing to correct the damage

What is Ozone?

Ozone is a molecular form of oxygen, having a different chemical property. Thus, it is an allotrope of oxygen. In large concentrations, ozone is considered to be a poisonous gas. The ozone layer, however, protects life on earth from damaging ultraviolet (UV) radiation. Ozone has a very pungent odor described by many as irritating. In high concentrations, it has a pale blue color. This is in contrast with oxygen (O), which is colorless, tasteless, and has no odor. Each molecule of ozone (O 3 ), an allotropic form of oxygen, contains three atoms of oxygen in contrast to the diatomic form, which contains two atoms of oxygen (O 2 ).

The Earth’s Atmosphere

The earth’s atmosphere is composed of a thin covering of gases that surround the globe and comprise an enormous mass. This mass is equivalent to about one million tons for every person living on earth. The atmosphere extends skyward for hundreds of miles (Figure 1-1). The lowest part of the atmosphere is the troposphere, which extends from ground level to about seven miles (11 kilometers) depending on the time of year and region of the globe. The troposphere has clouds, wind, storms, and a weather system. Above the troposphere is the

4 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Ionosphere 30–300 miles 48.28–482.8 km

Stratosphere 7–30 miles 11.27–48.28 km

Troposphere 0–7 miles 0–11.27 km FIGURE 1-1  The atmosphere extends skyward for hundreds of miles.

stratosphere which extends to an altitude of about 30 miles (48 kilometers). This is the region where the protective ozone layer resides. The next time when you see a very large anvil shaped thunderstorm cloud (cumulonimbus) with a flat top look at it closely. This flat top is caused by the top of the cloud reaching the highest level of the troposphere and flatting out just below the stratosphere as it is sheared off by high level winds. The major gases in the atmosphere are nitrogen (N), an inert gas, which comprises 78 percent of the atmosphere by volume, and oxygen, which is vital for life and comprises 21 percent. Water (H 2O) vapor, a portion of which is seen as clouds, accounts for less than 1 percent. The composition of atmospheric gases is as shown in Table 1-1. Several trace gases are also included in the other 0.00276 percent of the earth’s ­atmosphere. Though very small in volume, they play critical roles in the atmosphere. Carbon dioxide (CO 2 ), for example, is a trace gas with a concentration of only 350 parts per million by volume (ppmv). This accounts for less than 0.3 percent, but it absorbs infrared radiation, thus warming the atmosphere through the phenomenon of the greenhouse effect.

Nitrogen (N) is an odorless, colorless, tasteless element that forms 78 percent of our atmosphere. It is an essential element for plant and animal life. The air we breathe contains 1 percent rare gases, such as krypton (Kr).

TABLE 1-1  COMPOSITION OF THE EARTH’S ATMOSPHERE Gas

PPM by Volume

Percentage

Nitrogen (N)

780,840

78

Oxygen (O)

209,460

21

Argon (Ar) Carbon dioxide (CO2 ) Neon (Ne)

9,340

0.0934

350

0.0035

18.18

0.0002

Helium (He)

5.24

0.00005

Methane CH4

2.00

0.00002

Krypton (Kr)

1.14

0.00001

Hydrogen (H)

0.50

0.000005

Nitrous oxide N2O

0.50

0.000005

Ozone O3

0.40

0.000004

Xenon (Xe)

0.09

0.0000009

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Without its ability to retain this heat, the earth would be about 608F (338C) colder and could not support life as we know it. An increase of 25 percent in the concentration of carbon dioxide over the past century is one of the primary causes of global warming. Ozone (O 3 ), another trace gas, occurs at concentrations of only about 0.4 ppmv (0.000004 percent), but it is also essential for absorbing UV radiation from the sun. Excessive UV ­radiation is very damaging to life on earth.

Ozone in the Atmosphere

Ultraviolet (UV) radiation consists of invisible rays from the sun that have damaging effects on the earth. Ultraviolet radiation causes sunburns.

Ultraviolet (UV) radiation is to be avoided whenever possible.

Ozone depletion is the reduction of the ozone layer due to contamination, such as the release of chlorofluorocarbon (CFC) refrigerants into the atmosphere.

Ozone is measured in Dobson Units (DU).

Dobson Unit (DU) is a measure of ozone density level named after Gordon Dobson, a British meteorologist who was the inventor of the measuring device (called a spectrophotometer).

Unlike other gases that are concentrated in the troposphere, about 90 percent of the ozone occurs in the stratosphere, from an altitude of about 9–22 miles (15–35 km). Even at its highest concentration, ozone does not exceed 10 ppmv—equivalent to one ozone molecule in every 100,000 molecules. For example, if all the ozone in the atmosphere were concentrated at sea level, it would form a layer less than 0.125 in. (3 mm) thick. There are about 3,000 million tons of ozone in the atmosphere, equivalent to about 1,600 lb. (726 kg) per person on earth. Compared with the total mass of the atmosphere, however, the amount of ozone is negligible. Ozone is formed by the action of electrical discharges. For this reason, it is sometimes detected by odor near electrical equipment or just after a thunderstorm. More frequently, however, ozone is formed by the action of ultraviolet (UV) radiation on oxygen in the stratosphere. The atoms in the oxygen molecules split apart, and the separated atoms recombine with other oxygen molecules to form the triatomic ozone (O 3 ). Because sunlight is essential for the formation of stratospheric ozone, it is formed mainly over the equatorial region, where solar radiation is highest. From there, it is distributed throughout the stratosphere by the slight global wind circulation. Stratospheric ozone levels vary throughout the world, being highest at the equator and lowest toward the poles.

Absorption of Ultraviolet Radiation

Incoming radiation from the sun is of various wavelengths, ranging from UV to visible light to infrared. Ultraviolet radiation can cause sunburn, skin cancer, and damage to eyes, including cataracts. It can also cause premature aging and wrinkling of the skin. Ultraviolet radiation breaks down the food chain by destroying minute organisms such as plankton in the ocean, thereby depriving certain species of their natural food. Plant life and crops can also be devastated by excessive UV radiation. Fortunately, the damaging forms of UV radiation are absorbed by ozone in the atmosphere and do not reach the earth. The minute amount of atmospheric ozone is sufficient to absorb this radiation. The ozone layer, then, acts as a giant sunscreen or umbrella enveloping the earth, protecting life from the dangerous UV radiation. Ozone depletion results in weakening of this protective shield, however, and allows more UV radiation to strike the earth and living organisms, as shown in Figure 1-2. Another consequence of the absorption of solar energy by ozone is that the upper ­stratosphere is somewhat warmer than at lower altitudes, which helps to regulate the earth’s temperature. Stratospheric ozone absorbs about 3 percent of incoming solar radiation, thus serving as a heat sink. Loss of this ozone will decrease the temperature of the stratosphere, which will, in turn, affect the troposphere and consequently the weather and climate on the earth’s surface.

Measurement of Ozone

Although the ozone depletion problem was not to be officially addressed for another 50 years or so, the measurement of ozone in the atmosphere began in the 1920s. The standard term for measuring ozone levels is the Dobson Unit (DU), named after the British meteorologist Gordon Dobson, who was the first to use a spectrophotometer. This device is used to determine the intensity of various wavelengths in a spectrum of light and can thereby measure the density of the ozone layer.

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Ozone Depletion Process

3 O3

Cl 2

4

O3

O3

Cl

CFC

5 UV Radiation

UV Radiation CFC CFC

1

6

1 - CFCs released 4 - CI destroys ozone 2 - CFCs rise into ozone layer 5 - Depleted ozone -> more UV 3 - UV releases CI from CFCs 6 - More UV -> more skin cancer FIGURE 1-2  Ozone Depletion Process.

The Ozone Hole The term ozone hole refers to the loss of the blocking effect of ozone against UV radiation. With the depletion of the ozone barrier, a “hole” has been created that allows a much greater amount of UV radiation to penetrate to the earth. Like an umbrella with holes in it that allows the rain through, holes in the ozone layer allow dangerous UV radiation to pass through to the earth’s surface. When ozone measurements were first taken at the British base at Halley Bay in the Antarctic, levels were found to fall drastically in September and October to 150 DU—half the normal level. This is also half the levels measured in the northern hemisphere in the spring. Levels again rose in November to the expected pattern, confirming that the atmosphere over Antarctica differs from elsewhere in the world. At the center of the depleted area almost all of the ozone had disappeared. At Halley Bay between mid-August and early October, levels fall by 97 percent at a height of 10.25 miles (16.5 km). The hole occurs between 10.6 and 13.7 miles (17 and 22 km) above the earth. Recent studies by NASA indicate that by the year 2030 climate change may surpass chlorofluorocarbons as the main cause of ozone depletion. Greenhouse gases like methane and carbon dioxide are changing the earth’s climate. These effects could delay the recovery of the ozone layer even though most of the industrialized nations have signed international agreements to ban the production and use of CFCs. CFCs once used in the production of refrigerant and other commercial applications will last for decades in the upper stratosphere. Ozone thinning can also occur when water vapor makes its way to the stratosphere. At these high altitudes, water vapor can be broken down into molecules that attack the ozone molecules. This can occur when methane emissions that migrate to the stratosphere are transformed into water vapor. The greenhouse effect also heats up the lower stratosphere where most of the ozone is concentrated. As it heats up, the chemical reactions that destroy ozone are also accelerated. Computer modeling indicated that the hole in the ozone layer was the largest ever observed by NASA on September 21–30, 2006. Another study indicates that, as the level of CFCs decline and their effect on the ozone layer is taken by itself, the ozone layer will make a full recovery by the year 2065. Unfortunately, the same study indicates that when the other variables such as the greenhouse effect and water vapor in the stratosphere are added back into the equation, the ozone layer will only make a slight improvement by 2040. There is still hope, but CFC reduction is only one piece of the puzzle. 7 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Cl H

O

H

A

F

B

C

Cl

F

FIGURE 1-3  Chemical structure of (A) Water; (B) CFC-12.

How Ozone Is Being Destroyed

Chlorine (CI) is a poisonous, greenishyellow gas used in some refrigerants and known to be harmful to the ozone layer.

CFC stands for chlorofluorocarbon, a man-made compound used in refrigerants such as CFC-12 (R-12).

Toxicity refers to the toxic or poisonous quality of a substance.

The chlorine atoms in CFCs are hazardous to the ozone layer.

Ozone is both created and destroyed by the action of UV radiation on oxygen molecules. Chlorine (Cl) is the major gas causing the destruction of ozone and starts chain reactions in which a single molecule of chlorine can destroy 100,000 ozone molecules. Such reactions can continue for many years, even a century or more, until the chlorine drifts down into the troposphere or is chemically bound into another compound. The main sources of chlorine are chlorofluorocarbons (CFCs). CFCs (Figure 1-3) are artificially-made chemicals first developed in 1928 and are comprised of: ■■ Chlorine (Cl) ■■ Fluorine (F) ■■ Carbon (C) ■■ (Often) hydrogen (H) CFCs are very stable chemicals and are nonflammable, nonirritating, nonexplosive, noncorrosive, odorless, and relatively low in toxicity. They vaporize at low temperatures, which makes them very desirable for use as refrigerants in air conditioners and refrigerators. CFCs were also used as solvents for cleaning electronic components, for blowing bubbles in certain types of foam-blown plastics such as sponges and food packaging, in dry cleaning solvent, and as an aerosol propellant. Figure 1-4 depicts the consumption rates of the United States where CFCs were used to produce goods and services prior to the restriction in production under the Clean Air Act. As can be seen, refrigerant made up a large portion of the overall use of CFCs. During the 1960s and 1970s, aerosol use was widespread due to the stable nature and nonflammability of CFCs. Peak worldwide use of CFCs in the 1970s was on the order of about 700,000 tons (635,460 metric tons) each year. The scheduled phaseout caused drastic reductions, however, and with the decline in the use of aerosols, nonaerosol use has risen. The consumption of CFCs on a per capita basis in the United States is among the highest in the world (Figure 1-5), a reflection of our affluence and the popularity and use of air conditioners. Although industrialized nations are the major consumers of CFCs, developing nations such as China and India, because of their large populations, have an enormous potential to require CFCs for refrigerators and other uses. In 1974, two chemists at the University of California, Mario Molina and Sherwood Rowland, asked the simple question: “What has happened to the millions of tons of CFCs released over the previous four decades?” The only “sink” they could suggest was the stratosphere. They hypothesized that the chemical stability of CFCs would enable them to reach the stratosphere, be broken apart by the intense UV radiation, and release chlorine by a process known as photolysis. The chlorine would then react with the ozone, causing its depletion. It is not the CFCs, as such, that cause the destruction, but rather the chlorine released by the CFCs. The research of the British scientists at Halley Bay, together with international research programs in which samples of stratospheric air are obtained by high-altitude flights

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A

B

A E

E

C

D C

D

B

FIGURE 1-4  United States’ consumption rates prior to CFC use being restricted by the Clean Air Act: (A) A/C-Ref 35%, (B) Foam Blowing 35%, (C) Other 7%, (D) Sterilants 5%, (E) Solvents 18%. (Consumption rates are prior to CFC being restricted.)

FIGURE 1-5  Consumption of CFCs at the time of the signing of the Montreal Protocol, by country/ region: (A) The former Soviet Republics 14%, (B) Developing Nations 14%, (C) United States 29%, (D) China and India 2%, (E) Other Developed Nations 41%.

over Antarctica, have proven the link between CFCs and ozone destruction. A further factor identified as contributing to the loss of ozone is the polar stratospheric clouds that form during the Antarctic winter in the very cold stratospheric air. These comprise tiny particles of frozen water vapor, which condense and form clouds in spring. The clouds act as reservoirs of frozen chlorine during winter until thawed in spring. At that time, the chlorine is released and begins to react with the ozone over the following five to six weeks, then the vortex breaks up and the stratosphere becomes less stable. A chlorine atom reacts with an ozone molecule by splitting it apart and attaching itself to one of the oxygen atoms to form chlorine monoxide. A free oxygen atom splits the chlorine monoxide molecule to reform a molecule of oxygen (O2), and the chlorine atom is free to attack another ozone molecule (Figure 1-6). The CFCs take six to eight years to rise up through the atmosphere. Chlorine as used in swimming pools and bleach is unstable and breaks down rapidly without rising into the atmosphere. The concern is that the current hole and depletion that have resulted from CFCs released in early years will only worsen as their full effects are manifested over time in the stratosphere.

Chlorine atoms split ozone molecules to form chlorine monoxide.

Effects of Loss of Ozone on Human Health As we have seen, ozone protects life on earth from damaging UV radiation. It acts as a giant sunscreen absorbing the UV rays, preventing a certain percentage of them from reaching the earth. As already noted, loss of ozone will only allow more UV radiation to penetrate to the earth and adversely affect human health and the environment. The three areas of our bodies that are adversely affected are the skin, eyes, and the immune system. Exposure of skin to UV radiation can initially result in sunburn and suntan. If the exposure continues over a long period, as with those who work outdoors, the skin protects itself from UV radiation by gradually thickening and darkening as a pigment called melanin is released in the skin. Continuous exposure of the skin to UV radiation results in its aging and wrinkling and increases the risk of skin cancer. Excessive UV exposure to the eyes will increase the risk of cataracts, which cause cloudiness in the lens of the eye, limiting vision. Other eye problems such as retina damage, tumors on the cornea, and “snow blindness” may also be caused by exposure to increased levels of UV radiation.

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Chlorofluorocarbon (CFC) molecules accumulate in upper atmosphere.

1

Ultraviolet light 2 Chlorine atom

3

Ozone molecule (three oxygen atoms)

Chlorine monoxide

6

The chlorine attacks an ozone molecule and breaks it apart.

A molecule of chlorine monoxide and a molecule of oxygen are formed.

4

5

In the upper atmosphere, ultraviolet light breaks off a chlorine atom from a CFC molecule.

Oxygen

A free oxygen atom breaks up the chlorine monoxide molecule by attaching itself to the oxygen atom thereby freeing the chlorine atom. The chlorine atom is free to repeat the process. FIGURE 1-6  How CFCs destroy the ozone.

The body’s immune system protects it from foreign chemicals and infections. If ­damaged, the immune system cannot protect the body and infections spread more rapidly. Ultraviolet radiation reduces the ability of the immune system to reject cancers, although not much is known about why this happens. Overall, increased UV radiation resulting from ozone depletion has the potential to significantly increase human skin cancers and cataracts and damage the human immune system. It also adversely affects marine and terrestrial plants and animals. The extent of the damage will depend on the degree to which the earth’s ozone layer is depleted. To date, it has been reduced by about 2.5 percent, and it remains to be seen whether the actions taken to control the release of ozone-depleting substances will be sufficient. 10 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Climate Change and the Greenhouse Effect The loss of ozone and the greenhouse effect are separate phenomena, although CFC’s are a common agent in both. Greenhouse gases in effect work as a blanket, warming the lower atmosphere. The earth’s atmosphere contains many chemical compounds that act as “greenhouse” gases, and these gases allow sun light to entire the earth’s atmosphere freely. As this solar radiation passes through the atmosphere it then strikes and warms the earth. But some of this infrared radiation (heat) is re-emitted by the earth’s surface and is absorbed and reflected by greenhouse gas molecules in the atmosphere, in all directions (Figure 1-7). The effect of this is to warm the earth’s surface and lower atmosphere even further. It is similar to how a greenhouse is warmed by sunlight passing through the glass warming the interior and not allowing the heat to escape unless the vents are open. Think of the glass as the greenhouse gas molecules. Also, think of the interior of a car in the sun on a hot summer day with the windows rolled up. The interior will become much hotter than the outside temperature. Over time the amount of heat energy (infrared radiation) sent from the sun to heat the earth is radiated back into space, thus leaving the earth’s temperature relatively constant ideally, if nature is left alone. Many gases exhibit greenhouse gas properties, some occur naturally like water vapor, carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide. Others are man-made or increased by human activities. The greenhouse effect or global warming is the result of the release of increasing amounts of so-called “greenhouse gases” into the atmosphere, gases such as CO 2, CH 4 , and manmade gases such as CFCs and HFCs. These greenhouse gases act as a blanket around the earth retaining heat. Without any greenhouse effect, the earth would be about 608F (338C) colder, too cold to support life as we know it. Greenhouse gas emissions have increased by about 25 percent over the last 150 years (Figure 1-8). This is also the time period of large scale industrialization in the United States and Europe. In addition, 75 percent of the carbon dioxide emissions produced in the last 20 years was from the burning of fossil fuels. The earth has a natural processes by which concentrations of carbon dioxide in the atmosphere are regulated known as the “carbon cycle” (Figure 1-9). Through processes like plant photosynthesis carbon is moved from the atmosphere to the land and oceans of the earth. These natural processes are responsible for removing approximately 6.1 billion metric tons of man-made carbon dioxide emissions each year. But this leaves an additional 3.1 billion metric tons of man-made carbon dioxide emissions that are not removed by the carbon cycle and are added to the atmosphere each year. This results in an ever-increasing amount of greenhouse gases accumulating in our atmosphere that are not absorbed naturally.

Solar radiation passes through the clear atmosphere

Some solar radiation is reflected by the earth and the atmosphere

Infrared is the invisible light rays just beyond the red end of the visible spectrum and have a penetrating heating effect.

Greenhouse effect is a term based on the fact that a greenhouse is warmed because glass allows the sun’s radiant heat to enter, but prevents radiant heat from leaving. Likewise, global warming is caused by some gases in the atmosphere that act like greenhouse glass.

Global warming is the gradual warming of the earth’s atmosphere due to the greenhouse effect.

Some of the infrared radiation passes through the atmosphere, and some is absorbed and re-emitted in all directions by greenhouse gas molecules. The effect of this is to warm the earth’s surface and the lower atmosphere.

Infrared radiation is emitted from the earth’s surface

Most radiation is absorbed by the earth’s surface and warms it

FIGURE 1-7  The Greenhouse Effect

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7,000

360

6,000

340

5,000

320

4,000

300

3,000

280

2,000

260

1,000

0

1750

1800

1850

1900

Atmospheric concentrations

1950

CO2 emissions (million metric tons carbon)

CO2 concentrations (ppmv)

380

0

2000

Anthropogenic emissions

FIGURE 1-8  Trends in Atmospheric Concentrations and Man-made (Anthropogenic) Emissions of Carbon Dioxide

Fossil fuel combustion and industrial processes

Atmosphere 730

6.3

1.7 Changing land-use

120 119

Global gross primary production and respiration

88

90

1.9

Ocean 38,000

Vegetation and soils 2,000

Carbon flux indicated by arrows: Natural flux =

Anthropogenic flux =

FIGURE 1-9  The global carbon cycle in billions of metric tons.

Because the earth’s climate is naturally variable, it is difficult to determine the exact extent that human activity has had. Computer analysis has shown that increases in greenhouse gases have been correlated to increases in the earth’s temperature. This analysis also indicates that rising temperature may produce changes in sea level, and weather commonly referred to as “climate change.” A National Research Council study dated May 2001 stated, Greenhouse gases are accumulating in Earth’s atmosphere as a result of human activities, causing surface air temperatures and sub-surface ocean temperatures to rise. Temperatures are, in fact, rising The changes observed over the last several decades are likely mostly due to human activities, but we cannot rule out that some significant part of these changes is also a reflection of natural variability. In 1992, the National Climate Data Center (NCDC) declared that the winter of 1991–1992 was the warmest U.S. winter in the 97 years that the federal government had kept a record of climatic conditions. The average temperature was 36.878F (2.78C). The previous high average 12 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Departure for mean (˚F) (long-term)

1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 –0.2 –0.4 –0.6 –0.8

1880

1900

1920

1940

1960

1980

2000

FIGURE 1-10  U.S. National Climate Data Center 2011 showing an increase in global temperature.

temperature of 368F (2.228C) was recorded in 1953–1954. Then in 1999, the NCDC declared that 1998 was the warmest year on record. In North America, seven of the eight warmest years have occurred since 2001 with the ten warmest years occurring since 1995 (Figure 1-10). This increase in global warming has also increased worldwide rainfall amounts by about 1 percent. Some scientists predict that global surface temperatures could rise 1-4.5 percent over the next 15 years and by 2–10 percent during this century. This could result in sea levels rising by as much as 2 feet along most of the U.S. coastline. The U.S. is responsible for producing approximately 25 percent of the global CO 2 emissions by burning fossil fuels. Our economy is the largest in the world and 82 percent of our energy needs (i.e., electricity generation and transportation) are derived from the burning of petroleum and natural gas (Figure 1-11). Unfortunately both hybrid electric and battery electric vehicles in the United States still ultimately rely on fossil fuels for the majority of their energy. Man-made gases, which include hydro fluorocarbons (HFCs) used as refrigerants, represent two percent of total emissions. The good news is that the United States is predicted to lower its carbon intensity between 2001 and 2025 by 25 percent (Figure 1-12). The bad news is that worldwide CO 2 emissions levels are expected to increase by 1.9 percent annually over the same time period, primary due to increased levels of emissions by developing countries such as China and India. Developing countries CO 2 emissions levels are expected to increase by 2.7 percent annually between 2001 and 2025 causing industrialized countries gains to be negatively offset. According to recent statistics automobiles in the United States have leaked a­ pproximately 51 thousand tons of R134a refrigerant gas into the atmosphere, which is equivalent to Carbon dioxide from fossil fuel combustion 82%

Other carbon dioxide 2% Methane 9% Nitrous oxide 5%

HFCs, PFCs, and SF6 2%

FIGURE 1-11  United States greenhouse gas emissions by gas.

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12,000 10,000 Total World

8,000 6,000 4,000

Industrialized Countries Developing Countries

2,000 0 2001

2005

Eastern European/Former Soviet Union 2010 2015 2020 2025

FIGURE 1-12  Predicted world carbon dioxide emissions by region 2001–2025.

Global warming potential (GWP Global warming potential is an index number which is an estimate of how much a given mass of a gas will contribute to global warming compared to the same mass of carbon dioxide, where carbon dioxide is given the number 1.

72.8 million metric tons of greenhouse gases. Though this number seems large, it is a very small percentage when compared to the CO 2 emissions generated from the burning of fossil fuels as was noted in Figure 1-11. Beginning on January 1, 2011, the European Union EU 2006/40/EC Act provisions went into effect, though the deadline was extended to January 1, 2013, due to lack of a readily available supply of a new refrigerant. This law was designed to phase out global warming refrigerants with complete phaseout of R134a in Europe by January 1, 2017, for new vehicles sold in EU member countries. The act requires all new automotive platform refrigerant systems to use a refrigerant with a global warming potential (GWP) that is not to exceed 150. The GWP number is an index number that is an estimate of how much a given mass of a gas will contribute to global warming compared to the same mass of carbon dioxide, where carbon dioxide is given the number 1. The current refrigerant R134a has a GWP number of 1430, meaning it has 1400 times the greenhouse effect of carbon dioxide. The refrigerant that has been chosen to replace R-134A in Europe is R-1234yf, which has a GWP of 4. The environmental life span of CFC refrigerants like R-12 was over 100 years, whereas HFC refrigerants like R-134A have an environmental life span of 10 years compared to R1234yf, which has a much shorter atmospheric life span of only 11 days. Currently the United States has no plan to regulate the use of R134a as a refrigerant gas but is incentivizing manufacturers to choose a lower GWP refrigerant. Some automotive manufacturers such as General Motors began to phase in the use of R-1234yf, which has a lower GWP number beginning in 2013 on some platforms, and other manufacturers began to follow, offering R1234yf on some new platforms. Although higher costs and lack of federal regulation may deter automotive manufacturers from adopting alternative refrigerants in the U.S. market quickly, it is predicted that by 2021, R-134A may be phased out in the United States. Officially R-134a is not going away as far as the United States and the Environmental Protection Agency (EPA) are concerned, at least for the near term future, and R-134a will continue to be manufactured and installed in new and existing systems. Europe, on the other hand, as was stated earlier, has required the phaseout of R-134a by 2017. The European Union (EU) has enacted some very stiff environmental rules that are now driving the worldwide mobile HVAC industry to adopt low GWP refrigerants. The European Community mandated that beginning January 1, 2011, any “new type” vehicle platform must change over to a low-GWP refrigerant with a GWP number of 150 or below. R-134a’s GWP number is 1430. This does not mean a full-scale changeover is required to a new refrigerant, only on completely “new type” platforms. Existing platforms were allowed to continue to be produced using R-134a until full phaseout in 2017 in the EU. So, until a manufacturer developed a new platform (type), they could continue installing the R-134a system in vehicles until 2017.

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In the United States and Asia, manufacturers are not required to phase out R-134a, although some manufacturers that sell vehicles in the United States and elsewhere have chosen to switch to a refrigerant with a lower GWP number in an effort to receive EPA “carbon credits” on some of their platforms. A “carbon credit” is a credit that can be used to offset carbon dioxide (CO 2 ) production (emissions) above the EPA limit of 250 grams per mile (g/mi.) vehicle fleet average beginning in 2016, which also coincides with more stringent corporate average fuel economy (CAFÉ) regulations. Like many EPA regulations, the agency does not tell the industry how to achieve these limits, only what they are. The industry has many options on how they will meet these requirements. As an example, think about vehicle tailpipe emission requirements. The EPA did not tell the industry to abandon carburetors; the EPA set emission limits that required the industry to develop new technology in order to meet more stringent emission regulations. In the early stages, the industry developed electronic ignition systems and electronic feedback carburetors and later implemented more sophisticated fuel injection and computer-controlled subsystems. And today when you open the hood, it is almost unrecognizable from the engine compartments of the 1960s. This is the road we are taking once again, but this time the emission gas that is being regulated is CO 2, and if you remember from basic internal combustion engine theory, the higher the CO 2 levels produced after combustion, the more efficient the engine is running. But these CO 2 limits are not just related to tailpipe emissions, they apply to the entire vehicle. Now the industry must decide how they want to meet these new regulations. If a manufacturer decides to switch over to a lowGWP refrigerant, the EPA will issue carbon credits for a reduced carbon footprint. However, if R-134a systems are improved to provide greater fuel efficiency and reduce lifetime leakage, they may also receive carbon offset credits. Beginning in the 2009 model year, improvements in R-134a systems can receive carbon credits that can be carried forward to when the new regulations are implemented, which in turn reduces the urgency of needing to switch to a new refrigerant. The EPA formula is based in part on the SAE J2727 standard for calculating system improvements. As an example of carbon credits, an R-134a system with system improvements and an electric compressor can receive 9.5 g/mi. credit for cars and 11.7 g/mi. credit for trucks compared to the carbon credit received for switching over to R-1234yf of 13.8 g/mi. credit. So the question at many automotive manufacturer boardrooms is, “Do we need to switch to a new refrigerant to receive carbon credits or can we improve our current R-134a system in order to meet new EPA requirements?” Like many questions, there will be more than one answer and not every manufacturer will make the same choices. But with a global marketplace and economies of scale, the long-term choices will probably be similar.

The Clean Air Act The most significant legislation to affect the automotive air conditioning industry in the United States is the Clean Air Act (CAA). The CAA was signed into law by U.S. President George H. W. Bush on November 15, 1990. Most of the rules and regulations of the CAA were a result of the recommendations made at the Montreal Protocol. The Montreal Protocol and later amendments deal with the environmental problems and issues created by certain refrigerants depleting the ozone on an international level. The CAA deals with this problem on a national level. The Montreal Protocol is structured so that periodic meetings must take place in order to reassess the ozone problem. As new facts about the impact of refrigerants are brought to light, the protocol will be modified accordingly. The majority of protocol modifications will also result in the CAA being modified accordingly. Language exists in the CAA stating that the Environmental Protection Agency (EPA) can accelerate schedules for the phaseout of refrigerants if it is deemed necessary and practical. The CAA also mandates that phaseout may be accelerated if required by the Montreal Protocol. The CAA is somewhat more specific than the Montreal Protocol in addressing the ozone depletion problem. The Clean Air Act gives the EPA the authority to establish environmentally safe procedures with respect to the use and reuse of refrigerants. In addition, the EPA

Clean Air Act (CAA) is a Title 6 Amendment signed into law in 1990 that established national policy relative to the reduction and elimination of ozone-depleting substances.

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will establish standards for certifying those who service refrigeration equipment and for that service itself. These standards will be derived from the information furnished mainly by private sector organizations.

Stratospheric Ozone Protection—Title VI Title VI of the CAA concerns stratospheric ozone protection. It establishes regulations for the production, use, and phaseout of CFCs, halons, and HCFCs. Other chemicals such as carbon tetrachloride (CC14 ), also covered by Title VI, are not covered in this text. Title VI divides the substances to be regulated into two classes: Class I and Class II. The chemical that we are primarily concerned with in the automotive industry is CFC-12, a Class I refrigerant. Manufacture of this refrigerant ended in the United States on December 31, 1995. Hydrofluorocarbons (HFCs) are an alternative to ozone-damaging CFCs in refrigeration systems. The refrigerant currently used in automotive air-conditioning systems is HFC-134a, better known as R-134a. HFCs have been designated greenhouse gases, and HFC-134a has an atmospheric lifetime of about 14 years.

Ozone Protection Regulations For decades, R-12, or freon more properly known as CFC-12, was used as the refrigerant in motor vehicle air-conditioning systems. However, since the discovery that CFCs damage the ozone layer, the production of ozone-depleting substances has ended. To help ensure that existing CFC-12 is used and reused rather than being wasted and released to the atmosphere, the EPA has issued regulations under Section 609 of the CAA to require that automotive shop technicians use special machines to recover and recycle CFC-12. On December 31, 1995, the production of CFC-12 in the United States essentially ceased. It is legal, however, to use existing stockpiles of CFC-12, and several companies have also developed several new substitutes. These substitute refrigerants have been reviewed by the EPA’s Significant New Alternatives Policy (SNAP) program. It is also illegal to release these substitutes to the atmosphere. As of June 1, 1998, the EPA has allowed refrigerant blends used in motor vehicle air-conditioning systems to be recycled. The EPA stipulates that the equipment used must meet Underwriters Laboratories (UL) standards, and the refrigerant must be returned only to the vehicle from which it was removed. The California Automotive Repair Bureau (CARB) passed a law that went into effect on January 19, 2001, requiring that every shop in the state that performs mobile air conditioning service have a minimum set of diagnostic equipment.

CFC-12 (R-12)

Those who wish to service or repair motor vehicle air conditioners (MVACs) using CFC-12 as a refrigerant must be trained and certified by an EPA-approved organization. The training program must include pertinent information on the proper care and use of equipment, the regulatory requirements, the importance of refrigerant recovery, and the environmental effects of ozone depletion. To be certified, a technician must pass a test designed to demonstrate his or her knowledge in all of these areas. The supply tank for R-12 is white in color, which applies to both disposable and reusable tanks.

HFC-134a (R-134a)

Any automotive technician who wishes to repair or service HFC-134a MVACs must also be trained and certified by an EPA-approved agency. If, however, a technician is already trained and certified to repair and service CFC-12 systems, he or she does not have to be recertified to service HFC-134a systems. Characteristics of HFC134a (R-134a).  The automotive industry chose R-134a as the replacement refrigerant for CFC12 (R-12). R-134a is an HFC and does not contribute to the 16 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

depletion of the ozone layer. HFC134a is classified as a contributor to global warming and has a GWP of 1430 though, and as such, is regulated. HFC refrigerants replace the chlorine atom with hydrogen atoms. It is a single-composition refrigerant that changes state at a specified temperature and pressure and has similar performance and vapor pressure characteristics to that of R-12. The power consumption is slightly higher for R-134a, and it has a slightly lower refrigeration capacity of between 3 and 5 percent compared to R-12. The properties of R-134a also require the use of different refrigerant oils to provide proper compressor lubrication, which are not compatible with R-12. Components have been redesigned for the different characteristics of R-134a. The supply tank for R-134a is sky blue in color, which applies to both disposable and reusable tanks. Vehicles with R-134a have unique low- and high-side quick-connect coupler service fittings to avoid system contamination by another refrigerant.

Refrigerant HFO-1234yf (R-1234yf) The refrigerant that is the preferred replacement for R-134a today is R-1234yf, pronounced R twelve thirty four yf. The new refrigerant was developed by Honeywell and DuPont and is classified as HFO-1234yf (R-1234yf ); HFO stands for hydrofluoro olefin and has a chemical structure of CF3CF 5 CH2 2,3,3,3-tetrafluoropropene. The refrigerant has been determined to be mildly flammable gas. R-1234yf is an environmentally friendly refrigerant that has no ozone depletion potential; a global warming potential (GWP) of 4, which is 99.7% lower than R-134a; and has a vapor pressure of 583 kPa absolute at 208C and a boiling point of 229.28C. This new refrigerant received final EPA approval under the Significant New Alternative Program (SNAP) for use in mobile air-conditioning systems (MAC) in early 2011. But the changeover to this new refrigerant may be very slow. General Motors began rolling out a few platforms equipped with R-1234yf in the United States on a very limited basis beginning in 2013. Vehicles with R-1234yf have unique low- and high-side service fittings to avoid system contamination by another refrigerant. The fittings are similar to R-134a fittings, but smaller. Honeywell developed the commercially viable HFO-1234yf as a low-cost, low-GWP dropin refrigerant replacement for R134a refrigerant. This new refrigerant is expected to significantly reduce the global warming footprint associated with air-conditioning systems. The GWP of R-1234yf is 4 compared to R-134a, which has a GWP of 1430. Many environmental groups still favor other refrigerant options such as CO 2 (R744), which has a GWP of 1, but for now the higher production costs of these systems has stalled development and production for automotive applications. R-1234yf has an atmospheric lifetime of 11 days and the atmospheric breakdown products are the same as R-134a, which is trifluoroacetic acid (TFA) and does not pose a threat to the environment, based on industry evaluations that took place in the 1990s. In fact, TFA is found in large amounts in the oceans of the world and it has been suggested that TFA is a natural component of saltwater. Since it does not appear that the United States is going to regulate R-134a out of existence, manufacturers do not have to stop using R-134a in new vehicle platforms like they did with R-12. Because R-134a will still be produced and available, there may not be widespread acceptance of R-1234yf. In addition, it does not look like retrofitting from R-134a to R-1234yf will be approved or allowed by the EPA. In the end, what may keep the U.S. automotive industry from changing over to R-1234yf may be economic—higher product costs and a single supplier. Honeywell-DuPont is retaining sole patent and production rights and ultimately that may be too large an issue for the automotive industry to overlook. The supply tank for R-134a is white with a red band to denote flammability, which applies to both disposable and reusable tanks.

Blend Refrigerants

Automotive technicians who service or repair MVACs that use a blend refrigerant must be trained and certified by an EPA-approved agency. However, a technician that is already trained and certified to handle CFC-12 or HFC-134a does not have to be recertified to handle a blend refrigerant. 17 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

A

B

FIGURE 1-13  Refrigerant cylinders are designated for a particular type refrigerant; (A) pounds (12.08 kg) cylinder R-12; and (B) 30 pounds (12.08 kg) cylinder R-134a.

Refrigerant Cylinders

Refrigerant cylinders (Figure 1-13) are designed and constructed for definite maximum pressures and for definite quantities of refrigerant that are based on specified maximum temperatures, usually 1308F (548C). The color of the cylinder indicates the type of refrigerant gas that it contains. A white cylinder indicates R-12, sky blue identifies R-134a, and a white cylinder with a red band around the top indicates R-1234yf refrigerant (Figure 1-14). If the cylinders are subjected to temperatures above those specified, the liquid expands to entirely fill the cylinder; extremely high hydrostatic pressures develop, and the cylinder may burst. If the cylinders are filled with a greater amount of refrigerant than specified, hydrostatic pressures may develop at ordinary room temperatures, and the cylinder may burst. Flying pieces of the cylinder may travel at bullet velocity, or in the case of small cylinders or light containers, the container itself may travel like a rocket at projectile speed. Sometimes

SolsticeTM yf Refrigerant (R-1234yf) SolsticeTM yf Refrigerant (R-1234yf)

FIGURE 1-14  The R1234yf refrigerant tank is white with and identifying red band since it is a mildly flammable refrigerant.

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of equal or greater danger, the refrigerant itself may burst from the cylinder; technicians have been blinded or suffered freezing injuries from being sprayed with refrigerant. Many factory cylinders are equipped only with fusible plugs, which offer no protection against overfilling; nor do they offer adequate protection on most cylinders against excessive temperatures. Fusible plugs melt at about 1608F (718C) and most cylinders are liquid-full at 1308F (548C), so the fusible plug gives no protection between 1308F and 1608F. All refrigerant cylinders should be protected by means of pressure-activated relief valves, especially service cylinders, because they are more often abused by overfilling than are factoryfilled cylinders. Small combination service valves, with built-in pressure-relief safety valves, were developed by valve manufacturers in cooperation with the Refrigeration Service Engineers Society (RSES) safety and educational department and are available at moderate prices from refrigeration supply wholesalers. Every service cylinder should be equipped with one of the safety valves. Even with the best of care, cylinders become rusted, damaged, or otherwise weakened after several years of use and should be retested by a hydraulic test approved by the Interstate Commerce Commission (ICC). The ICC requires a retest of all service cylinders and most factory cylinders once every 5 years (Figure 1-15). Do not use cylinders beyond the five-year period without having them retested. It may save your life or prevent serious injury. Your refrigerant supplier should be able to suggest a laboratory for retesting refrigerant cylinders. If not, consult the Yellow Pages of your local telephone directory under Hydrostatic Testing for the nearest facility. Corrosion may occur inside a refrigerating system and may also affect external parts. It is commonly due to rusting in damp atmospheres or in areas in which there is a great deal of acidity in the air. As a rule, the parts most likely to be seriously affected are bolts, screws, nuts and rivets, or comparatively thin-walled vessels or tubes, especially those made of iron or steel. Particularly in damp or acid atmospheres, these parts should be inspected occasionally and repaired or replaced if necessary. Keeping parts subject to corrosion properly painted will greatly extend their useful life and lessen the possibility of their suddenly giving way and

It is a violation of federal law to reuse a disposable refrigerant cylinder.

FIGURE 1-15  Service cylinders must be reinspected every 5 years.

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causing an accident. Using protective paints and greases is an inexpensive preventative maintenance that guards against the dangerous and costly breakage of corroded and weakened parts. Water supply lines, gate valves, fittings, and automatic pressure and control valves should be inspected periodically; badly corroded or weakened parts should be replaced.

Technician Certification Automotive technicians who wish to service mobile air-conditioning systems and refrigeration equipment must be certified by an appropriate testing agency approved by the EPA and receive an EPA section 609 Technician Training Certification. This includes all who work with R-12, R-134a, and R1234yf, or any of the blend refrigerants available and approved for automotive use.

Certificating Agency

If there is any doubt about the integrity of the agency offering training and certification, check with the EPA. The EPA maintains an updated list of all of the approved agencies. The EPA has little mercy for anyone issuing bogus technician certificates to those who have not taken the required exam and can impose prison sentences and fines.

Injuries as a Result of High Pressure

Pressure relief valves are provided to release excess pressure.

A basic characteristic of a mechanical refrigeration system is the use of a fluid, both gas and liquid, that is at pressures above atmospheric pressure. The fluid must therefore be maintained and transmitted in tanks, pipes, and other vessels that do not allow the fluids to leak and that are strong enough to withstand maximum pressures without splitting or bursting under extreme conditions of use. It is also a basic characteristic of mechanical refrigeration that these pressures change with fluctuations in temperature or are increased by compressors or pumps. We must, therefore, guard against extra pressures caused by compressors and pumps, as well as the pressures existing in the system because of variations of temperature. Pressure-containing vessels (Figure 1-16) and tubes are designed and constructed to withstand normal pressures caused by normal temperatures, by normal degrees of compression, and normal filling of the vessels. If the vessel or tube is overheated, if an attempt is made to

FIGURE 1-16  An accumulator is a pressure vessel designed to withstand the normal pressures of an air-conditioning system.

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put too much fluid in it, or if the fluid is compressed above the pressure for which the vessel is designed or constructed, the vessel will “give” somewhat until it reaches its limit of elasticity; then the vessel will burst, often with explosive violence. Overpressure may cause large parts to be blown out, such as the welded ends of dryers or of receivers. Overpressure may also drive plugs or other small parts out with projectile speed and force. Explosions or bursting of vessels from overpressure sometimes start with overfilling the vessels with liquids at lower temperature. Then when the completely filled vessel warms up, the liquid expands and exerts tremendous pressure, known as hydrostatic pressure. In other words, hydrostatic pressure occurs when a cylinder is full of a liquid and there is no room for expansion as it heats up. As a result, something has to give, and it is the weakest part that gives. Oftentimes it is a hose or hose connection. Sometimes it is the compressor head gasket or a head, which may be most dangerous.

Hydrostatic pressure is the pressure exerted by a fluid.

Special Safety Precautions Because it is very important that the student be aware of the hazards involved in the use of any refrigerant, the following safety procedures must be observed at all times. Recall that refrigerant is: ■■ Odorless ■■ Undetectable in small quantities ■■ Colorless ■■ Nonstaining However, refrigerant is dangerous because of the damage it can cause if allowed to strike the human eye or come into contact with the skin. Suitable eye protection must be worn to protect the eyes from splashing refrigerant (Figure 1-17). If refrigerant does enter the eye, freezing of the eye can occur with resultant blindness. The following procedure is suggested if refrigerant enters the eye(s): 1. Do not rub the eye. 2. Splash large quantities of cool (not hot) water into the eye to raise the temperature. 3. Tape a sterile eye patch over the eye to prevent dirt from entering. Do not use salves or ointments. 4. Go immediately to a doctor or hospital for professional care. If liquid refrigerant strikes the skin, frostbite can occur. The same procedure outlined for emergency eye care can be used to combat the effects of refrigerant contact with the skin. Refrigerant in the air is harmless unless it is released in a confined space. In a refrigerated trailer with an evaporator leak, it is possible that the refrigerant could displace the oxygen, resulting in an oxygen-depleted environment. Always exercise caution when a refrigerant leak is suspected in a sealed or confined space and allow for adequate ventilation before performing

A

Do not attempt selftreatment for injury.

B FIGURE 1-17  Wear suitable eye protection: (A) monogoggle; (B) safety glasses.

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Do not refill disposable cylinders.

services. Under these conditions, refrigerant displaces oxygen in the air and may cause drowsiness or unconsciousness—even death. However, the automobile owner and the service technician need not be overly concerned about the safety of the automotive air-conditioning system under normal conditions. The small capacity of the system compared to the large area of the car interior or work area minimizes the concentration of any contamination. Refrigerant must not, however, be allowed to come into contact with an open flame or a very hot metal. Tests made by UL in 1933, shortly after the development of CFC-12, indicated that it produced a highly toxic gas known as phosgene during decomposition. Tests in recent years, however, prove that phosgene gas is not a product of decomposition in this manner. Decomposition does, however, result in the formation of carbonyl fluoride (COF2 ) and carbonyl chlorofluoride (COClF) with small amounts of free chlorine (C12 ). Though 20–50 times less toxic than phosgene, as discussed earlier, the decomposed gases of CFC-12 must be avoided. At high concentrations, the lack of oxygen, which results in asphyxiation, is the real hazard. A primary rule, then, is to avoid breathing these or any other fumes. The human body requires oxygen in the quantity found in noncontaminated air. Diluting air with any foreign gas can reduce the available oxygen to a level that may be harmful or, in some cases, fatal. The following rules must always be observed when handling refrigerants: 1. Never heat a refrigerant cylinder above 1258F (51.78C) or allow it to reach this temperature. Above 1308F (54.448C), expanding liquid refrigerant completely fills the container, and hydrostatic pressure builds up rapidly with each degree of temperature rise. 2. Never apply a direct flame to a refrigerant cylinder or container. Never place an electrical resistance heater near or in direct contact with a container of refrigerant. 3. Do not abuse a refrigerant cylinder or container. To avoid damage, use an approved valve wrench for opening and closing the valves. Secure all cylinders in an upright position for storing and withdrawing refrigerant. Carefully invert a refrigerant cylinder to dispense liquid refrigerant (first ensuring that the compressor is not running). Recovery cylinders are not to be inverted; use the liquid valve for dispensing liquid refrigerant (again ensuring that the compressor is not running). 4. Do not handle refrigerant without suitable eye protection. 5. Do not discharge (vent) refrigerant into the atmosphere. Remove refrigerant from a system using approved recovery equipment only. 6. Use only Department of Transportation (DOT) approved refrigerant recovery cylinders (Figure 1-18). Do not fill recovery cylinders beyond 80 percent of their rated capacity.

FIGURE 1-18  Use only DOTapproved recovery cylinders.

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7. Do not mix refrigerants. Cross-contaminated refrigerants must be destroyed or separated by an approved reclamation center. 8. For an automotive air-conditioning system, do not introduce anything but refrigerant acceptable under EPA’s SNAP program into the system. 9. Use only lubricant recommended for the refrigerant type. Properly identify, by label and fittings, refrigerant used. 10. Keep refrigerant containers out of direct sunlight. 11. Always work in a well-ventilated area. DO NOT work in a confined area.

Antifreeze/Coolant There are four key areas of engine protection. These are: Freeze protection ■■ Boil-over protection ■■ Corrosion prevention ■■ Adequate heat transfer ■■

Ethylene Glycol-Based Antifreeze

Ethylene glycol (EG) is the main ingredient of all major antifreeze brands and has long been known to be poisonous. When ingested, EG converts to oxalic acid, which damages the kidneys and may cause kidney failure and death. Just 2 ounces of undiluted EG antifreeze (Figure 1-19) can kill a dog; 1 teaspoon can be lethal to a cat; and 2 tablespoons can be hazardous to children. Data compiled by the American Association of Poison Control Centers show that about 3,400 poisonings related to EG occur annually. About 20 percent of these incidents are reported among children under 6 years of age.

Propylene Glycol-Based Antifreeze

A “new” antifreeze, formulated with propylene glycol (PG), is less toxic than EG antifreeze. Therefore, PG antifreeze (Figure 1-20) is much safer for children and animals. Actually, PG is used in specific amounts in the formulation of many consumer products. These products include, but are not limited to, cosmetics, pet food, and certain over-the-counter medications. Nonetheless, PG-based antifreeze should be considered toxic and handled as a hazardous substance.

FIGURE 1-19  Ethylene glycol antifreeze.

FIGURE 1-20  Propylene glycol antifreeze.

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In areas where recycling antifreeze is required, one may locate a facility through a local automotive parts house or in the telephone book’s Yellow Pages under Recycling Centers or Hazardous Materials and Waste Contractors.

Mixing EG and PG

It should be noted that EG-based antifreeze should not be mixed with PG-based antifreeze. Most antifreeze manufacturers caution against mixing the various types and suggest recovery and storage of the different types in separate containers. Also, most vehicle manufacturers require the same type antifreeze be used for top-off or refill that was originally installed in the factory fill to avoid warranty problems. It should be noted that there may be different formulations of antifreeze specified by some vehicle manufacturers. Always refer to manufacturer’s specifications before changing or adding antifreeze to a cooling system.

Vehicle Engine Protection

Either EG- or PG-based antifreeze offers excellent protection for vehicle engines against corrosion, freezing, and overheating. A 50/50 blend of ethylene glycol antifreeze and water has a freezing point of 2348F (236.78C). If a lower temperature protection is required, it can be attained by increasing the concentration of antifreeze. A 60/40 blend, for example, gives antifreeze protection to 2548F (247.88C). It also helps to prevent corrosion in all metals used in automotive cooling systems, including aluminum, brass, copper, cast iron, steel, and the elements contained in solder.

Disposal

Used coolant must be properly disposed of in compliance with local rules and regulations. In areas where recycling is available, both used EG and PG coolants should be offered to recyclers for recycling and reuse.

Hazardous Materials Refrigerants, refrigeration lubricants, solvents, and other chemicals used in an automotive repair facility may be considered hazardous materials and will include warning and caution labels that should be read and understood by everyone who uses them. All hazardous materials should be properly labeled, indicating what health, fire, or reactive hazard they pose and what protective equipment is necessary when handling each chemical. The manufacturer of the hazardous material must also provide all warnings and precautionary information that must be read and understood by all users before the material is used. One should pay particular attention to the label information. Using the product according to label directions helps to ensure proper and safe methods, thereby preventing a hazardous condition. A list of all hazardous materials used in the shop should be posted for all employees to see. Shops must also maintain documented records of the hazardous chemicals in the workplace, training programs, accidents, and spill incidents.

Material Safety Data Sheet

Every employee in a shop is protected by “right-to-know” laws concerning hazardous materials and wastes. The general intent of the law is to ensure that the employer provide a safe work environment. All employees must be trained about their rights under the legislation, the nature of the hazardous chemicals in their workplace, the labeling of chemicals, and the information about each chemical listed and described on Material Safety Data Sheets (MSDS). These sheets (Figure 1-21) are available from the manufacturers and suppliers of the chemicals. They detail the chemical composition and precautionary information for all products that can pose health or safety hazards.

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FIGURE 1-21  Typical Material Safety Data Sheet (MSDS) manual.

Employees must be familiar with the contents of the MSDS that contain information relative to the intended purposes of the substance, the recommended protective equipment, accident and spill procedures, and any other information regarding safe handling. Training must be provided by the employer annually, and new employees must be trained as a part of their job orientation. When handling any hazardous material, always wear the appropriate safety protection. Always follow the correct procedures while using the material, and be familiar with the information given in the MSDS for that material.

Hazardous Waste

Waste is considered hazardous if it is on the EPA list of known harmful materials. Those materials generally have one or more of the following characteristics: ■■ Ignitable ■■ Corrosive ■■ Reactive ■■ Toxic Many service procedures also generate products that may be considered hazardous wastes. Contaminated refrigerants or antifreezes are typical examples of hazardous waste.

Safety Precautions

The following safety precautions in working with hazardous materials should always be observed: ■■ Do not overfill refrigerant cylinders. ■■ Do not allow pressure-containing vessels to become overheated. ■■ Do not put a flame on a refrigerant cylinder, accumulator, receiver, or any other vessel that may contain refrigerant. ■■ Do not steam clean any vessels that may contain refrigerant. ■■ Do not change or add refrigerant to any system without first determining system compatibility. ■■ Always connect both low- and high-pressure gauges before servicing a system. Observe these gauges frequently. ■■ Before loosening bolts or screws, see that the pressure in the part has been relieved. Gaskets may hold the pressure temporarily, then release suddenly, throwing a full charge of refrigerant in the technician’s face.

It is a violation of federal law to intentionally vent refrigerant to the atmosphere.

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■■

■■ ■■ ■■ ■■ ■■ ■■

■■

Use pressure relief valves on all refrigerant cylinders and other vessels that may be subject to excessive pressures. Do not allow a compressor to pump liquid or “slug oil.” Wear suitable protective gear when handling any materials that may be considered toxic. Keep your mind on what you are doing. Be vigilant. If you are tired, take a break. Read and heed all caution labels. Those warning of high pressures, as in the antilock brake systems and the dangers of unexpected air bag deployment, are most important. Be aware of under-hood hazards and avoid their danger.

Author’s Note: When you first begin a new job in an automotive shop, you will have many concerns on your first day. Pay particular attention to the location of all exits from the building, fire extinguishers, eye wash stations, the emergency shower, and where the MSDS data book is located in case of emergency. An emergency situation is not the time to try to locate safety equipment or exits.

Breathing Toxic Gases Literally the word toxic means “poisonous,” so “toxicity” is the condition of being “poisonous.” In refrigeration terms, “toxic” is more frequently used with gases that we may breathe and that poison us by being taken into our blood by means of the lungs. Refrigerants vary a great deal in their degrees of toxicity. Some refrigerants, such as ammonia (NH 3 ), are so highly toxic that it is dangerous, as well as unpleasant, to breathe air that has only a few parts per million of these gases. Others, such as R-12, may be breathed in large percentages with air without noticeably harmful effects. It must be remembered, however, that the gas we as humans are suited to breathe is air, which is approximately 21 percent oxygen, 78 percent nitrogen, and 1 percent other inert gases. Any other gas, especially in large concentrations, may be harmful or fatal. Harmful effects depend upon: ■■ The nature of the gas itself, ■■ Its concentration in air, and ■■ How long a time it is breathed.

Decomposition of Gases Halogen refers to any of the five chemical elements that may be found in some refrigerants: astatine (At), bromine (Br), chlorine (Cl), fluorine (F), and iodine (I).

Some gases that may have a high safety rating or moderate safety ratings in their natural state become highly toxic if they are exposed to flames or hot surfaces. The heat “decomposes” these relatively safe gases and causes them to form other gases that are very toxic. The refrigerants thus decomposed are those that contain one or more of the halogens, a group of elements that includes chlorine (Cl), fluorine (F), bromine (Br), and iodine (I). Any of the refrigerants that have the symbols “Cl” or “F” in their chemical structure may be subject to hazardous decomposition. Refrigerants should not be allowed to come into contact with an open flame or a very hot metal. Until recently, it was believed that fluorocarbon refrigerants, such as R-12, produce phosgene gas when exposed to hot metal or an open flame. The original tests, made by UL shortly after the development of R-12, indicated that it produced this highly toxic gas during decomposition. Recent tests, however, have shown that phosgene gas is not produced in this manner.

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According to a technical specialist for SUVA® Refrigerants at DuPont Chemicals, which was one of the major manufacturers of R-12, commonly known as Freon®, the only products of decomposition of R-12 when in contact with an open flame or glowing metal surface, are hydrofluoric and hydrochloric acids. Though as much as 50 times less toxic than phosgene gas, the decomposed gases of R-12 must be avoided. At high concentrations, lack of oxygen, which results in asphyxiation, is the real hazard. Avoid breathing these or any other fumes. The human body requires oxygen in the quantity found in noncontaminated air. Diluting air with any foreign gas can reduce the available oxygen to a level that may be harmful or, in some cases, fatal. These gases of decomposition may not noticeably affect the person breathing them for several hours, so you should vacate the area contaminated by them as soon as you detect them by smell. Also, beware of the gases from burning plastics; one of these is the extremely dangerous phosgene (COC12 ). Precautions.  If the nature of the various refrigerants and other gases and fumes are understood and if reasonable care is exercised, a refrigeration service technician need have no fear of possible toxic hazards from refrigerants. ■■ One must use care, however, and in particular observe the following: ■■ Do not breathe any gas any more than is absolutely necessary. None of them is harmless under all conditions. ■■ Do not ignore the possible danger of a gas just because it has very little odor. The odor of a gas is no indication of its toxicity. Do not discharge any gas into any unventilated area. ■■ Do not discharge any of the hydrocarbon gases into a room in which there is a fire, flame, or electric heating element. ■■ Do not hesitate to use a gas mask if it is necessary to enter a room that you know or suspect has any of the toxic gases in it. ■■ Do not leave leaks in refrigerating equipment that may fill the room with gas and pose a danger to someone. ■■ Do not run an automobile engine in a closed garage; do not sit in a closed car with the engine running. ■■ Do not allow liquids to boil over on a gas stove; they may put out the flame, but the gas continues to escape. ■■ Do not use questionable tubing, flexible hose, or connectors. ■■ Do not work in an unventilated room with a heater having an open flame. ■■ Do not vent refrigerant. The EPA requires that all refrigerant be recovered. ■■ Do not breathe fumes from acids, caustics, carbontetrachloride (CC14 ), benzol, ketone, xylene, or other toxic cleaning materials. Always keep rooms well ventilated when using cleaning solvents. ■■ Do not breathe fumes from broken fluorescent lamps; they are poisonous.

The Industry Automobile air conditioning, once considered a luxury, has become a necessity. Millions enjoy the benefits it produces. Business people are able to drive to appointments in comfort and arrive fresh and alert. People with allergies are able to travel without the fear of coming into contact with excessive dust and airborne pollen and pollution. Because of the extensive use of the automobile, automobile air conditioning is playing an important role in promoting the comfort, health, and safety of travelers throughout the world. It is easy to understand how automotive air conditioning has become the industry’s most sought-after product. In the South and Southwest, many specialty auto repair shops base their entire trade on selling, installing, and servicing automotive air conditioners throughout the year.

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FIGURE 1-22  A typical ASE certificate.

ASE Certification The National Institute for Automotive Service Excellence (ASE) has established a certification program for the automotive heating and air conditioning technician (Figure 1-22). This is one of the eight automotive certification areas that lead to certification as a Master Auto Technician (Figure 1-23). ASE also offers other certification programs in other areas, such as heavy-duty truck, collision repair, school bus, engine machine shop technician, parts specialist, alternate fuels, and advanced engine performance.

FIGURE 1-23  A certified Master Auto Technician.

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ASE’s voluntary certification system combines on-the-job experience and tests to confirm that technicians have the necessary skills to work on today’s vehicles. The ASE Master Auto Technician status certification is awarded when a technician passes all eight tests that address diagnostic and repair problems in the following areas: 1. Engine repair 2. Automatic transmission/transaxle 3. Manual transmissions and drive axles 4. Suspension and steering 5. Brakes 6. Electrical/electronic systems 7. Heating and air conditioning 8. Engine performance (driveability) After passing at least one ASE-administered exam and providing proof of two years of hands-on work experience, the technician becomes ASE certified in that particular area. The ASE certification is valid for five years. Retesting is necessary every five years to renew certification.

Work Experience Credit

The technician may be given credit for one of the two years of work experience by substituting relevant formal training in one, or a combination, of the following: ■■ Secondary training: 3 years of high school training in automotive repair may be substituted for 1 year of work experience. ■■ Postsecondary training: 2 full years of training after high school in a public or private trade school, vocational-technical institute, community college, or 4-year college may be counted as 1 year of work experience. ■■ An apprenticeship program: The completion of a state-approved apprenticeship program may be counted as 1 year of work experience. Full credit for the experience requirement is given for satisfactorily completing a 3- or 4-year apprenticeship program. Specialty and short courses: For shorter periods of postsecondary training, one may substitute 1 month of work experience for every 2 months of training.

Test Content

The current heating and air conditioning test consists of 50 multiple-choice questions as follows: Content Area

Questions

Percent of Test

A/C system diagnosis and repair

17

34

Refrigeration system components diagnosis and repair

10

20

4

8

19

38

50

100%

  Compressor and clutch (5)   Evaporator, condenser, and related components (5) Heating and engine cooling systems diagnosis and repair Operating systems and related controls diagnosis and repair   Electrical (10)   Vacuum/mechanical (2)   Automatic and semiautomatic heating, ventilating, and    A/C systems (7) Total

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Additional Questions

The test could contain up to ten additional questions for statistical research purposes that will not affect your score. The 5-year recertification test covers the same content areas as those listed above; however, the number of questions in each content area will be reduced by about 50 percent.

The Questions

The questions are written by a panel of technical service experts, including domestic and import vehicle manufacturers, repair and test equipment and parts manufacturers, working automotive technicians, and automotive instructors. All questions are pretested by a national sample of technicians before they are included in the actual test. Many test questions force the student to choose between two distinct repair methods. Questions similar to the Technician A, Technician B format are included in the review questions at the end of each chapter in this text as well as in the Shop Manual.

Why Certify with ASE?

In a word, “recognition.” Being an ASE-certified technician provides credentials that attest to your professional abilities to your peers as well as to your prospective employer. As a matter of practice, although ASE certification is voluntary, many employers ask for certified applicants when advertising for employment, or they state “ASE certification preferred.” In no small part, certification demonstrates to the employer one’s ability to read—an important requirement for technicians of the future.

EPA Certification To purchase refrigerant or service air conditioning and refrigeration (ACR) systems, one must be certified under section 608 or 609 of the CAA through an agency approved by the EPA. A “609-certified technician” is someone certified by an EPA-approved agency for servicing MVAC and MVAC-like air-conditioning systems. The exam for this certification is open book and is generally available by mail from professional organizations, such as Mobile Air Conditioning Society (MACS), ASE, and others. Testing may also be available in an instructor-led classroom setting. Under the CAA, a 609-certified technician is not permitted to service domestic or commercial air conditioning or refrigeration equipment, even though the equipment may be similar to an automotive air-conditioning system. A small domestic air conditioner, for example, contains far less refrigerant than the average MVAC; however, a 609-certified technician cannot legally service it. This service requires a 608-certified technician. A 608-certified technician is someone certified by an EPA-approved agency for servicing particular types of ACR systems. The exam for this certification, with exception, is closed book and is proctored at an approved test site. There are actually four classes of certification, as follows: 1. Type I: One who services high-pressure ACR systems with a capacity of up to 5 pounds of refrigerant. 2. Type II: One who services high-pressure ACR systems with a capacity over 5 pounds of refrigerant. 3. Type III: One who services low-pressure systems, such as centrifugal systems, with up to hundreds of tons of refrigerating capacity. 4. UNIVERSAL: One who is certified in all three types. The exception to the above is that one may be certified for “small appliances” by taking an open-book exam that is generally administered by mail. This certification, equivalent to Type I, is much more convenient. It is available from trade organizations listed in the Appendix. 30 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

For simplicity, some automotive technicians are certified under both sections 608 and 609. For example, one may purchase refrigerant and other supplies at either an automotive parts or refrigeration supply store. When purchasing HFC-134a, for example, the automotive supplier only has cylinders with the “unique” fitting required by EPA. The refrigeration supply store, on the other hand, can supply the cylinder with either fitting: ½-in. Acme for automotive use or ¼-in. SAE for commercial use. Depending on geographical location, refrigerants may often be less expensive if purchased at a refrigeration supply store. Generally, refrigerant is a “price leader” to a refrigeration supply store as engine oil is to an automotive parts store.

Cost of Operation Because the air-conditioning system places an extra load on the engine, it seems apparent that the use of an air conditioner will reduce gasoline mileage. This is only true for stop-and-go driving. At highway speeds, air conditioned cars, with their windows closed and the air conditioning operating, actually average 2–3 percent better mileage than do cars without air conditioning that have their windows down. The aerodynamic design considerations of today’s cars are based upon having the windows closed. When the windows are closed, reduced wind resistance offsets the demand load of the air-conditioning system on the engine.

Price leader is an item that a merchant may sell at cost or near cost to attract customers.

The modern automobile is designed so it will offer less wind resistance with the windows closed.

Terms to Know

SUMMARY ■■ ■■

■■

■■ ■■ ■■

■■ ■■ ■■ ■■ ■■ ■■

■■ ■■

Refrigeration is the term given to a process by which heat is removed. Although the principles were known as long ago as 10,000 b.c., air conditioning and refrigeration were developments of the twentieth century. Automotive air conditioning has played a significant and important role in the comfort, health, and safety of the modern motorist. The ozone layer protects all life on earth from excess UV radiation. Ozone depletion seems to be the greatest during the early winter months. The mandatory phaseout in the manufacture and the eventual reduction of use of CFCs has had a positive effect on the ozone layer. Increased UV radiation affects the eyes, skin, and the immune system. The greenhouse effect is also affected by the release of pollutants. Solar radiation passes through the clear atmosphere. Most of the radiation is absorbed by the earth’s surface to warm it. Some of the solar radiation is reflected by the earth and the atmosphere. Some of the infrared radiation that passed through the atmosphere is absorbed and readmitted in all directions by greenhouse gas molecules. The effect of this is to warm the lower atmosphere. All areas of safety should be practiced at all times. Antifreeze is either ethylene glycol or propylene glycol based.

Air conditioning Allotropes Atmosphere CFCs Chlorine (Cl) Clean Air Act (CAA) Dobson Unit (DU) Global warming Greenhouse effect Halogen Hydrofluorocarbons (HFCs) Hydrostatic pressure Infrared Nitrogen (N) Oxygen (O) Ozone depletion Ozone (O3 ) Price leader Refrigeration Toxicity Ultraviolet (UV) radiation

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REVIEW QUESTIONS Short-Answer Essays 1. How did the early Egyptians cool water? 2. How was humidity controlled in the Northcotts’ home? 3. Define the term air conditioning. 4. What is the greenhouse effect? 5. Describe the location and conditions of the troposphere. 6. What does the term ozone hole refer to? 7. Compare the ozone layer to an umbrella. 8. What is the intent of Title VI of the Clean Air Act? 9. Briefly describe the term hydrostatic pressure. 10. What are some of the factors that contribute to the greenhouse effect and global warming?

Fill in the Blanks 1. Most of the earth’s protective ozone is found in the _______________. 2. The air we breathe is made up of 21 percent _______________. 3. Increased UV radiation is damaging to the eyes, skin, and _______________. 4. The common name or number used for the ­hydrofluorocarbon (HFC) refrigerant used in automotive refrigerant systems today is _______________. 5. The element for the chemical symbol O 3 is _______________. 6. The Clean Air Act was signed into law by __________. 7. The fluid in an air-conditioning system is called _______________. 8. Factory cylinders are equipped with _______________ plugs. 9. Over _______________ percent of all cars produced today are equipped with an air-conditioning system. 10. In the late 1920s and early 1930s, an “air ­conditioning” option meant that the car was equipped with a (n) _______________ and _______________ system.

Multiple Choice 1. What is the air we breathe made up of? A. 21 percent nitrogen and 78 percent oxygen B. 12 percent oxygen and 88 percent oxygen

C. 98 percent oxygen and 2 percent nitrogen D. 21 percent oxygen and 78 percent nitrogen 2. What is the main source of ozone-depleting chlorine in the stratosphere? A. Chlorine used in swimming pools B. Chlorine used in laundry detergent C. Chlorine contained in chlorofluorocarbons D. All of the above 3. Air conditioning is the process by which air is: A. Heated. C. Cleaned or filtered. B. Cooled. D. All of the above. 4. In what year did the first production vehicle automotive air conditioning unit appear on the market? A. 1907 C. 1940 B. 1925 D. 1962 5. We are concerned about ozone depletion in what layer of the atmosphere? A. Ionosphere C. Troposphere B. Stratosphere D. Ozonosphere 6. Because sunlight is essential for the formation of stratospheric ozone, it is formed mainly over what region of the globe? A. The south pole C. The equator B. The north pole D. The United States 7. What can ultraviolet radiation cause? A. Skin cancer C. Heart disease B. Damage to the eyes D. Both A and B 8. The hole in the ozone layer was detected over what region of the globe? A. The south pole C. The equator B. The north pole D. The United States 9. Technician A says that chlorine (Cl), an ingredient of CFC refrigerants, is harming the ozone layer. Technician B says that the ozone layer is important for pro tection from ultraviolet (UV) radiation. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 10. In the greenhouse effect what type of radiation is re-emitted by the earth’s surface and is absorbed and reflected by greenhouse gas molecules in the atmosphere warming the earth’s surface and lower atmosphere? A. Gama C. Infrared B. Ultraviolet D. Nuclear

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Chapter 2

Temperature and Pressure Fundamentals Upon Completion and Review of this Chapter, you should be able to: Describe the difference between humidity and relative humidity.

Explain the nature of atoms and molecules.

■■

Describe the differences between sensible, latent, and specific heat values.

■■

Discuss the fundamentals of temperature and pressure.

■■

Discuss the measurement of heat energy.

■■

Explain the term specific gravity.

■■

Describe how heat flows.

■■

■■ ■■

■■

Explain effects of radiation, conduction, and convection on personal comfort.

Discuss the fundamentals of Boyle’s Law, Charles’ Law, and Dalton’s Law.

Introduction Before we can enter into a discussion about the automotive heating and air-conditioning system, you must first have a basic understanding of the chemistry and physics involved in order to properly analyze both systems. The concepts and principles covered in this chapter will form the foundation for understanding heat transfer and the three changes in state of matter, which are the operating principles behind the climate control systems used on today’s vehicles. Diagnosing and servicing comfort control systems will become more clear after learning how and why heat transfer takes place. Theories are critical in developing your skills as a technician and, in turn, will increase your productivity and overall worth to the trade.

Elements and Matter Everything in nature is known as matter and is made up of one or more of the 106 known basic elements. Some of the more common and better known of these elements are described here.

Carbon

Carbon (C) is a nonmetallic element found in many inorganic compounds and in all organic compounds. Carbon is present in many chemical compounds and gases such as Refrigerant-12, a chlorofluorocarbon (CFC) refrigerant, and Refrigerant-134a, a hydrofluorocarbon (HFC) refrigerant. At atmospheric pressure and temperatures, carbon normally exists as a solid.

Chlorine

Chlorine (Cl) is a heavy, greenish-yellow gas used for the purification of water ( H 2O ) and the manufacture of CFC and HCFC refrigerants. Chlorine, it has been determined, is causing problems with the ozone layer of the atmosphere.

Matter is anything that occupies space and possesses mass. All things in nature are composed of matter.

Nearly pure carbon (C), in crystalline form, is known as a diamond.

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Aluminum

Aluminum (Al) is a lightweight, ductile metal that does not readily tarnish or corrode. ­Aluminum and aluminum alloys have widespread use in the manufacture of automotive ­components and parts.

Lead Lead (Pb) is currently used in the construction of the lead-acid automotive storage battery.

Lead (Pb) is a heavy, soft, blue-gray metal that was once used extensively as a filler material for soldering. It has now been determined that lead is a health hazard and its use is limited and in many cases prohibited.

Nitrogen

Ordinary air that we breathe is about 78 percent nitrogen (N). Nitrogen normally exists as a gas and is a very important element in plant life. Nitrogen is a compound of all living things.

Oxygen Water (H2O) is formed when hydrogen (H) is burned and it unites with oxygen (O).

Hydrogen (H) is a flammable, odorless, colorless gas and is the lightest of all known substances.

Oxygen (O) makes up 21 percent of the air we breathe. It is absolutely essential to all animal life. Oxygen is a very active element and combines readily with most of the other elements to form oxides or more complex chemicals. Oxygen normally exists as a gas.

Other Gases

The remaining 1 percent of the air we breathe consists of argon (Ar), hydrogen (H), neon (Ne), krypton (Kr), helium (He), xenon (Xe), and other trace nonelement gases, such as carbon dioxide ( CO 2 ) and ozone ( O 3 ). Hydrogen (H), an important element in oil, fuels, acids, and many other compounds, and is odorless, tasteless, and colorless. It is normally a gas and is the lightest of the elements. Hydrogen rarely exists alone in nature; its most commonly known mixture is with oxygen to form water ( H 2O ).

The Atom The atom is the smallest particle of matter.

Each of the elements consists of billions of tiny particles called atoms. An atom is so small that it can only be seen with the most powerful microscope. Scientists, however, can measure it and weigh it, and they have learned a great deal about its nature. An atom is the smallest particle of which an element is composed that still retains the characteristics of that element. For example, an atom of copper (Cu) is copper, and it is different from, say, an atom of aluminum (Al). For our purpose, consider the atom as indivisible and unchangeable. That is, it cannot be divided by ordinary means. Whenever we divide an atom physically and chemically, it retains the characteristics of that element. Atoms of all of the elements are different. Iron (Fe) is composed of iron atoms, lead (Pb) of lead atoms, tin (Sn) of tin atoms, and so on. An atom (Figure 2-1) is composed of still smaller particles called protons, neutrons, and electrons. The proton has a positive (1) charge; the electron has a negative (2) charge; and the neutron has neither a negative (2) nor a positive (1) charge. Scientists have been able to split some kinds of elements, such as uranium (U). For our purpose, however, we will focus on the following facts regarding atoms: ■■ ■■ ■■

The atom is the very smallest possible particle of matter. All of the elements are composed of atoms. The atoms of the different elements are different.

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Electron

2

Proton

1

FIGURE 2-1  A simple hydrogen (H) atom is composed of one proton and one electron.

The Molecule The next larger particle of a material is called a molecule. If the molecule contains only one kind of atom, the molecule will be a molecule of an element. The molecule of most of the elements has only one atom in it. However, a molecule may have several atoms in it, even though they are all the same kind. For example, a molecule of oxygen (Figure 2-2) contains 2 atoms of oxygen, a molecule of iron has but one atom of iron, and so on for all of the elements. Any substance consists of billions of molecules, and each of those molecules consists of one, two, or several atoms of that element.

A molecule is two or more atoms chemically bonded together.

Chemical Compounds A molecule may consist of two or more atoms of different elements. In such an instance, the material becomes entirely different and usually does not resemble either of the elements that constitute it. For example, if the molecule consists of one atom of iron (Fe) and one atom of oxygen (O), it becomes iron oxide (FeO), which is quite different from either iron (Fe) or oxygen (O). How different the compound material itself can be from the elements of which it is composed is illustrated by water ( H 2O ). The molecule of water, in any form, consists of two atoms of the element hydrogen (H), which is a very light, highly flammable gas, and one atom of the element oxygen (O), which is also a gas that aids combustion. The combination of these two elements, each a gas in its natural state, produces a liquid, water, which is unlike either hydrogen or oxygen.

When hydrogen (H), a flammable gas, and oxygen (O), required for combustion, are combined, water (H2O) is produced, which is not flammable.

2

2

2

2 111 1 1 111 2

2

2

2 FIGURE 2-2  An oxygen molecule O 2 has two atoms of oxygen (O).

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Cl

F

C

F

Cl

F FIGURE 2-3  Composition of Refrigerant-12.

F

F

C

C

F

H

H

FIGURE 2-4  Composition of Refrigerant-134a.

The molecule is often quite complex and may have several kinds of elements in it. ­Refrigerant-12 (CFC-12), which is normally a colorless gas, is a good example of this. The CFC-12 molecule consists of one atom of carbon (C), normally a black solid; two atoms of chlorine (Cl), normally a yellow-green gas; and two atoms of fluorine (F), normally a paleyellow gas. The chemical symbol for CFC-12 is CCl 2F2 (Figure 2-3). HFC-134a, an ozonefriendly refrigerant developed to replace CFC-12, consists of two carbon (C) atoms, four fluorine (F) atoms, and two hydrogen (H) atoms. The chemical symbol for HFC-134a is CF3CH 2F (Figure 2-4).

Motion of the Molecules

Because mechanical refrigeration is a physical rather than a chemical process, we deal with molecules and their movement. Rarely do we have a need to go into chemical processes that involve breaking down the molecules. It is nonetheless necessary to have an elementary understanding of the composition of matter to more easily understand how gases, liquids, and solids behave under various conditions. If the matter is a solid, such as copper (Cu) or ice ( H 2O ), the molecules are held together by their mutual attraction to each other. The mutual attraction of like molecules is called cohesion. The molecules are not tightly bound together, and they are not motionless (Figure 2-5). There are spaces between them, and although their motion is limited, they move somewhat. 328F (08C) and below

328F (08C) to 2128F (1008C)

2128F (1008C) and above

Molecules vibrate

Molecules move freely

Rapid movement

(Solid) ice

(Liquid) water

(Gas) steam

FIGURE 2-5  Freedom of water (H2O ) molecules in states of matter.

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The colder the solid, the less motion of the molecules. If the matter had absolutely no heat, if it were at a temperature of absolute zero (2459.678F ), there would be no motion of the molecules. If the absolute cold matter were heated, the molecules would begin to move. The motion of the molecules becomes greater the warmer the matter becomes.

Absolute zero is the complete absence of heat, believed to be 24598F (2273.158C).

Heat and Cold An appropriate definition of heat is the sensation of warmth or hotness. The definition of cold, then, is feeling no warmth—uncomfortably chilled. If you sense a temperature above the normal body temperature of 98.68F ( 378C ), you tend to feel warm; if the temperature is below normal body temperature, you feel cool. To understand what heat and cold are, you must first understand the law of heat.

Heat is any temperature above absolute zero.

The Law of Heat

Heat is ever-present in all matter. There are three basic terms used to describe the three types of heat: sensible, latent, and specific. Sensible Heat.  Sensible heat is any heat that we can feel and that can be measured with a thermometer. For example, water boils at 2128F (1008C ) at sea-level atmospheric pressure. The temperature of water from a spigot may be 588F (14.48C ). From the spigot temperature to the boiling point, the increase in temperature is 1548F ( 85.68C ). That increase in temperature is known as sensible heat. Latent Heat.  Latent heat cannot be measured with a thermometer. To explain, we know that a pan of boiling water does not all turn to steam (gas) as soon as it reaches its boiling point. If the pan is left on the burner and allowed to boil long enough, however, all of the water will boil away. The heat that is added to the boiling water to cause all of it to vaporize is called latent heat. Though it cannot be measured with a thermometer, latent heat is required to cause a change of state in matter. We cannot heat water at atmospheric pressure (sea level) hotter than 2128F (1008C ). The steam form of this water as it boils is also at 2128F (1008C ). We will discuss later the fact that water in a sealed container, such as an automobile radiator, may not boil until the temperature is further increased if the system is pressurized. Also, if the pressure is reduced or at a vacuum, water may boil at temperatures much below 2128F (1008C ). In fact, we will demonstrate how, under certain conditions, water will boil at 328F ( 08C )—its normal freezing point (Figure 2-6). As indicated earlier, latent heat must be added to the water to cause it to change to a gas. Because we cannot measure latent heat on a thermometer, we use as a unit of measure the British thermal unit (Btu). One Btu will cause a change of temperature of one degree Fahrenheit (18F) in one pint (1 lb., or 16 oz.) of water ( H 2O ). Metrically, one calorie (1 cal) will cause a change of temperature of one degree Celsius (18C) in one gram (1 g) of water ( H 2O ). One pound (0.4536 kg) of ice taken from the refrigerator at 328F (08C) requires 144 Btu of latent heat to cause a change in state to liquid at 328F (08C). An additional 180 Btu of sensible heat will bring the liquid to its boiling point of 2128F (1008C), and another 970 Btu of latent heat are required for a change in state to a gas, again at 2128F (1008C). Specific Heat.  Everything in nature has a specific heat. We are not to be particularly concerned with this term. It is important, at this time, to know that refrigerant used in automobile air-conditioning systems has an appropriate specific heat value for its application. It is interesting to note that water also has an appropriate specific heat value for its application as an engine coolant.

Sensible heat causes a change in the temperature of a substance but does not change the state of the substance.

Latent heat is the amount of heat required to cause a change of state of a substance without changing its temperature.

British thermal unit (Btu) is a measure of heat energy; one Btu is the amount of heat necessary to raise one pound of water 18F. Specific heat is the quantity of heat required to change one pound of a substance by 18F.

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Temperature 8F 8C 212

Vapor

100

Liquid

32

0 Solid

0

–18 BTUs

144

180

970

FIGURE 2-6  Sensible and latent heat values required to effect a temperature or physical change in 1 lb. (0.4536 kg) of water (H2O ) from the freezing to boiling temperature at sea level atmospheric pressure.

Sensible Heat of a Solid Energy is required to cause movement or to do work. The molecules must be given heat, a form of energy, in order to give motion. The more heat energy present, the greater the motion and the faster they move. The heat added to raise the temperature of the solid matter and give the molecules more movement is called sensible heat, for we can tell that heat has been added by one of our senses, the sense of feeling, which tells us that the solid is warmer than before. If we continue to add heat energy to the solid, it becomes warmer and the molecules move faster, but still within a very limited space, because they are still held to one another by their mutual attraction. Author’s Note: Air-conditioning systems are based on the laws of physics, and it is essential that technicians understand the principles of latent and sensible heat if they are to properly diagnose system function later in this text.

Melting or Fusion

Latent means hidden.

Finally, when sufficient heat is added to the molecules, they receive enough energy to partially overcome their attraction to each other. At that time, the molecules can move about freely and change state to become a liquid. The process of the molecules breaking away from each other and changing state from a solid to a liquid is called melting or fusion. The attraction of the molecules of a solid to one another is great; therefore, a considerable amount of heat energy is required for a solid to become a liquid. The heat energy required to melt a solid is relatively more than the amount required to warm it by raising its temperature a few degrees. The heat required to effect a change of state of matter from a solid to a liquid is called the latent heat of melting or, more correctly, the latent heat of fusion. The word latent means

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328F (08C)

One lb (0.453 6 kg) Water

328F (08C)

Latent heat of fusion

One lb (0.453 6 kg) Ice

FIGURE 2-7  The temperature of liquid and solid water

(H2O ) has not changed.

hidden. It is a term that is used to identify something that is present but not visible. The heat that causes a change of state cannot be measured on a thermometer; in this sense, it is hidden heat. Latent heat, then, is heat required to cause a change of state of matter without changing its temperature. The temperature of the solid immediately before it melts and immediately afterward when it has become a liquid are exactly the same. For example, if the matter (Figure 2-7) were water, its temperature as a solid (ice) and as a liquid would be 328F. The molecules, now moving more freely, are not held together. The matter can no longer stand rigidly by itself and must have a container to support it. The speed of the molecules is much greater as a liquid, yet not great enough to overcome the force of gravity. The molecules are therefore held downward in the container. The liquid, however, can be poured from a higher container to a lower one, or pumped from a lower container to a higher container. Matter in the liquid state has more heat in it than when it is in the solid state; and, except at the exact melting temperature, it will always be warmer. Because the liquid molecules are much freer in a liquid than in a solid, they are farther apart and require more room to move. Assuming that the same matter and the same weight, the volume of a liquid, then, is greater than the volume of a solid.

Sensible Heat of a Liquid Because the molecules of a liquid have considerable heat energy, they move about in a lively manner and at a rapid speed. They constantly bump into each other and into the side of their container. As heat energy is added to a liquid and it becomes warmer, the speed of its molecules increases. The heat energy that is added to it is called sensible heat.

Sensible heat is heat that is added to matter to cause it to become warmer.

Evaporation Not all of the molecules in the liquid move at the same speed. In fact, some of the molecules at the top of the liquid may attain enough speed to fly out of the liquid and into the space of air above the liquid and escape. Some of them escape from the liquid temporarily but do not have enough speed or energy to entirely escape and eventually fall back into the liquid. Some molecules, however, do escape to mix with the air or other gas above the liquid. Some of the molecules, then, are constantly escaping. They form a gas or vapor blanket above the liquid and tend to diffuse into and mix with the air. The process of the molecules escaping from the surface of the liquid is called evaporation. A good example of evaporation of a liquid is water ( H 2O ) in an open container (­ Figure 2-8). When water is placed over heat and its temperature exceeds 2128F (1008C ), it slowly evaporates into a gas (water vapor). Eventually all of the water evaporates. The warmer the water, the faster it evaporates. The more heat energy added, the more molecules gain sufficient velocity to escape from the liquid.

Evaporation is the process of forming a vapor.

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Water vapor 2128F (1008C) 2128F (1008C) Sensing element

Water

Heat FIGURE 2-8  Evaporation of liquid water (H2O ) by boiling.

Boiling or Vaporization

If more heat is added to the liquid above the boiling temperature, it becomes warmer and warmer and the molecules move faster and faster. When enough heat energy has been added, the molecules are moving so rapidly that they lose all restraint and fly out of the liquid, much the same as in evaporation, but in far greater numbers. At this very high temperature, the liquid disintegrates and breaks loose even from the force of gravity. The molecules fly in all directions. This condition is referred to as a gas or a vapor. As a vapor, the matter requires a great deal more space than when it was a liquid or a solid. The molecules are flying about and are, therefore, widely separated. The volume of the vapor, then, is much greater than when the matter was a liquid. The process of changing from a liquid to a vapor is called boiling or vaporization. The temperature at which this occurs is called the boiling temperature. A great amount of heat energy is required to boil a liquid and give the molecules enough energy to escape and form a vapor. This is referred to as the latent heat of boiling or, more correctly, the latent heat of vaporization. Note that this heat too is referred to as latent heat. It is heat that is required for a change of state without a change of temperature. If the liquid is water ( H 2O ) in an open container, the molecules that escape into the air form what is known as water vapor. Another term for water vapor is “moisture in the air.” A liquid can and does have its own vapor that forms just above its surface. It also diffuses or spreads through the space above the surface of the liquid.

Sensible Heat of a Vapor Sensible heat can be measured with a thermometer.

Matter in any state can be warmed; a vapor or gas can be warmed just as a solid or liquid can be warmed. If heat energy is added, the speed—or velocity—of the molecules increases and the matter is said to be warmer. The heat that is added to a vapor and causes it to become warmer is called the sensible heat of the vapor. It is also called superheat. Superheat is the temperature a substance is heated above its vapor saturation point for a given pressure so that a drop in temperature does not cause a reconversion to a liquid state. It is the added heat intensity given to a gas after the complete evaporation of a liquid. In Chapter 4 there are pressure/temperature charts for both R-134a and R-12 refrigerants. In a refrigerant system, if all the liquid refrigerant in the evaporator core at a given point has gone through a change of state from a liquid to a gas as it picked up heat, and these molecules still have 25 percent of

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the evaporator core left to travel through, this gas will pick up more heat from the heat load on the evaporator core as it removes heat from the air stream passing over it and even though it is at the same pressure it will become hotter than the pressure/temperature chart indicates it should be. This increase in heat above the normal pressure/temperature relationship is called superheat. This phenomenon only occurs when there are no liquid molecules nearby. Most refrigerant systems are designed to maintain 108F (2128C ) of superheat in the refrigerant leaving the evaporator so that the gas returning to the compressor is several degrees away from the condensation point of the refrigerant. This is to avoid the risk of liquid refrigerant entering the compressor. The compressor is designed to be a vapor pump and would be damaged if it had to compress liquid refrigerant.

Measuring the Amount of Heat Energy

To understand and apply these principles, we must measure temperature changes and the amounts of heat. If we cannot, for example, measure a material, an action, a process, or an energy, we really cannot properly understand it. Heat is one of the three forms of energy. Energy does work by causing things to happen. Energy is not a solid, liquid, or gas; and it cannot be measured in traditional terms, such as inches, feet, quarts, or cubic feet. Energy must be measured by what it does and by the effects it produces. Adding heat to water raises its temperature. We measure this heat by how much it raises the temperature of the water. For example, 1 lb. (0.45 kg) of water ( H 2O ), approximately 1 pt. (0.47 L), is at about 638F (15.68C ). It takes a certain amount of heat (Figure 2-9) to raise its temperature 18F, from 638F to 648F (15.68C to 17.88C). Most countries are on the metric system. The calorie is the heat unit in the metric system. The calorie is now used in the United States only in some scientific laboratories. The calorie is the amount of heat required to raise 1 g (0.035 oz.) of water ( H 2O ) 1.08C . The Btu is the standard measure of the amount of heat, and the degree of temperature is the standard measure of the effect of that heat on 1 lb. (0.45 kg) of water ( H 2O ). The amount of water must be known. Obviously, it will take two times as much heat (2 Btu) to warm 2 lb. (0.91 kg) of water ( H 2O ) 18F ( 0.568C ) as it would to warm 1 lb. (0.45 kg). It would also take twice as much heat (2 Btu) to warm 1 lb. (0.45 kg) of water ( H 2O ) 28F (1.18C ) as it would to warm 1 lb. (0.45 kg) of water ( H 2O ) 18F ( 0.568C ).

638F (17.28C)

The term thermal defines heat.

648F (17.78C)

1 BTU H2O

H2O FIGURE 2-9  One Btu raises 1 lb (O.45 kg) of water (H2O ) 18F (0.568C).

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To warm 10 lb. (4.54 kg) of water ( H 2O ) 108F ( 5.568C ) would require 100 Btu of added heat. 10 3 10 5 100 The amount of heat required in Btu to warm any amount of water through any known temperature change is found by multiplying the number of pounds of water by the number of degrees Fahrenheit the temperature is to be raised. The answer is the number of Btu of heat that must be added. Do not forget that the heat energy added to the water results in an increase in the active movement of the molecules to give them more rapidity of motion. This increased rapidity of motion produces the effect of a rise in temperature.

Specific Heat Materials vary in the amount of heat required to raise their temperature (Figure 2-10). Compared to most other materials—whether solid, liquid, or gas—water requires a great deal of heat energy to raise its temperature. Oil requires only about one-half as much heat energy as water, so it takes only ½ (0.5) Btu to warm 1 lb. (0.45 kg) of oil 18F ( 0.568C ). Mercury (Hg) requires only about 1 30 (0.034) Btu; alcohol about 3 5 (0.6) Btu; and so on. Gases vary greatly in the amount of heat required to warm them, depending on their original temperature and their pressure. At atmospheric pressure and room temperature: ■■ ■■ ■■ ■■

Air: oxygen, nitrogen, and carbon dioxide require 1 5 to ¼ Btu per pound per degree; Sulphur dioxide requires about 1 6 Btu per pound per degree; Ammonia requires about ½ Btu per pound per degree; and Refrigerant-12 or Refrigerant 134a requires about 1 7 Btu per pound per degree.

The amount of heat required to raise 1 lb. (0.45 kg) of matter 18F is called its specific heat. For water, the specific heat is 1.0. It takes 1 Btu to raise 1 lb. (0.45 kg) of water ( H 2O ) 18F, as demonstrated earlier. The specific heat of oil is ½ (0.5) Btu. Tables of specific heats are usually given in decimals, as ice (at 208F) 0.48, water vapor 0.46, iron 0.13 to 0.17, and so on. To calculate the amount of heat required to raise matter from one temperature to a higher temperature, first figure out the number of Btu just as if the material were water ( H 2O ), by multiplying the number of pounds (kg) of the matter by the number of degrees F (C) that it is to be warmed. Next, multiply this amount by the specific heat of that particular matter.

Air.................................................0.240

Nitrogen . . . . . . . . . . . . . . . . . . . .0.240

Alcohol ........................................0.600

Oxygen . . . . . . . . . . . . . . . . . . . . 0.220

Aluminum ....................................0.230

Rubber . . . . . . . . . . . . . . . . . . . . .0.481

Brass............................................0.086

Silver . . . . . . . . . . . . . . . . . . . . . .0.055

Carbon dioxide.............................0.200

Steel . . . . . . . . . . . . . . . . . . . . . . 0.118

Carbon tetrachloride ...................0.200

Tin . . . . . . . . . . . . . . . . . . . . . . . .0.045

Gasoline.......................................0.700

Water, fresh . . . . . . . . . . . . . . . . . 1.000

Lead ............................................0.031

Water, sea . . . . . . . . . . . . . . . . . . 0.940

FIGURE 2-10  Specific heat values of selected solids, liquids, and gases.

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Example

How many Btu are required to raise the temperature of 20 pounds of ice from 208F to 328F? If the ice were water, it would require 20 3 12 3 1 5 240 Btu The specific heat of ice, however, is 0.48, so 20 3 12 3 0.48 5 115.2 Btu

Latent Heat of Fusion To change 1 lb. (0.45 kg) of ice at 328F to water at 328F requires that the value of the latent heat of fusion of ice be added—144 Btu per pound (0.45 kg): 144 3 20 5 2,880 Btu Accordingly, 2,880 Btu are required to melt 20 lb. (9.1 kg) of ice. To warm the 20 lb. (9.1 kg) of water to 508F (an additional 188F), we would have to supply another 20 × 18 or 360 Btu. If, however, we want to heat the water from 328F to the boiling point of 2128F (through 1808F) instead of just to 508F, we will have to add 3,600 Btu (20 3 18 5 3,600 Btu). The latent heat of fusion also varies with the matter. For some other solids, the latent heats of fusion are: Aluminum (Al) 167.5 Btu per pound Copper (Cu) 78.0 Btu per pound Silver (Ag) 43.9 Btu per pound Gold (Au) 28.7 Btu per pound Tin (Sn) 25.4 Btu per pound Lead (Pb) 9.8 Btu per pound

Latent Heat of Vaporization To boil water at 2128F and turn it into steam, also at 2128F, requires latent heat of vaporization. For water in an open pan, the latent heat of vaporization is 970 Btu per lb. (0.45 kg), so 20 lb. (9.1 kg) at 2128F requires 20 × 970 or 19,400 Btu to turn it into steam or water vapor also at 2128F. If we want to superheat this steam to 2508F, to raise its temperature above the 2128F, we must add 20 × 38 × 0.46 (the specific heat of steam) or 349.6 Btu. To warm 20 lb. of ice from 208F to 328F, change it to water, heat the water to 2128F, change it to vapor (steam), and then heat the steam to 2508F will require these steps: ■■ ■■ ■■ ■■ ■■ ■■

To warm 20 lb. of ice from 208F to 328F: 20 3 12 3 0.48 5 115.2 Btu To change the 328F ice to water at 328F: 20 3 144 5 2,880.0 Btu To warm 20 lb. of water from 328F to 328F: 20 3 180 3 1 5 3,600.0 Btu To change the 2128F water to steam at 2128F: 20 3 970 5 9, 400.0 Btu To warm 20 lb. of steam from 2128F to 2508F: 20 3 38 3 0.46 5 349.6 Btu The total required to change 20 lb. of ice at 208F to steam at 2508F 5 26,344.8 Btu

From this example, it may be seen that the latent heats of fusion and of vaporization are very large compared with the sensible heats. Moreover, the latent heats of fusion and ­vaporization of water, to change their states from a solid to a liquid and from a liquid to a vapor, are quite large compared to other matter. Most matter has far less heat capacity than ice, water ( H 2O ), and steam (Figure 2-11). 43 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Degrees 8C 8F 121.1 250

Sensible heat 970 Btu latent heat

93.3 200

5

4

65.5 150

144 Btu latent heat

180 Btu sensible heat

37.8 100 16 Btu sensible heat 10.0 0.0

50 32

–17.8

0 1

0

2

3

16

160 100

200

1310

340 300

400

500

600 700 800 Heat content (Btu)

900 1,000 1,100 1,200 1,300 1,400

FIGURE 2-11  Latent and sensible heat values for water (H2O ).

Heat Flow

Natural heat flow from a warm to a less warm area or surface is called gravity.

Radiation is the transfer of heat without heating the medium through which it is transmitted.

Heat has been defined as the energy of the molecules in motion. Motion is transmitted to other molecules that have less motion. Some of the molecules give up some of their energy to other molecules that have less energy. Another way of saying this is that heat flows from the matter at a higher temperature to a matter at a lower temperature. Heat transfer, therefore, is always downward; from hot to warm, warm to cool, or cool to cold. Heat never flows from low-temperature matter to high-temperature matter. Natural heat flow from a warm to a less warm area or surface is called gravity. One method of studying heat flow is to place a hot object near, or touching, a colder object. Heat will flow from the hot object to the colder object. Actually, heat is neither added nor removed. It is simply transferred from one place where it is not wanted to another place where it is accepted. Heat moves in either or all of three ways. Heat moves by: ■■ Radiation ■■ Conduction ■■ Convection

Radiation If a hot object is placed near or against a cooler object, heat is transferred by radiation ­(Figure 2-12) across the space between the two objects to warm the cooler object. Radiation

FIGURE 2-12  Heat is transferred by radiation.

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There does not have to be any gas or other material in the space. An excellent example of radiation is how we receive heat from the sun. This heat radiates through some 92 million miles of vacuum to heat the earth without heating the space in between.

Conduction If one side of a material is heated, the heat will travel through it from the hot side to the cooler side. In turn, heat may be conducted to another cooler object touching it or radiated to a cooler object some distance away. The transfer of heat through a material is known as conduction (Figure 2-13). The warmer side gives motion to the molecules that, in turn, give motion to nearby molecules, and so through the material. In doing so, some of the heat energy is given up to the molecules and remains as heat energy. All of the heat, therefore, does not pass through the material. A material that transmits heat easily with little loss is called a conductor of heat. Some of the best conductors are also good conductors of electricity. They are copper (Cu), silver (Ag), and aluminum (Al). A material that does not conduct heat through itself easily is called an insulator. Some of the better insulators are cork, cotton, air, and other materials that are composed of thousands of tiny air cells. A good insulator is a poor conductor.

Conduction is the transmission of heat through the direct contact of two objects.

Coolant recovery reservoir Heater core Heater hose (return) Radiator cap

Thermostat Heater hose (inlet)

Upper radiator hose Water pump

Thermostatic engine fan

Lower radiator hose Radiator FIGURE 2-13  Heat is transferred by conduction.

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Convection

FIGURE 2-14  Heat is transferred by convection.

Convection Convection is the transfer of heat by the circulation of a vapor or liquid.

Twenty-five pounds of ice is equal to 150 Btus in today’s terms.

Deep-tissue or subsurface temperature is the core temperature of the body. Water (H2O) weighs 8.3453 pounds (3.79 kilograms) per gallon (3.785 liters). For practical purposes, it is considered that 1 pound (0.4536 kilogram) of water (H2O) is equal to 1 pint (0.473 liter).

Convection occurs only in fluids—liquids and gases or vapors. When a material is warmed, it expands in volume and therefore becomes lighter per cubic foot of volume. In the case of fluids, the cooled fluid is heavier and, as a result, crowds out the lighter, warmer fluid. This pushes the warmer fluid upward, setting up a cycle of circulation. This circulation of the fluid carries heat upward on one side and downward on the other side. This means of conducting heat is called convection (Figure 2-14). It is very important in refrigeration and heating, where a large part of the process is cooling or heating fluids. In many applications, the fluids are cooled as a means of carrying heat away from or to foods, human beings, or other objects.

Personal Comfort and Convenience

The normal body temperature of a human adult is 98.68F ( 378C ). This temperature is ­sometimes called subsurface or deep-tissue temperature, as opposed to surface or skin temperature. An understanding of the process by which the body maintains its t­ emperature is helpful to the student because it explains how air conditioning helps keep the body comfortable.

How the Body Produces Heat

All food and beverage taken into the body contains heat in the form of calories. The calorie is a term used to express the heat value of food. The calorie is the amount of heat required to raise 1 kilogram of water ( H 2O ) 1 degree Celsius (C). There are 252 calories in 1 Btu. As calories are taken into the body, they are converted into energy and stored for future use. The conversion process generates heat. All body movements use up the stored energy and, in doing so, add to the heat generated by the conversion process. The body consistently produces more heat than it requires. Therefore, for body comfort all of the excess heat produced must be given off by the body. The constant removal of body heat takes place through three natural processes ­(Figure 2-15) discussed earlier, which all occur at the same time. These are: ■■ ■■ ■■

Convection Radiation Evaporation

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Convection Radiation Evaporation FIGURE 2-15  The body gives up heat by convection, radiation, and evaporation.

Convection

The convection process of removing heat is based on two natural phenomena: ■■ Heat flows from a hot surface to a surface containing less heat. For example, heat flows from the body to the air surrounding the body when the air temperature is lower than the skin temperature (Figure 2-16). ■■ Heat rises. This is evident by watching the smoke from a burning cigarette or the steam from boiling water.

Gravity causes warm air to rise. Cool air is heavier than warm air, and as warm air rises, cool air falls to take its place.

When these two natural phenomena are applied to the bodily process of removing heat, the following changes occur: ■■ The body gives off heat to the surrounding air (which has a lower temperature). The surrounding air becomes warmer and moves upward. ■■ As the warmer air moves upward, air containing less heat takes its place. The convection cycle is then completed.

Radiation

Radiation is the process that moves heat from a heat source to an object by means of heat rays. This principle is based on the phenomenon that heat moves from a hot surface to a surface containing less heat. Radiation takes place independently of convection. The process

98.6°F

Radiation is the transfer of heat without heating the medium through which it is transmitted.

98.6°F

95°F ambient

A

B

FIGURE 2-16  The body rapidly gives up heat when the surrounding air temperature is below body temperature (A) and slows as the surrounding air temperature increases (B).

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Temperature Relative humidity Air motion FIGURE 2-17  Conditions that affect body comfort.

of radiation does not require air movement to complete the heat transfer. This process is not affected by air temperature, although it is affected by the temperature of the surrounding surfaces. The body quickly experiences the effects of sun radiation when one moves from a shady area to a sunny area. Evaporation is the changing of a liquid to a vapor while picking up heat.

Perspiration is the salty fluid secreted by sweat glands through the pores of the skin.

Evaporation

Evaporation is the process by which moisture becomes a vapor. As moisture vaporizes from a warm surface, it removes heat and thus lowers the temperature of the surface. This process takes place constantly on the surface of the body. Moisture is given off through the pores of the skin. As the moisture evaporates, it removes heat from the body. Perspiration appearing as drops of moisture on the body indicates that the body is producing more heat than is being removed by convection, radiation, and normal evaporation. The three main factors that affect body comfort (Figure 2-17) are: ■■ ■■ ■■

Temperature Relative humidity Air movement

Temperature

The temperature of an object can be described as that which determines the sensation of warmth or coldness when one comes into contact with it. When two objects are placed together, they are said to be in thermal contact. The object with the higher temperature is cooled while the object with the lower temperature is warmed. At some point in time, they will both be the same temperature and no more change will occur. When thermal changes between two objects stop, we say that they are in thermal equilibrium. To our senses, then, both objects would feel the same. When we say that something is cool or warm, we are speaking in relative terms. For example, consider the following experiment. You will need two pans approximately 7 × 7 × 2 in. (18 × 18 × 5 cm), one pan approximately 9 × 12 × 2 in. (23 × 30 × 5 cm), 9 cups (4.26 liters) tap water, 1 cup (0.47 liter) hot water, and a tray of ice cubes.

SetUp 1. Place the pans on a level surface with the large pan in the middle and the smaller pans on both sides. 2. Put 2 cups (0.473 liter) of tap water in each of the small pans. 3. Put 5 cups (1.18 liter) of water in the large pan. 48 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 2-18  Place ice cubes in the left pan.

4. Allow them to reach thermal equilibrium with the ambient room temperature. 5. Put a tray of ice cubes in the pan on the left (Figure 2-18). 6. Add 1 cup (0.24 liter) of hot water to the pan on the right. Water must not be so hot as to cause personal injury.

The Experiment 1. Place both hands in the center pan for 10–15 seconds (Figure 2-19). What do you feel? (You should experience a feeling of neither warmth nor cold because the water in this pan is in thermal equilibrium with the room temperature.) 2. Place the left hand in the pan with the ice cubes. What do you feel? (You should experience a sensation of cold because this water is below room temperature.) 3. Next, place the right hand in the pan with warm water. What do you feel? (You should experience a sensation of warmth because this water is above room temperature. Remember that we are speaking in relative terms—in this case, relative to the ambient temperature.) 4. Remove your left hand from the left pan and place it in the center pan for a few seconds. What do you feel? (The surface temperature of your left hand was lowered, so the water in this pan should now feel warm.) 5. Remove your right hand from the right pan and place it in the center pan for a few ­seconds. What do you feel? (The surface temperature of your right hand was raised, so the water should now feel cool.) Conclusion.  In relative terms, the left-hand felt warm because the temperature of the a­ mbient water was higher than the cold water. The right hand felt cool because the temperature of the ambient water was lower than the warm water.

FIGURE 2-19  Place both hands in pan for 10–15 seconds.

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It should now be obvious that the feeling of cold or warm is relative in relation to the temperature of an object or to the ambient environment. Cool air increases the rate of convection; warm air slows it down. Cool air lowers the temperature of the surrounding surfaces. Therefore, the rate of radiation increases. Because warm air raises the surrounding surface temperature, the radiation rate decreases. In general, cool air increases the rate of evaporation and warm air slows it down. The evaporation rate also depends on the amount of moisture already in the air and the amount of air movement. Relative humidity (RH) is the actual moisture content of the air in relation to the total moisture that the air can hold at a given temperature.

Humid is another term for damp. It is the feeling of dampness when the dew point of the air is close to the actual ambient air temperature, causing water in the air to condense. The closer the dew point temperature of the air is to the actual ambient air temperature, the more humid it feels.

Some older people are not comfortable in the normal “comfort range” and require special considerations.

Arid is another term for dry.

Humidity

The moisture of air is measured in terms of relative humidity (RH). The expression “50 percent relative humidity,” for example, means that the air contains half the amount of moisture that it is capable of holding at a given temperature. A low relative humidity permits heat to be taken away from the body by evaporation. Because low humidity means that the air is relatively dry, it can readily absorb moisture. A high relative humidity has the opposite effect. The evaporation process slows down in humid conditions; thus, the speed at which heat can be removed by evaporation decreases. An ­acceptable comfort range for the human body is 728F to 808F (22.28C to 26.68C) at 45 to 50 percent ­relative humidity (RH). In some areas of the country, the average RH is 50 percent or above most of the time. These areas are said to be “humid” regions, and dehumidification is generally required to provide an environment ideal for human comfort. In other parts of the country, average RH is less than 50 percent. These regions are said to be “dry” or “arid.” Humidification is usually required in arid areas to create an ideal environment. The recommended relative humidity for an occupied area is between 40 and 60 percent for a healthy environment. Recent studies show that bacteria, fungi, and viruses are more active below 40 percent RH and above 60 percent RH. The evaporator, that part of an airconditioning system that removes heat from the air, also removes moisture from the air. Some of this moisture, however, tends to cling to the fins and tubes of the evaporator after the system has been turned off. This creates a very high humidity condition within the evaporator, promoting fungi growth from the airborne impurities that were trapped by the moisture. It is not uncommon to hear a complaint of a “musty mildew odor” coming from the automotive air-conditioning system when it is first turned on. This odor is caused by the mildew-type fungi that were formed in the evaporator case during the off period of the air-conditioning system. To combat this problem, the blower motor of some systems is turned on for a few minutes after the air conditioner has been turned off for a period of time, generally 30 minutes. There is also a device that can be installed on most vehicles which operates the blower motor some time after the air-conditioning system has been turned off. A delay in this process is intended to provide sufficient time for the moisture to run off the tubes and fins of the evaporator and collect in the bottom of the evaporator case. The fan then forces the water out the drain tube and dries off the evaporator coil. Automotive evaporators may be cleaned of fungi following specific service procedures as given in the appropriate manufacturer’s service manual. A typical procedure for correcting this problem may be found in the Shop Manual, Chapter 9.

Air Movement

Another factor that affects the ability of the body to give off heat is the movement of air around the body. As the air movement increases, the following processes occur: ■■ The evaporation process of removing body heat speeds up because moisture in the air near the body is carried away at a faster rate. 50 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

The convection process increases because the layer of warm air surrounding the body is carried away rapidly. ■■ The radiation process increases because the heat on the surrounding surfaces is removed at a faster rate. As a result, heat radiates from the body at a faster rate. As the air movement decreases, the processes of evaporation, convection, and radiation decrease. As the air movement increases, so does evaporation, convection, and radiation, a process known as windchill factor. ■■

Windchill Factor

The windchill factor, developed in 1941, is a measure of relative personal discomfort due to combined cold and wind based on physiological studies of the rate of heat loss for various combinations of ambient temperature and wind speed (Table 2-1). The windchill factor is based on the actual air temperature when the wind speed is 4 mph (6.4 km/h) or less. At higher wind speeds, the windchill temperature is lower than the air temperature and measures the increased cold stress and discomfort associated with wind. The air temperature is not lowered by the windchill factor. Regardless of how strong the wind, the air temperature remains constant. The windchill factor is a measure of how rapidly heat is being removed from a body. If, for example, the air temperature is 408F ( 4.48C ) and the wind speed is 20 mph (32 km/h), it feels the same as 198F (278C ) with no wind blowing. A windchill factor near or below 08F (217.88C ) is an indication that there is a risk of frostbite or other injury to exposed human flesh. Between 108 and 158F (2128 and 2268C ), there is little danger; between 2308 and 2708F (2348 and 2578C), there is danger that human flesh may freeze within 1 minute of exposure. Below 2758F (2598C ), there is great danger that human flesh may freeze within 30 seconds of exposure. The effects of wind chill, however, depend on many factors such as the amount of clothing worn, health, age, gender, and body weight.

Cold

We have discussed heat and adding or removing heat, but what about “cold?” Actually, there is no such thing as “cold.” Remember the definition “feeling no warmth?” All matter, everything in nature or everything manufactured, contains heat. Some things contain more heat than others, but all contain heat to some degree.

TABLE 2-1:  THE EFFECT OF THE WINDCHILL FACTOR Air Temp ( 8F)

Wind Speed (mph) 5

10

15

20

25

30

35

40*

40

37

28

23

19

16

13

12

11

30

27

16

9

4

1

22

24

25

20

16

3

25

210

215

218

220

221

10

6

29

218

224

229

233

235

237

0

25

222

231

239

244

249

252

253

210

215

234

245

253

259

264

267

269

220

226

246

258

267

274

279

282

284

230

238

258

272

281

288

293

297

2100

240

247

271

285

295

2103

2109

2113

2115

*Winds above 40 mph (64 km/h) have little additional effect on windchill factor.

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Absolute cold is the absence of all heat, or 2459.678F.

Cold, then, refers to an object or matter in which some of its heat has been removed; therefore, an object has more or less of its original heat. In an air-conditioning system, we are not really producing cold air. We are simply transferring heat; removing some of the heat from the car’s interior where it is not wanted and transferring it to the outside air. The refrigerant in the air-conditioning system is the medium that is used for the transfer of this heat. The effect is that the car’s interior becomes cool.

Specific Gravity Specific gravity is the ratio of the mass or weight of a given volume of a substance divided by the density of an equal volume of water for solids and liquids. The specific gravity of water is 1.0, which is derived from the density of water divided by itself (62.4 lb/ft / 62.4 lb/ft 5 1). We measure the specific gravity of engine coolant to determine the mixture of ethylene glycol and water contained in the system with a refractometer, which gives an exact freeze point temperature of the mixture. The specific gravity of a lead acid batteries’ electrolyte solution when fully charged is 1.265.

Gas Laws To understand how the refrigerant system functions, it is necessary to understand how gases respond to pressure and temperature changes. Several laws will help you to understand the reaction of the refrigerant gas and the pressure-temperature-volume relationship of refrigerant in various parts of the refrigerant system. In addition, these laws help you understand the effect of gas contamination on refrigerant system operation. When using the gas law equations, pressure must be in the absolute pressure scale (psia) and temperature must be measured (1 Kelvin 5 18 Celsius), where 08C is the freezing point of water, or on the Rankine scale, where 08R is equal to 2459.678F, so water will freeze at 491.678R. If the correct scale is not used, the solution of the equation will be meaningless. The absolute scales use zero as their starting point. Gases exert pressure in all directions and will completely fill any container that holds them. Gas molecules have little attraction to each other and have neither definite shape nor volume.

Boyle’s Law

Boyle’s law was formulated by Robert Boyle (1627–1691) and states that the volume of a gas varies inversely with the absolute pressure at a constant temperature. In other words, as pressure is applied to a volume of gas in a closed container, the volume of gas will decrease and the pressure will increase. An example of this is the piston action of an engine. As the piston travels upward on the compression stroke, the pressure in the cylinder will increase (Figure 2-20). Boyle’s law on its own is not practical, because as the gas is compressed, some of the heat generated during compression is transferred to the gas, and when the gas is expanded, some of the heat is given off. Formula for Boyle’s Law: P1 3 V1 5 P2 3 V2 where P1 V1 P2 V2

5 original absolute pressure 5 original volume 5 new pressure 5 new volume

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14.696 psia

29.392 psia

Cylinder filled at atmospheric pressure

Piston at bottom of stroke

Airtight seals

Piston at ½ upward stroke

FIGURE 2-20  If the volume of a container is reduced by half, then the absolute pressure in the container will double.

As an example, if the original pressure in the container were 25 psia and the volume at the beginning were 25 in, what would the calculated new volume be when the pressure is increased to 50 psia? P 3 V1 V2 5 1 P2 25 3 25 V2 5 50 V2 5 12.5 in 3

Charles’ Law

Charles’ Law is also known as Gay-Lussac’s Law and states that the volume of a fixed mass of gas held at a constant pressure varies directly with a change in the absolute temperature. And conversely, when a gas is held at a constant volume, its pressure varies directly with the absolute temperature. V1 V2 V2 T2 5 or 5 or V1 3 T2 5 V2 3 T1 T1 T2 V1 T1 where V1 V2 T1 T2

5 original volume 5 new volume 5 original temperature 5 new temperature

If 100 ft of air were drawn in and passed over a vehicle heater core and were heated from 408F to 1408F, what would be the volume of the air entering the vehicle passenger ­compartment? (Figure 2-21). V1 5 100 ft V2 5 unknown volume T1 5 408F 1 4608 5 5008R (absolute) T2 5 1408F 1 4608 5 6008R (absolute) V1 3 T2 T1 100 ft 3 3 6008R V2 5 5008R V2 5 120 ft 3 The above formula shows that air expands as it is heated. V2 5

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Fan

Heater core

Passenger compartment air (120 ft3 of 1408F air)

Outside air (100 ft3 of 408F air)

FIGURE 2-21  As air is heated, it will expand.

The next formula demonstrates the relationship between pressure and temperature: P1 P 5 2 2 or PT 1 2 5 P2T1 T1 T2 where P1 P2 T1 T2

5 original pressure 5 new pressure 5 original temperature 5 new temperature

If a container containing 100 ft 3 of air were stored at 758F ( 248C ) and the container was placed in a vehicle trunk that is 1408F ( 608C ), what would the pressure be if the original pressure of the air were 30 psig at 758F ( 248C )? P1 P2 T1 T2

5 30 psig 1 14.696 (absolute pressure) 5 44.696 psia 5 unknown volume 5 758F 1 4608 5 5358R (absolute) 5 1408F 1 4608 5 6008R (absolute) P 3 T2 P2 5 1 T1 44.696 3 6008R P2 5 5 35.43 psi (absolute) 5358R P2 5 35.43 psia 2 14.696 5 20.734 psig

The above formula shows that when a volume of air in a closed container is heated, its pressure will increase.

Dalton’ Law

John Dalton discovered in the early 1800s that the atmosphere is made up of several different gases and that each gas creates its own pressure. The total pressure of a confined mixture in a sealed container is equal to the sum of the pressures of each gas in the mixture. As an example, if oxygen is combined with nitrogen in a container of a given size, the resulting pressure will be greater than if either gas stood alone in that same given size container (Figure 2-22). It is assumed in this law that the volume of the mixture is the same as the volume of each ­individual gas. Author’s Note: As you will see later in this text, if R134a is contaminated with R12, the resulting pressure at a given temperature will be greater than the individual pressure of the individual gas in its pure form.

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Pressure gage (30 psig)

Oxygen

Pressure gage (40 psig)

Nitrogen

Pressure gage (70 psig)

Mixture of oxygen and nitrogen

FIGURE 2-22  The total pressure in a closed container is the sum of the individual pressures of each gas.

SUMMARY ■■

■■

■■

■■ ■■

When the surrounding temperature, known as ambient temperature, is above normal body temperature, one is said to feel warm or hot; when it is below, one is said to feel cool or cold. Everything in nature contains heat. This heat is known as specific heat. Some things retain/conduct heat better than other things. The absence of heat is cold. Latent heat is hidden heat. It is the heat that is required for a change of state of matter and it cannot be measured with a thermometer. Sensible heat can be measured with a thermometer and can be felt (sensed). Heat flows from a warm surface or object to a less warm surface or object.

Terms to Know Absolute zero Arid Atom British thermal unit (Btu) Chlorofluorocarbon (CFC) Conduction Convection Deep-tissue (subsurface) temperature Evaporation Heat Humid Hydrogen (H) Insulator Latent heat Matter Molecule Perspiration Radiation Relative humidity (RH) Sensible heat Specific heat Superheat Temperature

REVIEW QUESTIONS Short-Answer Essays 1. Explain heat transfer by convection.

8. Briefly define latent heat. 9. Describe the transfer of heat by conduction.

2. Briefly define Dalton’s Law.

10. Briefly define sensible heat.

3. Describe the molecular movement of matter based on its temperature.

Fill in the Blanks

5. What is meant by the term subsurface temperature?

1. _______________ Law states that the volume of a fixed mass of gas held at a constant pressure varies directly with a change in absolute temperature.

6. What is the unit of measurement used to measure latent heat?

2. The absence of heat is cold; therefore, ______________ is ever present.

7. What does the term relative humidity mean?

3. Moisture in the air is known as _______________.

4. How does liquid water become water vapor?

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4. Latent heat is required to cause a change of _______________. 5. _______________ Law states that the volume of a gas varies inversely with the absolute pressure at a constant temperature. 6. Moisture becomes vapor by the natural process of _______________. 7. _______________ heat cannot be felt or measured with the use of a thermometer. 8. A unit of heat measure is the _______________ thermal unit. 9. _______________exert pressure in all directions and will completely fill any container that holds them. 10. The metric conversion of pounds (weight) is _______________.

Multiple Choice 1. Technician A says that latent heat is hidden heat and cannot be measured on a thermometer. Technician B says that latent heat is hidden heat that is required for a change of state of matter. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 2. The heat added to a vapor causing it to become warmer is called what? A. Sensible heat C. Latent heat B. Superheat D. Both A and B 3. What is a material called that can block the flow of heat? A. A conductor C. A radiant B. A convectant D. An insulator

4. All of the following are factors that affect body ­comfort except: A. Relative humidity. C. Concentration. B. Air movement. D. Temperature. 5. Heat transfer is being discussed: Technician A says that heat flows from a hot surface to a surface containing less heat. Technician B says that heat leaves the body by the ­process of evaporation. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 6. The acceptable comfort range for the human body is: A. 728 2 808F C. Both A and B D. Neither A nor B B. 45–50 percent relative humidity 7. Everything in nature contains what type of heat? A. Specific heat C. Sensible heat B. Latent heat D. Natural heat 8. What type of heat transfer requires air movement? A. Radiation C. Conduction B. Convection D. Evaporation 9. All of the following are processes by which heat moves, except: A. Radiation C. Conduction B. Latent D. Convection 10. All of the following are gas laws, except: A. Dalton’s Law C. Darwin’s Law B. Boyle’s Law D. Charles’ Law

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Chapter 3

Electricity and Electronic Fundamentals Upon Completion and Review of this Chapter, you should be able to: ■■

Explain the basics of voltage.

■■

■■

Explain the basics of amperage.

■■

■■

Explain the basics of resistance.

■■

Describe how to use Ohm’s law.

■■

Discuss the basic types of electrical circuits.

■■

Explain the use of digital multimeters.

■■

Describe the operation of a diode.

■■

■■

Discuss relay operation. Describe the operation of the HVAC blower motor and stepped resistor assemblies. Explain how the blower motor power transistor module functions in the blower motor circuit. Explain the application and function of an electromagnetic clutch assembly and the role of the clamping diode in the circuit.

Introduction In order to work on and diagnose electrical elements associated with the automotive ­heating and air-conditioning system, you must first have a basic understanding of electricity and electronics in order to properly analyze both control and activation of complex systems. The concepts and principles covered in this chapter will form the foundation for understanding basic electricity and electronics, which are the operating principles behind the climate control systems used on today’s vehicles. Diagnosing and servicing comfort control systems will become clear after learning basic electrical principles and component operation. Theories are critical in developing your skills as a technician and, in turn, will increase your productivity and overall worth to the trade.

Electrical Principles Many heating and air-conditioning components are controlled or powered by electricity. Examples of this are the air-conditioning compressor clutch, the blower motor, and the complex climate control system. Therefore, a basic understanding of some of the electrical principles, including voltage, amperage, and resistance, is required. The following section is meant to be a review or overview of these concepts. It is recommended that a technician receive indepth electrical and electronic training as part of their overall education. Electronics is part of every major system on the automobile and electrical failures have become routine complaints, though not always routine repairs.

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The Basics: Voltage, Amperage, and Resistance

For many, it is often easier to think of electricity in terms of water flowing in your home, hydraulic system principles, as there is a visible cause and effect. The flow of electricity is similar to the flow of water through your household plumbing. Where the water pressure is similar to electrical pressure or voltage, the water flow is similar to current flow in a conductor or amperage, and a restriction such as a kink in a hose is similar to the resistance in an electrical system. But, unlike water, electricity does not flow out the end of the wire and poor onto the ground if left open. Voltage (V) or electromotive force (EMF) is the electrical pressure and is measured in volts (V); it may be either direct current (DC) or alternating current (AC). In the automotive industry, especially on HEV and EV platforms, we deal with both. Current is the flow or rate of flow of electrons under pressure in a conductor between two points having a difference in potential and is measured in amperes (A) or amperage. A complete circuit is required for current to flow. A DC circuit requires a complete circuit or loop between positive (1) and negative (2) for current to flow. Resistance is the friction in an electrical circuit that restricts the flow of electrons under pressure and is measured in ohms (V). Electrical resistance is a load on the moving current that must be present to do any useful work. Resistance controls the amount of current flow in an electrical circuit. Electrical devices that use electricity to operate have a greater amount of resistance than a conductor (wire) and are considered loads in a circuit. A motor, light bulb, or solenoids are examples of electrical loads in a circuit; a load in a circuit is the electrical device that consumes electricity. Poor connections and corrosion are examples of unwanted electrical loads in a circuit. Resistance in an electrical circuit is measured in ohms (H). If there is resistance (H) in the conductor, electrons will not flow as readily. For all practical automotive purposes, electricity only flows through a good conductor; in the majority of automotive wiring, this is copper. It takes a high voltage (V) to flow current (A) through a poor conductor. Air, for example, is a poor conductor, but with a high enough voltage even air can flow electricity. Lightning with millions of volts is capable of flowing current through air! High-voltage electrical systems on HEV and EV platforms do not contain voltage as high as lightning, but it is not your 12-volt system either. To jump an inch of air it takes approximately 10,000 volts. Have you ever seen a faulty secondary ignition wire (spark plug wire) arcing to the engine? The voltage on the HEV and EV orange wiring harness is between 200 and 300 volts generally, which is too low to jump through air, but the capacitors and condensers in the system may contain much higher voltage. To summarize: ■■

■■

■■

Voltage is the pressure that moves electrons and is measured in either AC or DC volts (V). Current or amperage is the flow or volume of electrons flowing in a conductor and is measured in amps (A). Electrical resistance is a load or opposition on the moving electrons (current) in a circuit and is measured in ohms (H).

Ohm’s Law

The amount of current flow is determined by the amount of resistance in the loop of the circuit. In a fixed voltage circuit, if the amount of resistance in the loop of the circuit is high, the current flow will be low and if the amount of resistance in the loop of the circuit is low, the current flow will be high. This inverse relationship is known as Ohm’s law and is summarized by the mathematical equation in Figure 3-1. Ohm’s law states that it requires one volt of electrical pressure to move one amp through one ohm of resistance. Mathematically, Ohm’s

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E I

R

E=IxR I x R

E

E I= — R

E R=— I

R

E I

FIGURE 3-1  With Ohm’s law, if you know two of the three electrical factors, you can calculate the third.

law is expressed by the following equations, using the symbols E for voltage, I for current, and R for resistance: To find voltage E 5I 3R I 5E 4R To find current To find resistance R 5 E 4 I For example, if a 12.6-volt circuit has 2 ohms of resistance, you can use Ohm’s law to determine the current flow in the circuit as follows: I 5E 4R I 5 12.6 4 2 I 5 6.3 amps The current flow in the circuit is 6.3 amps. These equations can be used to calculate the voltage, current, or resistance of a circuit. It is the understanding of this relationship that is most important to you as a technician. You are not generally crunching numbers but instead you are making measurements on a circuit with a digital multimeter (DMM) and trying to understand what this information means. Ohm’s law can help to clear up what the meter is telling you for a given reading.

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Types of Circuits and Using Digital Multimeters

There are three basic types of circuits that we will be dealing with and a few ways to test these circuits for voltage, amperage, and resistance with a DMM. It is imperative that you understand these basic concepts and how to test a circuit with a DMM to avoid damage to the electrical circuit and components or damage to your expensive DMM. Remember, Snap-On does not warranty misuse of equipment and service managers do not understand expensive mistakes! Take your time and think before you test. Remember the best place to begin your diagnosis is with the electrical diagram and system operation description contained in the vehicle service information database. As stated earlier, this section is meant to be a review and not an in-depth training section, so please refer to Today’s Technician Automotive Electricity & Electronics for more information and training. Series circuit is a circuit that provides a single path for current flow from the electrical source through all the circuit’s components and back to the source (Figure 3-2). Series circuit laws: ■■ Current flow is the same at any point in the circuit (Figure 3-3). ■■ The sum of the individual voltage drops equals the source voltage (Figure 3-4). ■■ Total circuit resistance is the sum of the individual circuit resistances (Figure 3-5). C Lamp

Lamp

B

3A

3A

3A

A

Lamp

Switch

+

3A

–

3A

+

–

Battery Battery

FIGURE 3-2  A simple series circuit including a switch (A), a fuse (B), and a lamp (C). For all practical purposes, the only load in the circuit is the lamp.

FIGURE 3-3  Current flow is the same at any point in the circuit.

2V

4V

DIGITAL MULTIMETER RECORD

6V

DIGITAL MULTIMETER

MAX MIN

RECORD

DIGITAL MULTIMETER

MAX MIN

RECORD

MAX MIN

%

0 1 2 3 4 5 6 7 8

9 0

HZ

%

0 1 2 3 4 5 6 7 8

9 0

%

HZ

0 1 2 3 4 5 6 7 8

9 0

HZ

MIN MAX MIN MAX

MIN MAX

HZ HZ

mV V

mA A

COM

mV mA A

V A

V

A

HZ

mV

mA A

A

1Ω

mA A

COM

A

V

V

A

2Ω

+

mA A

V A

V

V

mA A

COM

V

3Ω

– 12 V

FIGURE 3-4  The sum of the individual voltage drops equals the source voltage (2V 1 4V 1 6V 5 12V or source voltage).

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1Ω

2Ω

Switch

R1

1Ω

Switch

+

–

+

Battery

R2

– 12 V

FIGURE 3-5  Total circuit resistance is the sum of the individual circuit resistances, 1V 1 2 V 1 1V 5 4 V of total circuit resistance.

FIGURE 3-6  There are multiple paths for current to flow in a parallel circuit. If R1 were to fail, R 2 would still work.

Parallel circuit is a circuit that provides two or more paths for current flow through all the circuit’s components and back to the source (Figure 3-6). In a parallel circuit, each path has separate resistances that operate independently or in conjunction with one another depending on the design of the circuit. Current can flow through more than one branch at a time and voltage is the same across each branch of the circuit. In this type of circuit, the failure of a component in one branch does not affect the operation of the components in the other branches of the circuit. Parallel circuit laws: ■■ Voltage is the same across each branch of the parallel circuit (Figure 3-7) and the ­voltage in each branch is used by the load(s) in that branch. The voltage dropped across each parallel branch will be the same; however, if the branch contains more than one resistor, the voltage drop across each of them will depend on the resistance of each resistor in the branch. 12 V DIGITAL MULTIMETER RECORD

MAX MIN

%

0 1 2 3 4 5 6 7 8

HZ

9 0

MIN MAX

HZ

mV mA A

V

A

V

A

mA A

+

V

COM

– Battery

1

0V DIGITAL MULTIMETER RECORD

MAX MIN

%

0 1 2 3 4 5 6 7 8

9 0

HZ

2

3

4

Current flows through lamps 1 & 2, which shine brightly.

MIN MAX

HZ

mV mA A

V

A

V

A

mA A

COM

V

FIGURE 3-7  Voltage is the same across each branch of the parallel circuit and the voltage in each branch is used by the load(s) in that branch.

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4 amps R1 A

10 amps

R2 6 amps FIGURE 3-8  Total current in a parallel circuit is equal to the sum of the individual branch circuits. 18 A 4A

Leg #1

3Ω

+

2A

Leg #2

6Ω

12 A

Leg #3

1Ω

– 12 V

FIGURE 3-9  Total resistance in a parallel circuit is always less than the smallest resistive branch. ■■

■■

Total current in a parallel circuit is equal to the sum of the individual branch currents (Figure 3-8). Total resistance in a parallel circuit is always less than the smallest resistive branch ­(Figure 3-9). 1 RT 5 1/ R1 1 1/ R 2 1 1/ R3 ...1/ R10 1 RT 5 1/ 3V 1 1/ 6V 1 1/1V 1 RT 5 0.333 1 0.166 1 1 1 RT 5 1.5 RT 5 0.667V

The series–parallel circuit has some loads that are in series and some that are in parallel with each other (Figure 3-10). A voltmeter can be used to check for available voltage at the battery, terminals of any component, or connectors. It can also be used to test voltage drops across electrical circuits, component loads, connectors, and switches. A voltmeter is connected in parallel with the circuit being tested (Figure 3-11). In Figure 3-12, voltage is being tested in a closed 12-volt series circuit with two loads. At test point A, the voltage should be the source voltage of 12 volts. At point B, the 1V resistor would have dropped half the voltage (there are two 1V loads 62 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

1A

Switch

0.5 A

0.5 A

4V

4V

V

10 V +

12 V Battery

– +

FIGURE 3-10  The series–parallel circuit has some load that are in series and some that are in parallel with each other.

– Battery

FIGURE 3-11  A voltmeter is connected in parallel with the circuit being tested. B

V

1V

M

1V

A

+

–

C

Battery FIGURE 3-12  A voltmeter testing for voltage at various points in the series circuit.

in the circuit) and the meter should read 6 volts. At test point C, all the voltage should have been used up by the two loads in the circuit and the meter reading should be 0 volts. These readings would indicate normal circuit operation. One of the most useful tests to perform is the voltage drop test. In a circuit, all of the voltage provided by the source power is used (dropped) by the circuit, with nothing left over. The voltage is used by resistance in wiring, connectors, switches, and loads. This loss or use of voltage is called a voltage drop and is the amount of electrical energy converted into another form of energy. Voltage dropped in wiring, connectors, and switches is converted into heat energy. When a circuit or branch of a circuit has only one load (resistance) source, voltage is dropped across that load (Figure 3-13). If there is more than one load in a circuit, each load will use a portion of the voltage. The total of all voltage drops in a circuit should equal source voltage. All of the voltage must be used by the circuit. You should verify that the circuit is turned on and that source voltage is available at the load and that the load drops source voltage. If the component (load) that is in the circuit drops source voltage, then the component is faulty. In Figure 3-14, if both lamp 1 and lamp 2 are the same resistance value (size), they will both share the source voltage equally. Lamp 1 will use 6 volts and lamp 2 will use 6 volts. If there is unwanted resistance in a circuit, the load in the circuit will not drop all source voltage (Figure 3-15). There is some allowable voltage drop by circuit components other than the load, but it is generally limited to a maximum of: 0.2 V (200 mV) for wires and cables 0.3 V (300 mV) for a switch 63 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

12 V 0V

Resistor

–

+ Switch

Battery

0V

FIGURE 3-13  Only the load will drop source voltage; the wiring and the switch should not drop significant voltage.

12 V

6V

A

B Lamp 1

Switch

–

+ Battery

6V

0.00 V

C

D Lamp 2

Available voltage point A = 12.00 V Minus available voltage point B = 6.00 V Voltage drop across lamp 1 = 6.00 V Available voltage point C = Minus available voltage point D = Voltage drop across lamp 2 =

6.00 V 0.00 V 6.00 V

Total voltage drop between points A and D = 12.00 V FIGURE 3-14  There should be source voltage before the first load. If there are two loads in a series circuit, each load will drop a portion of the source voltage. There should be no voltage after the last load.

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12 V

9V

DIGITAL MULTIMETER RECORD

DIGITAL MULTIMETER

MAX MIN

RECORD

MAX MIN

%

0 1 2 3 4 5 6 7 8

9 0

%

HZ

0 1 2 3 4 5 6 7 8

MIN MAX

mV mA A

V

COM

mA A

V A

V

mA A

HZ

HZ

mV

A

9 0

MIN MAX HZ

A

V

V

A

3Ω

mA A

COM

V

3Ω 1Ω

3A

4A

+

–

+

12 V

– 12 V

FIGURE 3-15  Only the load will drop source voltage; the wiring and the switch should not drop significant voltage. But if there is unwanted resistance in a circuit, source voltage will not be available and the bulb would be dimmer than normal or may not light at all.

TABLE 3-1:  CIRCUIT TEST CHART Type of Defect Open

Short to Ground

Short

Excessive Resistance

■■ ■■ ■■

Test Unit

Expected Results

Ohmmeter

∞ infinite resistance between conductor ends

Test light

No light after open

Voltmeter

Ø volts at end of conductor after the open

Ohmmeter

Ø resistance to ground

Test light

Lights if connected across fuse

Voltmeter

Generally not used to test for ground

Ohmmeter

Lower than specified resistance through load component Ø resistance to adjacent conductor

Test light

Light will illuminate on both conductors

Voltmeter

A voltage will be read on both conductors

Ohmmeter

Higher than specified resistance through circuit

Test light

Light illuminates dimly

Voltmeter

Voltage will be read when connected in parallel over resistance

0.1 (100 mV) for a ground 0 V for a connection or connectors Common circuit faults (Table 3-1): Short circuits Short to ground Opens in a circuit

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High resistance (may be caused by corrosion or poor connections) Low voltage When using an ammeter to measure amperage, be sure to first turn power off in the circuit before connecting the multimeter. The circuit must be opened (disconnected) from the load being tested. The multimeter is placed in series in the circuit, recompleting the disconnected circuit (Figure 3-16). Always verify that the multimeter is capable of handling the highest expected amperage in the circuit being tested. What size fuse protects the circuit being tested? Many multimeters are only internally protected to 10 amperes by their internal fuse and many automotive circuits can provide 20 or more amps. In these cases, an inductive amp probe is the best choice of tools to use to avoid multimeter damage (Figure 3-17). The inductive probe eliminates the need to connect the multimeter in series and is a safe noninvasive method of measuring amperage in a circuit. When using an ohmmeter to measure resistance, the power from the circuit must be removed and the circuit or component should be isolated (Figure 3-18). Ohmmeter leads are placed across or in parallel with the component or circuit being tested.

■■ ■■

1 ]

A

FIGURE 3-16  When testing amperage, the circuit must be opened (disconnected) from the load being tested and the multimeter is placed in series in the circuit.

FIGURE 3-17  A multimeter with an inductive amp probe is a safe, noninvasive method of measuring amperage in a circuit.

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1 ]

Fuse removed to de-energize circuit

FIGURE 3-18  When measuring resistance with an ohmmeter, the meter is connected in parallel with power removed from the circuit and the circuit or component isolated.

Fuses and Circuit Breakers A fuse or circuit breaker (Figure 3-19) is used to protect the air-conditioning and heating components and wiring. Usually rated at 20-30 amperes, they should not be replaced with one having a different rating. If a fuse or circuit breaker is rated too low, it will not carry the load and will quickly burn out (blow). If it is rated too high, the device it is intended to protect may be damaged due to excessive current. The fuse or circuit breaker is usually located in the main fuse block. Major circuits are often protected by a fusible link (Figure 3-20) or a maxi-fuse. Fuses may also be located in in-line fuse holders (Figure 3-21). Circuit breakers are constructed of a bimetallic strip and a set of contacts. Excessive current, caused by a defective component, produces heat that causes the bimetallic strip to bend. When the strip bends, the contacts open and current to the component is interrupted. When there is no current flow, the bimetallic strip cools and the contacts automatically close. This continues until the cause of the problem is corrected.

A fuse is an electrical device used to protect a circuit against accidental overload or unit malfunction.

A circuit breaker is a bimetallic electrical device used to protect a circuit against accidental overload or unit malfunction. It automatically resets once it cools down.

FIGURE 3-19  Fuses and circuit breakers.

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Most factoryinstalled heater and air-conditioner electrical schematics require two or more pages. Fusible links Wiring diagrams are also known as schematics.

FIGURE 3-20  A fusible link.

FIGURE 3-21  In-line fuse holders.

Circuit Resistance Resistors are devices constructed to introduce a measured amount of electrical resistance into a circuit. Resistors may be used to limit current flow, and thereby voltage, in a circuit where source current flow and voltage are not required or where too much voltage may cause damage. Resistance in a circuit may also be used to produce heat; an example would be the rear window defroster or light such as bulbs. There are three common types of resistors used in automotive circuits: fixed, tapped or stepped, and variable. Fixed resistors are designed to have a set value that should not change. These types of resistors are commonly used to control voltage. Tapped or stepped resistors have two or more fixed value resistors with wire taps after each to provide stepped voltage outputs (Figure 3-22). An example of this type of circuit is the basic blower motor speed control circuit, which will be discussed and described in the blower motor section of this chapter. Variable resistors have an infinite number of resistance values within a range. Two examples of variable resistors are the rheostat and the potentiometer. Rheostats have two wire connections (Figure 3-23), one to the fixed end of the resistor and one to a sliding variable resistance contact or wiper. Moving the sliding contact, wiper, connected to a knob or lever, moves the connection either away from or closer to the fixed end of the tap, causing the 68 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

12 V

12 V

10 V

8V

6V

4V

FIGURE 3-22  The use of a stepped resistor assembly is a common application of fixed resistors.

I I

I

FIGURE 3-23  A rheostat.

FIGURE 3-24  A potentiometer.

resistance to increase or decrease, respectively. A common use for a rheostat is the instrument panel lighting (dimmer) switch, which varies the amount of current to dash light bulbs. Potentiometers are similar to rheostats except that they have three wire connections ­(Figure 3-24), one at each end of the resistance and one connected to the sliding contact, wiper, with the resistor. Moving the wiper slide contact away from the reference voltage source (1) end of the resistance and toward the output end (2) increases the resistance, which in turn decreases the output voltage on the signal or sliding output side of the circuit. Potentiometers are a common type of input sensor used by vehicle computers to monitor linear movement. Examples are throttle position on the engine throttle body or the mode door position in the climate control duct system of the vehicle. Another form of variable resistor used is the thermistor (Figure 3-25). A thermistor changes resistance value with a change in temperature. There are two types of thermistors: negative temperature coefficient and positive temperature coefficient thermistors. Thermistors are used to provide compensating voltage in a component or to monitor temperature. As a temperature sender such as a coolant temperature sensor, the thermistor is connected to voltmeter circuit calibrated in degrees. As the temperature of the thermistor increases or decreases the resistance will also change. In a negative temperature coefficient resistor, the resistance goes up as the temperature decreases and in a positive temperature coefficient thermistor the resistance increases with an increase in temperature. These types of sensors are used extensively in the heating and air-conditioning systems used in the automotive industry as well as other areas of the vehicle. Coolant temperature sensor

Voltage sensing

FIGURE 3-25  A thermistor is used to measure temperature. The sensing unit measures the change in resistance and translates this into a temperature valve.

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Diodes A diode is one of the simplest semiconductor devices and functions as an electrical oneway check valve that allows current to flow in one direction only. It is formed by joining P-type (positive) semiconductor material with N-type (negative) semiconductor material. The positive side of the diode is called the anode and the negative side is called the cathode ­(Figure 3-26) and the point where the two join is called the PN junction. The outer housing of the diode will have a stripe painted around it on one end designating the cathode side. Diodes may be placed in a circuit in either forward or reverse biased position depending on the function of the diode in the circuit. Reverse biased means that the positive voltage is applied to the negative, cathode side of the diode and negative voltage is applied to the positive, anode side of the diode (Figure 3-27). Diodes are often used in circuits in reverse bias position to function as a clamping or protective device in a circuit. When a coil such as a solenoid or relay is turned off, the magnetic field surrounding the coil collapse and induces a voltage spike in reverse bias into the circuit (Figure 3-28). When these types of circuits are controlled by a microprocessor, a clamping device is needed to protect the solid-state components and diodes wired reverse biased are often chosen. A diode placed in parallel with the coil creates a bypass for the electrons when the circuit is turned off and will redirect this voltage spike back through the coil until all the voltage is used up by the coil. Light ON

Anode 1

Light OFF

Cathode –

6V

FIGURE 3-26  The top image is the symbol for a diodes and the lower two images show the location of the painted strip indicating the cathode or negative material side of the diode.

+

6V –

+

Forward Biased

–

Reverse Biased

FIGURE 3-27  A forward-biased diode in the circuit would allow current to flow and the bulb would be on. A reverse-biased diode in the circuit would not allow current to flow and the bulb would be off. Switch

Diode

+ Battery

+ – –

Electromagnet

– Current

+

Battery FIGURE 3-28  When a coil such as a solenoid or relay is turned off, the magnetic field surrounding the coil collapses and induces a voltage spike in reverse bias into the circuit. A diode will redirect this voltage spike back through the coil until all the voltage is used up.

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1 Anode

– Cathode

FIGURE 3-29  The photodiode allows reverse current flow only when a specific amount of light is received.

Another type of diode is the photodiode (Figure 3-29), which, like a standard diode, only allows current to flow in one direction. However, the direction of current flow is opposite that of a standard diode. Reverse current flow only occurs when the photodiode receives a specific amount of light. Photodiodes operate by the absorption of photons, which are charged particles that carry light and allow a flow of current proportional to the level of light received in the circuit they are connected to. Photodiodes can be used to detect minute amounts of light and can be calibrated for extremely accurate light measurements. As long as the photodiodes’ response to light is linear, the output voltage will be proportional to the light level detected by the photodiode.

Relays A relay is an electromagnetic switch that allows a small amount of current to control a large current (Figure 3-30). The low current control circuit is connected to the coil side of the relay. Relays are used where a low current control may be used to activate a high current load. Often, relays are used to control electric motors such as blower motors and air-conditioning compressor clutch coils. Many relay terminals are identified using the International Standards Organization (ISO) numbering convention (Figure 3-31) for common size and terminal patterns. Even if the circuit you are working on does not use the ISO numbering convention, if you think about all relays based on this convention and terminal identification, the diagnostic process is simplified.

From power source

Power circuit

Armature

To load

87a

86

Control circuit

30

87

87 87a

85

30 86

85

Terminal 86 is the coil high connection on the low current control side Terminal 85 is the coil low connection on the low current control side Terminal 30 is the common on the high current side Terminal 87 is the normally open (NO) contact on the high current side Terminal 87a is the normally closed (NC) contact on the high current side FIGURE 3-30  A typical relay.

FIGURE 3-31  Relay terminals are identified using the International Standards Organization (ISO) numbering convention.

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The relay low current coil side may be controlled by switching either the power (­terminal 86) (Figure 3-32) or ground (terminal 85) side of the circuit (Figure 3-33). The ­control circuit is wired using a very small diameter wire due to the low current flow required. The coil develops a magnetic field that closes the normally open contact (and opens the normally closed contact if equipped), which in turn energizes the high current load in the circuit. The relay contacts may control either the power (Figure 3-32) or the ground side (Figure 3-33) of the load to energize the circuit. The control circuit amperage is often as low as 0.25 amperes while the high current contact side of the relay may have 25 or more amperes to power the circuit load device. Relays are often controlled by a microprocessor. When relays are controlled by semiconductors such as transistors, they require some type of voltage suppression device to protect the circuit since solid-state circuits are vulnerable to voltage spikes. Voltage spikes are like bolts of lightning striking the transistors, destroying them. Some computer circuits have voltage suppression built inside the computer, others rely on voltage suppression from within the relay. Diodes, high-ohm resistors, or capacitors can be used for voltage suppression (Figure 3-34). Resistors and diodes are the most common suppression devices used. Generally, a relay is clearly marked if a suppression diode or resistors are used internally in the relay. Power

Power

Switch

Load Relay Relay

86 86 30

30

Load

85

Switch

85

87 87

FIGURE 3-32  The low current coil may be power switched.

FIGURE 3-33  The low current coil may be ground switched.

R

R

Resistor

Diode

L

Switch

1 ]

Switch

1 ]

FIGURE 3-34  Diodes and high ohm resistors can be used for voltage suppression to protect solid-state coil control components in a circuit.

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Relays are rated based on the control voltage for the coil side. In the automotive industry, this means that the typical relay is rated for 12 volts. The contact side of a relay is rated based on the amount of amperes that it can carry. Typical ampere ratings of automotive relays are 20, 25, and 30. It is important that the correct replacement relay is used. Relays may look identical but have different amperage ratings. Always use the relay that is specified for the circuit being repaired.

Blower Motor The blower motor fan is an essential part of the heating and air-conditioning system. It is responsible for drawing in air from the cowl or from inside (recirculated) the passenger compartment. The air is then forced through the duct system and directed over the heater core and evaporator and then on to the air distribution network. The most common blower motor design today is the single-wound brush or brushless motor (Figure 3-35). The motor is usually located in the HVAC housing. A fan switch controls the blower motor fan speed with settings ranging from low to high; some climate control systems in the FULL AUTO mode have the ability to automatically control the full range of blower speeds. Blower motors may have a single or a double shaft. Some have provisions for flange mounting and may also have provisions for internal cooling. Regardless of style or type, the blower motor drives a squirrel-cage blower to move air across the evaporator and heater core (Figure 3-36).

Control

Motor 12V Ground FIGURE 3-35  A single-wound motor.

Motor

Blower

FIGURE 3-36  A squirrel cage blower with motor.

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The high blower motor speed provides the greatest volume of air across the evaporator core for greatest refrigerant evaporation. Lowering fan speed decreases air volume and allows the slower moving air to remain in contact with the evaporator/heater core for a longer period of time, enabling more heat to be removed/picked up by the air stream. The result is colder/ hotter air being discharged at slower fan speeds. Several methods used by manufacturers to regulate blower motor speed will be discussed next. It should be noted that some replacement motors are reversible, whereas most are not. It is also important to note whether the defective motor turned clockwise or counterclockwise facing the shaft end. The replacement motor selected must turn in the same direction. If the wrong motor is installed, little or no airflow will circulate through the duct system. In addition, some replacement blower motors do not come with a blower cage. In these circumstances, the old cage must be reused. Ensure that the cage fits snugly on the motor shaft and does not slip. Other abbreviations relating to the selection of blower motors include a double shaft (DBL) and threaded shaft (THD) end. Author’s Note: You may notice a small steel clip on one of the blower motor cage fins; this is a weight to balance the assembly. Do not remove this clip or vibration will result, which could also lead to premature motor bearing failure and customer complaints. Blower Motor Resistor Block.  Historically one of the most popular methods of blower motor speed control on vehicles equipped with manual HVAC control has been through the use of resistors. Wire resistors are used with a single-winding blower motor to regulate motor speed. The blower motor resistor is generally a group of three or four wire resistors integrated into a block assembly (Figure 3-37). Each of the stepped resistors reduces the current flow through the blower motor to change blower motor speed (Figure 3-38).

FIGURE 3-37  The blower motor wire resistor block assembly consists of three to four wire-wound resistors mounted in a frame with integrated connection terminals.

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Battery

IPM

Run mix RD

Front blower fuse 40A

Resistor block A

B

2 1

C

34 5

D

Front blower motor

HVAC control head 1 = LO 2 = M1 3 = M2 4 = M3 5 = HI

FIGURE 3-38  Blower motor resistor speed control circuit. The blower motor control switch directs current through one to four resistors (A–D) to regulate motor speed.

The blower motor switch directs current flow through the correct resistor wire to obtain the selected speed. For low blower speed, the switch is in position 1 and current is directed through all four resistors, A–D, which will drop current in the circuit, limiting motor speed. The resistor assembly may be wired on either the power or ground side of the blower motor. The resistor block is mounted in the HVAC ventilation duct to allow for air stream cooling of the resistors. There are several design variations, including ceramic and credit card type. Regardless of the physical design or the side of the circuit they are wired to, the operation is the same. Author’s Note: Never remove the resistor block from the air stream and ­operate the blower motor. The resistor block will heat up rapidly and could be damaged or burn whatever it contacts.

Some blower speed control systems have a high-speed blower control relay (Figure 3-39). When high speed is selected, the resistor block is bypassed and full current is directed through the blower motor. Note that this five-speed blower has two fuses protecting the circuit: one (20A) for the first four speeds and one (30A) for high speed. Blower Motor Credit Card Resistor.  The blower motor credit card resistor works in a similar manner as the wire-wound resistor block, by dropping current flow in the blower motor circuit (Figure 3-40) with the addition of a thermal limiter switch. The thermal limiter switch is a protection device designed to turn off the blower motor at all speeds, except high, if resistor temperatures exceed 3638F (183.898C). The credit card resistor consists of an integrated 75 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

20A Fuse Heater A/C control assembly

LOW HI

M3 M2

M1

R1 R2 R3 Blower motor relay

R4

Fuse 30A

Hot at all times

Blower motor FIGURE 3-39  High-speed blower motor relay.

FIGURE 3-40  The credit card resistor consists of an integrated circuit board mounted to a molded plastic mounting plate and integral connector assembly.

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Four-wire connector

Two-wire connector

Power module

Blower motor

Cooling hose

Evaporator and blower assembly

FIGURE 3-41  A typical power control module located in the HVAC duct system.

circuit board mounted to a molded plastic mounting plate and integral connector assembly. Like the wire resistor block, it is also mounted in the HVAC ventilation duct to allow for air stream cooling of the resistors. Blower Motor Power Transistor Module.  A power transistor module, also called a power module (Figure 3-41), is a solid-state semiconductor located on the ventilation duct of the HVAC system and cooled by the blower motor fan. The power transistor takes the place of the stepped resistor block and controls blower speeds by varying the amount of resistance in the blower motor’s ground circuit. The climate control module or body control module (BCM) applies a pulse width–­ modulated (PWM) (duty-cycled) voltage (Figure 3-42) to the base of the transistor, which in turn determines the level of conductivity through the power transistor. This type of control provides infinite blower fan speed control within the limits of the motor, between fast and slow, with a smooth transition between speeds. If the amount of ON time is equal to the OFF time in a cycle, then the duty cycle is 50 percent, and the motor will run at half speed. Duty cycle ON

OFF

33 Hz

33 Hz 50 percent duty cycle ( 1 /2 speed)

33 Hz

25 percent duty cycle

75 percent duty cycle

( /4 speed)

( 3 /4 speed)

1

Pulse width modulation (PWM) On-off duty cycling of a component. The period of time for each cycle does not change; only the amount of ON time in each cycle changes. The length of time in milliseconds that an actuator is energized.

FIGURE 3-42  Typical duty cycle patterns, as viewed with an oscilloscope, to achieve various blower motor speeds through the use of pulse-width modulation.

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+12V

Power module 5V

12 V Blower motor Logic driver 5V

Blower motor supply

Power module

Blower motor control signal M Automatic zone control head

Body control module or HVAC control head FIGURE 3-43  The blower motor power transistor is pulse-width modulated by the BCM or climate control module on the ground side of the blower motor with a high- or low-voltage signal.

Variable input from blower switch FIGURE 3-44  The blower motor power transistor is pulse-width modulated by the BCM or climate control module on the power side of the blower motor with a high- or low-voltage signal.

Regardless of the specific circuit design, the power transistor regulates blower motor current flow to vary fan speed. The BCM or HVAC control module pulse width modulates the signal wire to the power transistor module to provide this speed regulation (Figure 3-43). On some systems, the command signal is pulled high for high blower speeds and on other systems the command signal is set low for high blower speeds (Figure 3-44). Always refer to vehicle-specific service information when diagnosing a fault in the system. On an automatic climate control system, if the system is set to the FULL AUTO mode, the control module will decide when and at what speed the blower motor should run based on input sensor data and system demands. If the in-car temperature is considerably higher than the selected temperature when using the air conditioning, the control module will send a signal to the power transistor to increase blower motor speed until the temperature inside the vehicle begins to drop. Once the temperature begins to drop, the power control module will reduce the blower speed to a level that will maintain the temperature selected at the control panel.

Electromagnetic Clutch An electromagnetic clutch (Figure 3-45) is used in automotive air-conditioning systems as a means of engaging the compressor when cooling is desired and disengaging it when cooling is not required. For example, the compressor is disengaged when the air conditioner is not being used or when the desired temperature is reached in the vehicle. All clutches operate on the same basic principle—that of magnetic attraction. This is accomplished by energizing a stationary field coil. The magnetic attraction of the field coil, in turn, pulls an armature into contact with a rotating member, the pulley. All automotive air-conditioning systems have an electromagnetic clutch. Not all, however, are used to cycle the compressor for temperature control. For those that do, the electrical circuit to the clutch coil is interrupted when a set of contacts, thermostatically controlled or

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Lead wire

Armature

Bearing

Snapring

Snapring

Clutch field coil assembly

Pulley assembly rotor assembly FIGURE 3-45  Electromagnetic clutch assembly.

pressure actuated, open as the set temperature or pressure is reached. Those that do not cycle to affect the desired temperature rely on the operation of a variable displacement compressor as a means of temperature control.

Clutch Diode

The clutch coil is an electromagnet with a strong magnetic field when current is applied. This magnetic field is constant as long as power is applied to the coil. When power is removed, the magnetic field collapses and creates high-voltage spikes. These spikes are harmful to delicate electronic circuits of the computer and must be prevented. A diode placed across the clutch coil (Figure 3-46) provides a path to ground back through the clutch coil until the electrical energy is dissipated, thereby holding the spikes to a safe level. This diode is usually taped inside the clutch coil connector, across the 12-volt lead and ground lead. A diode may be checked with either an analog ohmmeter or DMM set to the diode test mode. Many DMMs have provisions for diode quick-testing procedures; this is the preferred method for testing diodes.

Diode

From clutch coil Clutch coil

Ground

FIGURE 3-46  A diode is placed across the clutch coil to reduce spikes as the clutch is cycled on.

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Terms to Know Amperage (AMP) Circuit breaker Diode Duty cycle Fuse Ohms ( V ) Ohm’s law Pulse-width modulated (PWM) Voltage

SUMMARY ■■

■■

■■ ■■

Voltage (V) or electromotive force (EMF) is the electrical pressure and is measured in volts (V); it may be either direct current (DC) or alternating current (AC). Current is the flow or rate of flow of electrons under pressure in a conductor between two points having a difference in potential and is measured in amperes (A) or amperage. Resistance is defined as the opposition to current flow and is measured in ohms (V ). Ohm’s law defines the relationship between voltage, current, and resistance. It is the basic electrical law.

REVIEW QUESTIONS Short-Answer Essays 1. Briefly define the term voltage. 2. Briefly define the term current. 3. Briefly define the term resistance. 4. What are three common types of resistors used in automotive circuits? 5. What can photodiodes be used to detect? 6. Describe a series-parallel circuit. 7. What is a diode? 8. Briefly define Ohm’s law. 9. Where are electromagnetic clutches used? 10. Describe parallel circuit principles.

Fill in the Blanks 1. _______________ is the electrical pressure; it may be either direct current (DC) or alternating current (AC). 2. A _______________ is one of the simplest ­semiconductor devices and functions as an electrical one-way check valve. 3. _______________law defines the relationship between voltage, current, and resistance. It is the basic electrical law. 4. A _______________ changes resistance value with a change in temperature.

5. Many relay terminals are identified using the _______________ numbering convention for common size and terminal patterns. 6. _______________ is the flow or rate of flow of electrons under pressure in a conductor between two points having a difference in potential and is measured in _______________. 7. _______________ are a common type of input ­sensor used by vehicle computers to monitor linear movement. 8. _______________ have an infinite number of resistance values within a range. 9. _______________ controls the amount of current flow in an electrical circuit. 10. A _______________ can be used to detect minute amounts of light.

Multiple Choice 1. In a parallel circuit: A. Total circuit resistance is less than the lowest resistance. B. Amperage will decrease as more branches are added. C. Total resistance is the sum of all of the resistances in the circuit. D. All of the above

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2. In a series circuit: A. Total circuit resistance is the sum of the individual circuit resistances. B. The sum of the individual voltage drops equals the source voltage. C. Current flow is the same at any point in the circuit. D. All of the above 3. All of the following are common circuit faults except: A. Short to ground. C. Voltage drop test. B. Open in circuits. D. High resistance. 4. All of the following are true of voltage drops except: A. Voltage drop can be measured with a voltmeter. B. All of the source voltage in a circuit must be dropped. C. Corrosion in a circuit does not cause a voltage drop. D. Voltage drop is the conversion of electrical energy into another form of energy. 5. Ohm’s law defines the relationship between all of the following except: A. Voltage C. Resistance B. Corrosion D. Current

6. Resistance is defined as the opposition to current flow and is measured in: A. Volts C. Amperes B. Resistance D. Ohm’s 7. Current is defined as the flow of electrons and is ­measured in: A. Volts C. Amperes B. Resistance D. Ohm’s 8. Voltage is defined as electrical pressure and is ­measured in: A. Volts C. Amperes B. Resistance D. Ohm’s 9. A relay is an electromagnetic switch that allows a small amount of current to control: A. A large voltage C. A small voltage B. A large current D. A large resistance 10. A photodiodes can be used to detect minute amounts of: A. Light C. Voltage B. Current D. Resistance

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Chapter 4

Engine Cooling and Comfort Heating Systems Upon Completion and Review of this Chapter, you should be able to: ■■ ■■

■■ ■■

Explain the engine cooling system and its components.

■■

Recognize the various components of the automotive cooling system.

■■

Identify the different types of radiators.

■■

Explain the operation and function of the coolant (water) pump.

■■

Discuss the requirements for a closed cooling system. Explain the purpose, advantage, and operation of a thermostat. Recognize the safety hazards associated with a cooling system service. Explain the operation of various types of cooling fans.

Introduction

Shop Manual Chapter 4, page 101

A defective cooling system may impair air conditioning performance.

Normal operation of the automobile engine produces heat that must be carried away. This excessive engine heat, which is a product of combustion, is transferred to the coolant and then dissipated in the radiator. This is accomplished by two heat transfer principles known as conduction and convention. The cooling system, when operating properly, maintains an operational design temperature for the engine and automatic transmission. The cooling system functions by circulating a liquid coolant through the engine and the radiator. Engine heat is picked up by the coolant by conduction and is given up to the less hot outside air passing through the radiator by convection. Coolant is also circulated through the heater core, which also uses the convection process to supply heated air to the passenger compartment.

The Cooling System The purpose of the automotive cooling system is to carry the heat that is generated by the engine during the combustion process away from the engine (Figure 4-1) to maintain a near constant engine operating temperature during varying engine speeds and operating conditions. Due to inefficiencies of the internal combustion engine, as much as 70 percent of the energy from gasoline is converted into heat. The cooling system has a difficult task with internal combustion temperatures, which may exceed 4,5008F (2, 4828C). Actually, most of the engine’s heat is sent out the exhaust system and is absorbed and dissipated by the cylinder walls, heads, and pistons into the ambient air. The cooling system is designed, therefore, to remove about 35 percent of the total heat produced by the engine. Another important function of the cooling system is to allow the engine to reach operating temperatures as quickly as possible. When engines are below operating temperature, exhaust emissions are increased, internal components wear faster, and operation is less efficient.

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Overflow recovery tank

Radiator Radiator cap hose Thermostat

Heater control

Heater core

AIR FLOW Heater hoses Radiator Water pump

Combustion chamber

Water jacket

FIGURE 4-1  A typical engine cooling system and heating core.

An automobile engine’s heat is given up in the radiator by the two heat transfer processes of radiation and convection. The overall surface area of most radiators is on the order of about 28 to 35 sq. ft. (2.6 to 3.2 m 2 ), though their physical size does not imply that they have that much cooling area. Heat, as discussed earlier, is always ready to flow from a hot to a less hot object or area. The heat that is picked up by the coolant in the engine block is given off to the less hot air passing over the fins and coils of the radiator. Air movement across the radiator is created in two ways: (1) by the engine fan, known as forced air, and (2) by the forward motion of the car, known as ram air. The high-limit properties of engine lubricating oil necessitate proper heat removal to prevent destroying its formulated lubricating characteristics. On the other hand, removing too much heat lowers the thermal efficiency of the engine. To prevent the removal of too much heat, a condition known as overcooling, a thermostat is used in the engine outlet water ­passage. The thermostat, a temperature-sensitive device, controls the flow of coolant from the engine into the radiator. In addition to hoses required, the closed cooling system (Figure 4-2) consists of the following: ■■ Water pump ■■ Engine water passages ■■ Cooling fan ■■ Radiator ■■ Recovery or expansion tank ■■ Pressure cap ■■ Thermostat ■■ Air baffles and body seals Each of these components is covered individually in this chapter.

The radiator is a coolant-to-air heat exchanger that removes heat from the coolant passing through it. Ram air is air forced through the radiator by the forward movement of the vehicle.

Shop Manual Chapter 4, page 108

The thermostat is a temperaturesensitive device used to regulate the cooling system operating temperature.

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Coolant reservoir Heater hose (return)

Heater core

Fan shroud

Thermostat

Heater hose (inlet)

Upper hose

Cooling fan Lower hose A/C condenser

Radiator

FIGURE 4-2  A closed cooling system.

Cooling systems also include a heater core as part of the cooling system circuit. Some car lines may also include a thermostatic vacuum switch (TVS), which is also known as a ported vacuum switch. This vacuum-controlled device advances ignition timing if the engine overheats during prolonged idle periods. Because of modern electronics technology, this component was discontinued on most car lines in the mid to late 1980s, though it was used on some Ford and Jeep car lines through 1991. If a vehicle was not equipped with a factory-installed air conditioner, the cooling system is most likely not designed to handle the additional heat load. Under normal circumstances, however, the addition of an aftermarket air-conditioning system will cause no problems with the automotive cooling system. This is only true if the cooling system has been well maintained and in good working condition. An aftermarket installation kit often contains a smaller water pump pulley to provide increased coolant flow and a fan system to provide additional airflow. It is necessary to have a good understanding of the purpose and operation of the cooling system to properly diagnose, troubleshoot, and correct cooling system problems.

Heat Measurement Today’s technicians use both mechanical and electronic thermometers. High-temperature electronic pyrometer probes, which are part of many automotive digital multimeters, are used by touching the surface to be tested or infrared thermometers may be used by simply aiming at the surface or area to be measured (Figure 4-3). The infrared pyrometer is by far the most popular method of determining the temperature of a component. In fact, in some states, they have become a required tool for emission technicians. 84 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 4-3  Infrared pyrometer and DVOM with temperature probe.

For safety reasons, temperature measurements are usually taken just after turning the engine off. Beware of moving parts, such as the radiator cooling fan, that can start at any time even when the ignition switch is in the OFF position. Specific methods and procedures for taking temperature measurements are covered throughout this manual, as well as in the Shop Manual where applicable.

Radiator The radiator is a heat exchanger that consists of a core and two tanks. It is used to remove heat from the coolant passing through it. It performs a critical job, and if the radiator fails to remove excess heat, the engine may overheat and extensive damage, such as blown head gaskets or cracked or warped cylinder heads, may result. Excessive heat could also result in scuffed piston skirts and cylinder walls as well as valve stem and guide damage. There are two basic radiator design types: (1) cross-flow tube and fin type, and (2) vertical flow tube and fin type (Figure 4-4). In a cross-flow radiator, popular on most late model vehicles, the coolant flows from the inlet tank (generally the upper radiator hose tank) to the outlet tank. In the vertical flow design, coolant flow is from the top tank to the bottom tank. This design is not as popular today. A cross-flow radiator is 40 percent smaller than a downflow radiator and has a flatter design well suited for more compact designs. Radiators are generally constructed of an aluminum (Al) core and high-temperature, nylon-reinforced plastic tanks and are used on most late-model vehicles or with copper (Cu) core with brass tanks on early radiators through the late 1980s and early 1990s. On the aluminum core radiator, the high-temperature plastic tanks are held in place by clinch tabs, which are part of the aluminum header at each end of the core, and a special high-temperature rubber gasket seal between the core header and tank flange edge to prevent leakage (Figure 4-5).

A

Shop Manual Chapter 4, page 103

The terms “vertical flow” and “down flow” for radiators are used interchangeably for the same design. Radiator tanks are also referred to as “headers.”

B

FIGURE 4-4  Two radiator designs: (A) cross flow and (B) vertical flow.

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Inlet tank (plastic)

Outlet tank (plastic)

Bending tangs

Draincock

Transmission oil cooler

O-Ring gasket

Radiator core (aluminum)

O-Ring gasket

FIGURE 4-5  A typical aluminum core/plastic header radiator.

The cellular core is often called a honeycomb.

There are, however, occasional variations in how these four materials are combined. Some manufactures have also been using full aluminum radiators on some of their platforms. These radiators offer reduced overall depth and are up to 11 percent lighter, feature a higher burst pressure, and they are fully recyclable, but they are more expensive. In our discussion, we refer to the first tank as the inlet tank because it receives hot coolant after it passes through the engine and distributes it to the radiator core. The second tank will be referred to as the outlet tank because it collects the less hot coolant after it has passed through the many tubes in the radiator core. At the bottom of one of the tanks, there is a draincock to aid in the removal of coolant. The inlet tank usually contains a baffle plate to aid in the even distribution of coolant through the passages of the core. The outlet tank may also be considered a storage tank for the coolant after it has given up much of its heat after passing through the core. From the outlet tank, coolant is directed to the water pump inlet via a radiator hose (lower). The outlet tank often contains an internal coil used as automatic transmission oil cooler (Figure 4-6). Transmission fluid is pumped from the transmission through the coil and back to the transmission. This transmission fluid has no other connection with the engine coolant. Though not common, the transmission oil cooler sometimes develops a leak. Because transmission oil pressure is usually greater than cooling system pressure, the oil will leak into the cooling system, creating an oily, strawberry-colored foam in the cooling system. There could, on the other hand, be a coolant leakage into the transmission depending on pressure differential (Dp). Some vehicles equipped with a trailer-towing package may also have an external transmission cooler. Two common designs for cores are the cellular core (A) and the tubular core (B) ­(Figure 4-7). The tubular core has a series of long, narrow, oblong tubes that connect the inlet and outlet tanks. There are fins around the outside of the tubes to improve heat transfer from the coolant flowing in the tubes. The fins on the core absorb heat from the coolant passing

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Oil cooler

Oil cooler lines FIGURE 4-6  Transmission oil cooler details.

Top header

A

Water passage tubes

Cellular fin core

Top header

Water passage tubes

Flat plate fin core

Top header

B

Water passage tubes

Serpentine fin core

FIGURE 4-7  Two types of radiator core designs: (A) cellular and (B) tubular.

through the tubes and release it to the ambient air passing through the core and across the fins and tubes, thus carrying off heat and cooling the coolant (Figure 4-8). A process of soldering together thin, preformed sheets of metal fabricates the cellular core, usually made of aluminum, copper, or brass. During engine operation, the coolant heats up and expands. As the coolant expands, it is displaced into the recovery or expansion tank. In addition, as the coolant circulates, air bubbles are allowed to escape. The advantage to allowing air bubbles to escape is that coolant without bubbles absorbs heat much better than if they were allowed to flow through the system. Under certain applications, there may be a need to increase the cooling capacity of the system by recommending the upgrade to a heavy-duty or performance radiator. Vehicles that could benefit from an upgrade include those used for towing, carrying heavy loads, off-roading, and other uses that would put increased demand on the cooling system. These radiators will have additional rows of tubes, added thickness, and may have a more efficient design. The walls of either type of core are not much thicker than the paper you are now reading. Their passages are about the size of a pencil lead. This should give some idea of how fragile radiators are and the care that must be taken to avoid costly damage.

The expansion tank is a pressurized auxiliary tank that is usually connected to the inlet tank on a radiator to provide additional storage space for heated coolant. It is often called a coolant recovery tank or an overflow tank when not pressurized and under atmospheric pressure.

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FIGURE 4-8  Cellular core (A) and tubular core (B) radiator details.

Electrolysis is the decomposition of an electrolyte (coolant in this case) by the action of an electric current passing through it.

The cooling system should also be checked for signs of electrolysis. Electrolysis occurs when an electrical component is not properly grounded and routes itself through the cooling system in search of one. Likely sources are electrical accessories that are bolted to the engine and components in the cooling system, such as the starter motor or engine block to the battery ground connection. The destructive effect of electrolysis may be in the form of recurring pinholes in the coolant tube of the heater and radiator core or where mounting brackets are attached. Increases in the current draw of poorly grounded accessories will increase the destructiveness of electrolysis. Small amounts of voltage may be measurable in a cooling system that has become slightly acidic, and the coolant reacts with the metal in the system but should never exceed a tenth of a volt (0.10V) in engines with aluminum cylinder heads or blocks. Using a digital DC voltmeter may test for this. Connect the negative lead to the battery negative post and place the positive lead into the coolant at the filler neck; make sure not to touch any metal, and note the reading as accessories are turned on, including the starter. If higher voltage is found, determine the source to avoid damage to the cooling system. Cooling system electrolysis is becoming a more frequent problem in today’s cars and should not be overlooked. The primary cause of a radiator’s failure is that they develop leaks or become clogged. Whenever a failure occurs, the radiator must be repaired or replaced. It is common practice to perform an off-vehicle radiator leak test by pressurizing the radiator to 20 psig (138 kPa) and submerging it in a test tank. If you are performing a leak test on an aluminum core radiator, however, do not use a tank that has been used for brass/copper radiators. The flux, acids, and caustic cleaner residue in the tank will attack the aluminum and cause early radiator failure. On-vehicle leak testing of an aluminum radiator is performed in the same manner as for a brass/copper radiator cooling system. Due to the high cost of labor, it is generally less

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expensive to replace a radiator than to have it repaired. Radiator repairs should be attempted only by those with the proper tools, equipment, and knowledge.

Pressure Cap

Concentration

The pressure cap both seals and pressurizes the cooling system. One of the functions of the pressure cap is to allow pressure to build up in the cooling system. It is known that water boils at 2128F (1008C) at sea level atmospheric pressure –14.69 psia (101.3 kPa) (Figure 4-9). As pressure builds up in the cooling system, the boiling point of the coolant also goes up. For each pound of pressure (6.9 kPa), the boiling point of the coolant (water) is increased about 38F (1.78C). For example, if an 8 psig (55.2 kPa) pressure cap were used, the boiling point of coolant would be raised to 2368F (113.38C). This allows the cooling system to be safely run at temperatures far above the boiling point of coolant at atmospheric pressure. This enables the engine to reach operating temperature sooner and adds to the overall efficiency of the engine.

°C

The pressure cap increases the pressure of the cooling system and allows higher operating temperatures.

°F

CONCENTRATION OF ETHYLENE GLYCOL

FIGURE 4-9  The boiling-point temperature of various ethylene glycol/water concentrations is increased by increasing pressure.

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Metal seal Spring Overflow hose

Vacuum valve

Gasket for pressure valve

FIGURE 4-10  Pressure and vacuum valve details of a pressure cap.

The pressure valve is also referred to as the blow-off valve, whereas the vacuum valve may be referred to as the atmospheric valve. Never exceed the Original Equipment Manufacturer (OEM) specifications for a pressure cap.

Today’s vehicle cooling systems are closed systems, with coolant being displaced to or drawn from a recovery tank (as cooling system pressure increases or decreases) connected to the radiator by a hose connected at the radiator filler neck (Figure 4-10). The pressure cap contains an external seal and two spring-loaded valves; the larger valve is called the pressure valve and the smaller one is called the vacuum valve. The pressure valve contains a spring of a predetermined strength, which is indicated by a pressure rating on the top of the cap. This spring holds the valve closed against its seat. As the coolant heats up, it begins to expand, increasing the internal cooling system pressure. When pressure exceeds the rated value (i.e., 15 psig) on the cap, the pressure valve lifts off its seat to relieve excess pressure in order to maintain correct system pressure and to protect the cooling system from overpressurization (Figure 4-11A). The vacuum valve is also held against its seat by a calibrated spring. When the engine is stopped,

FIGURE 4-11  Radiator cap details: (A) pressure operation and (B) vacuum operation.

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the cooling systems cool down, the system pressure begins to drop from a positive pressure to a negative pressure, and a vacuum develops inside the cooling system. At a predetermined point, the vacuum valve opens to draw coolant back out of the expansion tank and into the radiator to equalize internal pressure with atmospheric pressure, thereby preventing the radiator and other cooling system components from collapsing (Figure 4-11B). A vacuum valve that fails to open to release negative pressure in the cooling system may cause system damage. A collapsed upper radiator hose generally notes this condition as the system cools or during heavy acceleration. Components likely to be damaged by a defective vacuum valve are the radiator and heater core tanks, which may collapse, as well as sealing surfaces. Remember that there are three gasket-sealing surfaces that are part of the pressure cap assembly. If the gasket-sealing surface of the pressure valve fails, the system will not become properly pressurized. The outer gasket between the cap top and the radiator neck both seals coolant from leaking out the top of the radiator neck and keeps air from leaking into the system as it cools down. If this seal allows air to leak past during the cool-down process, the coolant in the expansion tank will not be drawn back into the cooling system, and a low coolant level in the cooling system will result. The vacuum valve-sealing surface must also be inspected. Gaskets should be checked for distortion or damage, and the radiator neckmounting surface must be clean and undamaged. If a good seal is not maintained, overheating and coolant loss will result. A pressure cap rated at a higher pressure or a lower pressure than the one designed for the system should not be used. A cap with a higher pressure rating could cause the radiator or other cooling system element to rupture or leak. Using a cap of a lower rated value could cause the engine to overheat to a point that could damage internal components. If in doubt about the proper rating for the replacement cap, check the manufacturer’s specifications and replace with one of equal design and rating. Radiator caps range from 4 psig (27.6 kPa) to 18 psig (241 kPa). Always remove the radiator cap slowly. Removing the radiator cap on a hot cooling system can cause serious burns as steam and coolant escape. Extreme caution should be used when working on closed systems. Most cooling system test kits include adapters for both pressurizing the cooling system and pressure testing the pressure cap. The pressure cap should be tested annually or any time service is performed to the cooling system. It is an inexpensive repair that will avoid costly system failures. If the pressure cap fails the test, it should be replaced with one of equal pressure ratings. It should also be noted that special aluminum caps are required on aluminum radiators.

Due to heat soak, the temperature of the coolant in the engine will increase several degrees a few minutes after the engine is stopped. The heater core is a heat exchanger used to transfer heat from the engine coolant to the air passing through it. It is used in the comfort heating system to heat the passenger compartment. The pressure valve is also referred to as the blow-off valve, whereas the vacuum valve may be referred to as the atmospheric valve. Never exceed the OEM specifications for a pressure cap.

Coolant Recovery System Coolant recovery systems have been standard equipment on most cars since 1969. Coolant expands by about ten percent of its original volume when it reaches operating temperature. There can be air and vapor present in every cooling system that can cause serious problems if not removed. Coolant without air bubbles trapped in it absorbs heat better than coolant with air bubbles. Air is the leading contributor to the formation of rust and corrosion that causes early cooling system component failure as well as increasing the formation of sludge in the system by breaking down the coolant additives. Air that becomes trapped in the cooling system may create an air lock blocking the flow of coolant. This is especially common on systems that have been recently filled after service. This trapped air and vapor can cause pump cavitation, which inhibits the pump’s ability to move the coolant and creates hot spots in the coolant galleys. To eliminate this problem, systems use either a nonpressurized overflow tank or a pressurized expansion tank (Figure 4-12). These systems, when properly maintained, prevent air from entering the cooling system and ensure proper coolant capacity. In addition, many systems today also have a manual air bleed valve, which is often placed on top of the thermostat housing (Figure 4-13).

An overflow tank (or catch tank) is a nonpressurized coolant recovery tank.

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Nonpressurized snap cap

Pressure cap

Cap

Pressure relief cap B

A

Degas bottle

Line may also be routed to engine.

FIGURE 4-12  Nonpressurized (A) and pressurized (B) coolant recovery tanks.

FIGURE 4-13  Manual air bleed on thermostat housing.

Recovery Tank

A nonpressurized recovery tank, usually of ½ to 1 gal. (1.9 to 3.8 L) capacity, is connected to the pressurized cooling system through the overflow fitting at the filler cap. It is used to capture and store vented coolant and vapor from the radiator as it is being heated to operating temperature. Heating causes expansion, and the excess coolant is expelled through the pressure valve of the radiator cap to the recovery tank (Figure 4-14A). When the coolant cools, it retracts, and the vacuum valve of the radiator cap opens, allowing the same vented coolant to be metered back into the cooling system from the recovery tank (Figure 4-14B). Any vapor is vented to the atmosphere and is not returned to the cooling system as long as the proper level of coolant is maintained in the recovery tank. The coolant level of the cooling system is easily determined by noting the coolant level in the recovery tank. It is not necessary to remove the radiator cap to check or add coolant. If a low coolant condition is noted, it should be filled to either the hot or cold mark on the side of the recovery tank, depending on engine temperature (Figure 4-15). Unlike the pressurized system, the cap on the recovery tank can be removed at any time for service. The small hose that connects the recovery tank to the filler neck provisions of the radiator is an important link in the proper performance of the system. Its purpose is to allow coolant to flow back and forth between the recovery tank and the radiator filler neck. If it is clogged or kinked, coolant cannot be transferred from the recovery tank to the radiator. If it is disconnected or leaking, coolant will be lost or ambient air will be drawn into the system. This condition will result in poor performance and early failure of the cooling system. 92 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Radiator pressure cap Spring A

Rubber seal Radiator tank

To recovery tank

Overflow tube Full (hot)

B

Vacuum valve

Full (cold)

To recovery tank

Recovery tank

FIGURE 4-14  Coolant is vented to the recovery tank (A) as internal pressure increases and is returned to the radiator (B) as pressure in the cooling system decreases.

Overflow tube

Atmospheric-type pressure cap

Full hot

Full cold

Overflow tank

FIGURE 4-15  A coolant recovery system tank.

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Expansion Tank

Some manufacturers have addressed the problem of trapped air by using a pressurized ­expansion tank or surge tank placed at the high point in the cooling system to allow air and vapor to rise and be purged out of the cooling system. It is usually mounted on the inner fender (Figure 4-16). It is an integral part of the cooling system and continuously separates and removes air from the system’s coolant. When the engine coolant thermostat is open, coolant flows from the top of the radiator outlet tank through a small hose to the expansion tank. The pressurized system recovery tank should have 17–34 oz. (0.5–1.0 L) of air when the coolant is cold, to allow space for coolant expansion. Unlike the nonpressurized recovery tank, the pressurized expansion tank cap must not be removed for service when the coolant is hot, or serious injury could result. Some expansion tanks on European vehicles use a weighted vacuum relief valve (sometimes referred to as a pressure vent–type cap), which is normally open. The vacuum valve on this style cap hangs freely on the pressure valve and is calibrated with a small weight. Under normal operation, this system operates at atmospheric pressure. If rapid expansion takes place, such as under heavy acceleration, the vacuum valve is closed by the escaping pressure or steam and the pressure valve comes into play. The cap operates in the same way a constant pressure cap operates. As pressure subsides, the weight causes the valve to open, returning the system to atmospheric pressure.

Expansion tank cap

Spring Rubber seal

PRESSURE OPERATION

VACUUM OPERATION FIGURE 4-16  Closed system pressurized coolant recovery/ expansion tank.

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Engine Block and Cylinder Head Coolant Passages Water jackets are a collection of passages molded into the engine block and cylinder heads. The passages of the water jackets in the cylinder block and head(s) are designed to control coolant flow and circulation to provide proper cooling around the hot spots of the engine. The water jackets in the cylinder block completely surround the cylinders to dissipate the heat generated during the combustion process. The cylinder head contains water jackets that surround the combustion chamber and contain passages around the valve seats in order to cool them off (Figure 4-17). If the vehicle overheats and the coolant boils, gas pockets may form in the cylinder block or cylinder head, causing hot spots due to the poor heat transfer characteristics of a gas. In most systems, coolant flows through the water pump to the engine block, around the cylinder wall, and then back to the radiator. The flow then proceeds to the cylinder heads. On the reverse flow cooling system, coolant first flows to the hotter cylinder head and around the valves and combustion chamber, where most of the heat is centralized. The coolant then flows to the less hot engine block and cylinder walls. This process of coolant flow results in more even engine temperatures, reduces wear, and increases horsepower and fuel economy.

Expansion Plugs

Expansion plugs are small steel plugs that are pressed into casting holes located in engine blocks and cylinder heads to produce a watertight seal. The casting holes are the result of the casting process. Expansion plugs that fail are a source of external coolant leaks and need to be inspected for signs of leakage, especially if a system is loosing coolant. Their failure is generally due to corrosion from inadequate maintenance of the cooling system, specifically not flushing the coolant at the recommended intervals.

Coolant Pump Coolant is circulated through the cooling system by a centrifugal impeller–type pump ­(Figure 4-18), which is usually driven by a belt off the engine crankshaft pulley. This pump may turn as fast as 5,000 revolutions per minute and carry coolant as fast as 10,000 gal./h (631 L/min.). At an average road speed, the coolant may be circulated as much as 160 to 170 gal. (605 to 643 L) per minute.

Reverse flow cooling systems first flow coolant through cylinder head(s), then through the engine block for more even heat transfer. Expansion core plugs are also referred to as freeze plugs. Though they may pop out if the coolant freezes, their purpose is not to protect the engine from damage caused by coolant that freezes. A centrifugal impeller–type pump uses rotational force to pull coolant from the center of the pump to the outside coolant passage connected to the engine.

FIGURE 4-17  Cutaway of cylinder head water jackets.

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Bypass

Serpentine pulley hub

Housing

Seal

Impeller

Shaft

Bearings

Drain

Inlet from radiator FIGURE 4-18  Parts of a water pump.

Coolant pumps are generally referred to as water pumps.

Shop Manual Chapter 4, page 105

The bypass redirects coolant away from the thermostat and back to the water pump to enable coolant circulation in the engine block during the warm-up cycle. The thermostat outlet hosing is sometimes referred to as the gooseneck.

The pump consists of a housing with an inlet and outlet, an impeller blade, nonserviceable sealed bearing(s), and seals. The impeller is the internal rotating part of the pump that moves coolant through the cooling system. The impeller consists of a flat plate with a series of flat or curved blades or vanes and is mounted to a shaft that passes through the pump casting. This shaft, which is generally stainless steel to prevent rust, is equipped with one or more sealed bearing assemblies and an internal and external seal to support the shaft. As the impeller rotates, coolant is drawn in from the center and is forced outward to the passage entering the engine block by centrifugal force. A belt pulley is mounted on the shaft end opposite the impeller. On vehicles equipped with an engine-mounted cooling fan, the fan is also attached. A defective coolant pump is not generally rebuilt because of the special tools required and is replaced as an assembly. Some vehicles may have a coolant pump that is driven by the timing belt (Figure 4-19). This coolant pump is generally replaced when the timing belt is serviced as preven-tative maintenance to avoid a future repair because most timing belts are serviced at 90,000 miles and the pump has been in service for millions of rotations (Figure 4-20). On most engines, the coolant pump inlet is connected to the bottom of the radiator with a rubber hose. This hose is preformed to fit a particular year and model engine, and it generally contains a spiral wire to prevent it from collapsing due to the suction action of the coolant pump impeller when the engine is revved up. The coolant pump outlet is through passages behind the impeller, which pushes the coolant through the engine block. After the coolant has passed through the engine block, it is returned to the radiator through the thermostat housing and upper radiator hose. A centrifugal water pump is a variable-displacement pump. Restricting the flow of coolant does not harm the pump. When the thermostat is closed, restricting coolant flow, coolant circulates through the engine via a bypass passage below the thermostat leading from the engine block to the water pump. When the thermostat is open, coolant flow is through the cooling system. The most frequent cause of coolant pump failure is leaks, which are often the result of bearing failure. Industry studies have linked these leaks and bearing failures to improper

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Water pump

Timing belt

Timing belt tensioner FIGURE 4-19  A typical timing-belt-driven water pump.

O-ring Water pump

Drive pulley (cog belt) from crankshaft FIGURE 4-20  Details of a typical timing-belt-driven water pump.

cooling system maintenance and service as antifreeze additives are depleted or contaminated. We will discuss proper service under the antifreeze section.

Auxiliary Water Pump Hybrid Electric Engine

On hybrid electric vehicles that use a coolant-based heater core, an auxiliary electric water pump may be required when the internal combustion engine is not running, to provide stable heater performance even if the engine is stopped. During normal engine operation, the electric water pump does not operate. Some early designs incorporated a bypass valve that would open when the engine water pump was operating to minimize the resistance to coolant flow (Figure 4-21). Later designs discontinued the bypass valve as new pump designs minimized water flow resistance. In addition to an electric coolant circulation pump, Toyota hybrid platforms utilize a large vacuum-insulated coolant heat storage tank that recovers and stores hot coolant generated from the engine. This hot coolant is stored at 1768F for up to 3 days and is used to preheat the engine on cold engine start-up to lower engine HC emissions, as well as to supply heat to the 97 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

WATER PUMP COOLANT FLOW

By-pass valve Water pump OFF (Engine ON)

Water pump ON (Engine OFF)

FIGURE 4-21  A hybrid electric vehicle requires an electric water pump to keep coolant circulating through the heater core when the engine is not running.

Engine coolant temperature sensor

To heater core Water pump for heat storage

Heat storage tank

Coolant flow control valve Coolant temperature sensor COOLANT HEAT STORAGE TANK FIGURE 4-22  A hybrid electric vehicle hot coolant storage tank and water pump.

heater core (Figure 4-22). When a cold engine is started, the auxiliary electric coolant pump is energized to circulate this hot coolant. Rotary Water Valve on Hybrid Electric Engine.  An electric rotary control valve is used on some hybrid electric platforms to control the flow of hot coolant throughout the cooling system. The control valve can switch between three positions to control the flow of coolant to and from the coolant heat storage tank (Figure 4-23). During the preheat cycle, the water control valve directs the stored heated coolant to the engine cylinder head prior to engine start-up (Figure 4-24). After the engine has started and is in the warm-up cycle, the water control valve directs coolant through the heater core and then back to the engine (Figure 4-25). Once the engine has reached operating temperature, the water control valve allows heated coolant leaving the engine to flow to both the heater core and the coolant heat storage tank so 98 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Coolant heat storage tank Motor

Heater core Engine FIGURE 4-23  A hybrid electric vehicle rotary water control value.

Heater core

Coolant heat storage tank

Water valve Temp. sensor Engine water pump

Cylinder head

Temp. sensor

Cylinder block

ON Water pump Radiator PREHEAT

FIGURE 4-24  A hybrid electric vehicle engine coolant storage system during preheat operation.

Heater core

Coolant heat storage tank

Water valve

Temp. sensor Engine water pump

Cylinder head

Temp. sensor

Cylinder block

OFF Water pump Radiator ENGINE WARM-UP

FIGURE 4-25  Hybrid electric vehicle engine coolant storage system during engine warm-up operation.

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Coolant heat storage tank

Heater core

Water valve Temp. sensor Engine water pump

Cylinder head

Temp. sensor

Cylinder block

OFF Water pump Radiator STORAGE - DRIVING

FIGURE 4-26  Hybrid electric vehicle engine coolant storage system while engine is running and while driving vehicle.

Heater core

Coolant heat storage tank

Water valve Temp. sensor Engine water pump

Cylinder head

Temp. sensor

Cylinder block

OFF Water pump Radiator Storage-Power Off

FIGURE 4-27  Hybrid electric vehicle engine coolant storage system with the engine off.

that hot coolant will be available during the next preheat cycle (Figure 4-26). After the engine is shut down, the water control valve isolates the coolant heat storage tank so that coolant will not flow to or from it (Figure 4-27).

Fan Shrouds, Air Baffles, and Seals Air deflectors are commonly damaged by curb impacts. If damaged, they should be repaired or replaced, not discarded.

Airflow can make up to a 30 percent difference in cooling system capacity. There are several air deflectors used in the cooling system to improve overall cooling and air conditioner condenser performance. These include fan shrouds, deflectors, air baffles, and air seals. The radiator fan shroud directs all the air handled by the fan through the radiator, thereby improving the efficiency of the fan. Air deflectors are installed under the vehicle to redirect airflow through the radiator to increase flow. Air baffles are also used to direct airflow through the radiator. Air seals, which are mounted to seal the hood to the body, prevent air from bypassing the

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radiator and air conditioning condenser. In addition, the air seals help to prevent recirculation of air from under the hood to improve hot weather cooling.

Thermostat The thermostat is the automatic temperature control component that controls coolant flow in the cooling system and is necessary for efficient engine operation, improving both performance and economy. The primary purpose of the thermostat is to ensure that the minimum operating temperature of the engine is reached as soon as possible. This improves fuel economy and vehicle emissions, as well as preventing the formation of sludge in the engine crankcase. The water pump begins to circulate the coolant the moment the engine is started. The thermostat restricts the circulation of coolant from entering the radiator until the engine has warmed up in order to provide hot coolant to the heater core and improve passenger comfort during the warm-up cycle. This is particularly important for cars driven only a short distance. When the thermostat is closed, a bypass passage in the water pump or coolant passage allows coolant to circulate through the engine. The thermostat also provides a restriction in the cooling system both before and after it has opened. The purpose of this restriction is to provide a pressure difference for the water pump in order to prevent pump cavitation, and it aids in forcing the coolant through the passages in the engine block. Under no circumstances should the thermostat be left out of the system. The rating of the thermostat is the temperature at which it is designed to begin to open and is usually stamped on the thermostat body. Different engines use thermostats with different temperature ratings, though the most common rating today is 1958F (918C). Engines are designed to operate at a minimum coolant temperature of 1408F to 1958F (608C to 918C). When coolant temperature is below its rated value, the thermostat remains closed. Engine coolant temperature is sensed by a temperature-sensitive element within the thermostat. This causes the normally closed (nc) thermostat to open at a predetermined rating. A typical 1958F (918C) thermostat will start to open at this rated temperature and will be fully open at 2208F (1058C). This restricts initial circulation to allow for proper engine warm-up. A thermostat’s opening and closing are gradual as the temperature of the coolant increases or decreases (Figure 4-28). While the thermostat is closed, coolant flows through the bypass passage in the water jackets. For example, if a thermostat rated at 1958F (918C) is used, the coolant will not circulate through the cooling system and the radiator until the engine coolant has reached this temperature, and circulation to the radiator will increase as the temperature of the coolant rises. The purpose of a thermostat, then, is to protect against engine overcooling.

To radiator

To radiator

Bypass

A

Overcooling is a condition where the engine never reaches operating temperature due to a thermostat that is opening before the engine reaches operating temperature. Overcooling can also occur if the thermostat has failed in the open position or if it has been removed from the system.

Bypass

From engine

B

From engine

FIGURE 4-28  A thermostat opening (A) and closing (B).

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A thermostat usually starts to open at its rated value and is fully open with a 258F (148C) temperature rise.

Shop Manual Chapter 4, page 108

The engine should take between 5 and 15 minutes to warm up, depending on ambient air temperature. If the engine requires long warm-ups or if the engine always runs hot, you may need to remove and test the thermostat operation by suspending it in a water bath and heating the water to boiling. You will need to note the temperature at which the thermostat begins to open and the temperature at which the thermostat is fully open and compare this to its rated value. Unless it is defective, a thermostat will not cause overheating. A thermostat rated at 1808F (828C) is wide open at 2058F (968C), and full coolant flow is provided through the cooling system. A thermostat rated at 1958F (918C) is wide open at 2208F (1058C), and full coolant flow is provided through the cooling system. The 1958F (918C) thermostat provides neither more nor less coolant flow than the 1808F (828C) thermostat, but it does change the operating temperature of the engine and the amount of heat the passenger compartment heater can produce. Refer to Chapter 4 of the Shop Manual for additional information on both overcooling and overheating conditions and the manufacturer service information. The cooling system thermostat (Figure 4-29) is located between the engine and the radiator. It is housed at the outlet of the engine coolant passage under a return hose flange called a thermostat housing and, in most cases, is bolted onto the cylinder head or intake manifold. There is a gasket or O-ring seal between the thermostat housing and mounting surface that must be torqued to specifications to avoid leaks. Thermostats may have either a bleed notch or a jiggle pin that is designed to let trapped air out of the system after refilling in order to eliminate hot spots in the coolant passages during engine warm-up. Many closed cooling systems today require air pockets to be bled out of the system after servicing, using a bleed-off valve for air that may be part of the thermostat housing; see Figure 4-13. Some manufacturers have chosen to locate the thermostat at the engine inlet. This reduces the risk of thermal shock that may result as cold coolant enters the engine block when the thermostat opens. Inlet thermostats slowly bleed cold coolant into the engine until the entire cooling system comes up to operating temperature. Thermostat Engine Hot Fan

Water pump

Radiator

Water jackets Warm FIGURE 4-29  Location of thermostat in typical cooling system.

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Six important facts regarding thermostats should be noted. 1. Thermostats are a design component of the engine cooling system and should not be omitted. 2. The design temperature of a thermostat should not be altered. 3. A thermostat will cause engine overheating if stuck closed. 4. A thermostat will cause engine overcooling if stuck open. 5. A vehicle may fail an emissions test due to an improperly functioning thermostat. 6. An improperly functioning thermostat will affect passenger compartment heater efficiency.

Thermostats are a design consideration of the cooling system and should not be permanently removed or changed to one of a different rating.

Solid Expansion Thermostat

The solid expansion thermostat (Figure 4-30) is a heat motor that utilizes a thermally responsive wax pellet sealed in a heat-conducting copper cup containing a flexible rubber diaphragm and piston. This is by far the most popular style thermostat used today. Heat causes expansion of the now liquid wax compound, exerting pressure on the diaphragm and pushing a stainless steel piston plunger up to open a valve. As the element cools, the compound contracts, and a spring is allowed to push the thermostat valve closed. There are currently three popular variations of the solid expansion type; the balanced sleeve, the reverse poppet, and the three-way thermostat (Figure 4-31). These styles function similarly but with some design differences. The balanced-sleeve thermostat allows pressurized coolant to flow around all of its moving parts, whereas the reverse-flow thermostat opens against the direction of coolant flow and water pump pressure. In this manner, it is able to use water pump pressure to hold it closed when it is cool. The reverse-poppet thermostat is engineered with a self-cleaning, self-aligning stainless steel valve and offers improved coolant flow. The three-way thermostat has a bypass passage located directly below it. When the engine is cold, the thermostat restricts flow to the radiator and allows coolant to flow through the bypass passage. As the thermostat opens, allowing coolant to flow to the radiator, it also closes off the bypass passage. Corrosion and age will cause a calibration change in this type of thermostat. If the thermostat is found to be defective or inoperative, a new one of equal design and rating should be installed.

Vent open

Vent closed

Case end rest in coolant

Wax pellet Rubber diaphragm

The solid expansion thermostat is also known as the “pellet” type, so called because of the wax pellet used.

Case and valve assembly are forced down, causing the valve to open

Wax pellet Rubber diaphragm

FIGURE 4-30  A typical solid expansion thermostat, as wax pellet melts it exerts pressure in the capsule pushing value rod out of the pellet.

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To radiator

Thermostat (closed) Bypass (open)

Thermostat (open) Bypass (closed)

COLD

HOT

Pump

Pump

FIGURE 4-31  Three-way thermostat.

Electronic Thermostat

Air mass (kg/h) 90°C

Nominal temperature (°C)

Nominal temperature (°C)

The development of the electronically controlled cooling system (ECCS) was to enable the control module to set the operating temperature of the engine to a specified value based on engine load. The optimal operating temperature is determined by a “mapping” program in the power train control module (Figure 4-32). Engine cooling temperature is adapted to the engine’s overall performance and load state by heating the thermostat electronically and adjusting the radiator fan speed settings. The advantages of adjusting coolant temperature to current operating demands of the engine are lower fuel consumption, reduced emissions, and longer engine life. Differences to the conventional cooling system may include thermostat and coolant distributor housing that may be integrated into a single module (Figure 4-33). The thermostat no longer needs to be near or on the cylinder head. The electronic thermostat contains a resistive heating element embedded in the wax pellet (Figure 4-34) that heats the wax pellet to regulate the opening and closing of the thermostat if temperature mapping requires a lower

85°C

v (km/h)

n (1/min)

t (°C)

FIGURE 4-32  An example of a typical electronic thermostat mapping program analysis of optimum engine coolant temperature based on various inputs.

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Coolant temperature sensor Feed to cooler

To heat exchanger

Return from cooler

To gearing oil cooler

Heating thermostat connection To coolant pump

Coolant control unit

From heat exchanger Oil cooler line Coolant feed from engine from the upper level of the coolant distributor unit

Coolant return pipe from radiator closed

No-flow zone of coolant

From heater head exchanger

From oil radiator

From radiator To coolant pump

FIGURE 4-33  A typical electronically controlled cooling system housing containing electronic thermostat.

Pressure springs for closing of coolant channels Resistance heating element Expansion material thermostat (with wax element) FIGURE 4-34  A typical electronic thermostat.

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coolant temperature. Or if engine coolant temperature is high, coolant temperature alone can cause the wax pellet to liquefy and expand causing the thermostat to open just as it did on a conventional thermostat but at a much higher temperature than a conventional thermostat. The melting temperature of the wax pellet is 2308F (1108C) compared to a conventional thermostat where the wax pellets began melting at 1958F (908C). Think of it as a standard thermostat with a heater. Optimum engine performance is dependent on proper engine temperature for a given engine demand. An example of this in an electronically controlled cooling system is the partthrottle optimum temperature range of 2038F to 2308F (958C to 1108C) and in the full-throttle optimum temperature range of 1858F to 2038F (858C to 958C) depending on load and engine speed as an example. A higher temperature in the part-throttle range improves fuel economy and lowers emissions by improving engine efficiency. A lower coolant temperature at full throttle increases engine power output boosting performance. While maintaining these temperature variations on a conventional cooling system precisely was not possible, it is achievable on an ECCS (Figure 4-35). One of the effects of this style of engine temperature regulation is a fluctuation of coolant temperature between 2308F (1108C) and 1858F (858C) when driven between part throttle and full throttle, which in turn would affect heater core temperature. A 458F (258C) coolant temperature fluctuation would make the passenger compartment uncomfortable when heating mode is selected and the driver would be constantly readjusting the temperature range selected. To avoid broad temperature fluctuation the electronic control module monitors the passenger compartment temperature control selector. Based on the temperature selected and the actual temperature of the engine coolant the control module will regulate coolant flow to the heater core by regulating flow with the heater core control valve which is either vacuum or electronically activated (Figure 4-36).

Bimetallic Thermostat

The bimetallic thermostat (Figure 4-37) uses a bimetallic strip of two dissimilar metals fused together to form a coil. One metal expands faster than the other when heated, causing the coil to unwind and opening a butterfly valve. Again, corrosion and age will cause a calibration change in this type of thermostat. It must be replaced if found to be defective or inoperative.

Bellows-Type Thermostat

The bellows-type thermostat (Figure 4-38) is made up of a thin metal bellows assembly filled with a low-boiling point fluid, usually alcohol, and is sealed under a vacuum. They were popular before the advent of the pressurized cooling system. When increased coolant temperature causes the fluid to boil, the bellows expands. This expansion opens the thermostat, allowing engine coolant to circulate through the cooling system. As the volatile fluid cools, the bellows retracts, restricting the flow of engine coolant. The pressurized cooling system made this style obsolete. Pressure in the cooling system would prevent the bellows from opening at the correct temperature.

Thermostat Service Thermostats generally fail in the closed position.

Thermostats fail and can cause excessive engine wear and waste fuel. If failure occurs while the thermostat is in the closed position, severe engine overheating will result. An extremely hot engine and a cool-to-warm radiator may be noted. If failure occurs while the thermostat is in the open position, a longer than normal warm-up period may be noted by the temperature gauge, or poor passenger compartment heating may be noted. Often a thermostat that is stuck open will go undetected in warmer months, but lack of heater performance reveals this condition during cooler months.

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Actuator

(Thermostat for mapped engine cooling) F265

Engine speed sender G23

Simos 3.3 J361 control unit

Air-mass flow meter G70 with intake air temperature sender G 42

CAN

Coolant temperature sender G62

Radiator fan control unit J293

Radiator fan V7

Diagnostic connection Radiator outlet coolant temperature sender G83

Radiator fan-2-V177

Potentiometer for rotary temperature selection knob G267

Road speed signal from ABS control unit J104 Control cut-off valve two-way valve N147

Temperature flap position switch F269

Input signal

Output signal

Communications

Bidirectional

FIGURE 4-35  An example of a typical electronic thermostat system.

It should be noted that a defective thermostat could have an adverse effect on the computer’s engine control system. A thermostat that is stuck open or opens prematurely may cause the closed-loop status to be delayed, resulting in erratic or fast idle and/or richer than normal fuel conditions which may result in an engine service indicator light illuminating. It is therefore important that the engine coolant thermostat be replaced with the correct temperature range thermostat if it is found to be defective. Thermostats should also be replaced as part of any cooling system repair service.

Shop Manual Chapter 4, page 109

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Battery

Battery

Ign.

Fuel pump relay

Ign.

Potentiometer

Ign. Flap switch

Power supply relay

Thermostat Diagnostic connection ABS

Air mass meter

Electronic control module

Control unit for radiator fan

Radiator fan

Radiator fan 2 M

M

Engine speed sender

Positive

Output signal

Ground

Coolant temperature sender

Radiator outlet sender

Input signal

Bidirectional

FIGURE 4-36  An example of a typical electronic thermostat wiring diagram.

Author’s Note: If a vehicle comes into your shop overheating, do not add ­coolant or water to the system until it has completely cooled down. The c­ ool-down process is necessary to avoid thermal shock to the engine and cooling system components. Thermal shock could cause components to crack and gaskets to fail, making a bad situation worse.

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This end towards radiator

Valve Bimetal spring FIGURE 4-37  A typical bimetal thermostat.

This end towards radiator

Valve

Fluid filled bellows expands as heated. FIGURE 4-38  A typical bellows-type thermostat.

Pulley and Belt Two types of belt systems are used to drive the air conditioning compressor and many water pumps, as well as other accessories: the serpentine belt (Figure 4-39) and the V belt ­(Figure 4-40). The serpentine belt system is found on most late model vehicles. This is often a single-belt system whereby one belt drives all the accessories (Figure 4-41). Serpentine belts may be constructed of either neoprene or ethylene propylene diene M-class rubber more commonly called EPDM. Today most belts are constructed of EPDM, but vehicles produced prior to 2001 or inexpensive aftermarket replacement belts may still be made of neoprene. Visually it is difficult to tell the two materials apart. Older neoprene belts were designed to last between 50,000–60,000 miles and often showed signs of wear by that time. EPDM belts are designed to last 80,000–100,000 miles and seldom show signs of outward visual wear unless there is a problem. The EPDM belt is more elastic than a standard neoprene belt and resists cracking even at higher mileage. A better indicator of when to replace EPDM belts is rib wear. Belts are designed to have clearance between the rib peaks and the pulley grooves. All belts are exposed to dirt, grit, rocks, road salt, and water. Over time

Shop Manual Chapter 4, page 110

There are several different sizes of both types of belts.

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Cross section Cross section

FIGURE 4-39  A typical serpentine belt.

FIGURE 4-40  A typical V belt.

Alternator pulley

AC compressor pulley

Tensioner

Water pump pulley Power steering pump pulley n

tio

ota lt r

Air pump pulley

Be

Crankshaft pulley FIGURE 4-41  A serpentine belt drive system.

these contaminants cause the EPDM belt to gradually lose material on the ribbing similar to the way a tire wears out causing the belt to ride deeper in the grooves. A 5–10 percent loss of material is enough to cause belt slippage, overheating, and hydroplaning. Hydroplaning occurs when the belt ribs sit deeper in the pulley grooves due to wear and there is not enough room for water to escape. Instead, the water is trapped between the belt ribs and the pulley grooves lifting the belt away from the pulley and causing slippage. A slipping serpentine belt can cause check engine lights associated with misfire codes, air conditioning compressor codes, reduced alternator output, reduced engine cooling, and poor air conditioning performance to name a few. Belts should be checked for wear beginning at 50,000 miles. See Chapter 4 in the Shop Manual for further detail on diagnosing both neoprene and EDPM belts and how to measure for belt grove wear. It is wise to replace the drive belt when any pulley-driven component is replaced. Another change that has occurred in belts is the use of stretch fit belts that self t­ ension on the drive pulleys. They do not require any mechanical adjustment and are used in limited applications such as a single drive belt for an air conditioning compressor. As the name implies, 110 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

they contain an elastomeric material and with the use of a special tool they are stretched on to the pulley system, there is no mechanical means to loosen or tighten the belt and as with the standard EPDM belt they are designed to last 80,000–100,000 miles. The pitch and width of belts in the V belt system are important in that they must match those of the drive (engine crank shaft) and driven (engine accessories) pulleys (Figure 4-42). If the compressor and alternator are driven with two V belts, they should be replaced as a pair with a matched set. This is true even though only one of the pair may appear to be damaged. Belts should be tensioned in foot-pounds (ft.-lb.) or Newton meters (N ⋅ m), according to manufactures’ specifications. It is recommended that the belt be retensioned after a “run-in” period of a few hundred miles (kilometers) to ensure proper belt tensioning. Belts must be replaced with exact duplicates. Their length, width, and groove characteristics are important to ensure proper fit and alignment. Manual belt tension should be set to ½ inch deflection per 12 inches of distance spanned between pulleys. The serpentine system may have a spring-loaded idler pulley used as a belt tensioner. It is therefore not necessary to manually tension this type of belt tension system. If the belt will not remain tight, the tensioner must be replaced. It should be noted that some coolant pump pulleys turn in the opposite direction from others (Figure 4-43). Therefore, it is possible that the same engine in two different vehicles

A

B

C

The pitch of a belt is the degree or slope of the V shape of the belt.

D

FIGURE 4-42  The belt should fit the pulley snugly, as shown in A and D. The belt in pulley B is too narrow and has an improper pitch. The belt in pulley C (exaggerated) is too wide and has an improper pitch.

FIGURE 4-43  Some coolant pumps turn in opposite directions.

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with either different drive belt styles (V belt versus serpentine belt) or belt routing due to bolton belt-driven accessories (one system with A/C and one without) will require two different water pumps and two different mechanical cooling fans. Water pump rotation may be either clockwise or counterclockwise based on drive belt routing.

Fans The fan is used in the cooling system to increase airflow across the radiator in order to improve the efficiency of the cooling system. Engine coolant fans are essential for idle and low-speed driving to pull sufficient air through the condenser, radiator, and the engine to affect adequate cooling. At road speeds, ram air is sufficient for this purpose. To satisfy the needs for low-speed cooling and to reduce the engine load at high speed, a fan clutch or flexible fan is often used. An electric fan, which replaces the coolant pump-mounted fan, is found on most late-model vehicles.

Engine-Mounted Fan

Shop Manual Chapter 4, page 119

The engine-driven cooling fan is mounted onto the water pump shaft in front of the pulley (Figure 4-44). Five- or six-blade fans (Figure 4-45) are found on air conditioned vehicles, and four-blade fans are found on vehicles without air conditioning. Fans are made of steel, nylon, fiberglass, or a combination of materials. They are precisely balanced to prevent noise, vibration, coolant pump bearing failure, and seal damage. It must be noted that engine-driven fans are designed to turn either clockwise or counterclockwise, depending on pulley rotation. For proper airflow, it is important that the replacement fan be suitable for the design. An improper fan will result in little (or no) air circulation and will cause engine overheating.

Rigid leading edge Flexible trailing edge Water pump pulley Spacer

Flex fan assembly 0 RPM FIGURE 4-44  A typical engine-mounted cooling fan.

2,500 RPM

FIGURE 4-45  As engine speed increases, the pitch of the blade decreases, and this reduces load on the engine.

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Declutching Fan.  The declutching fan is used on some rear-wheel-drive vehicles with air conditioning and consists of a fan blade assembly attached to a special clutch. The clutch is attached to the water pump shaft. There are two types of fan clutches: one that is sensitive to engine speed, known as a centrifugal clutch, and one that is sensitive to temperature, often referred to as a thermostatic clutch, which is designed with an internal bimetallic control valve. Either type of fan clutch uses a silicone fluid to engage and disengage the fan blades (Figure 4-46). Either method causes the clutch to be sensitive to engine speed and under-the-hood temperature. The declutching fan is used as a method of solving a problem of increased air needs at low speed and, at the same time, of eliminating air noise problems during high speed. A smaller fan pulley allows for higher fan speed at low engine speed and at the same time provides for increased coolant circulation. The increased air and coolant flow is important when the forward motion of the automobile is not sufficient to produce a strong ram air effect. The centrifugal clutch is engaged at low engine speed and disengaged at high engine speed. As engine speed is increased, the fluid coupling of the fan clutch increases until the fan reaches its maximum speed. The fan clutch allows the fan to turn at coolant pump speeds up to about 800 rpm. Thereafter, there is slippage that limits the fan speed to between 1,100–1,350 rpm when the engine is cold and between 1,500–1,750 rpm when the engine is hot. The maximum speed of the fan is limited to about 2,000 rpm regardless of engine speed. At maximum speed, the fan will not turn any faster, regardless of how much the engine speed is increased. The thermostatic clutch has a fluid coupling partially filled with silicone oil. When the temperature is above 1608F (718C), a bimetal coil spring uncoils or expands. As it expands, it allows additional oil to enter the fluid coupling, causing less slippage and enabling the fan to turn at about the same speed as the coolant pump, up to a maximum of about 2,000 rpm. Minimum fan speed should be between 1,500–2,000 rpm. When the under-hood temperature is below about 1608F (718C), the opposite will occur; the bimetal coil contracts and fluid is bled off the fluid coupling, causing increased slippage and slowing the fan speed. It now turns at less than coolant-pump speed. Slower fan speeds when additional cooling is not required save fuel, lower engine noise, and increase engine power.

Shop Manual Chapter 4, page 120

A fan clutch limits the terminal (top) speed of the fan.

Working chamber

Silicone oil

Shaft

Clutch plate

Fan hub FIGURE 4-46  Sectional view of a fluid-coupled declutching fan clutch.

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The coolant pump pulley generally turns faster than the crankshaft pulley. The ratio varies from vehicle model to model. For example, if the ratio is determined to be 1.25:1, the coolant pump will turn 1,000 rpm at an engine speed of 800 rpm. Failure of a fan clutch is usually due to lockup of the clutch or a leak of the silicone fluid, which allows “free-wheeling” of the fan blade. A lockup is generally noted by excessive noise when the engine is revved up and may reduce engine power due to increased drag on the engine. It should be noted, however, that some noise is to be expected during initial cold engine start-up. A fluid leak is most noticeable by a tacky residue substance at the shaft area of the clutch bearing. It is possible for a neglected fan clutch assembly to become detached from the shaft and cause serious damage to the radiator. Also, a defective fan clutch can cause vibrations in the coolant pump shaft, leading to its early failure. The fan clutch is not repairable and, if found to be defective, must be replaced. Many technicians are injured each year by defective fans. Fan blades have been known to come off the hub assembly. Before working under the hood of a vehicle, particularly if looking to locate a noise problem, inspect the fan assembly before starting the engine. Check for loose, bent, or damaged blades.

The power train control module (PCM) is the microprocessor (computer) that monitors input sensors related to engine and transmission operation, interprets this data, and sends commands to output devices.

Electronically Controlled Viscous Cooling Fan.  The electronically controlled viscous cooling fan (Figure 4-47) is similar in operation to the standard declutching fan but its operation is controlled by the power train control module (PCM). Several advantages to this system are reduced noise, improved air conditioning performance during idle and city traffic, reduced air conditioning compressor failures because of lower A/C system pressure at low speeds, and improved fuel economy. The electro-viscous (EV) cooling fan design allows for infinitely variable regulation by means of sensors. The regulation process uses data from engine coolant temperature, oil temperature, air charge temperature, engine speed, ignition timing, and air conditioning load. This allows for demand controlled cooling which will lower noise levels, improve coolant temperature for a given load, and reduce fuel consumption. The silicone oil circulation between the supply chamber and the working chamber affects the fan speed (Figure 4-48). The more silicone oil that is allowed into the working chamber, the higher the fan speed and when the working chamber is empty, the fan is in idle mode ­(Figure 4-49). There is approximately a five percent slippage rate when fully engaged. But instead of using a bimetallic spring to control oil flow the valve is operated by an electrical solenoid. This solenoid is pulse-width-modulated (PWM) signal from the power train control

FIGURE 4-47  A typical electro-viscous cooling fan is most easily identified by the addition of an electrical connector.

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Connector

Return bore hole

Speed sensor Oil circuit

Primary disk

Bearing

Valve lever

Magnetic field

Silicone oil supply tank Electromagnet Housing FIGURE 4-48  A typically electronically controlled cooling system housing containing electronic thermostat.

Solenoid and hall effect sensor

Valve in open position

Fluid coupling

Valve in closed position

Input shaft

FIGURE 4-49  Electronic viscous fan clutch operation in the disengaged and engaged mode.

module (PCM). The EV fan is fully engaged at 100 percent duty cycle and is disengaged at 0 percent duty cycle. To determine duty cycle, the control module uses information from: ■■ Engine coolant sensor ■■ Ambient air temperature sensor ■■ Vehicle speed sensor ■■ Air conditioning-system pressure sensors ■■ Electro-viscous fan Hall Effect sensor ■■ Transmission oil temperature sensor The Hall Effect sensor provides the control module with fan speed information, every 1 rpm of actual fan speed is represented by a 1 Hz signal from the Hall Effect sensor. The

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Pitch

Pitch

Engine

A

Water pump

Engine

B

Water pump

FIGURE 4-50  Extreme pitch at low speed (A); reduced pitch at high speed (B).

control module is able to determine if the fan is functioning correctly by comparing the actual fan speed to the desire fan speed. If a fault is determined, a DTC will be set. The 100 percent duty cycle mode is commanded only if: ■■ The temperature of the engine coolant exceeds 2648F (1298C). ■■ The temperature of the transmission oil exceeds 3048F (1518C). ■■ The air conditioning refrigerant pressure exceeds 240 psi (1655 kPa). ■■ A DTC is set and the control module determines that as a fail-safe the coolant fan should be engaged. Under all other conditions, the fan duty cycle will be less than 100 percent. The EV fan operation may be tested with an enhanced scan tool which can be used to command the fan on/off in 10 percent increments. The engine speed should be maintained at 2,000 rpm to ensure that there is enough fluid movement to fully engage and disengage the coupling. Flexible Fans.  Flexible, or flex, fans (Figure 4-50) have blades that are made of a material (metal, plastic, fiberglass, or nylon) that will flex, or change pitch, based on engine speed. As engine speed increases, the pitch of the blade decreases. The extreme pitch at low speeds provides maximum airflow to cool the engine and coolant. At higher engine speeds, the vehicle is moving faster and the need for forced air is provided by ram air provided by the forward motion of the vehicle. The flex blades feather reducing pitch, which in turn saves engine power and reduces the noise level.

Electric Fans

Most late-model vehicles use one or more electric-driven coolant fan motors (Figure 4-51) that are often controlled by the PCM, which have replaced the belt-driven fans. The electric motor and fan assembly are generally mounted to the radiator shroud (Figure 4-52) and are not connected mechanically or physically to the engine coolant pump. Either or both of the following two input methods electronically controls the 12V motor-driven fan: ■■ Engine coolant temperature switch (thermostat) or sensor ■■ Air conditioner select switch There are many variations of electric cooling fan operation. Some provide a cool-down period whereby the fan continues to operate after the engine has been stopped even with the ignition switch in the OFF position. The fan stops only when the engine coolant temperature falls to a predetermined safe value, usually 2108F (998C). In addition, some air conditioned 116 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Radiator support (upper) Front

Front cross member

Electric motor

FIGURE 4-51  An electrically-driven engine cooling fan.

FIGURE 4-52  A typical electric cooling fan and radiator shroud assembly.

vehicles will have two electric cooling fans working independently of each other, depending on temperature conditions. Because of the many variations of electric fan systems, manufacturers’ specifications must be consulted for troubleshooting and repairing any particular year and model vehicle. For example, the computerized engine management system also often plays an important part in controlling the electrically operated engine-cooling fan, and in many systems, the PCM determines when to energize the fan relay control coil. Electric cooling fans may start without warning, even with the ignition in the OFF position. Many technicians are injured each year by defective fans. There are several methods of controlling fan operation. In the wiring schematic in ­Figure 4-53, the fan is controlled by both a coolant temperature sensor and the air conditioner selection switch. The cooling fan motor is connected to the 12V battery supply through a normally open set of contacts (points) in the cooling fan relay. A fusible link provides protection for this circuit. During normal operation, with the air conditioner off and the engine coolant below a predetermined temperature of approximately 2158F (1028C), the relay contacts are open and the fan motor does not operate. If the coolant temperature exceeds approximately 2308F (1108C), the engine coolant temperature switch will close (Figure 4-54) to energize the fan relay coil. This action, in turn, will create an electromagnet to close the relay contact, assuming that the ignition switch is in the run position.

Shop Manual Chapter 4, page 120

The temperature of the coolant in the engine will increase several degrees a few minutes after the engine is stopped. Dual fan systems often operate independently of each other; either or both may start without warning.

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12-V Batt

F/L

Thermostat*

12-V Ign Fan motor Fuse

Fan relay Selector switch

Norm Max Off

* (Thermostat) engine coolant temperature switch

Bi-level Vent Heat Def

FIGURE 4-53  A typical cooling fan schematic.

12-V Batt

F/L

Thermostat*

12-V Ign Fan motor Fuse

Fan relay Selector switch

* (Thermostat) engine coolant temperature switch

Norm Max Off

Bi-level Vent Heat Def

FIGURE 4-54  The cooling fan switch closes at a predetermined high temperature.

The 12V supply for the relay coil circuit is independent of the 12V supply for the fan motor circuit. The coil circuit is from the run terminal of the ignition switch, through a fuse in the fuse panel, and to ground through the relay coil control device. In some systems, if the air conditioner select switch is turned to any cool position ­(Figure 4-55), regardless of engine coolant temperature, a circuit will be completed through the relay coil to ground (–) through the selection switch. This action closes the relay contacts to provide 12 volts to the fan motor. The fan then operates as long as both the air conditioner and ignition switches are on. In other systems, the fan does not start when the air conditioner select switch is turned on unless the air-conditioning system high-side pressure is above a predetermined high pressure value. Although, if the air conditioning high-side pressure level is below the predetermined pressure but the engine coolant temperature is above a predetermined level, usually 2308F (1108C), the cooling fan will still come on. Many fan control systems are ultimately controlled by the PCM, which supplies a ground path to the fan relay coil if it is determined that the fan operation is required. There are several 118 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Norm

Selector switch

Max Off

Bi-level Vent Heat Def

FIGURE 4-55  The cooling fan will run if the A/C switch is turned to any COOL position.

inputs that the PCM may look at in order to determine the need to engage the fan. These inputs include, but are not limited to, the following: ■■ Coolant temperature sensor ■■ Air conditioning selection switch ■■ Air conditioning high pressure switch ■■ Vehicle speed Some PCM systems also have the ability to vary the fan speed based on cooling requirements. This is usually accomplished through an arrangement of relays arranged in a series/parallel configuration (Figure 4-56), allowing the fan(s) to be operated at low or high speeds.

Hot in run and start

Hot at all times Fan #1 Fuse 49 30A

Fan #32 Fuse 46 30A

Cooling fan #2 relay 43

Cooling fan #1 relay 45 M

Fan #3 Fuse 14 10A

Cooling fan #3 relay 44

Left cooling fan

PCM C2 C1

33 Fan control (HI) 42 Fan control (LO)

M

Right cooling fan

FIGURE 4-56  Wiring diagram of multi-relay fan control.

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Hoses And Clamps

Shop Manual Chapter 4, page 123

Radiators usually have two hoses: an inlet (upper) hose and an outlet (lower) hose. Radiator hoses are constructed of an ozone- and oil-resistant reinforced synthetic rubber. They must be the proper length to allow for engine movement on the motor mounts. Preformed hoses (Figure 4-57A) often have a spiral tempered steel wire installed in the lower radiator hose to prevent collapse due to the suction action of the coolant pump impeller. Upper hoses, not subject to this condition, usually do not have this wire. If the original hose has a wire, make sure the replacement hose also has one. Aside from the radiator hoses, the cooling system also contains heater hoses, a bypass hose in some applications, and may also contain steel piping. These hoses are smaller and somewhat more flexible. For high-heat applications, silicone rubber hoses are available. They are usually identified by a green coloration of the hose and are often found on fleet application vehicles, such as police cruisers. Universal flexible hoses (Figure 4-57B) have wire inserts available for use when preformed hoses are not available. Because of body and engine parts, hoses must often be critically routed. The universal flexible hoses, however, are not always easily routed. Also, it has been determined that the use of a flexible hose may place an unwanted stress on the radiator connecting flange, resulting in early failure of the radiator due to stress cracks. Preformed hoses designed for the specific vehicle application should always be used whenever possible. Many types of hose clamp styles are available in several sizes. A popular replacement type is the worm-gear clamp, which has a carbon steel screw and stainless steel band (Figure 4-58). Hose clamp sizes are given by number or letter designations, which are stamped on the side of the clamp. The important consideration is that the clamp is properly positioned and not overtightened, which could cut into the hose. Worm-gear clamp tension should be rechecked periodically to avoid a source of coolant leakage. Many manufacturers have chosen to use constant tension spring clamps (Figure 4-59) because of their ability to maintain consistent

B

A

FIGURE 4-57  Preformed (A) and (B) flexible cooling system hoses.

Typical constant tension hose clamp

Radiator hose FIGURE 4-58  A worm-gear clamp.

FIGURE 4-59  A typical constant tension hose clamp.

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FIGURE 4-60  A hose that is defective on the inside.

clamping pressure as components and hoses expand and contract due to thermal cycling, thereby eliminating temperature-related leaks. Some vehicles today use quick-connect couplings on smaller hose connections at the heater core and intake manifold connections. Quick-connect couplings may require special tools to disconnect them, and special care should be exercised when servicing them. Engine coolant hoses and clamps should be replaced every four years as a preventative maintenance item. One of the major reasons for vehicles breaking down today is a poor cooling system maintenance service schedule. Avoid damaging components by first loosening the clamp and sliding it out of the way. Then make a small slice lengthwise so the hose may be peeled off. Hoses should be inspected on a regular basis for defects or contamination. Oil contamination may cause the rubber to soften or swell, whereas heat will cause the hoses to become hard and brittle. Hoses should be checked by squeezing them near the clamp or connection and in the middle, feeling for any differences. Soft spots, cracks, and channels can often be detected in this manner. Failure of cooling system hoses may also be due to electrochemical degradation ­(Figure 4-60) or electrolysis. As the coolant ages and the additives break down or are depleted, the coolant, engine, and radiator actually form a galvanic cell, a type of battery. As was noted under the Radiator section, electrolysis occurs when an electrical component is not properly grounded and routes itself through the cooling system in search of a ground. This electrochemical action causes microscopic cracks on the inside of the hose that allow coolant to reach and weaken the reinforcement material. This action is accelerated by high heat and flexing and continues until the hose develops a leak or ruptures. Damage is generally more severe within an inch or two of the end of the hose where it is attached to a metal component. A sign that the interior of the hose is damaged is indicated by a green residue on the reinforcement fibers at the end of the hose where the coolant was wicked out.

Heater System The automotive heater system consists of two parts in addition to the hoses and clamps. They are the heater core and the coolant flow control valve on some vehicles. The heater housing and duct are part of the passenger compartment’s air distribution system.

If one hose is found to be defective, all should be replaced.

The control valve is a mechanical valve that regulates coolant flow through the heater core assembly.

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Heater Core

The automobile heater and heater core are actually part of the engine cooling system, though the heater does not provide the removal of heat from the engine as a normal function. It is meant to provide in-car passenger comfort during the cold winter months. The heater core is mounted in the air distribution duct system and is usually under the dash area of the front passenger side of the vehicle. The heater core (Figure 4-61) resembles a small radiator and also functions as a heat exchanger with the engine coolant flowing from the top of the engine through the heater core and back to the water pump in most designs. Engine heat is picked up by the coolant through the process of conduction and is transferred by convection to the cooler outside air passing through the heater core to the vehicle’s interior. An electric blower motor is used to force the air through the heater core. This provides a ready source of heated air to be used to improve passenger comfort when needed. In some systems, the engine coolant is constantly flowing through the heater core any time the engine is running, whereas in other systems, a control valve is used to stop the flow of coolant when heat is not required. Heater cores may be of tubular or cellular construction similar to the construction of radiators. The tanks on the heater core serve to direct coolant flow through the core. They may be constructed of brass and copper or of plastic and aluminum (Figure 4-62). Inlet/outlet tank Inlet pipe

Header Side plate Tubes

Header

Outlet pipe Return tank Side plate Air centers FIGURE 4-61  A typical heater core with associated elements labeled.

FIGURE 4-62  A typical plastic heater core.

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If a vehicle is running hot, a temporary solution that is sometimes effective is to turn the vehicle passenger heater on the maximum hot position to use the heater core as an additional heat exchanger in order to keep a vehicle from overheating. Leaks are the most common cause of heater core problems. Leaks in a heater core are detected by an obvious loss of engine coolant that is leaking at the firewall or engine compartment ductwork. Other signs that a heater core is leaking may be steam on the windshield when the defroster is on, or the passenger floor carpets could be wet with coolant. A slight leak can also be indicated by a sweet smell coming from the passenger compartment vents. If heater cores are found to be leaking, they are replaced as an assembly and not generally repaired. The replacement heater core should be physically matched to the original to ensure proper fit. In addition, some heater cores are placed higher than the radiator cap in the system. Air can become trapped in these systems, so it is critical to follow manufacturer’s recommendations on proper bleeding procedures. Occasionally, a heater core may become plugged due to poor cooling system maintenance. If this occurs, little or no coolant will flow through the heater core, resulting in no heated air being available for the passenger compartment. A quick method of determining this is by comparing the temperature of the inlet with the outlet hose at the heater core. If the core is blocked or severely restricted, there will be a large temperature difference between the two hoses. Procedures for replacing the heater core vary with the year, make, and model of the vehicle. It is therefore necessary to consult the manufacturer’s repair manual for the proper procedure for replacement.

Control Valve

The heater control valve regulates the flow of coolant through the heater core to control core temperature by opening and closing a passage to increase or decrease flow. The heater control valve may be located in the inlet or outlet line to the heater core. When the control valve is open, a portion of the heated engine coolant circulates through the heater core. This provides a means of providing warm air to the passenger compartment when desired. The heater control valve may be cable operated, vacuum operated, or operated by a bidirectional electric solenoid or motor (Figure 4-63). The control valve, depending on the valve position selected, meters the amount of heated coolant that is allowed to enter the heater core, from full off to full flow. The HVAC control panel temperature selector regulates the operation of most heater control valves, whether actuated by a Bowden cable, vacuum diaphragm, or electrically energized. Some heater core assemblies have a mechanical heater control valve integrated into them to regulate coolant flow through the core.

FIGURE 4-63  Various types of control valves.

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Heater Core and PTC Heater

The engine on a hybrid electric vehicle is relatively small compared to a similar vehicle equipped with only an internal combustion engine. In addition, the hybrid engine is thermally efficient and only runs when needed; therefore, the engine coolant may not always be hot enough to supply adequate heat to the heater core. If the heater core does not become hot, then there will not be enough thermal energy to heat the passenger compartment to a comfortable temperature. In addition to hybrids, positive temperature coefficient (PTC) heaters are also used on some direct injection gasoline and diesel engines due to their low waste heat, which is often insufficient on cold days for fast passenger compartment heating. The PTC heater is also needed during stop-and-go traffic and city driving on many platforms. To combat this lack of usable thermal energy available consistently in the engine coolant, an electric heating element is required to supply the passenger compartment with heat. Toyota has incorporated two 165 watt 12 volts direct current (vdc) PTC electric heating elements into the conventional heater core (Figure 4-64) to supplement the required thermal energy in order to maintain the passenger compartment at the desired temperature setting when the engine coolant is not warm enough. The PTC thermistor elements are a ceramic honeycomb design that heats the air directly as it passes over them and enters the passenger compartment (Figure 4-65). The primary source of heat for the heater core is still hot coolant from the engine. When the engine is first started and the cooling system has not come up to temperature, it is advisable to set the heater duct fan to low to maximize heat output from the PTC elements, then increase the fan speed as the engine coolant temperature rises. Lack of sufficient passenger compartment heat during the winter months is a common complaint of hybrid vehicle owners, as well as a decrease in fuel economy during this same time. Using additives is not recommended as a matter of practice.

Additives Many additives, inhibitors, and “remedies” are available for use in the automotive cooling system. These include but are not limited to stop-leak, water pump lubricant, engine flush, and acid neutralizers. Extreme caution should be exercised when using any additive in the cooling

Connector terminals

PTC element

Electrodes

Insulation film

FIGURE 4-64  A hybrid electric vehicle heater core with PTC heating element.

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PTC heater

Heater core Evaporator

FIGURE 4-65  A typical location of cooling and heating system elements in the case of duct system.

system. Read the label directions and precautions to know what the end results of using any additive may be. For example, caustic solutions should not be used in aluminum radiators; alcohol-based “remedies” should not be used in any cooling system. If a cooling system is maintained in good order by a program of preventative maintenance, additives and inhibitors should not be necessary. Only manufacturer-recommended ethylene glycol-based antifreeze and additives should be added to the cooling system.

Antifreeze There are four key areas of engine protection. They are freeze protection, heating (boil over) protection, corrosion prevention, and adequate heat transfer. The coolant in an automotive cooling system is the medium used to transport engine heat to the radiator. A 50/50 mixture of water (H 2 O) and ethylene glycol (C 2 H 4 [OH]2 ), an ­antifreeze, is the recommended coolant formula generally considered best for the engine. This solution is capable of quickly absorbing and giving up large amounts of heat. Ethylene glycol, a main ingredient of antifreeze, is poisonous. When ingested, ethylene glycol converts into oxalic acid, (COOH)2, which damages the kidneys and may result in kidney failure and death. Just 2 oz. (59 mL) of ethylene antifreeze can kill a dog; 1 tsp. (4.93 mL) can be lethal to a cat; and 2 tbsp. (29.6 mL) can be hazardous to a child. Most automobile manufacturers recommend a 50/50 percent mixture of antifreeze and water for adequate year-round cooling system protection. Also, most manufacturers warn against the use of an alcohol-based antifreeze solution or the use of straight water. Instead, they recommend a mixture of ethylene glycol (Figure 4-66) or propylene glycol (Figure 4-67) with distilled water (Figure 4-68). Either mixture in the cooling system is sufficient to: ■■ Lower the freezing temperature point of the coolant ■■ Raise the boiling temperature point of the coolant ■■ Help maintain the proper engine temperature ■■ Provide water pump lubrication ■■ Inhibit rust and corrosion ■■ Allow coolant-immersed sensors and switches to operate properly

Antifreeze is a generic term used to refer to engine coolant mixtures, whether they be ethylene glycol- or propylene glycolbased, used to raise the boiling temperature and lower the freezing temperature of an engine coolant mixture.

Shop Manual Chapter 4, page 129

Ethylene glycol (HOCH2CH2OH) is the base stock used for most automotive antifreezes and is a colorless, viscous liquid in its pure form.

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FIGURE 4-66  Ethylene glycol antifreeze.

A BIT OF HISTORY Prior to 1930, methyl alcohol was the most commonly used engine antifreeze and required constant maintenance to ensure proper freeze protection. Ethylene glycol was first introduced by Prestone in 1927, but it did not become a standard year-round factory fill until the early 1960s.

Propylene glycol (C 3H8O2 ) is the base stock used for most automotive antifreezes and is a colorless, viscous liquid in its pure form, has a low toxicity, and is considered an environmentallyfriendly alternative to ethylene glycol.

FIGURE 4-67  Propylene glycol antifreeze.

FIGURE 4-68  Distilled water.

The freezing temperature of water as a coolant, at ambient sea-level atmospheric pressure, is 328F (08C) and the boiling point is 2128F (1008C). Water in a radiator with a 15 psi cap will boil at 2508F (1208C). Water should never be used straight as a coolant in an engine because it offers no corrosion protection, lubricating properties, or other necessary additives that are available in antifreezes. Standard ethylene glycol is generally green or yellow in color but can also be red (­ Toyota), blue, or pink. The recommended mixture of 50/50 percent ethylene glycol and water ­(Figure 4-69) has a freeze point of 2348F (236.78C) and a boiling point of 2658F (129.48C) in a radiator with a 15 psi cap. If the percentage of ethylene glycol to distilled water is increased to 70/30 percent, the freeze point is decreased to 2848F (264.48C) and the boiling point is increased to 2768F (135.68C). It is not recommended that the mixture be increased beyond 70 percent ethylene glycol. The ability of the coolant to carry away heat decreases as the percentage of ethylene glycol increases. Straight ethylene glycol only provides freeze protection down to 228F (218.98C) but has a boiling point of 2768F (135.68C). A straight mixture of ethylene glycol should never be used because ethylene glycol is 15 percent less efficient than water at removing heat and could cause hot spots to develop, resulting in severe engine damage. The protection level selected should be to the lowest temperature expected In warmer climate zones, such as southern Florida and Southern California, protection is required for the antirust and anticorrosion inhibitors, as well as for anti-boiling protection. In any climate zone, antifreeze is essential for this protection, as well as coolant pump lubrication. The coolant should contain no less than 30 percent antifreeze, which will provide protection to 258F (2158C). A safer alternative to ethylene glycol coolant is antifreeze formulated with propylene glycol. Unlike ethylene glycol, propylene glycol is essentially nontoxic and safer for animal life, children, and the environment. Also, propylene glycol is classified “Generally Recognized as Safe” by the U.S. Food and Drug Administration. Low toxicity does not mean that it is safe to drink, but the risk of poisoning is a greatly reduced. Propylene glycol is available on the aftermarket and not currently used as factory-fill antifreeze. Popular brands are Prestone Low Tox® and Safe Brands Sierra®. Propylene glycol has similar thermal characteristics as ethylene glycol. A 50/50 mixture of propylene glycol and water has a freeze point of 2268F (232.28C) and a boiling point of 2568F (124.48C) in a radiator with a 15 psi cap, whereas a 100 percent mixture has a freeze point of 2708F (256.78C) and a boiling point of 3708F (187.88C) in a radiator with a 15 psi cap.

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ANTIFREEZE

FIGURE 4-69  A coolant percentage/protection chart.

Propylene glycol and ethylene glycol are compatible antifreezes and can be mixed, but mixing the two antifreezes eliminates the low toxicity characteristics of propylene glycol and makes it impossible to test the coolant’s strength using a hydrometer. This is due to the differences in the specific gravities of the two coolants. Antifreezes contain many additives to improve their performance in the cooling system, about 2 to 3 percent of the total volume in pure coolant. Corrosion inhibitors protect metal surfaces from rust, corrosion, and electrolysis. This is particularly important for thin, lightweight aluminum radiators and heater cores. Most ethylene glycol formulated in North America contains inorganic salts of borate, phosphate, and silicate to prevent rust and corrosion of metal components. The additives produce an alkaline mixture with a pH range of 7.5–11.0, depending on the manufacturer. The silicates in the mixture form a protective coating on the surface of metal components and are especially effective at protecting aluminum. The additive package usually offers enough protection for at least 2 years or 30,000 miles in most vehicles, or longer if mixed with distilled water. The ability of a coolant to neutralize acids is referred to as the coolant’s reserve alkalinity and varies among manufacturers. Time, heat, dissolved oxygen, and minerals contained in water as well as glycol degradation will eventually

Distilled water is pure water produced by distillation. It is available at grocery stores and pharmacies.

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Organic acid technology (OAT) is used in extendedlife antifreeze based on carboxylates of organic acids and does not contain silicates, phosphates, borates, amines, or nitrates. Hybrid organic acid technology (HOAT) G-05 extendedlife coolants are ethylene-glycol Glysantin-based formula refrigerants that are low in silicate, have low pH, and are phosphatefree. HOAT coolants use both organic and inorganic carbonbased additives for long life protection.

deplete these protective additives, and acids will form. Once the pH level drops to 7.0 or lower, corrosion and electrostatic discharge accelerates, leading to radiator, heater core, water pump, and hose failure. Chemical test strips can be used to check the pH level of the cooling system. Electrolytic corrosion, as was discussed under Hoses, is of special concern with today’s bimetal engines. The different metals contained in radiator cylinder blocks and heads can create an electrochemical action (battery) that promotes corrosion. One metal becomes the anode (aluminum), while the other becomes the cathode (iron), and the coolant is the electrolyte. The higher the percentage of dissolved impurities in the coolant, the greater its ability to conduct electricity, which increases the rate of electrolysis. Aluminum and thin metal components, such as the radiator and heater core, are generally the first to suffer damage. Other failures can also accelerate the depletion of coolant additives. Air pockets from low coolant levels or improper bleeding during service, exhaust gases leaking into the cooling system due to leaky head gaskets, or cracks in the combustion chamber all lead to rapid coolant failure. Some European vehicle manufacturers recommend the use of phosphate-free coolants because phosphates can react with calcium and magnesium contained in some water to form sediment and scale, while Asian vehicle manufacturers may recommend using coolants containing phosphates but low or no silicate additives. Regardless of the coolant chosen, under no circumstances should softened water be used in a cooling system. Domestic water softeners use salt (sodium), which is very corrosive to all metals and could lead to serious damage to the cooling system and engine components. The latest coolant to be developed is the extended-life coolant. General Motors first introduced it in 1995 under the name of Dex-Cool® (Texico/Havoline) and by 1996 was using it in most of their vehicle platforms as the factory fill. It uses a corrosion-inhibiting package referred to as organic acid technology (OAT). It contains organic salts of mono and dicarboxylic acids such as sebasic and octanoic acids plus tolytriazole, and is less alkaline than standard coolants, with a pH of 8.3. Extended-life coolant offers protection for five years or 150,000 miles and is still an ethylene glycol-based coolant. As such, extended-life coolants are compatible with standard coolants but, if combined, will only offer the corrosion protection of the conventional coolant. If the system becomes contaminated or is to be converted to an extended-life coolant, it must be thoroughly drained and flushed to remove all traces of the conventional coolant in order to gain the benefits of the longer-lasting antifreeze formula. Both Ford and Chrysler products use hybrid organic acid technology (HOAT) extended-life coolants, which are also rated for five years or 100,000 to 150,000 miles. The HOAT coolant is an ethylene-glycol glysantin-based formula that is low silicate, low pH, and phosphate free. HOAT coolant uses both organic and inorganic, carbon-based additives for long life protection. It is commonly marketed as G-05 extended-life coolant and comes in several colors, such as yellow (Ford) and orange (Chrysler). The low-silicate formula is designed to offer aluminum protection and water pump lubrication. Extended-life OAT-based coolant should not be mixed with HOAT-based coolant according to vehicle manufacturers, and Ford has gone as far as to state that orange coolant, meaning Dex-Cool, should not be added to their systems. In addition, German automotive manufacturers require G11 blue, G12 red, and G12 plus purple long-life coolants in their car lines and do not want any blending of coolants to take place. Both G11 and G12 coolants are ethylene glycol-based phosphate, nitrite, and amine free coolants. Beginning in 2010, Ford began a multiyear change over worldwide to an orange OAT based extended life coolant, but does not recommend using this coolant in older models designed for HOAT based coolants. Beginning in 2009, Nissan/Infinity introduced a blue long life coolant. The blue long life coolant is rated for 10 years or 135,000 miles. VW, Audi, BMW, and Volvo are using a hybrid formula based on low silicates and 2-EHA (ethyl hexanoate) organic acid. In addition, Volvo, VW, and Audi do not specify a change interval for their coolant. The industry is a rainbow of colors and it is important to use the engine coolant that is recommended by the manufacturer and flush the cooling system based on the

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manufacturers guidelines to avoid damage to gaskets, water pumps, and water jackets as well as heat exchangers. Accidental antifreeze poisoning kills many pets and livestock every year. Beginning in 2010, many states enacted laws that require manufacturers to add a bittering agent (bitter flavor) to antifreeze and engine coolant. The purposes of the laws are to require antifreezes to be produced with an objectionable taste so pets and children will not mistake the poisonous substances for a sweet drink. While newer antifreezes will contain a bitter flavor, older antifreeze will still have a sweet taste and will probably be in vehicles for many years to come. So whether sweet or sour, be sure to clean up spills and dispose of properly, and never leave open pans unattended or keep in unmarked containers. The percent of antifreeze concentrations in a cooling system mixture can be determined by several methods, which will indicate the freeze point of the mixture and its specific gravity. Common methods for determining the freeze point are the coolant hydrometer, test strips, and the refractometer. A separate hydrometer for propylene glycol and ethylene glycol is required because they have different specific gravities. The most accurate methods for determining the concentration of antifreeze in the mixture are with the use of a refractometer. A refractometer can measure the specific gravity of propylene glycol, ethylene glycol, and battery electrolyte. It does this by analyzing the way the light bends as it passes though the liquid. Ethylene glycol never wears as additives do, however, and none of these methods will indicate the condition of the coolant additives. Standard propylene glycol and ethylene glycol offer full protection for two years of normal driving. To determine the amount of antifreeze to add to the cooling system after flushing with water, refer to the manufacturer’s specifications for total cooling system volume, and divide by two. Example: If the total cooling system volume is 16 quarts (15 liters), you will need to add 8 quarts (7.5 liters) of pure antifreeze, and then finish filling the system with water. Remember that after flushing the system with water, some of the water may still remain in the water jackets. Although propylene glycol is much less hazardous than ethylene glycol antifreeze, it still should be considered hazardous. At the present time, the Environmental Protection Agency has no restrictions on the disposal of antifreeze unless it is contaminated with lead (Pb). Lead, a byproduct of the material used to solder the seams and joints of the radiator, is considered hazardous in any quantity. State and local governments, however, may have requirements for safe disposal, reclamation, or recycling. To protect animal life and the environment, follow these simple rules: ■■ Do not mix different types of antifreezes. ■■ Wipe up and wash away spills. ■■ Keep stored antifreeze off the floor and away from animals. ■■ Keep antifreeze in its original container, or use a container that is specifically labeled for the product it contains. ■■ Store used antifreeze, before recycling or reclamation, in a sealed container that is properly labeled with its contents (in other words, used ethylene glycol). ■■ Ensure that the vehicle’s cooling system has no leaks.

Preventive Maintenance The cooling system, which is often neglected, is one of the most important systems of the car. If it is kept in good shape and provided with routine preventive maintenance, the cooling system should give years of trouble-free service. The cost of maintenance every 12,000– 15,000 miles (19,308–24,135 km) is more than offset by the cost of breakdown and consequent repairs. These repairs, incidentally, often result in expensive engine service. Replace belts that are frayed, glazed, or obviously damaged. Replace any hoses that are found to be brittle, soft, or otherwise deteriorated (Figure 4-70).

Mineral-free distilled water is preferred over tap water for maximum cooling system performance and integrity.

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Swollen

Chafed

Soft

Hardened

Terms to Know Antifreeze Bypass Centrifugal impeller Control valve Distilled water Electrolysis Ethylene glycol Expansion tank Heater core Hybrid organic acid technology (HOAT) Organic acid technology (OAT) Overcooling Overflow tank Pitch Power train control module (PCM) Pressure cap Propylene glycol Radiator Ram air Recovery tank Reverse flow Thermostat

FIGURE 4-70  Typical hose defects.

The design consideration of a cooling system is to provide for a minimum sustained road speed operation of 90 mph (144.8 km/h) at an ambient temperature of 1258F (528C). Another criteria is for 30 minutes of driving in congested stop-and-go traffic in an ambient temperature of 1158F (468C) without experiencing any overheating problems. These design considerations exceed the conditions that one is likely to encounter in regular day-to-day driving. If the engine overheats, the problem should be found and corrected. The life of an engine or a transmission that is habitually allowed to overheat is greatly reduced. The high-limit properties of lubricating oil require adequate and proper heat removal to preserve formulated lubricating characteristics.

SUMMARY The preventive maintenance program should include the following procedures: ■■ ■■ ■■ ■■ ■■ ■■ ■■

Test or replace the thermostat. Test or replace the pressure cap. Inspect or replace the radiator hose(s). Inspect or replace the heater hoses. Pressure test the cooling system. Test or replace the antifreeze solution. Visually inspect the coolant pump, heater, control valve, and belt(s).

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REVIEW QUESTIONS Short-Answer Essays 1. What is the purpose of the automotive cooling system? 2. What are the two types of radiator core that are found in the automotive cooling system? 3. What method(s) is used to increase the boiling point temperature of the coolant in an automotive cooling system? 4. Describe the operation of a typical cooling system thermostat. 5. What are the advantages of engine temperature being adjusted to current operating demands on the electronically controlled cooling system? 6. Describe an advantage of a declutching engine-driven cooling fan. 7. Describe an advantage of an electric-motor-driven cooling fan. 8. Briefly, what is the purpose of the coolant recovery tank? 9. What is a PTC heater and on what vehicles can it be found? 10. What are the advantages of a 50/50 mix of antifreeze and water?

Fill in the Blanks 1. Radiators are constructed of _______________, _______________, and/or plastic. 2. A frequent coolant pump failure is due to _______________ often caused by worn _______________. 3. If the gasket or sealing surfaces of a pressure cap are damaged, the cooling system cannot be _______________. 4. A thermostat failing in the _______________ position will result in engine _______________. 5. Engine-driven fans are balanced to prevent _______________, _______________, coolant pump _______________ failure, and/or seal damage. 6. Many electric cooling fans are ultimately controlled by the _______________ _______________ _______________. 7. Electric cooling fans may _______________ without warning, even with the ignition in the _______________ position.

8. Heater core leaks are detected by a loss of _______________ and a wet _______________ _______________. 9. An antifreeze solution _______________ the freezing temperature and _______________ the boiling temperature of the coolant. 10. A typical cooling system contains a mixture of _______________ antifreeze and _______________ water which offers an excellent balance of both _______________ freeze point and _______________ boiling point protection.

Multiple Choice 1. All of the follow are true about engine thermostats except: A. A stuck open thermostat will cause engine overcooling. B. A stuck closed thermostat will cause engine overheating. C. A faulty thermostat will effect vehicle emissions. D. A thermostat may be removed from a system if it is running hot. 2. Engine coolant is designed to provide all of the following except: A. Provide water pump lubrication. B. Inhibit rust and corrosion. C. Lower the boiling point of the solution. D. Lower the freezing temperature of the solution. 3. If a thermostat fails in the open position, all of the following will occur, except: A. A vehicle may fail emissions test. B. A loss of engine coolant. C. Poor heater performance. D. A longer than normal warm-up period. 4. All of the following statements about engine cooling systems are true EXCEPT: A. Extended life coolant and standard life coolant are both ethylene glycol based. B. It is ok for a technician to install a thermostat with a low temperature rating than the original thermostat. C. Extended life coolant is rated to last in excess of 100k miles. D. Electric cooling fans may turn on even when an engine is not running.

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5. All of the following are the function of the radiator pressure cap except: A. To seal the cooling system. B. To lower the freeze point of the coolant. C. To raise the boiling point of the coolant. D. To pressurize the cooling system. 6. Air in the cooling system can cause all of the following except: A. The formation of rust and/or corrosion in the ­cooling system. B. Creating an air lock, blocking coolant flow through the cooling system. C. Water pump cavitation inhibiting the pump’s ability to circulate coolant. D. The coolant hoses bursting due to air pressure. 7. When the cooling system is placed under pressure, for each pound per square inch (psi) of cooling system pressure, the boiling point of the coolant is increased by: A. 18F C. 38F B. 28F D. 48F

8. A common engine thermostat has a temperature ­rating of: A. 1858F C. 2058F B. 1958F D. 2258F 9. Engine coolant loss could be caused by all of the following except: A. A leaking transmission cooler line B. A leaking engine head gasket C. A faulty radiator pressure cap D. A leaking transmission oil cooler 10. A vehicle is driven for 15–20 miles and the vehicle’s passenger compartment blower motor continues to blow cold air. What is the most likely cause of this condition? A. Stuck closed thermostat B. Partially restricted heater core C. Partially restricted radiator core D. Damaged water pump impeller blades

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Chapter 5

Air-Conditioning System Operating Principles Upon Completion And Review Of This Chapter, You Should Be Able To: ■■ ■■

■■

■■

Discuss heat transfer in the refrigerant system.

■■

Discuss the role of refrigerant in the system.

Describe the effect humidity has on the air-conditioning system.

■■

Explain the pressure versus temperature relationship.

Explain the pressure and vacuum relationship in the air-conditioning system.

■■

Know the physical state, pressure, and temperature of the refrigerant in different areas of the refrigerant system.

Understand the basic functions of the various airconditioning components.

Introduction Automotive air-conditioning systems are divided into two sections: the high pressure side and the low pressure side. The air-conditioning system is a closed system that circulates a fixed charge of refrigerant through the system over and over again in a looping cycle. The general function of the system is the absorption of heat when the refrigerant boils in the evaporator. It is this process of allowing the correct volume of refrigerant into the evaporator that removes heat and humidity from the passenger compartment. The basic automotive air-conditioning system components consist of these: ■■ Compressor ■■ Lines and hoses ■■ Condenser ■■ Expansion device ●● ●●

■■ ■■

Expansion valve Orifice tube

Evaporator Storage vessel

Receiver-drier—used with expansion valve Accumulator—used with orifice tube The two basic system designs are the expansion valve (Figure 5-1) or the orifice tube (Figure 5-2) refrigerant system. ●● ●●

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Evaporator Expansion valve

Condenser A/C pressure transducer

Compressor

Radiator High-pressure gas Receiver-drier

High-pressure gas

Low-pressure liquid

High-pressure liquid

Low-pressure gas

FIGURE 5-1  Refrigerant cycle and components in the expansion value air-conditioning system.

Heat Transfer in the Refrigerant System The basic function of the automotive air conditioner is to remove heat from the passenger compartment and transfer this heat to the outside air. The system also dehumidifies the air before it enters the passenger cabin. To perform these functions, the air-conditioning system uses two heat exchangers. One of these heat exchangers is the evaporator core, which is located in the passenger compartment duct work. Its role is to remove heat from the incoming or recirculated air as it flows across the cooling fins of the core and to transfer this heat energy into the refrigerant system (Figure 5-3). The cooled air is then directed into the passenger compartment. The other heat exchanger in the system is the condenser, which is located in front of the engine radiator and just behind the body grille assembly. Its role is to remove the heat that was absorbed by the evaporator from the refrigerant system and transfer (radiate) this heat back into the atmosphere (Figure 5-4). The following is a summary of heat transfer as it relates to the vehicle refrigerant system: ■■ Convection—the heat content of the outside air is transferred to the evaporator core as the air is blown across the core fins. ■■ Conduction—the heat is absorbed by the cooler refrigerant gas flowing inside the coils of the evaporator core. 134 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Accumulator

Evaporator Low-pressure liquid Orifice tube

Condenser

Compressor

Radiator

High-pressure gas

Low-pressure liquid

High-pressure liquid

Low-pressure gas

FIGURE 5-2  Refrigerant cycle and components in the orifice tube air-conditioning system.

Sun

FIGURE 5-3  Heat transfer in the refrigerant system.

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Heated refrigerant flow Heat absorbed from inside the car

Evaporator

Heat given off to outside air

Condenser

Passenger cabin Engine compartment FIGURE 5-4  Heat movement through the refrigerant system.

■■ ■■ ■■ ■■

Convection—the heat absorbed by the refrigerant is circulated to the condenser. Conduction—the cooler condenser fins absorb the heat from the refrigerant. Radiation—the condenser fins then give off heat to the cooler air. Convection—the air then moves the heat away from the condenser.

Air Conditioning and Humidity To maximize the effectiveness of the evaporator core’s ability to remove heat from the passenger compartment, the moisture content of the air must be reduced. The moisture content in air (humidity) contains heat; thereby increased humidity increases the heat load on the refrigerant system (Figure 5-5). To improve the efficiency and the operation of the refrigerant system and provide maximum cooling of the passenger compartment on hot humid days, the air-conditioning system must remove both heat and moisture from the air. Thus maximum refrigerant performance and passenger compartment cooling is achieved by selecting the air Recirculation mode (air inside the passenger compartment is recirculated through the evaporator core) on the climate control panel instead of the Fresh air mode (outside air). Humidity in the passenger compartment can be increased by many factors including but not limited to hot muggy days, rainy days, and even passengers in the vehicle contributing to humidity load by breathing. When the humidity level in the passenger compartment rises, it

HIGH HUMIDITY

FIGURE 5-5  Humidity increases the heat load on the refrigerant system.

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can create a safety concern beyond passenger comfort if the moisture condenses on the inside of the windows, obscuring the driver’s vision. This condensation on the inside of the windows occurs when the water vapor suspended in the air contacts a surface (window) that is cooler than the air temperature and the moisture condenses into water droplets on the cold surface. This same process can be used to lower the humidity level of the air in the passenger compartment. As air is passed over the cold evaporator core fins, the air gives up its heat, and the moisture contained in the air condenses against the surface of the evaporator (Figure 5-6). If the air Recirculation mode is selected, the air in the passenger compartment is looped from the passenger compartment back through the evaporator core, providing maximum dehumidification of the passenger compartment air. If we analyze the process a little further and think about the principle of latent heat and the change of state as a vapor becomes a liquid, we will recall that a large amount of thermal energy (Btu’s) must be exchanged for this to occur. This means that the evaporator must absorb hundreds of Btu’s in heat, removing energy as humid air is passed over it. If humid outside air is continually drawn over the evaporator, thermal energy is used to condense the moisture out of the air stream during the dehumidification process, meaning that less energy will be available to lower air temperature further and thus will not be available to lower passenger compartment temperature. In other words, the energy used to condense out moisture and dehumidify the air will overstress the system, and the air-conditioning system will not be able to cool the air as well as it could if the air were dryer (less humid). During air-conditioning system performance testing and analysis, it is advisable to run the air conditioner with the Recirculation mode selected and the vehicle windows closed in order to achieve maximum system efficiency. In addition, if this procedure were used on each vehicle tested, results would be more consistent regardless of humidity levels on a particular day.

Humid air carries moisture, which condenses on the cold evaporator.

Evaporator

Water FIGURE 5-6  The dehumidification process produced by the refrigerant system evaporator.

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Author’s Note: Whether your home has a window air conditioner or a ­central air-conditioning system, both use the benefit in performance achieved by ­recirculating the air inside the room back through the evaporator to lower room humidity and thus increase the efficiency of the system by cooling ever dryer air.

The atmospheric relative humidity has a dramatic effect on the effectiveness of the airconditioning system. The vehicle air-conditioning system will be able to lower the passenger compartment temperature substantially further on a 90-degree day at 30 percent relative humidity than it can on a 90-degree day at 80 percent relative humidity. The higher the relative humidity level of the air, the less energy will be available for cooling the air stream. It should be stated that by itself the effect of removing humidity from the air will have a positive effect on passenger comfort as high humidity levels prevent the body from dissipating heat easily on its own. So, lowering humidity alone will increase personal comfort on a hot day as the body’s evaporational cooling will improve. The dew point temperature of the air is another indicator of the humidity level. The higher the dew point temperature, the more moisture the air contains by volume, because warm air is less dense and can hold more water vapor. Dew point is a better comfort indicator than relative humidity, the higher the dew point temperature the more uncomfortable humans are. At a dew point temperature 508F (108C) if the ambient air temperature is 608F (168C) and the relative humidity is 100 percent we still feel comfortable because our body is able to give up heat because the air temperature is far below our body surface temperature. Dew points above 658F (188C) make it feel sticky and humid outside while dew points less than 658F are comfortable with respect to the stickiness of the air. The higher the dew point temperature is, the more moisture that is in the air. The higher the dew point is above 658F (188C), the stickier it will feel outside. If the dew point temperature is 758F (248C) or above the air really feels sticky and humid. The dew point temperature is the temperature at which the humidity level becomes 100 percent; that is to say, it is the temperature at which air has become saturated and cannot retain any additional water vapor. Dew point is a better comfort indicator than relative humidity, the higher the dew point temperature the more uncomfortable humans are. At a dew point temperature 508F (108C) if the ambient air temperature is 608F (168C) and the relative humidity is 100 percent we still feel comfortable because our body is able to give up heat because the air temperature is far below our body surface temperature. Dew points above 658F (188C) make it feel sticky and humid outside while dew points less than 658F are comfortable with respect to the stickiness of the air. The higher the dew point temperature is, the more moisture that is in the air. The higher the dew point is above 658F (188C), the stickier it will feel outside. If the dew point temperature is 758F (248C) or above the air really feels sticky and humid. It is this dew point temperature, when water vapor cannot remain in the vapor state and condensation begins to form on any surface, that is cooler than the air temperature. This occurs at the refrigerant system’s evaporator core, where the air temperature is lowered to below the dew point temperature of the air flowing across it, and water vapor condenses on the evaporator.

The Relationship of Pressure and Vacuum in the Air-Conditioning System Pressure must be understood in order to properly diagnose an air-conditioning system. We are exposed to air pressure every day in the form of atmospheric pressure. This is the pressure created by the atmosphere that surrounds the earth and extends nearly 600 miles above the earth’s surface, and which is held in place by the gravitational forces generated by the earth’s rotation and magnetic field (Figure 5-7). 138 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

1 square inch Atmosphere

14.7 psia (101.4 kPa absolute)

600 miles (965.6 km)

FIGURE 5-7  Atmospheric pressure at sea level is 14.7 psia (101.4 kPa Absolute).

Atmospheric pressure at sea level is 14.7 pounds per square inch absolute (psia) (101.4 kPa absolute). Most of us only notice a difference in pressure when it is either more or less than the normal level (14.7 psia). In the automotive field, we usually use gauges that are calibrated to 0 pounds per square inch at atmospheric pressure, called 0 psig. A pressure gauge reading of 30 psi means 30 psig—pounds per square inch gauge. On a set of absolute gauges, the gauge would read 14.7 psia at sea level and the 30 psig reading previously stated would read 44.7 psia on a set of absolute gauges (Figure 5-8). Pounds per square inch absolute is the amount of pressure measured above absolute zero. As stated above, this is the gauge pressure plus 14.7 psi. Automotive air-conditioning pressures listed and gauge sets used for diagnosis and repair are normally in psig unless otherwise stated (Figure 5-9). We also deal with pressures below atmospheric pressure (0 psig) when servicing automotive air-conditioning systems. Any pressure below atmospheric pressure is referred to

10 5

15

30 35 40 20 25

0 10 20 30

A

45

25 20 15 10 5 0

30

45 50 35 40 55

60

B

Comparisons of low-side gauge scales at atmospheric pressure: (A) Scaled in pounds per square inch gauge (psig) (B) Scaled in pounds per square inch absolute (psia) FIGURE 5-8  The two gauges illustrated above show a comparison of the low-side gauge scales at atmospheric pressure sea level. Gauge A is scaled in pounds per square inch gauge (psig). Gauge B is scaled in pounds per square inch absolute (psia). Atmospheric pressure at sea level is 14.7 psia (101.4 kPa absolute).

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80

100

80

40

90 100

0

110 W LO ure 120 ss e r p

160

H Pre IGH ssu re

0

260

HI

40

20

50 60 70

80

90 100

110 W LO ure 120 ss pre

100

80

40

120

0

30

LO

Normal pressure at 70°F (R-134a)

160

H Pre IGH ssu re

20

0

220

LO

0 10

20

220

30

30 20 10

120

24 0

20

50 60 70

24 0

0 10

40

260

30 20 10

HI

Normal pressure at 70°F (R-12)

FIGURE 5-9  Automotive air conditioning pressure gauge sets used for diagnosis and repair are normally in psig.

Gauge pressure

0 Hg 5

85.3 psig Atmospheric pressure

Gauge pressure

10 15 20

0 psig/0 in. Hg

Inches of Mercury

25 30

Vacuum gauge 29.99 in. Hg Vacuum is a pressure which is less than atmospheric pressure

Mercury container Principles of vacuum measurement

FIGURE 5-10  Vacuum is any pressure that is less than atmospheric pressure with 29 in. Hg being a perfect vacuum.

as a vacuum or partial vacuum. A standard psig pressure gauge is only capable of reading a value if the pressure is greater than atmospheric pressure (0 psig). To read a pressure value less than atmospheric pressure, a vacuum gauge is required. A vacuum is generally calibrated in inches or centimeters of mercury (Hg). A complete vacuum (devoid of all air) is 29 inches Hg and is only achievable at sea level. A partial vacuum is any vacuum between 0 and 29 inches Hg ­(Figure 5-10). The low-side gauge (blue gauge) on a compound set of air-conditioning gauges reads both positive pressures (0–120 psig) and negative pressures (vacuum) levels from 0–30 in. Hg.

Air Conditioning 101 To understand how an air-conditioning system functions, you must first know all the components that make up that system. You must also learn what role each of these components plays in the system and how each component interrelates with one another. During the discussion on air-conditioning components that follows in this chapter, it may be helpful to refer to Figure 5-25 and Figure 5-26 to understand how the basic components relate to one another. 140 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

The remainder of this chapter will discuss the various components in the air-conditioning system and the role that each plays in the overall system, as well as the physical state of the refrigerant in various areas of the system. Knowing basic component location and terminology is required of all automotive technicians. Both customers and your peers in the trade expect you to know and use basic trade terminology and have an in-depth knowledge of the systems you are working on. This is all part of being a professional technician. In addition, it will be all but impossible to diagnose and repair a system if you do not grasp the basic operating principles and relationships of the various system components.

Compressor The refrigerant compressor (Figure 5-11) is the heart of the refrigerant system. Its purpose is to compress and pump refrigerant through the system. This specially designed pump raises the pressure of the refrigerant from approximately 20 to 30 psi to approximately 180 to 220 psi. As you may recall from Chapter 2, according to the laws of physics, when a gas is compressed, its pressure and temperature are increased proportionally. By increasing the refrigerant’s pressure, we also increase the temperature at which it will condense. Compressor designs may use one or more reciprocating pistons, rotary vanes, or scroll-type design. They may have a fixed displacement or a variable displacement. There are many compressor designs and styles in use today, and these will be addressed in more detail in Chapter 8. Though many compressors may look alike, they are not interchangeable. Refer to manufacturer specifications for the correct compressor for each application. The compressor is one of the points in the air-conditioning system where there is a separation between high and low pressure. The low side is also referred to as the suction side of the system and connects the compressor inlet to the evaporator side of the system. The high side of the system is also referred to as the discharge side and connects the compressor outlet to the condenser inlet. The refrigerant leaves the evaporator as a low-pressure gas (vapor) with as much heat as it can transport for its pressure. It goes into the compressor on the low-pressure (suction) side. There it is compressed by compressor action into a high-pressure vapor and is then pumped out of the smaller, outlet (discharge) side of the compressor.

Reciprocating piston(s) move(s) up and down or back and forth in a linear motion.

The compressor increases refrigerant vapor pressure.

FIGURE 5-11  Typical compressors.

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The compressor pumps the low-pressure refrigerant vapor out of the evaporator by suction, raises its pressure, and then pumps it, under high pressure, into the condenser.

Quick-Connect Valve

The service valve used for R-134a systems is a positive-coupled, quick-connect type. There is a Schrader valve similar to the R-12 Schrader access fitting, with the exception that it is recessed further into the fitting (Figure 5-12). The high-side service port, at 16 mm, is larger than the low-side service port, which is 13 mm. Service hoses for automotive air-conditioning system use must have unique fittings that attach to the service ports (Figure 5-13) and refrigerant cylinder. This combination, required by the Environmental Protection Agency (EPA), prevents reversing the hoses as well as introducing the wrong refrigerant.

Service Valves

Some compressors may be equipped with service valves, though most have Schrader-type service valves (Figure 5-14) located on suction and discharge lines. On some systems, the suction and discharge service valves are located on the compressor cylinder heads. The suction and discharge lines or hoses are connected to the compressor at the service valves. If the service valve is not found on the compressor, the suction service valve will be found somewhere between the evaporator outlet and compressor inlet. The discharge service valve will be found somewhere between the compressor outlet and condenser inlet. Schrader-type valve depressor High-side service port

Low-side service port

FIGURE 5-12  R-134a (HFC-134a) service port details.

FIGURE 5-13  Typical R-134a service port adapters.

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Schrader valve

FIGURE 5-14  A typical Schrader-type service valve for R-12 systems.

Hand Shutoff Valve

The hand-type shut-off service valve located on the compressor, once a very popular type, is likely encountered today only on older R-12 mobile air-conditioning system applications. It may also be found on some off-road air-conditioning systems using the two-cylinder Tecumseh and York compressors. Though no longer found frequently, it is important that the technician be familiar with its operation. Unlike the now familiar Schrader-type valve, the shut-off service valve has, for all practical purposes, three positions: front seated, back seated, and midpositioned.

Shop Manual Chapter 5, page 166

Front Seated.  When the valve stem is turned clockwise (cw) all the way in, it is said to be front seated (Figure 5-15A). This is not a normal operating position for either hand valve. The compressor should not be operated with the discharge service valve front seated. To do so will result in serious compressor damage due to excessive high pressure. It may possibly burst, causing personal injury. Do not operate the compressor with service valve(s) in the front-seated position. Back Seated.  When the service valve is turned counterclockwise (ccw) all the way out, it is said to be in the back-seated position. In this position (Figure 5-15B), the gauge port is closed, and the line port and compressor circuit are open. This is the normal operating position for both service valves. Midpositioned.  When the service valve is in midposition (Figure 5-15C), it is said to be cracked. In this position, the line port, gauge port, and compressor are in the circuit. This is not the normal operating position, but it is the position for service when the manifold and Service fitting Refrigerant hose

1

1

1

2

2

2 3 Front seated

A Compressor

3 Back seated

B

3

C

Midpositioned (cracked)

FIGURE 5-15  (A) Service value in the front-seated position; (B) back-seated position; and (C) midposition (cracked).

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gauge set is installed. To midposition a service valve, turn the stem two turns clockwise off its back-seated position. This is sufficient to allow system pressure to the gauge port. Do not front seat, then midposition. It should be noted that the hand shut-off type service valve is not to be midpositioned or front seated unless the manifold and gauge set is attached. The compressor should not be operated with the high-side service valve front seated.

Schrader-Type Valve

The Schrader-type service valve is self-opening when a manifold hose is attached. It operates in much the same manner as a tire valve. Because of its design, the Schrader-type service valve may only be cracked, or back seated.

Condenser The condenser is a heat exchanger located in front of the vehicle radiator. It is the component of the refrigerant system in which refrigerant is changed from a gas to a liquid by the removal of heat. Superheated is the process of adding heat intensity to a liquid above its boiling point without vaporization or heating a gas above its saturation point so that a drop in temperature will not cause reconversion to liquid.

The condenser is a heat exchanger for the superheated refrigerant in the system. Refrigerant containing heat is compressed by the compressor and, in both a high-pressure and high-temperature (superheated) gaseous state, flows to the condenser. This super-heated high-pressure vapor enters the top of the condenser. As it passes through the condenser coils, the outside air passing over the coils and fins picks up heat from the refrigerant. This occurs because the outside air at this point has less heat than the refrigerant in the coil. As the heat leaves the refrigerant, the refrigerant condenses, changing from a high-pressure vapor to a high-pressure liquid, which exits at the bottom of the condenser. This pressured liquid refrigerant is a liquid at a temperature lower than the minimum temperature (saturation temperature) at a given pressure required to keep it from boiling (changing from a liquid to a gas). Subcooling occurs in the condenser when additional heat is removed below the condensation temperature. The difference between the saturation temperature and the actual liquid refrigerant temperature is the amount of subcooling. Subcooling increases the efficiency of the refrigerant system by increasing the amount of heat removed per pound of refrigerant circulated. Stated another way, less refrigerant is pumped through the system to maintain the desired refrigerant temperature which in turn reduces the amount of time a compressor must run. Subcooling prevents the liquid refrigerant from changing to a vapor before it reaches the evaporator. In a refrigerant system, inadequate subcooling will prevent the proper metering of refrigerant into the evaporator due to flash gassing (change of state to a vapor), resulting in poor system performance. The condenser is that part of the air conditioner that removes heat from the refrigerant and dissipates this heat to the outside air. The engine cooling system fan pulls air through the condenser, which is located in front of the radiator. Air passes through the condenser, then through the radiator. Ambient air is also forced through the condenser and radiator by the forward movement of the vehicle. This is known as ram air.

Receiver-Drier Accumulator The receiver-drier and suction-line accumulator are tank-type devices that have nearly the same external appearance. The functions of the two devices are somewhat different, however. The function of the receiver-drier is to store a liquid refrigerant reserve to ensure a constant liquid supply to the expansion valve. A strainer and a drying agent (called a desic-cant) are in the receiver-drier to remove moisture and clean the refrigerant. The function of the accumulator is to catch and trap liquid refrigerant from the evaporator to protect the compressor. The accumulator also contains a strainer and desiccant for refrigerant cleaning and purification.

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Receiver-Drier

From the condenser, the high-pressure liquid refrigerant enters the receiver-drier (Figure 5-16), where it is stored until it is needed by the expansion valve. The receiver-drier performs three functions in the automobile air-conditioning system: ■■ The receiver section is the storage tank for excess (reserve) liquid refrigerant that is ­necessary for proper operation of the air-conditioning system. ■■ The drier section collects small droplets of moisture that may have entered the system at the time of installation or repair. ■■ The pickup tube ensures a vapor-free stream of liquid to the expansion valve.

Accumulator

The suction-line accumulator (Figure 5-17) is located at the outlet of the evaporator and before the inlet of the compressor. The purpose of the accumulator is to trap excess liquid refrigerant, preventing it from entering the compressor. Liquid refrigerant in the compressor could cause serious damage. The accumulator is a storage container for refrigerant vapor and any small amount of liquid refrigerant that did not reach the vapor point as it passed through the evaporator as well as lubrication oil that may be atomized and traveling with the refrigerant.

The receiver-drier is a storage container on the high pressure side of the system between the condenser and the thermostatic expansion valve. It is used to separate out refrigerant vapor from liquid refrigerant, allowing only liquefied refrigerant to travel onto the thermostatic expansion valve, and it contains a drying agentinadesiccant bag inside the container.

Sight glass

In

Out

Dessicant bag

Pickup tube

Strainer

The accumulator is a storage container on the low-pressure side of the system between the evaporator and the compressor. It is used to separate out refrigerant liquid from vaporized refrigerant, allowing only vaporized refrigerant to travel onto the compressor assembly. It contains a drying agent in a desiccant bag inside the container.

The receiver-drier or accumulator contains the drying agent known as desiccant.

Fusible plug FIGURE 5-16  Cutaway of a typical receiver-drier.

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Baffle (liquid deflector)

Test port

To compressor

From evaporator

Internal tube Desiccant bag Filter

Bleed hole

FIGURE 5-17  Cutaway of a typical accumulator.

The system will have either an accumulator or a receiver-drier, not both. The thermostatic expansion valve is the component in the refrigerant system that regulates the rate of flow of refrigerant into the evaporator core through the use of a variable valve opening as governed by a remote bulbsensing evaporator temperature. It is located just before the evaporator and after the receiverdryer. It is one of the points in the air-conditioning system where there is a separation between a high and low pressure. A system that uses a thermostatic expansion valve also uses a receiver-dryer assembly.

Any liquid sinks to the bottom of the accumulator. As the vaporized refrigerant is drawn out of the accumulator through the internal tube, a small amount of liquid, if present, is drawn into the tube by venturi action through the bleed hole in the bottom loop. This bleed hole keeps the accumulator from becoming flooded with liquid refrigerant and refrigerant oil and allows a small volume of liquid refrigerant and lubricating oil to pass on to the compressor. In this manor, a compressor hydrostatic lock condition is avoided. Hydrostatic lock occurs if liquid refrigerant in excess of the compressors compressed cylinder volume were to be drawn in on the intake stroke, compressor seizure and damage would result. It is important to never overfill a refrigerant system with lubricating oil or refrigerant. In addition to storing refrigerant, the accumulator contains a desiccant bag which contains a drying agent. This drying agent captures any moisture that could have entered the system during original assembly or service procedures. Moisture is one of the worst enemies of a refrigerant system and can cause both physical damage to components and system performance complaints. The accumulator is used in systems that have a fixed orifice tube as a metering device. Those systems that have a thermostatic expansion valve have liquid-line receivers and not suction accumulators. The system will have either an accumulator or a receiver-drier, not both, depending on system design.

Metering Devices At the present time, there are two types of metering devices used in automotive air-­conditioning systems. The most widely used device is the thermostatic expansion valve, more commonly called an expansion valve and often abbreviated TXV. Another device, originally introduced by General Motors and now found on many car lines, is the expansion tube, more commonly referred to as an orifice tube. ■■ Systems that have an expansion valve will have a receiver-drier in the liquid line before the device. ■■ Systems that have an orifice tube will have an accumulator in the suction line after the device.

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D D

C

A

B

FIGURE 5-18  Thermostatic expansion values: (A) H-valve; (B) block type; (C) internally equalized; (D) externally equalized.

Expansion Valves

The expansion valve (Figure 5-18) controls the amount of refrigerant entering the evaporator under ever-changing heat load conditions. Heat load conditions of the car’s interior depend on many factors, such as the number of occupants and heat gain from the sun through windows and the car’s body, as well as heat gain from the engine compartment and exhaust system.

Expansion Tubes

The expansion tube, better known as a fixed orifice tube (FOT), is a nonadjustable device that has a fixed orifice metering element and a fine-mesh strainer. Unlike the expansion valve, the FOT (Figure 5-19) has no remote bulb, no moving parts, and does not vary the amount of refrigerant entering the evaporator in the same manner. The FOT meters the proper amount of refrigerant into the evaporator based on a pressure differential (high side to low side). A pressure differential is known as delta P (Dp).

Author’s Note: The easiest way to determine whether you have a fixed ­orifice tube system with an accumulator or an expansion valve system with a ­receiver-drier is to pay attention to line diameter. Accumulators are located in the larger diameter suction line and receiver-driers are located in the smaller diameter liquid line.

Outlet

Inlet

Direction of flow FIGURE 5-19  A typical fixed orifice.

The expansion tube is the component in the refrigerant system that regulates the rate of flow of refrigerant into the evaporator core. It is often referred to as the FOT and is a fixed metering device equipped with a filter screen. It is located between the condenser and the evaporator core and is one of the points in the airconditioning system where there is a separation between high and low pressure. A system that uses a fixed orifice tube also uses an accumulator assembly placed between the evaporator and the compressor.

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Evaporator The evaporator is physically located in the air distribution duct work for the passenger compartment comfort heating and cooling system and looks like a small radiator (Figure 5-20). The evaporator is a heat exchanger that removes heat from the air flowing across the evaporator cooling fins. The source of the air blown over the evaporator fins and coils may be from outside the passenger compartment or recirculated from inside the passenger compartment when the MAX mode or Recirculation mode is selected on the heater control panel. Heat in the air is picked up by the fins and coils and transferred to the refrigerant passing through the coil. The refrigerant inside the evaporator coil is at a low pressure because it was metered into the coil through the small orifice of the expansion valve or by the orifice tube. Also, the compressor is pulling refrigerant out of the evaporator by a suction action. As the low-pressure liquid refrigerant absorbs heat from the evaporator coils and fins, it boils, turning into a vapor. Because heat was taken out of the air inside the car, its temperature is lower (cooler), and the passenger compartment becomes conditioned or more comfortable. As air continues to recirculate over the evaporator coil, more heat is removed and the air continues to cool. Actual temperature control is by the action of a thermostat or a low-pressure control. Humidity is an important factor in the quality and temperature of the air delivered to the interior of the car. The service technician must understand the effect that relative humidity (RH) has on the performance of the system. Relative humidity is the term that is used to denote the amount of moisture in the air. For example, a relative humidity of 80 percent means that the air contains 80 percent of the moisture that it can contain at a given temperature. When the relative humidity is high, the evaporator has a double function. It must lower the air temperature as well as the temperature of the moisture carried in the air. The process of condensing the moisture in the air transfers a great amount of heat energy in the

Expansion tubes are often referred to as fixed orifice tubes. The evaporator is a heat exchanger that removes heat from the air flowing across the evaporator cooling fins and into the passenger compartment. The evaporator core contains no moving parts to wear out.

FIGURE 5-20  A typical evaporator core.

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evaporator. Consequently, the amount of heat that can be absorbed from the air in the evaporator is greatly reduced. The evaporator capacity required to reduce the amount of moisture in the air is not wasted, however. Lowering the moisture content in the air in the vehicle adds to the comfort of the passengers. The average person is comfortable at a temperature of 78°F to 80°F at a relative humidity (RH) of 45 to 50 percent.

Hoses and Lines Hoses and lines carry refrigerant, as a liquid or vapor, from one component to another in the system. Hoses are constructed of a special synthetic reinforced rubber. Because of the properties of refrigerants and the high pressure of the system, only this type of hose should be used. Lines may be constructed of aluminum (Al) or steel tubing. Any good grade of aluminum tubing may be used, provided it is rated at a working pressure of 400 psig (2,760 kPa) or higher. If steel is used, it must be clean and dry. Just like the other components of the system, each hose or line is referred to by name. Follow the system layout for identification of the following components (Figure 5-21).

Suction Line

The suction line is also referred to as the low-pressure line or the low-pressure vapor line. It connects the evaporator outlet to the compressor inlet. This line, which usually has the ­largest diameter in the system, carries low-pressure refrigerant vapor from the evaporator to the compressor. The suction line is cool to the touch.

Discharge Line

Also referred to as the high-pressure discharge line, the discharge line connects the compressor outlet to the condenser inlet. This line carries high-pressure refrigerant vapor. In a properly operating system, this line is hot. It may be very hot in an improperly ­operating system, so taking care to avoid burns is important in many cases.

Air conditioning outlets

Expansion tube

Rust in the system is undesirable and will cause early component failure.

The suction line should be cool to the touch. The suction line is the line connecting the evaporator outlet to the compressor inlet. The discharge line is the line connecting the compressor outlet to the condenser inlet.

High-pressure test port

Evaporator

Liquid line Blower

Accumulator/ dehydrator

Condenser

Low-pressure test port

Muffler Compressor and clutch

FIGURE 5-21  A typical system layout.

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The liquid line connects the condenser to the receiver-dryer inlet and the receiverdryer outlet with the expansion valve inlet.

Liquid Line

The liquid line is also referred to as the high-pressure liquid line. It connects the condenser outlet to the receiver-drier inlet. It also connects the receiver-drier outlet to the evaporator metering device inlet. This line, which is usually warm, may be hot under certain conditions. This line carries high-pressure liquid/vapor from the condenser to the receiver-drier and high-pressure liquid from the receiver-drier to the metering device.

Refrigerant Refrigerant is the term used when referring to the fluid that is used in an automotive airconditioning system. By definition, refrigerant is “a gas used in mechanical refrigeration systems.” Actually, there are many types of refrigerant in use today, depending on application (Figure 5-22). Refrigerant is any fluid or vapor that is used to transfer heat from one area or space to another. One may not think of water (H 2 O) as a refrigerant, but, when used to remove engine heat from a vehicle, it is a refrigerant. As a matter of fact, water is assigned a refrigerant number: R-718. This refrigerant evaporates (boils) and condenses at 2128F (1008C) at sea level atmospheric pressure (14.696 psia or 101.3 kPa absolute). Refrigerant-12, which has been used in automotive air-conditioning systems for many years, was also used on other applications such as domestic refrigeration. Refrigerant-12, more commonly known as R-12 or CFC-12, has the highest human safety factor of any refrigerant available that is capable of withstanding high pressures and temperatures without deteriorating or decomposing. The boiling point of R-12 at sea level atmospheric pressure is 221.678F(229.88C). Therefore, it must be kept contained to prevent it from immediately boiling away. The basic chemical, a fluorinated hydrocarbon known as carbon tetrachloride (CCl 4) was selected. It met the requirements most closely with only a few minor changes. Carbon tetrachloride (CCl 4 ) consists of one atom of carbon (C) and four atoms of chlorine (Cl). To change carbon tetrachloride (CCl 4 ) into a suitable refrigerant, two of the chlorine (Cl) atoms were removed, and two atoms of fluorine (F) were introduced in their place.

FIGURE 5-22  Two types of refrigerant are used in the automotive air-conditioning system: (A) R-12 and (B) R-l34a.

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F

Cl C F

Cl

FIGURE 5-23  The chemical structure of R-12 (CFC-12).

The new compound, known as dichlorodifluoromethane, is R-12. R-12 has many applications in various types of domestic and commercial refrigeration and air-conditioning systems as well as automotive air conditioners. The chemical symbol for R-12 is CCl 2 F2. This means that one molecule of this refrigerant contains one atom of carbon, two atoms of chlorine, and two atoms of fluorine (Figure 5-23). Until the late 1980s, R-12 was considered ideal for automotive use because of its relatively low operating pressures. Its stability at high and low operating temperatures is also desirable. It does not react with most metals such as iron (Fe), aluminum (Al), or copper (Cu). Liquid R-12, however, may cause discoloration of chrome (Cr) and stainless steel (SS) if large quantities are allowed to strike these surfaces. R-12 is soluble in mineral oil and does not react with rubber. Some synthetic rubber compositions, however, may deteriorate if used as refrigerant hose. Synthetic rubber hose, such as Buna N, designated for refrigeration service is to be used. In applications since the late 1980s, refrigeration hoses have been lined with nylon, nytril, or polyamide veneer to provide a better barrier against leaks. R-12 is odorless in concentrations of 20 percent or less. In greater concentrations, it can be detected by the faint odor of its original compound, carbon tetrachloride (CCl 4 ). R-12 does not affect the taste, odor, or color of water or food. It was believed that it was not harmful to animal or plant life. Recent discoveries, however, dispel this belief. Unfortunately, it has been determined that R-12 is, by far, the leading single cause of ozone depletion. The United States and 22 other countries signed an agreement in 1987 known as the Montreal Protocol. At that meeting, it was agreed that the production of chlorofluorocarbon (CFC) refrigerants would be phased out in a timely manner. The automotive air-conditioning industry was the first to be regulated because it was found that the automotive industry was the greatest offender. It was determined that 30 percent of all R-12 released to the atmosphere was from mobile air-conditioning systems. The production of R-12 ended in the United States on December 31, 1995. Importing virgin R-12 into the United States from other countries is illegal, with the exception of limited quantities that are used for such medical purposes as metered-dose inhalers. It is, however, legal to import used and recovered R-12 under close scrutiny of the federal government. Those who wish to export R-12 to the United States must first petition the EPA with specific and verifiable information about its source. The industry, then, must now rely on surplus and recycled R-12 or equipment conversion to another type refrigerant, such as R-134a. An alternate refrigerant has been developed to take the place of R-12. Tetrafluoro-ethane, referred to as R-134a, has many of the same characteristics of R-12 but poses no threat to the ozone. It does not contain ozone-depleting chlorine. Its chemical formula is CF3 CFH 2 (Figure 5-24). Though chemically it is referred to as HFC-134a, it is generally called R-l34a in the industry.

Carbon tetrachloride (CCl4 ), a cleaning agent, is not considered safe for personal use.

Hoses with liners are called barrier hoses.

Protocol: The plan of a scientific experiment or treatment.

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F

C H

F

F

C

H

F FIGURE 5-24  The chemical structure of R-134a (HFC-134a).

Use the proper refrigerant.

The substance that flows through the refrigeration system is referred to as the refrigerant. It circulates through the system to provide a cooling effect by absorbing heat from the evaporator. Liquid refrigerant flows into the evaporator and absorbs the heat transferred to it from the air flowing across the outside of the evaporator. This heat causes the refrigerant to vaporize as heat is drawn away from the evaporator and air stream. Refrigerant in the liquid form is clear and translucent. The refrigerant used in all new vehicles is R-134a (HFC-134a). Several refrigerants have been approved by the EPA for use in automotive air-conditioning systems. Only two types, however, are approved by the automotive industry for use. The use of a refrigerant not approved by industry may void manufacturer’s warranties on the system as well as on replacement components. The two industry approved refrigerants are: 1. R-12 (CFC-12) 2. R-134a (HFC-134a) Other refrigerants approved by the EPA for automotive use include: ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■

FRIGC FR-12 Freeze-12 Free Zone (also, RB-276) GHG-HP GHG-X4 (also, Autofrost and Chill-It) GHG-X5 Hot Shot (also, Kar Kool) Ikon-12 R-406A (also, GHG)

Many substances could be used as refrigerants but may have undesirable properties that make them unsuitable in a mobile air-conditioning system. The following is a list of the most important properties of a refrigerant: 1. A refrigerant must not be explosive or flammable. 2. A refrigerant must not be hazardous and a leak should be easily detectable.

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3. The refrigerant must be highly stable and allow for repeated use without decomposing or changing its properties. 4. The refrigerant must not cause damage to parts or materials used in the compressor or other components. 5. The refrigerant must vaporize easily in the evaporator. 6. The larger the latent heat value at the vaporization point of the refrigerant, the smaller the volume of refrigerant that will be required for circulation and the smaller the total size of the refrigeration system. 7. The critical temperature of the refrigerant must be higher than the condensation temperature of the system. 8. Evaporator pressure must be higher than atmospheric pressure. The characteristics and properties of refrigerant R-134a made it a very good choice for use in automotive air-conditioning systems. It is nonexplosive, noncorrosive, nonflammable, nonpoisonous, odorless, and harmless to food and clothing. Never use air in combination with refrigerants. Both HCFC-22 and R-134a fall into a category of refrigerants known as combustible. If exposed to oxygen, they will both burn when under pressure or when exposed to high temperatures, but they will not ignite in air at atmospheric pressure and temperature.

De Minimis Release

The practice of purging small amounts of refrigerant in the course of repair and service is known as a de minimis release. The word minimis is not to be confused with the Latin word minimus, which means “smallest.” De minimis is taken from the Latin phrase “De minimis non curat lex,” which means “The law does not concern itself with trifles.”

Refrigerant R-134a (Hfc-134a) Refrigerant 134a (HFC-134a) is at present the automotive industry’s refrigerant of choice and replaced R-12 in automotive systems in the early 1990s. By 1995, all new cars manufactured contained R-134a. When servicing a refrigerant system, the most important characteristic of R-134a is its relationship between temperature and pressure. If the pressure of R-134a is high, the temperature will also be high. If the pressure is low, the temperature will also be low. At atmospheric pressure, R-134a boils at –16.4°F (–26.8°C) and water boils at 2128F (1008C). If we place R-134a under 10 psig of pressure, it will boil at 212.88F (210.68C) and water boils at 2508F (1218C) (Figure 5-25). If R-134a is released into room temperature air at atmospheric pressure, it would instantly vaporize into a gas as it absorbs heat from the air. R-134a will also condense back to a liquid state if it is placed under pressure and heat content is removed. The graphs in Figure 5-26 represent the relationship of pressure and temperature of R-134a. The curve in the graph shows the change-of-state point of R-134a between a liquid and a gas under various pressures and temperatures. The upper portion of the graph is R-134a in the vapor state and the lower portion of the graph is R-134a in the liquid state. In example 1, we can see that refrigerant in the vapor (gaseous) state can make a change of state to a liquid by increasing the pressure on the refrigerant without changing its temperature. In example 2, we can see that refrigerant in the vapor (gaseous) state can make a change of state to a liquid by decreasing the temperature of the refrigerant without changing its pressure. The refrigerant system utilizes both of these principles at the condenser, where pressure has been increased (by the compressor) and temperature has been decreased (air flow across the condenser) to allow the refrigerant to change back to a liquid. In example 3, we can see that refrigerant in the liquid state can make a change of state to a gas (vapor) by decreasing the pressure on the refrigerant without changing its temperature.

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Boils at 250°F Boils at 212°F

10 psi

WATER

Boils at –12.8°F

Boils at –16.4°F

10 psi

R-134a FIGURE 5-25  Boiling point of refrigerant R-134a compared to water at both atmospheric pressure and at 10 psig.

EXAMPLES 1 AND 2 T e m p e r a t u r e

°F

180 160 140 120 100 80 60 40 20 0 –20

°C

80 70 60 50 40 30 20 10 0 –10 –20 –30

EXAMPLES 3 AND 4 T e m p e r a t u r e

2

GAS 1

Liquid

0

5

10

7

14

15

20

25

21

28

35

30 kg/cm 2 G 43 psig

Gauge pressure

°F

180 160 140 120 100 80 60 40 20 0 –20

°C

80 70 60 50 40 30 20 10 0 –10 –20 –30

GAS 4 3

0

5

10

7

14

Liquid

15

20

25

21

28

35

30 kg/cm 2 G 43 psig

Gauge pressure

FIGURE 5-26  Refrigerant saturation curve. In Examples 1 and 3, if temperature is held constant, refrigerant may be a gas or a liquid, depending on pressure. In Examples 2 and 4, if pressure is held constant, refrigerant may be a gas or a liquid, depending on temperature.

In example 4, we can see that refrigerant in the liquid state can make a change of state to a gas (vapor) by increasing the temperature of the refrigerant without changing its pressure. The basic conditions of R-134a based on the temperature-pressure fundamental at various locations in the refrigerant system is the foundation on which system operation and diagnosis is based. 154 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Refrigerant HFO-1234yf (R-1234yf) R-1234yf is classified as HFO-1234yf. HFO stands for hydrofluoro olefin and has a chemical structure of CF3CF 5 CH2 2,3,3,3-tetrafluoropropene. From a performance standpoint, R-1234yf is almost identical to R-134a (Figure 5-27), with similar system sizes and operating pressures, it is compatible with current R-134a components, and it has similar temperature– pressure relationship tables to R134a. Honeywell-DuPont states that R-1234yf is a potential direct substitute for R-134a. Cross contamination with R-134a is not a problem from a system durability standpoint, though performance would be affected. The desiccant that is currently recommended is XH7 and XH9, which is the current desiccant in use with R-134a, in the same amount (size) that is currently used. Some are calling R-1234yf a drop-in refrigerant, as has been indicated by HoneywellDuPont, though the EPA has indicated it will not accept it as such in existing R-134a systems or vice versa. As such, technicians will have very little difficulty diagnosing or working on this new refrigerant system as working pressures and diagnosis are virtually identical. It will be very similar to the transition from R-12 to R-134a as far as serviceability and diagnosis are concerned and in many respects simpler since there will be no retrofitting allowed and R134a and R1234yf have almost identical pressure–temperature relationships. Shop owners may not feel the same way because R-1234yf, like all refrigerants, will require the purchase of a dedicated recovery/recycling/recharging machine (J2927) equipped with a new refrigerant analyzer (J2912) and new leak detection equipment (J2913). Honeywell-DuPont states that current R-134a leak detection equipment will work on R-1234yf systems as long as it was manufactured to meet J2913 requirements. Verify that your leak analyzer meets the new SAE J2913 standard, as older equipment may have been manufactured before this requirement. Like all SNAP refrigerants, R-1234yf will have a unique service connection fitting to avoid cross contamination. One concern the service industry has is since R-1234yf and R-134a are so similar from a functionality standpoint, we may find an R-1234yf system filled with the lowercost R-134a after system repairs. This is one reason that the SAE J2927 standard required that a refrigerant identifier be integrated into recovery/recycling/recharging equipment. Unlike the changeover from R-12 to R-134a, where R-134a was much less expensive than R-12, it is

3500 3000

R134a R1234y

Pressure [kPaA]

2500 2000 1500

R1234yf has higher saturation pressure

1000

R1234yf has lower saturation pressure

500 0 –10

0

10

20

30

40

50

60

70

80

90

Temperature [C] FIGURE 5-27  R1234yf refrigerant performance compared to R134A refrigerant. Both are very similar at working pressures and temperatures.

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Acute Toxicity Exposure Limit Refrigerant

ATEL (ppm)

R-12

18,000

R-134a

50,000

R-744

50,000

R-1234yf

101,000

FIGURE 5-28  This chart is an estimate of the maximum exposure limit for a short time period of less than 30 minutes with no adverse health effects. This is meant as an example only and should not be used as an actual guide for computing exposure time.

expected that R-1234yf is considerably more expensive than R-134a. Some have called for a tax on R-134a that will raise its price to be more in line with R1234yf, but this is not a popular idea and is unlikely to gain political support. As a refrigerant, both the capacity and the coefficient of performance (COP) of R-1234fy systems are within 5 percent of R-134a systems. In addition, R-1234yf has a lower compression ratio and lower discharge temperatures, 548F (128C) lower at peak conditions. Also, further improvements are expected in systems designed to use R-1234yf, such as improved TXV optimization of superheat and lower AP suction line performance. Furthermore, R-1234yf has a lower acute toxicity exposure limit (ATEL) as compared to either R-12 or R-134a (Figure 5-28). There are 18 new standards and revisions published by SAE related to both R-134a and HFC-1234fy refrigerants for use in mobile air-conditioning systems (MAC): ■■ J639 – Safety Standards for Motor Vehicle Refrigerant Vapor Compression Systems (revised 2/2011). ■■ J2064 – R134a Refrigerant Automotive Air-Conditioned Hose (revised 2/2011). ■■ J2099 – Standard of Purity for Recycled R-134a (HFC-134a) and R-1234yf (HFO-1234yf ) for Use in Mobile Air-Conditioning Systems (revised 2/2011). ■■ J2297 – Ultraviolet Leak Detection: Stability and Compatibility Criteria of Fluorescent Refrigerant Leak Detection Dyes for Mobile R-134a and R-1234yf (HFO-1234yf ) AirConditioning Systems (revised 2/2011). ■■ J2670 – Stability and Compatibility Criteria for Additives and Flushing Materials Intended for Aftermarket Use in R-134a (HFC-134a) and R-1234yf (HFO-1234yf ) Vehicle Air-Conditioning Systems (revised 2/2011). ■■ J2762 – Method for Removal of Refrigerant from Mobile Air-Conditioning System to Quantify Charge Amount (revised 2/2011). ■■ J2772 – Measurement of Passenger Compartment Refrigerant Concentrations Under System Refrigerant Leakage Conditions (revised 2/2011). ■■ J2773 – Standard for Refrigerant Risk Analysis for Mobile Air-Conditioning Systems (revised 2/2011). ■■ J2842 – R-1234yf and R744 Design Criteria and Certification for OEM Mobile Air-­ Conditioning Evaporator and Service Replacements (revised 2/2011). ■■ J2843 – R-1234yf (HFO-1234yf ) Recovery/Recycling/Recharging Equipment for ­Flammable Refrigerants for Mobile Air-Conditioning Systems (revised 2/2011). ■■ J2844 – R-1234yf (HFO-1234yf ) New Refrigerant Purity and Container Requirements for Use in Mobile Air-Conditioning Systems (revised 2/2011). ■■ J2844 – R-1234yf New Refrigerant Purity and Container Requirements Used in MVAC Systems

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■■

■■

■■

■■

■■

■■

■■

J2845 – R-1234yf (HFO-1234yf ) and R-744 Technician Training for Service and ­Containment of Refrigerants Used in Mobile A/C Systems (revised 2/2011). J2851 – R-1234yf (HFO-1234yf ) Refrigerant Recovery Equipment for Mobile Automotive Air-Conditioning Systems (revised 2/2011). J2888 – HFO-1234yf Service Hose, Fittings, and Couplers for Mobile Refrigerant Systems Service Equipment (revised 2/2011). J2911 – Procedure for Certification that Requirements for Mobile Air-Conditioning ­System Components, Service Equipment, and Service Technician Training Meet SAE J Standards (revised 2/2011). J2912 – Performance Requirements for R-134a and R-1234yf Refrigerant Diagnostic ­Identifiers for Use with Mobile Air-Conditioning Systems (revised 2/2011). J2913 – R-1234yf (HFO-1234yf ) Refrigerant Electronic Leak Detectors, Minimum ­Performance Criteria (revised 2/2011). J2927 – R-1234yf Refrigerant Identifier Installed in Recovery and Recycling Equipment for Use with Mobile A/C Systems (revised 2/2011). For larger shops with more than one R/R/R machine, a portable refrigerant analyzer that meets J2912 may be connected via a USB cable to the R/R/R unit, thereby reducing investment costs.

R-1234yf Refrigerant System Design Fundamentally the R-1234yf system is almost identical to R-134a system design and operation. The temperature–pressure characteristics of R-1234yf are shown in Figure 5-29 and are very similar to that of R-134a.

R-1234yf Fahrenheit Pressure/Temperature Chart 77 80 83 86 89 92 96 99 102 106 110 113 117 121 125 129 133 137 142 146 148 150 155 160 164 169 174 179 184 190 195

200 206 212 218 223 229 236 242 248 255 261 268 275 282 289 296 304 311 319 326 334 342 351 359 368 376 385 394 403 413

0 4 8 12 16 17 18 22 23 24 28 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70

72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 102 104 106 108 110 111 112 114 116 118 120 122 124 126 128 130

132 134 136 138 140 142 144 146 148 150 152 154 156 158 160 162 164 166 168 170 172 174 176 178 180 182 184 186 188 190

62 75 90 105 120 137 155 174 194 214 225 236 248 260 272 284 297 309 323 336 350 364 379 394 409 425 440 457 473 490 508 526

°C

kPa

°C

kPa

°C

-18 -16 -14 -12 -10 -8 -6 -4 -2 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

544 562 581 601 620 641 661 682 704 726 748 771 794 818 842 866 891 917 943 970 997 1024 1052 1081 1110 1140 1170 1201 1232 1264 1297 1330

23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54

1363 1398 1432 1468 1504 1541 1578 1616 1654 1694 1733 1774 1815 1857 1900 1943 1987 2032 2078 2124 2171 2219 2267 2317 2367 2418 2523 2631 2743 2859 2979

55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 82 84 86 88 90

Condenser

9 11 14 16 19 19 20 23 24 25 28 31 33 35 37 38 40 42 44 47 49 51 53 56 58 61 63 66 68 71 74

kPa

Evaporator

PSIG °F

Condenser

PSIG °F

Evaporator

PSIG °F

R-1234yf Celsius Pressure/Temperature Chart

FIGURE 5-29  Temperature/pressure chart for R-1234yf refrigerant.

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A/C System with an Internal Heat Exchanger (IHX): To Compressor To Evaporator

Compressor

Evaporator Inner tube

Low-Temperature, Low-Pressure Gaseous Refrigerant

IHX

Outer tube Condenser

Expansion Device

High-Temperature, High-Pressure Liquid Refrigerant

Low-Temperature, Low-Pressure Liquid refrigerant

High pressure liquid after addition heat has been removed by IHX

Low temperature, low pressure refrigerant from the evaporator outlet line flow through this out corrugated honey comb tube. Tube-within-a-Tube Design FIGURE 5-30  R1234yf system performance is improved with the addition of an internal heat exchanger (IHX) between the high side liquid line and the low side vapor return line. Otherwise the system is fundamental the same as an R134A system. In fact, some manufacturers are using an IHX to improve performance on smaller R134A systems making an R134A and an R1234yf system virtually identical.

One difference is the use of an internal heat exchanger (Figure 5-30) to improve system performance to meet that of an R-134a system.

Pressure versus Temperature Relationship The temperature at which refrigerant vaporizes or condenses is the saturation temperature. The saturation temperature of a gas or liquid increases or decreases based on the pressure applied to the refrigerant. The refrigerant in the air-conditioning system cannot stay a gas at temperatures below a corresponding pressure. Nor can a refrigerant stay a liquid at temperatures above a corresponding pressure. The refrigerant cycle of repeated heat absorption at the evaporator and heat transfer at the condenser cannot happen without pressurizing and raising the temperature of the refrigerant (Figure 5-31). In order for the refrigerant in the evaporator to boil at the correct temperature, the pressure of the refrigerant must be lowered. If the pressure is lowered the proper amount, the temperature will eventually be less than that of the surrounding air. When this pressure is reached, the refrigerant will absorb the heat from the air, and a change of state from a liquid 158 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Evaporator

Condenser

Circulation of refrigerant Vapor

Heat absorbed from inside the car

Heat given off to outside air Liquid

Passenger cabin Engine compartment FIGURE 5-31  Refrigerant cycle of heat exchange.

to a vapor (vaporization process) will occur. This process will transfer a large quantity of heat from the air to the refrigerant. The net effect is that the air temperature will be lowered to enable cooling of the passenger compartment. Now that the refrigerant has absorbed a large quantity of heat, it must release this heat before the next cycle through the evaporator core. For the refrigerant to release this heat, the pressure must be increased, which will also raise its temperature. The compressor will raise the refrigerant pressure and heat concentration. This increase in pressure and temperature is required so that the refrigerant can give off its heat at the condenser and a change of state can occur from a vapor to a liquid (condensation process). The cycle can now be repeated to cool more air entering the passenger compartment.

Refrigerant R-12 (CFC-12)

A refrigerant, known as R-12 or CFC-12, was used in automotive air-conditioning systems through the early 1990s. Because of environmental concerns, its production and use has been phased out. Certain system changes, however, have to be made in order to use the new ­refrigerant. There is no drop-in refrigerant available that is approved for automotive use.

Other Refrigerants

In 1994, the EPA established the Significant New Alternatives Policy (SNAP) Program to review alternatives to ozone-depleting substances. Under authority of the 1990 Clean Air Act, the EPA also examines potential substitute refrigerants as to their flammability, effects on global warming, and toxicity. As of this writing, the agency has determined that ten “new” refrigerants, including R-134a, are acceptable for use as an R-12 replacement in motor vehicle air-conditioning systems. They are all, however, “acceptable subject to use conditions.” All alternate refrigerants except R-134a are “blends,” which means that they contain more than one component in their composition. “Acceptable subject to use conditions” indicates that the EPA believes these refrigerants, when used in accordance with the use conditions, to be safer for human health and for the environment than the R-12 they are meant to replace. This designation, however, is not intended to imply that the refrigerant will work as satisfactorily as R-12 in any specific system. Also, it is not intended to imply that the refrigerant is perfectly safe regardless of how it may be used. The EPA does not test refrigerants and therefore does not specifically approve or endorse any one refrigerant over any others. The agency reviews all of the information about a refrigerant submitted by its manufacturer and independent testing laboratories. The EPA does not determine what effect, if any, a “new” refrigerant may have on vehicle warranty.

Do not contaminate recovery system equipment or cylinders.

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Contaminated is a term generally used when referring to a refrigerant cylinder or system that fails a purity test and is known to contain foreign substances such as other incompatible or hazardous refrigerants.

Some refrigerant manufacturers use the term drop-in to imply that their refrigerant will perform identically to R-12 and that no modification is required for its use. The term also implies that the alternate refrigerant can be used alone or mixed with R-12. The EPA believes the term drop-in confuses and obscures at least two important regulatory points: 1. Charging one refrigerant into a system before extracting the old refrigerant is a violation of the SNAP use conditions and is therefore illegal. 2. Certain components may be required by law, such as hoses and compressor shutoff switches. If these components are not present, they must be installed. Five blends, for example, contain HCFC-22 and require barrier hoses. It may also be noted that system performance is affected by such variables as outside temperature, relative humidity, and driving conditions. Therefore, it is not possible to ensure equal performance of any refrigerant under all of these conditions. The service facility must have service and recovery equipment specifically designed for each type of refrigerant that is to be serviced. This means that at least two systems are required: one for R-12, and one for R-134a. A third set is required if contaminated systems are to be serviced, and a fourth set is required if a blend refrigerant is to be used. Each new alternate refrigerant must be used with a unique set of fittings attached on the service ports, all recovery and recycling equipment, on can taps and other charging equipment, and on all refrigerant containers. A unique label must be affixed over the original label to identify the type of refrigerant as well as lubricant used in the air-conditioning system.

Handling Refrigerant All refrigerants must be properly stored, handled, and used. Liquid refrigerant can cause blindness if sprayed into the eyes. Also, if liquid refrigerant comes into contact with the skin, frostbite may result. A refrigerant container should never be exposed to heat above 1258F (51.78C). This means that it should not be allowed to come into contact with an open flame or any type of heating device, and it should not be stored in direct sunlight. The increase in refrigerant pressure inside the container, known as hydrostatic pressure, as a result of excessive heat can become great enough to cause the container to explode. If refrigerant is allowed to come into contact with an open flame or heated metal, a poisonous gas is created. Anyone breathing this gas may become ill. Remember—refrigerant is not a toy. Refrigerant should be handled only by a properly trained and experienced automotive service technician. The term Freon is frequently used when referring to refrigerant. Freon and Freon-12 are registered trademarks of E. I. DuPont de Nemours and Company. These terms, then, should be used only when referring lo refrigerant manufactured by this company. A new term, SUVA, is used by DuPont to identify a new ozone-friendly group of refrigerants that includes R-134a (HFC-134a). Both refrigerants, as well as others, are also produced by several other manufacturers and are packaged under various tradenames. Either refrigerant is available in sizes from “pound” cans to 1-ton (907-kg) cylinders. Actually, the “pound” can of R-12 contains 12 oz. (340 g). The R-134a can also contains 12 oz. (340 g) (Figure 5-32). After November 15, 1992, it became unlawful to sell or distribute to the general public R-12 in containers of less than 20 lb. (9 kg). Proper certification is now required for the purchase of refrigerant, in any quantity, to ensure that those dispensing refrigerants are knowledgeable in their profession and may be held accountable for their actions. Some states also require special licensing of the service facility in addition to the federal certification requirements. Also, to legally service automotive air-conditioning systems, the service facility must have proper, adequate, and EPA-approved refrigerant service equipment for each type refrigerant they wish to service.

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FIGURE 5-32  Typical “pound” cans of R-12 (CFC-12) and R-134a (HFC-134a).

The industry has adopted a standard color code to identify refrigerant containers. An R-12 container is white, and an HCFC-22 container is green. Light blue identifies an R-134a container, which must not be confused with R-114, which is packaged in a dark blue container. This color code, however does not apply to “pound” cans. It cannot be overemphasized that R-12, a chlorofluorocarbon refrigerant; HCFC-22, a hydrochlorofluorocarbon; and R-l34a, a hydrofluorocarbon refrigerant, are not compatible with each other. They must not be mixed under any circumstances or in any other manner substituted one for the other. Mixing refrigerants, even in small quantities, will result in exceptionally high pressures that may cause serious damage to system components, such as the evaporator and hoses. An improper refrigerant may also cause damage to the system due to the incompatibility of the lubricant and desiccant The appropriate equipment—such as manifold and gauge set, recovery system, and charging station—must be used for each refrigerant.

Air-Conditioning Circuit To better understand the function of an automotive air-conditioning system, it is helpful to know the physical state of the refrigerant in the various sections of the system. Actually, there are only six such states to be considered: 1. Low-pressure vapor (A) 2. Low-pressure liquid (B) 3. Low-pressure vapor and liquid (C) 4. High-pressure vapor (D) 5. High-pressure liquid (E) 6. High-pressure liquid and vapor (F) Following is a brief overview of each of these states. For component location, refer to callouts (A through F) in Figure 5-33 for an expansion valve system or Figure 5-34 for an orifice tube system.

Low-Pressure Vapor

The refrigerant is a low-pressure vapor in the section of the system from the evaporator outlet to the compressor inlet (A). This includes any devices found in the suction line, such as a suction-line drier, muffler, or accumulator. 161 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

A Flow

D Discharge line

Suction line

Compressor

C

Clutch

Evaporator

Condenser

F

Liquid line Flow

Thermostatic expansion valve

Receiver-drier

B

E

FIGURE 5-33  Thermostatic expansion valve system.

A

D

Suction line Flow

Discharge line Compressor

C

Clutch

Evaporator

Accumulator

Condenser

F

Fixed orifice tube Liquid line Flow

B

E

FIGURE 5-34  Orifice tube system.

Low-Pressure Liquid

Immediately after the metering device, the entrance to the evaporator (B) is the only part of the system that may contain low-pressure liquid. Even this section contains vapor, called flash gas, having just passed through the metering device.

Low-Pressure Vapor and Liquid

In the evaporator (C), low-pressure liquid refrigerant boils as it picks up heat and is changed to low-pressure vapor.

High-Pressure Vapor

The refrigerant is at high pressure in a vapor state in the line from the compressor outlet to the condenser inlet (D). This includes any devices that may be in the discharge line, such as a muffler.

High-Pressure Liquid

The high-pressure liquid refrigerant section extends from the condenser outlet to the metering device inlet (E). This includes any devices in the liquid line, such as receiver, drier, and sight glass.

High-Pressure Liquid and Vapor

In giving up its heat, the high-pressure refrigerant vapor is changed to liquid in the condenser (F). 162 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

System Review

Heat is picked up inside the automobile driver/passenger compartment from the air passing through the coils and fins of the evaporator. This heat is picked up by the liquid refrigerant as it evaporates. The heat-laden refrigerant vapor is then pumped by the compressor into the condenser on the outside of the automobile, usually located in front of the radiator. In the condenser, the refrigerant’s heat is given up to the less hot air passing across the coils and fins as it condenses back to a liquid. The transfer of heat in an air-conditioning system is accomplished by two pressure and two temperature systems: a low-pressure system of 21–35 psig (145–241 kPa) with a low temperature of 248F2408F (248C to 48C), and a high-pressure system of 180–220 psig (1,241–1,517 kPa) with a high temperature of 1238F21378F (518C2588C). Any time there is a pressure change, there is a temperature change. During this pressure-temperature change with R-134a and R-12, there is also a change of state (Figure 5-31). In the low-pressure side, the change is from a liquid to a vapor; in the high-pressure side, the change is from a vapor to a liquid. It is important that you understand this pressure–temperature relationship as you use the manifold and gauge set as a diagnostic tool. The manifold and gauge set is used as a diagnostic tool to determine many system problems that relate to abnormal gauge pressures. If you will recall from Chapter 2, superheat is the added heat intensity given to a gas after the complete evaporation of a liquid. In a refrigerant system, if all the liquid refrigerant in the evaporator core at a given point has gone through a change of state from a liquid to a gas as it picked up heat it may only be 75 percent of the way through the core. These refrigerant molecules still have 25 percent of the evaporator core left to travel through. As the refrigerant gas continues to travel through the evaporator, this gas will pick up additional heat from the core as more heat is given up by the air passing over its surface. Even though the refrigerant is at the same pressure, it will become hotter than the pressure/temperature chart in Figure 5-35 may indicate it should be. This increase in heat above the normal pressure/temperature relationship is called superheat. This phenomenon only occurs when there are no liquid refrigerant molecules nearby. Refrigerant systems are designed to maintain approximately 108F (128C) of superheat in the refrigerant leaving the evaporator so that the gas returning to the compressor is several degrees away from the condensation point of the refrigerant. This is to avoid the risk of liquid refrigerant entering the compressor. The compressor is designed to be a vapor pump and would be damaged if it had to compress liquid refrigerant. The pressure of the refrigerant is increased by the compressor. The compressor pumps low-pressure refrigerant vapor from the evaporator to the condenser at a high pressure. The pressure of the refrigerant is decreased by the metering device (expansion valve or orifice tube) at the inlet of the evaporator. The flow of refrigerant is regulated into the evaporator by a metering device such as a TXV or an FOT. Just before entering the metering device, the refrigerant is a high-pressure liquid. Refrigerant is metered into the evaporator through a small orifice, changing it to a low-pressure liquid. From what we have outlined, it may be concluded that the compressor is the dividing line, low- to high-side, and the metering device is the dividing line, high- to low-side. Whenever necessary, refer to the basic principles previously discussed.

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FIGURE 5-35  Typical temperature-pressure charts.

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SUMMARY ■■

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The automotive air-conditioning system is a combination of mechanical systems circulating a chemical medium (refrigerant). The refrigerant absorbs heat from the air entering or recirculating through the passenger compartment and transfers this heat to the outside air. The conditioned air in the passenger compartment contains less moisture, which adds to the cooling sensation felt by the passengers. In principle, the air-conditioning system does not cool; it removes heat from the air entering the passenger compartment. The air-conditioning compressor is the heart of the heating and cooling system. The compressor is one of the points in the air-conditioning system where there is a separation between high and low pressure. Its purpose is to pull refrigerant into the compressor through the suction line and compress and pump refrigerant out the discharge (pressure) line. The condenser is a heat exchanger for the superheated refrigerant in the system. It removes the heat energy from the refrigerant that was gained in the evaporator. The evaporator is a heat exchanger that removes heat from the air flowing across the evaporator cooling fins in the passenger compartment duct system to cool the passenger compartment. The accumulator and receiver-drier are storage and distribution components used to clean and dry the refrigerant. Refrigerant lines are of barrier design for R134a refrigerant and are used to transport refrigerant through the system. The air-conditioning system is designed to maintain in-car temperature and humidity at a predetermined level.

Terms to Know Accumulator Air conditioning Condenser Contaminated Discharge line Evaporator Expansion tube Liquid line Receiver-drier Reciprocating piston(s) Suction line Superheated Thermostatic expansion valve

REVIEW QUESTIONS Short-Answer Essays

Fill in the Blanks

1. Why is the air-conditioning system’s efficiency improved when the Recirculation mode is selected?

1. Humidity in the passenger compartment can be increased by many factors, including but not ­limited to, _______________, _______________, and even _______________ in the vehicle contributing to ­humidity load by _______________.

2. How is liquid refrigerant used to lower passenger ­compartment temperature? 3. What can affect the saturation temperature of gas or liquid refrigerant? 4. Explain the term dew point temperature.

2. When the pressure of R-134a is high, the temperature will be _______________. When the pressure is low, the temperature will be _______________.

5. What is the basic function of the automotive air-­ conditioning system?

3. The temperature at which refrigerant vaporizes or condenses is _______________ the temperature.

6. What is the difference between the accumulator and the receiver-drier?

4. An air-conditioning system that uses a fixed orifice tube has a(n) _______________ in the suction line.

7. Where is the receiver-drier located, and what state is the refrigerant in that flows through it?

5. An air-conditioning system that uses a thermostatic expansion valve has a(n) _______________ in the liquid line.

8. Where is the accumulator located, and what state is the refrigerant in that flows through it? 9. What is the purpose of a compressor? 10. How does the expansion tube differ from the ­expansion valve?

6. The _______________ is a heat exchanger for the superheated refrigerant in the system. 7. The _______________ is one of the points in the air-conditioning system where there is a separation between high and low pressure. 165

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8. There is a direct relationship between temperature and _______________ in an automotive air-conditioning system. 9. The refrigerant changes from a _______________ to a _______________ in the condenser. 10. Two types of metering devices are the _______________ valve and the _______________ _______________ tube.

Multiple Choice 1. All of the following are forms of heat transfer that take place as it relates to the vehicle air-conditioning system except: A. Convection C. Radiation B. Conduction D. Perspiration 2. All of the following are important properties that an automotive refrigerant must exhibit except: A. The refrigerant must be highly stable and allow for repeated use without decomposing or changing its properties. B. A refrigerant must be explosive or flammable. C. The critical temperature of the refrigerant must be higher than the condensation temperature of the system. D. Evaporator pressure must be higher than ­atmospheric pressure. 3. R-134a, when used as a refrigerant, exhibits a predict able relationship between pressure and temperature, and a stable change of state point between a liquid and a gas under various pressures and temperatures. All of the following are true of the temperature pressure relationship of R-134a except: A. Refrigerant in the vapor (gaseous) state can make a change of state to a liquid by increasing the pressure on the refrigerant without changing its temperature. B. Refrigerant in the vapor (gaseous) state can make a change of state to a liquid by decreasing the temperature of the refrigerant without changing its pressure. C. Refrigerant in the liquid state can make a change of state to a gas (vapor) by increasing the pressure on the refrigerant without changing its temperature. D. Refrigerant in the liquid state can make a change of state to a gas (vapor) by increasing the temperature of the refrigerant without changing its pressure. 4. In a normally operating system, the refrigerant is in different physical states (vapor or liquid) at the various sections of the system. All of the following are physical states the refrigerant would be found in at various specific locations except: A. A low-pressure vapor at the suction line B. A low-pressure vapor and liquid at the evaporator

C. A high-pressure vapor at the discharge line D. A high-pressure liquid at the condenser 5. Under normal operating conditions all of the following occurs inside the evaporator, except: A. The refrigerant absorbs heat. B. Heat entering the refrigerant causes it to change state. C. The refrigerant removes heat from the outside air drawn across evaporator core. D. The refrigerant changes from a vapor to a liquid. 6. Technician A says the condenser is a heat exchanger for the superheated refrigerant in the system. Technician B says the accumulator is a heat exchanger that removes heat from the air flowing across the evaporator cooling fins. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 7. Technician A says the compressor is one of the points in the air-conditioning system where there is a separation between a high and a low pressure. Technician B says the metering device is one of the points in the air-conditioning system where there is a separation between a high and a low pressure. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 8. The metering device changes high-pressure liquid to A. A low-pressure B. A high-pressure C. A low-pressure liquid D. Any of the above, vapor depending on the outside air vapor temperature 9. Technician A says the fixed orifice tube can vary the amount of refrigerant allowed to flow to the evaporator. Technician B says the thermostatic expansion valve has a fixed opening and cannot vary the amount of refrigerant allowed to flow to the evaporator. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 10. Technician A says that the line or hose that connects the compressor outlet to the condenser inlet is called the discharge line. Technician B says that the line or hose that connects the evaporator outlet to the compressor inlet of a TXV system is called a suction line. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

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Chapter 6

Refrigerant System Components Upon Completion and Review of this Chapter, you should be able to: ■■

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Explain the purpose and operation of an automotive air conditioner compressor.

■■

a. The receiver-drier

Identify and compare the state of the refrigerant in each section of the automotive air-conditioning system. Discuss the change of state of the refrigerant:

Explain the purpose of: b. The accumulator

■■

Compare the function of the thermostatic expansion valve (TXV) to the fixed orifice tube (FOT).

a. In the evaporator b. In the condenser

Introduction In the following discussion, the purpose and function of each component of the basic automotive air-conditioning system are discussed. The sizes of the system refrigerant hoses are given, as are the states of the refrigerant in each of them. The state of the refrigerant in each of the components is also discussed (Figure 6-1). Although hose sizes may vary slightly from vehicle to vehicle, the state of the refrigerant at various points in all systems is basically the same. For the purpose of this discussion of the air-conditioning cycle, we will start with the compressor. It is the compressor’s function to circulate the refrigerant throughout the system.

The Refrigeration Cycle What we learned in Chapter 2 was that to cool down an object, heat must be removed or given off. In an automotive refrigerant system, we use a pressurized refrigeration system. The refrigerant in the automotive refrigerant system circulates under pressure in a sealed closed loop circuit continually changing from a liquid to a gas (vapor) and from a gas back to a liquid while the system is operating. The entire refrigerant cycle exhibits several processes as the refrigerant changes state, from liquid to vapor and from vapor to liquid. For the following discussion refer to Figure 6-2. Refrigerant is compressed in the vapor state at the compressor, entering as a low pressure vapor and leaving as a high pressure vapor. The compressor raises both the pressure and the temperature of the refrigerant. From there it moves on to the condenser where the pressurized heat (Btu) concentrated refrigerant gives up its heat energy to the surrounding air being drawn across its core, making a change of state as it condenses from a high pressure vapor into a high pressure liquid. Next, the pressure of the refrigerant drops as it passes through the metering device. The refrigerant enters the

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High-side gauge

Low-side gauge Vapor: low pressure and temperature

Vapor: high pressure and temperature

Manifold Hose set

Refrigerant, changing from liquid to vapor. Removes heat from the passenger compartment Accumulator in the evaporator.

Flow

Refrigerant, changing from vapor to liquid. Gives up heat to the outside air in the condenser.

Compressor Evaporator

Clutch

Condenser

Flow Liquid: low pressure and temperature

Orifice tube Orifice tube system

Liquid: high pressure and temperature

A

High-side gauge

Low-side gauge Vapor: low pressure and temperature

Hose set

Refrigerant, changing from liquid to vapor. Removes heat from the passenger compartment in the evaporator. Flow

Flow Remote bulb

Clutch

Flow Thermostatic expansion valve

Refrigerant, changing from vapor to liquid. Gives up heat to the outside air in the condenser.

Compressor

Evaporator

Liquid: low pressure and temperature

Vapor: high pressure and temperature

Manifold

Condenser

Receiver/drier Sight glass

Liquid: high pressure and temperature

Expansion valve system

B FIGURE 6-1  Typical air conditioning circuit showing the state of the refrigerant in each section: (A) orifice tube system and (B) expansion valve system.

metering device as a high pressure liquid and leaves as a low pressure liquid. It is second of the two dividing lines between the high pressure side and low pressure sides of the refrigerant system, the first was the compressor. The low pressure liquid refrigerant enters the evaporator core where heat is absorbed from the air traveling across its surface causing another change of state as the low pressure liquid refrigerant boils as it absorbs heat from the air blowing across it and changes from a low pressure liquid into a low pressure vapor. Cool air is not produced; heat is removed from the air flowing into the vehicles duct system and finally to the passenger 168 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

4 Evaporator

Accumulator

3

1

Metering device

2 Condenser Compressor

Radiator

High pressure gas

Low pressure liquid

High pressure liquid

Low pressure gas

FIGURE 6-2  The compressor (1) is one of the dividing line between the low pressure and high pressure side of the system, the refrigerant is a low pressure vapor on the inlet side and a high pressure vapor on the discharge side. The condenser (2) is a heat exchange where a change of state takes place from a high pressure vapor to a high pressure liquid. The metering device (3) is the other dividing line between the high pressure and low pressure side of the system, the refrigerant is a high pressure liquid on the inlet side and a low pressure liquid on the outlet side. The evaporator (4) is a heat exchanger where a change of state takes place from a low pressure liquid to a low pressure vapor.

compartment. So, the refrigerant system picks up heat at the evaporator core that it removed from the air entering the passenger compartment and gives up this heat at the condenser to the outside air passing across its surface transferring this heat back into the environment. This process is repeated continuously as the system is operated. This is the basic air-conditioning circuit from which all of the other automotive refrigerant circuits are patterned. A good understanding of the basic circuit makes an understanding of other circuits much easier. To reiterate what was stated previously, the compressor draws in (suction) vaporized refrigerant from the evaporator and increases the gas pressure thereby separating the low side of the system from the high side. The metering device used by automotive refrigerant systems is either a thermostatic expansion valve (TXV) or a fixed orifice tube (FOT) and is the device that controls the refrigerant flow into the evaporator and as such separates the high side from the low side of the system. This information is also important when trying to locate where the manufacturer located both the high side and the low side service ports when trying to attach a manifold and gauge set.

A BIT OF HISTORY Recovery of R-134a became mandatory on November 15, 1995, and the recycling of R-134a became mandatory on January 29, 1998. 169

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FIGURE 6-3  A typical air conditioning compressor.

There are three basic types of compressors: reciprocating, rotary, and scroll. Reciprocating motion is to move to and fro, fore and aft, or up and down. Electromagnetic is a temporary magnet created by passing electrical current through a coil of wire. A clutch coil is a good example of an electromagnet.

Compressor The compressor (Figure 6-3) in an air-conditioning system is a pump especially designed to raise the pressure of the refrigerant and circulate it through the system. According to the laws of physics, when the pressure of a gas or vapor is increased, its temperature is also increased. When pressure and temperature are increased, refrigerant condenses more rapidly in the next component, the condenser. With some exceptions, automotive air-conditioning compressors are of the same design, reciprocating piston. This means that the pistons move in a linear motion, back and forth or up and down. The only exceptions are the rotary vane (RV) and scroll compressors, which are both increasing in popularity. The automotive air-conditioning system uses a fixed- or variable-displacement compressor to move the refrigerant and to compress low-pressure, low-temperature refrigerant vapor from the evaporator into a high-pressure, high-temperature vapor to the condenser. A label is generally found on the compressor to identify the type of refrigerant for which it is designed. This is a requirement to comply with the rules of the Environmental Protection Agency (EPA). Compressors are belt driven from the engine crankshaft through an electromagnetic clutch pulley (Figure 6-4). When not energized, the compressor clutch pulley rotates freely without turning the compressor shaft. When voltage is applied, the electromagnetic clutch coil is energized, and the pulley engages with a clutch plate, often referred to as an armature, mounted on the compressor shaft. The magnetic field locks the clutch plate and pulley together as one unit to drive the compressor shaft. Clutch pulley

Compressor

Clutch hub

Snapring Hub key

Field coil

Pulley bearing

Dust shield

Snapring

Shims

Locknut

FIGURE 6-4  A typical compressor showing clutch details.

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Piston

Wobble plate assembly

Pressures Crankcase Low pressure Discharge

Control valve

Shaft Piston stroke

FIGURE 6-5  Cutaway of a typical swash plate compressor.

Some compressors cannot be repaired and, if defective or damaged, must be replaced. Many rebuilt replacement compressors contain lubricant that must be drained and replaced with the proper type and amount. Most new compressors, on the other hand, are supplied without lubricant. Fill the rebuilt or new compressor with the same amount and type lubricant as removed from the defective compressor or as recommended in the manufacturer’s service manual. Piston motion is caused by action of a crankshaft or a swash plate, often referred to as a wobble plate. Some swash plate compressors have double-ended pistons, such as General Motors DA-6, whereas others have single-ended pistons, such as Sanden’s SD-5 (Figure 6-5). A more detailed explanation of compressors is given in Chapter 9 of this Manual, with troubleshooting and repair procedures given in Chapter 9 of the Shop Manual. The following brief description is of the operation of the pistons and valves of a typical reciprocating compressor.

Operation

Each piston in a compressor has a set of reed valves and valve plates—one suction and one discharge valve. Assume a simple two-cylinder compressor for the following description of operation (Figure 6-6). While one piston is on the suction (intake) stroke, the other piston is on the discharge (compression) stroke. The piston draws refrigerant into the compressor through the suction valve and forces it out of the compressor through the discharge valve. When the piston is on the suction (or intake) stroke, the discharge valve is held closed by the higher pressure above it. At the same time, the suction valve is opened to allow low-pressure refrigerant vapor to enter. When the piston is on the compression (or discharge) stroke, refrigerant vapor is forced through the discharge valve; the suction valve is held closed by this same pressure. The compressor separates the low side from the high side of the system (Figure 6-7). Refrigerant entering the compressor is a low-pressure, slightly superheated, vapor. When the refrigerant leaves the compressor, it is a high-pressure, highly superheated, vapor. The compressor in some air-conditioning systems has service valves that are used to access the air-conditioning system. The manifold and gauge set is connected into the system at the service valve ports. All service procedures—such as recovering, evacuating, and charging the system—are performed with the use of a manifold and gauge set and the proper recovery and charging equipment.

The intake stroke of the compressor is also called the suction stroke. The compression stroke of the compressor is also called the discharge stroke. Reed valves are the leaves of steel located on the valve plate of a compressor that allow refrigerant to enter or leave the compressor. Stroke is the distance a piston travels from its lowest point to its highest point. Compression is the act of reducing volume by pressure.

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Downstroke of piston creates vacuum in cylinder. Pressure in suction line forces suction valve open.

Pressure in cylinder raises discharge valve; gas flows into discharge pipe.

Pressure in discharge line holds discharge valve closed.

Pressure in cylinder holds suction valve closed.

Piston on downstroke

Piston on upstroke

FIGURE 6-6  Typical operation of a single-cylinder compressor.

FIGURE 6-7  Refrigerant entering the compressor is lowpressure vapor and is high-pressure vapor when leaving.

Refrigeration lubricant, most often referred to as oil, is stored in the compressor and is essential in keeping the internal parts of the compressor lubricated. A small amount of this lubricant circulates with the refrigerant through the system. The velocity of the refrigerant through the tubes and hoses, however, allows this lubricant to return to the compressor. Chapter 9 will provide greater detail on the various oils used in refrigerant systems.

Hoses And Lines Refrigerant fluid and vapor lines may be made of aluminum or steel. Hoses are usually made of synthetic rubber covered with nylon braid for strength and have an inner lining of nylon to ensure integrity and to form a barrier wall to prevent refrigerant leakage. This hose design is classified as a barrier hose and is found on all R-134a refrigerant systems. Older R-12 systems used hoses with inner liners typically made of Buna “N,” a synthetic rubber. Buna “N,” which is not affected by R-12, is not acceptable for R-134a systems. Barrier hoses with a nylon lining are compatible with both R-134a and R12 systems. 172 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

There are several ways to identify whether a hose or pipe is on the high-pressure side or low-pressure side of the system: ■■ The low-side pressure lines are cold to the touch when the system is operating normally and are larger in diameter than those on the high-pressure side. ■■ The high-side pressure lines are hot to the touch when the system is operating normally and are smaller in diameter than those on the low-pressure side. Special consideration must be given for hoses and other components used in an R-134a air-conditioning system. Many materials that were compatible for an R-12 system, such as nitrile or epichlorohydrin, cannot be used for R-134a service. For example, O-rings used with fittings in an R-12 system, such as nitrile, and those used in an R-134a system, such as neoprene, are not interchangeable. Standard hose sizes are given a number designation, such as #6, #8, #10, and #12. Size #6 is usually used for the liquid line, #8 or #10 as the hot gas discharge line, and #10 or #12 as the suction line. Figure 6-8 gives the inside diameter (ID) and outside diameter (OD) of two types of hoses used in automotive air-conditioning service. Most early R-12 hoses were not barrier hoses, which have a nylon liner inside the hose designed to stop the leakage of the smaller particles of R-134a refrigerants. Though not of a barrier design, the old hoses used in R-12 systems are oil soaked on the inside with the mineral oil lubricant used in these systems. The idea is that R-134a is not compatible with mineral oil and will not go through it. Although true in most cases, the constant refrigerant pressure eventually opens a path and allows the refrigerant to escape to the atmosphere. Most original equipment manufacturer (OEM) retrofit procedures, as far back as 1984, do not require replacing hoses. Many feel, however, that if a retrofit is to be done properly, all nonbarrier hoses should be replaced with barrier hoses (Figure 6-9). The EPA does not require replacement of hoses or seals during the retrofit of a vehicle from R-12 to R-134a. Always refer to manufacturer recommendations. Figure 6-10 is a comparison table of R-134a and R-12 refrigerants. As the table indicates, barrier hoses are an option for the R-12 system. The best practice is to always follow the manufacturer’s procedures and recommendations when retrofitting an air-conditioning system. The hose type is generally distinguished by the crimp style used on the fitting (Figure 6-11). Either the finger style crimp, used with a nonbarrier hose having a barb fitting, or the bubble style beadlock crimp, used specifically with a nylon barrier hose, will generally be found. Also, fittings with worm gear hose clamps are used with nonbarrier-type hoses. A worm gear hose clamp should never be used with nylon-barrier hose fittings. Depending on design and application, several types of fittings are used to connect the hoses to the various components of an air-conditioning system. The line connections on

English

Metric

/16 in.

7.94 mm

/32 in.

10.32 mm

#6

5

#8

13

#10

1

/2 in.

12.7 mm

#12

5

/8 in.

15.87 mm

Shop Manual Chapter 6, page 188

When refrigerant changes from vapor to liquid, it gives up heat. When refrigerant changes from liquid to vapor, it takes on heat. Do not mix refrigerants.

Outside Diameter (OD)

Inside Diameter (ID) Hose Size

Most early R-12 (CFC-12) hoses are not compatible with R-134a (HFC-134a) refrigerant.

Rubber Hose English

Metric

Nylon Hose

/32 in.1

11.9 mm3

/64 in.1

13.89 mm3

/16 in.1

17.46 mm3

3

/4 in.

19.05 mm

15

/64 in.1

23.42 mm3

35

1- 1/32 in.2

25.8 mm4

11

1- 5/32 in.2

29.37 mm4

59

Metric

English

NA

NA

+ 1/64 inch + 1/32 inch 3 + 0.4 mm 4 + 0.8 mm

1 2

FIGURE 6-8  Inside and outside diameter of hoses used for air conditioning service.

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Butyl

Braid

Rubber

Nylon Rubber

FIGURE 6-9  Barrier hose details.

R-134a System

R-12 System

Chemical Name

Tetrafluoroethane

Dichlorodifluoromethane

Refrigerant container identification

Labeled R-134a sky-blue container

Labeled R-12 white container

Refrigerant container fitting

1

7

Boiling point at sea level

–15.07°F (–26.15°C)

–21.62°F (–29.79°C)

Desiccant

XH7, XH9

XH5, XH7, XH9

Hose construction

Barrier nylon liner required

Barrier nylon liner optional

Valve core

M6 thread, O-ring seal

TV thread, Teflon seal

Refrigerant oil

Polyalkylene glycol (PAG) or polyol ester (Ester)

Mineral based

Refrigerant oil hygroscopicity

2.3%–5.6% by weight

0.005% by weight

Condenser

Improved heat transfer design

Standard

/2" x 16 ACME

/16" x 20, 1/4" Flare

FIGURE 6-10  R-134a/R-12 comparison table.

Beadlock Fitting Crimp Style

Barb Fitting Crimp Style

Finger-style crimp For old all-rubber hose only

Bubble-style crimp For nylon barrier hose

FIGURE 6-11  Hose crimp styles.

anR134a system have moved the O-ring to the midpoint (captured) of the connection from the base of the connection that was used on R-12 systems (Figure 6-12). There are many types and styles of line connections, including block joint fittings (Figure 6-13) and spring lock fittings (Figure 6-14). Specially designed O-rings are used in conjunction with line connections to provide a seal between joints. If an air-conditioning system component or line is removed for service, the O-ring seals must be replaced (Figure 6-15). A small amount of clean refrigerant oil should be applied to the new O-ring (Figure 6-16) before installation. 174 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Inch thread

EARLY (R-12) TYPE

LATE (R-134a) TYPE

Metric thread

EARLY (R12) TYPE

LATE (R-134a) TYPE FIGURE 6-12  Threaded nut-type pipe connections.

FIGURE 6-13  Block fitting-type pipe connections.

Garter spring Cage

Female fitting

Female fitting

Male fitting

O-rings

Garter spring

Cage

Detail of spring lock (garter) connector FIGURE 6-14  Spring lock fitting used on some refrigerant system lines.

FIGURE 6-15  New O-rings should always be installed once they are disturbed.

Author’s Note: Only clean refrigerant oil should be used to lubricate refrigerant seals or connections. Never use petroleum-based oils, grease, or silicone as a lubricant. Some air-conditioning systems require a muffler on the compressor discharge line to reduce noise and vibration caused by compressor pulses. The muffler contains several chambers or baffles that redirect refrigerant flow, generating a cancelling frequency to reduce noise (Figure 6-17).

Discharge Line The hose leaving the compressor contains high-pressure refrigerant vapor. This hose, which is made of synthetic rubber, generally has a nylon barrier lining. It typically has a 13 32 in (10.3 mm) inside diameter and often has extended preformed metal (steel or aluminum) ends

Barrier is a term given to something that stands in the way, separates, keeps apart, or restricts—an obstruction. Barrier hoses are used on R134a systems due to their smaller molecular size than R12 refrigerant.

175 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

ND

-O

I

34a R1 L FIGURE 6-16  A small amount of oil should be applied to new O-rings.

FIGURE 6-17  Refrigerant system highside discharge muffler used to dampen noised and vibration generated by compressor pump pulsations.

with fittings. It is known as the hot gas discharge line and connects the outlet of the compressor to the inlet of the condenser. Under normal operating conditions, this line is very warm. During certain system malfunctions, however, it is very hot. Because of the refrigerant temperature and pressure in this line, it is generally the most susceptible to leaks. Ideally, the refrigerant will be all liquid when it leaves the condenser.

Condenser The condenser, which is located in front of the engine cooling radiator, is a heat exchanger made up of cooling fins and tubes that carry refrigerant. The condenser provides a rapid transfer of heat from the refrigerant passing through the tubes to the air passing through the fins and across the tubes. Part of a preventive maintenance service is to ensure that the condenser is clean and free of all debris. If found to be bent, a fin comb may be used to straighten the condenser fins. Heat-laden refrigerant in the vapor state liquifies or condenses in the condenser. To do so, the refrigerant must give up its heat. As cooler air passing over the condenser carries its heat away, the vapor condenses. Heat that is removed from the refrigerant in the condenser as it changes from a vapor to a liquid, is the same heat that was absorbed in the evaporator as it changed from a liquid to a vapor. The refrigerant from the compressor is almost 100 percent vapor as it enters the condenser. On certain occasions, a very small amount of vapor may condense in the hot gas discharge line. The amount is so small, however, that it is not considered in the overall operation of the system. The refrigerant is not always 100 percent liquid when it leaves the condenser, however. Only a certain amount of heat can be dissipated by the condenser at any given time. A small percentage of refrigerant, then, may leave the condenser in the vapor state. This condition does not affect overall system performance because the next component is a long liquid line or a receiver-drier. The refrigerant in the condenser is a combination of liquid and vapor under high pressure. To avoid personal injury, extreme care must be exercised when servicing the condenser. The inlet of the condenser must be at the top so the refrigerant vapor, as it condenses, will collect at the outlet at the bottom of the condenser. To ensure that all of the refrigerant vapor has condensed to a liquid when leaving the condenser, some systems are equipped with a small, second (auxiliary) condenser. This auxiliary condenser, called a subcondenser, provides the additional heat transfer surface required in some air-conditioning systems for the refrigerant to condense to a liquid.

176 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

B

A

Serpentine flow

Parallel flow

FIGURE 6-18  Two common flow paths through air conditioning condensers are (A) serpentine flow, and (B) parallel flow.

The outlet of a condenser in a TXV system is connected to the receiver-drier, then to the metering device, by the liquid line. In a FOT system, the outlet of the condenser is connected by a liquid line to the metering device. The condenser for an R-134a system has a larger capacity and is designed for increased heat transfer compared to the standard R-12 system. This is necessary due to the differences in heat transfer characteristic of R-134a. The volume of gas entering the condenser is about 1,000 times the volume of the condensed liquid leaving the condenser. The efficiency of the condenser affects the overall performance of the refrigerant system. There are several condenser designs and flow paths in use today. The two flow paths for refrigerant through the condenser’s tubing are either a serpentine path flowing back and forth on older designs or a multipass flat tube parallel cross flow (Figure 6-18). The condenser may be a tube and fin with older designs using 3 8 in. tubing and newer designs using a 6 mm tube. They have similar heat transfer characteristics of the serpentine design and 15 percent better heat transfer than older 3 8 in. designs. Condenser tubes may also be extruded aluminum tubing with honeycomb serpentine passages for increased surface area and airflow for improved heat transfer (Figure 6-19). This design is physically smaller for the same level of heat transfer, making them popular for compact car designs. All aluminum parallel flow condensers with Tube Fin Extruded aluminum

Tube and fin

Serpentine flow

Parallel flow

A

B

C

FIGURE 6-19  Condensers may be (A) tube and fin, extruder aluminum; (B) serpentine; or (C) parallel flow.

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extruded aluminum tubing with honeycomb are currently popular with original equipment manufacturers (OEM) where limited space and airflow is a concern. The multipass extruded aluminum designs are virtually impossible to flush after a catastrophic compressor failure and should be replaced if a restriction is suspected. The subcooling or supercooling condenser is similar in design to the multipass extruded aluminum designs but have even smaller passages and a modulator assembly with an integrated receiver dryer (Figure 6-20). On the modulated flow design the condenser is divided into two sections for condensing and supercooling. The modulator separates the refrigerant in the middle of the cycle after the first pass that is still in the gaseous state and recirculates it with liquid refrigerant to cool it again, which enables almost 100% liquid refrigerant too pass on to the metering device (Figure 6-21). The modulator performs the same function as the conventional receiver-drier with the major difference being the design of the condenser (Figure 6-22). After the refrigerant’s first Receiver cycle

Supercooling cycle

Multiflow condenser

Sight glass

Multiflow condenser

Receiver tank

Gas and liquid separator (Modulator)

Sight glass

FIGURE 6-20  On a super- or sub-cooling condenser there is a modulator assembly that contains the desiccant so there is no need for a separate receiver dryer that is required on a conventional system. Modulator (Gas and liquid separator)

Condensing section Cool the gas refrigerant into liquid refrigerant

Desiccant Gas refrigerant Filter Removes foreign material from the cycle Liquid refrigerant Supercooling section The liquid refrigerant (includes some gas) is cooled again after passing through the condensing section and modulator to produce close to 100% liquid refrigerant. FIGURE 6-21  On the modulated flow design the liquid refrigerant and any gas still remaining is cooled again after passing through the modulator which enables almost 100% liquid refrigerant too pass on to the metering device.

178 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Modulator Gas

Condensing section High pressure gas

Liquid Supercooling section

Modulator

When gas increases ases

Gas

Supercooling liquid

Modulator Gas

Condensing section Liquid level drops

Liquid

When gas decreases ses

Condensing section Liquid level raises

Gas increases Sub-cooling section

Liquid

Gas decreases Sub-cooling section

FIGURE 6-22  On the modulated flow design the liquid refrigerant and any gas still remaining is cooled again after passing through the modulator which enables almost 100% liquid refrigerant too pass on to the metering device.

pass through the condenser, only liquid refrigerant is allowed to pass through the lower supercooling section of the condenser. The liquid level in the modulator is maintained at a balancing point with liquid and gaseous particles. If the amount of incoming gas increases under highload operating conditions, the liquid level is pushed downward. This process allows additional liquid refrigerant to be supplied to the metering device. When system load and demand is low, the liquid level inside the modulator will increase as incoming gas flow decreases and the gaseous refrigerant condenses. The excess liquid is stored in the modulator just as it would be in a receiver-drier until system heat load and demand increases. There may be a sight glass on the liquid line leaving the condenser, but bubbles in the sight glass are only an indicator of low refrigerant level and should not be used as a charge indicator. The bubble-free point in a super cooling condenser is 50–100 grams of refrigerant less than the optimal charge level (Figure 6-23). Proper charge level is approximately 100–150 grams of refrigerant above the point at which bubbles in the sight glass disappear. Cooling efficiency will be insufficient if gas charging is stopped at the bubble-free point and will leave the system undercharged. Overcharging will also cause insufficient cooling. It is important to follow manufacturer charging-level recommendations and not charge any system based on sight glass bubbles. Some modulators have a serviceable desiccant bag while others integrate a nonserviceable desiccant. If a condenser with a serviceable desiccant is to be flushed the removable service plug and desiccant must first be removed prior to beginning the flushing procedure. Once the flushing is complete, a new desiccant bag should be installed. Those condensers that integrate a nonserviceable receiver-drier cannot be flushed and must be replaced if a failure in either is suspected. If a catastrophic compressor failure occurs, these condensers must be replaced as an assembly when the new compressor is installed since debris and contaminated oil will be trapped in the condenser and desiccant. 179 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Receiver cycle Supercooling cycle Range of correct amount

High pressure force

Replenishment: 50–100 g Level area Refrigerant charging amount Bubble-free point

50 g

Overcharging area

Level area Refrigerant charging amount

Refrigerant amount FIGURE 6-23  On subcooling condenser designs the proper refrigerant charge level is 100–150 grams more than on a traditional receiver drier designed system.

Condenser problems usually result from external clogging, damage, or from leaks. External clogging is caused by dirt, bugs, leaves, or other foreign debris that collects onthe condenser fins and restricts airflow. This lessens the condenser’s ability to transfer heat, resulting in poor cooling of the car interior. The condenser and the radiator must be kept clean for best performance. To clean the condenser, use a soft bristle brush (such as a hair brush) and a strong stream of water. Take care not to bend the fins, which would also restrict the flow of air. Clean the radiator/condenser assembly with clean water directed from the back (engine side) to the front. If air is used, use only low-pressure air to prevent damage to the delicate and fragile fins of the radiator. Do not use a steam cleaner to remove debris from the condenser. To do so may cause an increase in air-conditioning system pressure. Because temperature and pressure are high in the condenser, a leak is not always successfully repaired. It is generally recommended that the condenser be repaired by a professional or be replaced if it is found to be leaking. Shop Manual Chapter 6, page 204

The receiver-drier is often called a “receiver” or “drier.”

Receiver-Drier The receiver-drier, often referred to simply as a drier, is located in the high-pressure side of the air-conditioning system between the condenser outlet and the metering device inlet. Construction of the drier is such that refrigerant vapor and liquid are separated to ensure that 100 percent liquid is available at the metering device, the TXV. The receiver-drier (Figure 6-24) is used in systems that have a TXV as a metering device. The receiver-drier has five basic functions: it acts as a reservoir to store liquid refrigerant from the condenser and ensures a vapor-free liquid column to the TXV under a wide range of heat loads. The liquid refrigerant will sink to the bottom while any vapor present will rise to the top of the container. The receiver absorbs moisture and acts as a filter to remove solid contamination. In addition, the receiver-drier dampens compressor pulses, ensuring a steady flow of refrigerant. The receiver-drier is a cylindrical container with both the inlet and outlet tubes at the top of the assembly (Figure 6-25). Some models have a sight glass at the top, but this feature has been phased out. The outlet pickup tube extends almost to the bottom of the container to ensure that only liquid refrigerant will flow out of the receiver-drier.

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FIGURE 6-24  Typical receiver-drier assembly.

Sight glass

Inlet

Receiver tube outlet

Outlet

Inlet

Pickup tube

Desiccant changed silica-gelzeolite (R-134a type) and filter section

Dryer

Pickup tube

Desiccant

R-134a TYPE

Filter R-12 TYPE

FIGURE 6-25  Both R-134a and older R-12 receiver-driers are similar in design and appearance.

The amount of refrigerant demanded by the evaporator varies depending on heat load and compressor output. When the heat load is low, such as on cooler days, the thermostatic expansion valve is only partially open, resulting in low refrigerant flow to the evaporator, and the level of liquid refrigerant in the receiver-drier will be high. But on days when the heat load is high, such as on hot humid midsummer days, the system demand for refrigerant is high because the thermostatic expansion valve is open, resulting in higher refrigerant flow to the evaporator, and the level of liquid refrigerant in the receiver-drier will be low. The receiver-drier acts as an accumulator of refrigerant. It must be able to store enough liquid refrigerant for both cool (low-heat load), and hot, humid (high-heat load) days. In addition, the receiver-drier allows for the expansion and contraction of refrigerant when the system is not in operation but under-hood temperatures and varying ambient air temperatures are high. 181 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Remove plug and change drier bag

Condenser Receiver drier

FIGURE 6-26  On some systems the receiver drier is integrated into the outlet liquid tank of the condenser assembly and may also contain a serviceable desiccant bag.

On some smaller systems today, the receiver-drier is integrated into the liquid line outlet of the condenser assembly (Figure 6-26). When the receiver-drier is located in the liquid outlet tank of the condenser, the desiccant bag may also be serviceable separately. If it is serviceable, there will be a removable plug on either end of the drier.

Receiver Section

The receiver section of the receiver-drier is a tank-like storage compartment. This section holds the proper amount of reserve refrigerant required to ensure proper performance of the air-conditioning system under variable operating conditions. The receiver also ensures that a steady flow of liquid refrigerant can be supplied to the thermostatic expansion valve.

Drier Section Desiccant is a drying agent used to remove excess moisture in refrigeration systems. The desiccant is located in a bag in the receiver-drier or accumulator.

The drier section of the receiver-drier is generally nothing more than a fabric bag filled with desiccant, which is a chemical drying agent that can absorb and hold a small quantity of moisture to prevent it from circulating through the system. The desiccant used in an R-12 receiver-drier may not be compatible with R-134a refrigerant. The desiccants are classified XH5 (silica-gel), XH7 (molecular sieve), and XH9 (zeolite). Only XH7 and XH9 are acceptable for use on R-134a systems. Therefore, to ensure that the desiccant will be compatible with the refrigerant and refrigeration lubricant in the system, use only replacement components that are designated for a particular application. The receiver-drier should be changed any time a major component of the air-conditioning system has been replaced. Most vendors will not honor warranty claims on a new or rebuilt replacement compressor if the receiver-drier is not replaced at the time the system is serviced.

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Screen/Strainer

A screen or strainer is included inside the receiver-drier. This is intended to prevent the circulation of any debris throughout the system that may have entered during careless service procedures. This screen cannot be serviced as a component; the receiver-drier must be replaced as an assembly if the screen is found to be restricted. A condenser-mounted receiver-drier should be mounted as level as possible, usually by adjusting its bracket or the condenser mounting brackets. The vertical-type drier should be mounted in a position as vertical as possible, with no more than a 15-degree slant off vertical. Receiver-driers are available in a variety of sizes and have different fittings for different applications. Universal-type receiver-driers are available and may be used if exact replacement units are not available. Driers are also available without the receiver. This type drier is usually used in series with a receiver-drier in a “problem” air-conditioning system when a great deal of debris is encountered. It should be noted that receiver-driers and driers are not omnidirectional. They are designed for refrigerant to flow in one direction only. Most driers are marked IN and OUT or have an arrow (→) to indicate direction of refrigerant flow. Remember, the refrigerant flow is away from the condenser and toward the evaporator.

Liquid Line High-pressure liquid refrigerant moves from the condenser or receiver-drier through a hose or tube called the liquid line to the evaporator metering device. The liquid line, which is usually made of aluminum, is generally ¼ in. to 5 16 in. (6.3–7.9 mm) inside diameter. In some installations, such as a dual evaporator system, the inside diameter of the liquid line may be as large as ⅜ in. (9.5 mm). This line is sized so the refrigerant flow is not restricted yet maintains the constant pressure that is required to ensure proper metering of the refrigerant into the evaporator. The liquid line may also be made of copper, steel, or a combination of rubber or nylon and copper, steel, or aluminum. As its name implies, the state of refrigerant in the liquid line is liquid under high pressure.

Thermostatic Expansion Valve The TXV (Figure 6-27), located at the inlet side of the evaporator, is the metering device for the system. The TXV separates the high side of the system from the low side of the system. A small variable orifice in the valve allows only a small amount of liquid refrigerant to enter the evaporator. The amount of refrigerant passing through the valve is governed by the

The liquid line is usually identified as the smallest line in the system. The two types of TXV are internal equalized and external equalized. They are not interchangeable. Orifice is a small hole of calibrated dimensions for metering fluid or gas in exact proportions.

A B

FIGURE 6-27  Typical thermostatic expansion values: (A) internal equalized and (B) external equalized.

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Fully closed

Fully open

Closed Open Valve position Desired temperature reached Heat soaked Passenger compartment Low High Sensing element temperature High Low Evaporator pressure FIGURE 6-28  Expansion valves provide a variable restriction to refrigerant flow.

Shop Manual Chapter 6, page 196

evaporator temperature. A tapered pin is raised or lowered in an orifice to change the size of the opening up to 0.008 in. (0.2 mm) diameter when the valve is wide open (Figure 6-28). The thermostatic expansion valve is designed to provide two basic functions: ■■ Based on various heat loads and compressor output, the expansion valve meters the flow of refrigerant into the evaporator. ■■ Refrigerant pressure is reduced as high-pressure liquid entering the valve passes through a restriction and suddenly expands and vaporizes into a low-pressure mist. Refrigerant, as it passes through the thermostatic expansion valve and immediately after it, is 100 percent liquid. A very small amount of liquid refrigerant, known as flash gas, vaporizes immediately after passing through the valve due to the severe pressure drop. All of the liquid refrigerant soon changes state; as the pressure drops, the liquid refrigerant begins to boil. All liquid should boil off before reaching the outlet of the evaporator. As it boils, it must absorb heat from the air passing over the coils and fins of the evaporator. The air, then, feels cool; heat is being removed from the air; cold air is not being created. At the point of total evaporation, the refrigerant is said to be saturated. The saturated vapor continues to pick up heat in the evaporator and in the suction line until it reaches the compressor. The refrigerant is then said to be superheated. There are three distinct physical types of thermostatic expansion valves. They are the external equalizing type, the internal equalizing type, and the box or H-Block internal equalizing type (Figure 6-29). The thermostatic expansion valves used in automotive air-conditioning systems are designed for a specific use and are manufactured as precision components. They are calibrated to provide the correct amount of refrigerant and superheat in the evaporator. No attempt should be made by the inexperienced to disassemble, repair, or adjust the expansion valve. It is possible, however, to clean or replace the inlet screen (strainer) should it become clogged. The thermostatic expansion valve acts as a variable metering orifice that regulates the flow of refrigerant by sensing the system’s temperature and pressure. The expansion valve has a sensing element called a remote bulb attached to the evaporator outlet line (suction line) by a capillary tube (Figure 6-30). This bulb, which is attached to the evaporator tailpipe, senses outlet temperature.

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A

B

C

FIGURE 6-29  Three distinct types of thermostatic expansion values, (A) the external equalizing type, (B) the internal equalizing type, and (C) the Box or H-Block internal equalizing type.

FIGURE 6-30  The (H-block) thermostatic expansion valve showing the remote bulb attached to the outlet of the evaporator.

The expansion valve is regulated by the temperature-sensing bulb that is tightly clamped to the evaporator outlet tube. In operation, the sensing bulb senses the temperature of the refrigerant as it leaves the evaporator core. Expansion valves are either externally or internally pressure regulated (equalized) through an equalization tube to provide a variable restriction to refrigerant flow. The expansion valve allows the air-conditioning system to maintain peak performance regardless of the passenger compartment temperature change that affects the thermal load on the evaporator. The amount of refrigerant allowed to flow is determined by the movement of the internal valve. The openings and closings of the valve are regulated by the difference between the following: ■■ The internal return spring pressure returning the valve to its seat (closed). ■■ The refrigerant pressure at the inlet of the evaporator on internally equalized expansion valves or the refrigerant pressure at the outlet of the evaporator on externally equalized expansion valves. ■■ The temperature-sensing bulb gas pressure. The temperature-sensing bulb pressure is relative to the evaporator outlet temperature. 185 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

If the refrigerant outlet line is warm due to high thermal load (high passenger-compartment or intake air temperature), the vapor temperature of the refrigerant leaving the evaporator outlet will also be high. The charge of refrigerant (or other volatile liquid) in the sensing bulb expands (high pressure), putting pressure on the valve diaphragm through a small capillary tube. The diaphragm then forces a needle valve off its seat, and the valve opens to allow more refrigerant to enter the evaporator (Figure 6-31). As the evaporator outlet tube becomes cooler due to low thermal load (cool passengercompartment or intake air temperature), the vapor temperature of the refrigerant leaving the evaporator outlet will also be low. The charge of volatile liquid in the sensing bulb will contract and there will be less pressure on the diaphragm. The needle valve will then close, decreasing the amount of refrigerant that is allowed to enter the evaporator core (Figure 6-32). Author’s Note: A special insulating cover wraps around the sensing bulb on the evaporator outlet pipe to insulate it from external heat sources. It is critical that the bulb make good contact with the outlet pipe and that the insulating cover be properly placed around it after replacement of the expansion valve. As a precision metering device, the thermostatic expansion valve also senses system pressure. The valve either has an external or internal pressure equalization tube that allows the pressure of the vaporized refrigerant (evaporator outlet) to oppose the gas pressure from the temperature-sensing bulb. This pressure is on the opposite side of the expansion valve’s diaphragm from that of the sensing bulb. Increases or decreases in refrigerant velocity and pressure are affected by compressor speed. The main difference between the external or internal pressure-equalized valve is the side the evaporator pressure is received from. The internally equalized expansion valve uses low-side pressure from the inlet side of the evaporator to apply opposing pressure to the

Temperaturesensing bulb

Out to compressor

Temperaturesensing bulb

Out to compressor

In from receiverdrier

In from receiverdrier External equalizing tube

Valve

Evaporator FIGURE 6-31  Expansion valve open when heat load is high.

External equalizing tube

Valve

Evaporator FIGURE 6-32  Expansion valve closed when heat load is low.

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diaphragm. The externally equalized expansion valve uses low-side pressure from the outlet side of the evaporator to apply opposing pressure to the diaphragm. Under normal conditions, a certain length of the evaporator outlet contains superheated refrigerant vapor (Figure 6-33). Superheat is the difference between the inlet and outlet temperatures of the evaporator core. The outlet temperature should be higher than the inlet temperature. If the evaporator is filled with refrigerant, the pressure at the evaporator outlet (suction) line increases and the evaporator temperature will decrease; the amount of superheated refrigerant will also decrease. The sensing bulb will react to the low temperature by contracting the gas (lowering pressure in bulb) and relieving pressure on the diaphragm. While this is occurring, the high pressure in the evaporator or outlet line will increase pressure on the opposite side of the diaphragm through the equalization tube (passage), accelerating the closing of the valve, and limiting additional refrigerant from entering the evaporator. If there is less than the ideal amount of refrigerant in the evaporator, the refrigerant will vaporize faster and cause a greater portion (length) of the evaporator outlet to be superheated. This in turn will cause the temperature of the outlet to increase and the pressure to decrease. The sensing bulb will react to the high temperature by expanding the gas (increasing pressure in the bulb) and relieving pressure on the diaphragm. The low pressure in the evaporator or outlet line will decrease pressure on the opposite side of the diaphragm through the equalization tube (passage), accelerating the opening of the valve, allowing additional refrigerant to enter the evaporator. The pressure-sensing connections (equalization tube) to the thermostatic expansion valve diaphragm have a dampening effect to keep the expansion valve from opening and closing erratically. This allows a quicker response time by opening and closing the valve rapidly in response to changes in heat load and compressor speed. Using a manifold gauge set and watching the low-side pressure, it is possible to see some of the minute, rapid, and continuous changes in pressure that take place. After the air-conditioning system has been turned on and allowed to stabilize, the low-side gauge needle may fluctuate smoothly, 3–4 psig, as the expansion valve makes minute adjustments to maintain passenger-compartment temperature. If the expansion valve is found to be defective, the sensing bulb may have lost its charge or the internal parts may be seized due to corrosion or foreign matter. The sensing bulb cannot be recharged. If seized, the valve may be in the fully open or fully closed position. If either is the case, the valve must be replaced as an assembly.

Capillary tube

Liquid Saturated vapor Vapor (gas) Pf = Gas pressure within the temperaturesensing bulb Ps = Spring force Pe = Vapor pressure within the evaporator

Pf Pe Refrigerant inlet

Superheated vapor part (L)

Equalizer Valve

Saturated vapor part

Pressure spring (Ps) Evaporator

FIGURE 6-33  An increase/decrease in the area of superheat at the evaporator outlet will cause the expansion valve to open or close.

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H-valve is an expansion valve with all parts contained within. The H-valve is internally equalized. Block valve: Another term for H-valve.

H-Valve The H-valve (Figure 6-34), often called a block valve, is used on many car lines. The most common block-type expansion valve is internally regulated (Figure 6-35). The refrigerant enters the valve through the high-pressure liquid line and passes through a variable restriction that regulates the pressure to the evaporator. As the refrigerant leaves the evaporator, it travels back through the H-valve’s upper outlet port and passes over the temperature-sensing sleeve (internal sensing bulb) contained in the passage, transferring some heat to the refrigerant contained in the power dome diaphragm. This causes the refrigerant contained in the power dome to expand and contract based on the temperature of the refrigerant leaving the evaporator. The expansion and contraction exerts pressure on the sensing cavity diaphragm, causing the valve pin to move up and down and in turn regulates the flow of refrigerant through the evaporator core, thus regulating core temperature. Its purpose, like the standard TXV, is to sense suction line refrigerant temperature. Operation and function of the H-valve, or block valve, are essentially the same as for the TXV. The equalizing passage, whether it is internal or external, is a direct passage to the low side of the system to the opposite side of the power dome diaphragm that the sensing bulb connects to. The equalizing pressure ensures smooth, consistent opening and closing of the

Evaporator H-valve

Condenser A/C pressure transducer

Compressor

Radiator

Receiver/Drier

High pressure gas

Low pressure liquid

High pressure liquid

Low pressure gas

FIGURE 6-34  An H-valve, also known as a block valve or just H-block, is located between both the evaporator inlet an outline lines. It has the unique role of have high pressure liquid (1), low pressure liquid (2), and low pressure vaporized (3) refrigerant at various locations flowing either into or out of it.

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Power dome

Hollow rider pin Low-pressure cold gas from evaporator

Diaphragm Low-pressure cold gas return to compressor Temperature sensing sleeve

Low-pressure cold liquid to evaporator Ball

Operating pin High-pressure hot liquid from condenser

Calibration spring FIGURE 6-35  Details of H-block style expansion valve.

expansion valve. It allows for fine adjustments, thus reducing broad temperature fluctuations of the evaporator core, and more consistent temperature levels are maintained within an acceptable operating range. A similar design used on some vehicles is a new generation expansion valve (Figure 6-36), which does not have an external power dome like a standard H-valve but instead has an internal thermal head. The internal thermal head controls a globe valve at the H-valve inlet Thermal head with special gas filling

Low-pressure cold vapor from evaporator Pressure-equalizing hole Low-pressure cold liquid to evaporator Globe valve

Low-pressure cold vapor to compressor

Operating pin

High-pressure hot liquid from condenser

Regulation spring FIGURE 6-36  New generation H-valve has an internally mounted thermal head and control diaphragm located in the outlet passage of the evaporator discharge instead of an external power dome.

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A

C

B

D

FIGURE 6-37  New generation expansion valves have a thermal gas dome that is in direct contact with the evaporator outlet refrigerant (A) which allows precise control of the opening of the globe valve (B) to allow more refrigerant into the evaporator when heat loads are high. When the evaporator refrigerant outlet temperature drops and heat load is low the pressure in the thermal head decreases (C) and the globe valve closes (D) decreasing the amount of refrigerant entering the evaporator. This design allows for faster response time to changing evaporator heat load conditions.

which regulates refrigerant flow. The thermal head is a capsule filled with a special gas on one side of a membrane (diaphragm) and the other side is connected to the evaporator outlet through pressure equalizing passages. The globe valve is actuated by a push rod attached to the membrane. The operation of the new generation H-valve is similar to the other styles of thermal expansion valve that have been described. An increase in cooling load will cause an increase in the evaporator outlet temperature as the refrigerant leaving contains more heat. This in turn will cause the special gas contained within the thermal head to expand, which will increase the chamber pressure and push against the diaphragm (Figure 6-37A). The pressure increase on the diaphragm will cause the globe valve to open the inlet passage to the evaporator allowing more refrigerant to flow into the evaporator (Figure 6-37B), thereby lowering the temperature of the evaporator. When the heat load is low and the temperature of the refrigerant at the evaporator outlet drops the pressure in the thermal head will also decrease (Figure 6-37C). The pressure decrease on the diaphragm will cause the globe valve to close the inlet passage to the evaporator reducing refrigerant flow into the evaporator (Figure 6-37D). The globe valve opening ratio is dependent on the evaporator refrigerant outlet line refrigerant temperature. The expansion valve regulates the evaporator temperature based on the thermal heat load it detects. Though this design is essentially the same in operating principles as all other expansion valves, having the thermal head placed directly in the refrigerant outlet passage allows for precise control of expansion valve refrigerant flow regulation and precise evaporator temperature based on thermal load. So even though the operation is similar, its response time to changes in thermal load is enhanced.

The Orifice Tube The orifice tube (Figure 6-38) is a calibrated restrictor used as a means of metering liquid refrigerant into the evaporator. Its purpose is to meter high-pressure liquid refrigerant into the evaporator as a low-pressure liquid. The orifice tube establishes a pressure differential at the 190 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Direction of flow Finemesh screen

Inlet

O-rings

Color-coded body

Flow direction

Orifice tube

Outlet

FIGURE 6-38  A typical fixed orifice tube (FOT).

restriction, with the high-pressure liquid line and condenser on one side and the low-pressure liquid line and evaporator on the other side. The amount of refrigerant entering the evaporator with an orifice tube system is dependent on the size of the orifice, subcooling of the refrigerant, and the pressure difference (Ap) between the inlet and outlet of the orifice device. It is frequently referred to as a FOT because of its fixed orifice and tubular shape. The orifice tube is available in sizes ranging from 0.047 in. (1.19 mm) to 0.072 in. (1.83 mm), depending on application, and are generally color coded (Figure 6-39). Fine-mesh filter screens protect the inlet and outlet of the orifice tube. If foreign matter blocks or partially blocks the orifice, the air-conditioning system will not function to full efficiency. If the blockage is severe enough, the system may not function at all. The fixed orifice tube, with few exceptions, is located in a cavity in the liquid line or at the inlet connection of the evaporator and is easily accessible. Exceptions are that some vehicles have an inaccessible FOT located inside the liquid line. If found to be defective, the

FIGURE 6-39  Fixed orifice tubes are available in a variety of sizes and are generally color coded.

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Direction of flow Outlet

Bimetal spring

Fixed orifice

Inlet

Diffuser screen Variable orifice

Variable port

Inlet filter screen

FIGURE 6-40  Details of a variable orifice tube.

Shop Manual Chapter 6, page 198

Cycling clutch systems turn the compressor clutch on and off to control evaporator temperature. The orifice tube, if clogged, may be cleaned. Variable displacement (VD) changes the displacement of the compressor by changing the stoke of the piston(s).

liquid line either has to be replaced, or a repair kit must be used to replace a section of the liquid line containing the FOT. Procedures for replacing the FOT are found in Chapter 6 of the Shop Manual. Some “aftermarket engineers” replace the standard original equipment manufacturers (OEM) fixed orifice tube with an aftermarket Smart variable orifice valve (VOV). The Smart VOV utilizes system pressure to move a metering piston relative to a fixed opening in the sleeve. This is claimed to compensate for reduced compressor output at idle speeds and increase the cooling performance. The Smart VOV manufacturer claims that it is a “drop in” replacement for ineffective OEM orifice tubes and that it can offer a “dramatic improvement on factory R-134a systems.” Before making any changes to an automotive air-conditioning system, it is strongly suggested that manufacturer’s recommendations be followed. The factory-installed air-conditioning system in some Jeep models, beginning in 1999, are equipped with a variable orifice tube. The Jeep design, however, is slightly different from after-market VOVs. There are two parallel paths for refrigerant to flow through the variable orifice valve (Figure 6-40). One is a fixed orifice opening, and the other is a variable orifice opening. As the temperature of the refrigerant flowing though the VOV changes, a bimetal coil opens or closes the variable port. High temperatures cause the port to close. The opening through the fixed orifice tube is normally 0.047 in. (1.1938 mm), and the variable orifice tube opening ranges from 0–0.015 in. (0–0.381 mm). The advantage of the variable orifice tube is improved air-conditioning cooling during high-heat load conditions, such as in stop-and-go traffic or extremely hot days. On General Motors orifice tube systems, two methods of temperature control are used. One method, called a cycling clutch orifice tube (CCOT) system, uses a fixed displacement compressor. A pressure- or temperature-actuated cycling switch is used to turn the compressor’s electromagnetic clutch on and off. This action starts and stops the compressor to maintain the desired in-car temperature. The other orifice tube system used by General Motors has a variable displacement (VD) compressor. This regulates the quantity of refrigerant that flows through the system to maintain the selected in-car temperature. This system, called the variable displacement orifice tube (VDOT) system, eliminates the need to cycle the clutch on and off for temperature control. Many Ford Motor Company car lines use the cycling clutch method of temperature control on their orifice tube systems. Either a temperature- or pressure-actuated control may be used to cycle the clutch on and off to maintain selected in-car temperature. Their system is called a fixed orifice tube/cycling clutch (FOTCC) system. All orifice tube air-conditioning systems have an accumulator located at the evaporator outlet (Figure 6-41). The accumulator prevents unwanted quantities of liquid refrigerant and oil from returning to the compressor at any one time.

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A/C evaporator housing

To compressor

Liquid Line Suction accumulator/drier FIGURE 6-41  A typical accumulator, located at the outlet of the evaporator.

Orifice Tube Failure

The primary cause of failure of the FOT is clogging of the metering element orifice and strainer screen. This is often caused by failure of the desiccant inside the accumulator. Cleaning a clogged FOT seldom provides satisfactory results. The time and expense of having to do the repairs a second time far outweigh the cost of a new FOT. For this reason, if the FOT is found to be clogged, it should be replaced. Also, if the FOT is clogged, the accumulator should be replaced as well.

Evaporator The evaporator’s purpose is to cool and dehumidify the incoming air when the air-conditioning system is operating. The evaporator (Figure 6-42) is that part of the air-conditioning system where the refrigerant vaporizes as it picks up heat. The expansion device (orifice tube or thermal expansion valve) allows low-pressure, low-temperature, atomized liquid refrigerant into the evaporator. As this cold refrigerant flows through the evaporator core, the heat from the warmer air passing over the evaporator fins will transfer its thermal energy (heat) into the cooler refrigerant, lowering the air’s temperature and causing the refrigerant to vaporize (boil) in the evaporator. The refrigerant has now received enough heat to change from a lowpressure, low-temperature liquid into a low-pressure, low-temperature gas. The expansion device and the compressor work in conjunction to meter the exact amount of refrigerant into the evaporator to provide maximum efficiency. This process will ensure that all the liquid refrigerant will be in the vapor state by the time it leaves the evaporator outlet. The evaporator core is housed inside an insulated box section of the passenger compartment air duct system called the evaporator housing. The case is designed to direct all airflow through the core and reduce radiant heat loads on the evaporator. The common designs of evaporators are the laminated (drawn cup) type (Figure 6-43) and the serpentine fin type (Figure 6-44). The laminated design has more refrigerant passage area and allows for a U-turn pattern of flow in the evaporator from front to rear and left to right, which improves cooling capacity. Important considerations in the design of evaporators are ■■ Size and length of the tubing ■■ Number and size of the fins ■■ Number of return bends ■■ Amount of air passing through and past the fins ■■ The heat load (NOTE: Heat load refers to the amount of heat, in Btu’s, to be removed.)

Heat load is the load imposed on an air conditioner due to ambient temperature, humidity, and other factors that may produce unwanted heat.

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Evaporator

OR Thermostatic expansion valve

Orifice tube

A plate

B plate Brazing

Tubes FIGURE 6-42  A typical evaporator core.

Flooded refers to a condition whereby too much refrigerant is metered into the evaporator. Starved refers to a condition whereby too little refrigerant is metered into the evaporator. Automotive airconditioning compressors are not designed to “pump” liquid.

FIGURE 6-43  Laminated core evaporator assembly construction.

Refrigerant, as it leaves the evaporator, should be a low-pressure, slightly superheated vapor. If too much refrigerant is metered into the evaporator, it is said to be flooded. As a result, a flooded evaporator will not cool well because the pressure of the refrigerant in the evaporator is high, and it does not boil away as rapidly. When the evaporator is full of liquid refrigerant, there is no room for expansion. In this case, the refrigerant cannot vaporize properly, which is necessary if the refrigerant is to take on heat. A flooded evaporator also allows an excess of liquid refrigerant to leave the evaporator. The result is that serious damage can be done to the compressor. An accumulator is included in a FOT system to prevent liquid slugging of the compressor. There is no superheat if the evaporator is flooded. If too little refrigerant is metered into the evaporator, the system is said to be starved. Again, the unit does not cool because the refrigerant boils off too rapidly, long before it passes through the evaporator. Under this condition, the superheat is very high. Under ideal conditions, the refrigerant should boil off about two-thirds to three-quarters of the way through the evaporator. At this point, the refrigerant is said to be saturated. It has picked up all of the latent heat required to change from a liquid to a vapor without undergoing a temperature change. From this point, the vaporized refrigerant will pick up additional heat before leaving the evaporator. The refrigerant will also pick up under-hood heat in the suction line before reaching the compressor. This superheat is sensible heat that is added to a vapor, raising its temperature without increasing its pressure. The ideal superheat for an airconditioning system is between 108F and 208F (5.68C211.18C). In humid regions of the

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Sprayed liquid refrigerant from expansion valve

Fin

Evaporator assembly Tube Gaseous refrigerant to compressor

Evaporator drainpipe

FIGURE 6-44  Construction of the Serpentine fin evaporator core assembly.

FIGURE 6-45  Evaporator drainpipe located at the bottom of the case assembly.

country, it is the addition of superheat that often causes the suction line to sweat and, in some cases, ice over. During normal operation, the air blowing across the evaporator contains some moisture. This moisture is removed from the air and collects on the surface of the evaporator. The moisture will drain to the bottom of the evaporator housing in the HVAC housing and then out a drainpipe at the bottom of the case assembly (Figure 6-45). It is normal to see a puddle of water forming under a vehicle while the air conditioning is operating; this indicates that the drain vent is not blocked. A blocked vent can lead to moisture building up in the case, causing bacterial growth and odor as well as water dripping into the passenger compartment. The dehumidification process adds to passenger comfort. In addition, the air-conditioning system is used to control the fogging of the vehicle’s interior windows. In fact,many vehicles’ climate control systems will engage the air-conditioning system anytime the defrost mode is selected at any temperature range to aid in clearing the windshield. There are three problems that could occur with the evaporator, resulting in poor cooling: ■■ Leaks ■■ Dirty cooling fins ■■ Blocked or kinked refrigerant passages

Latent heat cannot be measured with a thermometer.

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Author’s Note: While on a summer vacation with my family, my daughter noticed a large puddle of water forming on the passenger side floor. Shortly after she noticed the puddle, water mist began to blow out of the dash vents. After arriving at our destination and recovering from the laughter that this incident had generated, I crawled under the vehicle and, with a piece of coat hanger, carefully cleaned out the case vent tube drain. No less than a gallon of water drained from the HVAC case, and another two gallons of water had to be wet/dry vacuumed off the passenger compartment floor. This was one vacation that was not soon forgotten.

Evaporators on R-1234yf systems must meet more stringent SAE J2842, which imposes severe durability testing due to the fact that the refrigerant is mildly flammable. If an evaporator is removed on an R-1234yf system, it must be replaced. No used or repaired evaporators should be used on an R-1234yf system. In 2010, Toyota introduced a new design evaporator for their Prius platform. The design is essentially two evaporators face-butted together into one assembly with a secondary restriction device called an injector built-in. After the refrigerant passes though the metering device it has two parallel paths into the evaporator dual core (Figure 6-46). The core has an injector, which is a specially shaped tube that produces a pumping action from the pressurized refrigerant flow, creating a venturi effect. The majority of the refrigerant, called the drive flow, flows through the injector while a smaller volume of refrigerant, called the suction flow, flows into a capillary tube and continues through the downwind evaporator where it vaporizes, reducing the temperature of the air passing over the core. At the same time, a venturi effect occurs as the refrigerant passes through the tapered nozzle of the injector, drawing refrigerant out of the downwind evaporator core. This is referred to as the jet pump effect. The drive and suction flow refrigerant mix before they pass into a wider section of pipe in the injector assembly called the diffuser (Figure 6-47). Since the diffuser is larger in diameter, Condenser

Flow adjustment valve

Compressor

Ejector

Primary evaporator

Capillary tube

Compressor power

Pressure rising effect II Decrease in power consumption

ECS evaporator Secondary (downwind) EVAP

FIGURE 6-46  Toyota introduced an injector cycle evaporator core on the 2010 Prius.

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High velocity and low pressure refrigerant flow at the nozzle outlet

Pressure recovery due to decreased flow velocity

Drive flow

To primary evaporator (upwind)

Nozzle

Mixing section

Diffuser

Secondary flow from Downwind evaporator (suction flow)

To primary evaporator

From metering device (drive flow) Nozzle

Mixing portion

Diffuser portion

Pressure

From secondary (suction flow) Evaporator

Suction due to decrease in pressure

Pressure rise due to decrease in speed

FIGURE 6-47  Evaporator injection assembly located internally in the dual core evaporator.

the mixed refrigerant slows down, raising the pressure in this section of the injector. This pressure increase translates into compressor work recovery, meaning the compressor does not need to work as hard to achieve the same cooling effect. This higher-pressure refrigerant passes into the upwind evaporator, removing additional heat from the air that previously passed over the downwind evaporator, improving cooling system performance. In effect the upwind evaporator is cooled by the downwind evaporator. The system is also referred to as a two-temperature evaporator.

Internal Heat Exchanger (IHX) The internal heat exchanger is generally used on R-1234yf systems but can also be used on R-134a systems to improve their efficiency. The internal heat exchanger (IHX) (Figure 6-48) replaces the suction and liquid refrigerant lines with a coaxial tube that allows heat to be transferred from hot high-pressure liquid line and the cold vapor-filled suction line. The internal heat exchanger is located before the metering device (Figure 6-49). By increasing the amount of thermal energy that can be transferred away from the high-pressure liquid line before the refrigerant passes through the metering device, the evaporator core cooling capacity is increased without increasing system size. This increased cooling capacity in a smaller system reduces energy consumption used by the air-conditioning system, which improves fuel economy, lowers carbon emissions, and increases the air-conditioning system’s overall efficiency.

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Tube-within-a-Tube Design FIGURE 6-48  An internal heat exchanger (IHX) between the high side liquid line and the low side vapor return line is used to improve system performance by removing thermal heat energy from the high pressure liquid line before the expansion device and moving this heat to the low pressure vapor line after the evaporator. The low pressure cold refrigerant gas flows around the hot high pressure gas line in effect cooling the refrigerant before it passes into the evaporator allowing the evaporator to cool more effectively. A/C system with an Internal Heat Exchanger (IHX):

Compressor

Condenser

IHX

Expansion Device

Evaporator

FIGURE 6-49  The internal heat exchanger (IHX) is located before the metering device.

Shop Manual Chapter 6, page 203

The accumulator may be considered a liquid trap.

Accumulator The accumulator, a tank-like vessel, is located at the outlet of the evaporator (Figure 6-50). It is an essential part of an orifice tube air-conditioning system. The orifice tube, under certain conditions, may meter more liquid refrigerant into the evaporator than can be evaporated. If it were not for the accumulator, excess liquid refrigerant leaving the evaporator would enter the compressor, causing damage. To compressor

From evaporator Test port

Pickup tube Desiccant

Bleed hole Strainer FIGURE 6-50  Construction details of the accumulator.

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To prevent this problem, all refrigerant and oil leaving the evaporator enters the accumulator, where the liquid (heavier than vapor) falls to the bottom of the tank. A U-shaped pickup tube ensures that only refrigerant vapor enters and leaves the accumulator to the compressor inlet, while trapping the liquid refrigerant and oil. A metered oil bleed hole (orifice) at the bottom of the U-bend meters a small amount of liquid (when present) into the suction line. This orificeis calibrated to ensure that liquid is metered in an amount that will vaporize before it reaches the compressor. The orifice also allows small quantities of refrigerant oil to return to the compressor. Another important function of the accumulator is that it contains the desiccant, a chemical drying agent. The desiccant attracts, absorbs, and holds moisture that may have entered the system due to improper or inadequate service procedures. The desiccant is not serviced as a component of the accumulator. If desiccant replacement is indicated, the accumulator must be replaced as an assembly. The desiccant used in R-12 accumulators may not be compatible in an R-134a system. The desiccants are classified XH5, XH7, and XH9. Only XH7 and XH9 are acceptable for use on R-134a systems. To be sure of system compatibility, use only replacement components specifically designated for a particular application. A fine-mesh screen is placed in the accumulator to catch and prevent the circulation of any debris that may be in the system. This screen cannot be serviced; if it is clogged, the entire unit must be replaced as an assembly. The accumulator should be replaced any time a major component of the air-conditioning system is replaced or repaired. Most vendors will not honor the warranty on new or rebuilt compressors unless the accumulator is replaced at the time of service. Author’s Note: In general, students have difficulty in the beginning distinguishing what type of system they are dealing with, whether orifice tube or expansion valve. First, find the lines entering and leaving the evaporator. Follow the outlet line, which leads to the compressor. If there is a metal canister attached to this line you have found the accumulator and you are dealing with an orifice tube system. If no canister is found, you are dealing with an expansion valve system.

What Type System There are basically two methods of temperature control for automotive air-conditioning systems: ■■ Cycling clutch ■■ Noncycling clutch

Cycling Clutch

The cycling clutch system relies on two methods for temperature control: 1. Temperature cycling switch. The temperature cycling switch is a temperature-sensitive switch that cycles the compressor clutch on and off at predetermined temperature levels. 2. Pressure cycling switch. The pressure cycling switch, as its name implies, is sensitive to system pressure and turns the compressor clutch on and off at predetermined pressure levels.

Noncycling Clutch

The noncycling clutch system relies on a variable displacement (VD) compressor to control the incar temperature. The amount of refrigerant permitted to flow through the system is controlled by the compressor’s ability to alter the stroke of the pistons as required by varying system conditions. The only purpose of the clutch in a noncycling system, then, is to disengage the compressor when the air conditioner is not in use and to engage the compressor when the driver calls for cooling.

Predetermined is a set of fixed values or parameters that have been programmed or otherwise fixed into an operating system.

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Terms to Know Barrier Change of state Compression Cycling clutch Desiccant Electromagnetic Flooded Heat load H-valve Orifice Predetermined Reciprocating Reed valve Starved Stroke Variable displacement (VD)

SUMMARY ■■

■■

■■ ■■ ■■

The compressor is the prime mover of the refrigerant. Its purpose is to pump refrigerant throughout the air-conditioning system. Refrigerant changes state: vapor to liquid in the condenser, and liquid to vapor in the evaporator. The receiver-drier ensures a gas-free liquid supply to the metering device. The accumulator ensures that no liquid refrigerant is returned to the compressor. A thermostatic expansion valve (TXV), H-valve, or orifice tube (OT) is essential to meter the proper amount of refrigerant into the evaporator. These restrictive devices establish a pressure differential between the high side and the low side in the system.

REVIEW QUESTIONS Short-Answer Essays 1. How does compressor action increase the condensation rate of refrigerant? 2. Briefly, how does a compressor “pump” refrigerant? 3. Why is it important that the inlet of the condenser be at the top? 4. What are two purposes of the receiver-drier? 5. Explain the term flash gas and what causes it. 6. What two factors determine how much refrigerant enters the evaporator in a fixed orifice tube system? 7. Briefly describe the state of the refrigerant as it leaves the evaporator in a properly operating system. 8. What is the primary purpose of an accumulator? 9. Briefly describe the refrigeration cycle. 10. What are the two basic functions of the thermostatic expansion valve?

Fill-in-the-Blanks 1. The compressor’s function is to _______________ the refrigerant throughout the system. 2. Refrigerant ______________ is stored in the ______________ and is essential to keeping the internal parts of the compressor lubricated.

3. Heat-laden refrigerant gives up its heat in the _______________ as it changes from a _______________ to a _______________. 4. High-pressure liquid refrigerant moves through a hose called a _______________. 5. As cold refrigerant flows through the evaporator core, the heat from the warmer air passing over the evaporator fins will transfer its _______________ into the cooler refrigerant _______________ the air’s temperature and causing the refrigerant to _______________ in the evaporator. 6. All orifice tube systems have a(n) _______________ at the _______________ of the evaporator. 7. The evaporator is said to be _______________ if too little refrigerant is metered into it and _______________ if too much refrigerant is metered into it. 8. The _______________, a drying agent, is found in the _______________ or _______________. 9. The compressor separates the _______________ side of the system from the _______________ side of the system; the metering device separates the _______________ side from the _______________ side of the system. 10. The air-conditioning system low- and high-pressure pipes and hoses are different in diameter. To identify the pipes, the high-side line is _______________ in diameter than the low-side line.

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Multiple Choice

Refer to Figure 5-51 to answer questions 1 through 7.

1. Technician A says that the component identified by A is a receiver-drier. Technician B says that the component identified by D is a condenser. Who is correct? A. A only (if the illustration depicts a thermostatic expansion valve [TXV] system) B. B only C. Both A and B D. Neither A nor B 2. Technician A says that the component identified by B is an evaporator. Technician B says that the component identified by A is a condenser. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

3. What component is shown as C? Technician A says that it is an accumulator. Technician B says that it is a receiver-drier. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 4. What is the state of the refrigerant in line 4? Technician A says that it is high-pressure vapor. Technician B says that it is high-pressure liquid. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 5. What is the state of the refrigerant in line 5? Technician A says that it is low pressure. Technician B says that it is a vapor. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

B

1

A

2

5 E

4

6

D C 3 FIGURE 6-51  The automotive air-conditioning system.

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6. Which of the following statements identifies the correct state and pressure of the refrigerant throughout the system? A. The refrigerant is low pressure at points 1, 2, and 3 in the system and high pressure at points 4, 5, and 6 in the system. B. The refrigerant is low pressure at points 1 and 5 in the system and high pressure at points 2, 3, 4, and 6 in the system. C. The refrigerant is high pressure at points 1, 2, and 3 in the system and low pressure at points 4, 5, and 6 in the system. D. The pressure varies from high pressure to low pressure throughout the system, depending on heat loads.

8. What is the purpose of the desiccant? Technician A says it is to clean the refrigerant. Technician B says it is to dry the refrigerant. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

7. What is the state of the refrigerant as it immediatelyenters the evaporator, line 1? Technician A says it is all liquid with some flash gas. Technician B says it is all vapor. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

10. Technician A says that the ideal superheat for an automotive air-conditioning system is 102208 F . Technician B says that flash gas is a contributing factor of superheat. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

9. One of the functions of the air-conditioning compressor is to increase the pressure of the refrigerant. Another function of the compressor is to increase: A. The heat (temperature) of the refrigerant B. The volume of the refrigerant C. The vaporization point of the refrigerant D. Pump the liquid refrigerant

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Chapter 7

Refrigerant System Servicing and Testing Upon Completion and Review of this Chapter, you should be able to: ■■ ■■

Describe a refrigerant system performance test. Explain how moisture collects in an air-conditioning system.

■■

Explain the importance of a moisture-free system.

■■

Discuss noncondensable gas contamination.

■■

■■

Describe the methods used to remove moisture from a system.

■■

■■

Describe the leak test procedures for an automotive airconditioning system using soap trace solutions, halide leak detectors, halogen leak detectors, and dye solutions. Discuss the other types of leak detector devices available to the automotive technician. Discuss the acceptable methods for charging a system with refrigerant.

Introduction Testing and servicing an automotive air-conditioning system is a skill that is generally ­developed with practice and experience. This chapter gives a basic fundamental understanding of these procedures, including leak testing, moisture removal, refrigerant recovery, charging the system, and diagnostics.

Performance Testing An air-conditioning system performance test is an initial test that determines whether the refrigerant system is operating as designed. As a service technician, you should always follow the manufacturer’s service and diagnostic information. There are two basic types of performance tests that may be done to aid in analyzing system operation: the load test and the unloaded test. Many service manuals specify a loaded test in which a heat load is applied to the evaporator in the form of outside ambient air temperature and humidity. The test should be performed in a shaded area, not in direct sunlight. The front windows are left open and the hood is opened. The vent fan is turned on high and the air-conditioning system is turned on. The ambient air humidity is measured. Next, the engine is run at 1,500 rpm and the system is allowed to stabilize for 10 minutes. The air temperature leaving the center vents is then measured. The unloaded test has you select the Recirculation mode, which dries the air as it is recirculating during system stabilization. The test should be performed in a shaded area, not in direct sunlight. Close all windows and doors. Open the vehicle hood. The vent fan is turned on high and the air-conditioning system is turned on and set to Recirculation mode.

Moisture is defined as droplets of water in the air: humidity, dampness, or wetness.

Shop Manual Chapter 7, page 238

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Next, the engine is run at 1,000 rpm and the system is allowed to stabilize for 15 minutes. The air temperature leaving the center vents is then measured. The unloaded test strips the air in the passenger compartment of heat and humidity as it is recirculated through the evaporator, allowing for the lowest possible vent temperatures to be achieved. The temperature–pressure performance charts in Figure 7-1 for the unloaded performance test require that the engine speed be 1,000 rpm (650 rpm) to be accurate. The key difference between the loaded and unloaded performance tests is how the tests deal with humidity and ambient heat load. Because the loaded performance test allows outside ambient air to pass over the evaporator, the test yields different results, depending on ambient temperatures and humidity levels. The unloaded performance test’s use of recirculated dry air allows for consistent achievement of the lowest possible vent temperatures and provides a consistent performance comparison of similar vehicles, regardless of ambient air temperatures or humidity levels on a particular day.

300 260 High-side pressure (psig)

240 200 160 120 60

65

70

75

80

85

90

95

100

105

110

115

120

Ambient temperature (˚F) 50

45 Center vent temperature (˚F)

40

35 32 10

Ambient temperature Low-side pressure (1000 rpm) High-side pressure (1000 rpm) Low-side pressure (1000 rpm) High-side pressure (1000 rpm)

15

˚F (psig) (psig) (psig) (psig)

25 20 Low-side pressure (psig)

Rear A/C OFF Rear A/C OFF Rear A/C ON Rear A/C ON

30

Center vent temperature Rear vent temperature Low-side pressure (3000 rpm) Left corner vent temperature Right corner vent temperature

- ˚F ˚F ˚F ˚F ˚F

FIGURE 7-1  R-134a air-conditioning system unloaded performance test data chart requires that the vehicles windows and doors are closed and that the recirculation vent control mode be selected for accurate test results.

204 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Refrigerant Analyzer Before attempting to recover refrigerant or charge an automotive air-conditioning system, one should use a refrigerant analyzer, also called a refrigerant identifier, to test samples taken from the air-conditioning system or storage container to determine their purity. Recovered refrigerant should contain less than two percent impurities. It is important to follow the instructions that are included with the analyzer to obtain the test sample. The analyzer, such as the one shown in Figure 7-2, will display the following: ■■ R-134a percentage, a fault is triggered if the refrigerant purity is less than 98 percent or better by weight. ■■ R-12 percentage, a fault is triggered if the refrigerant is less than 98 percent pure. ■■ R-22 percentage. ■■ HC, if the sample contains hydrocarbons (flammable material) some units will sound a audible warning signal. ■■ Air Contamination also referred to as noncondensable gas contamination. ■■ J2099–Standard of Purity for Recycled R-134a (HFC-134a) and R-1234yf (HFO-1234yf ) for Use in Mobile Air-Conditioning Systems (revised 2/2011). For recycled R-134a refrigerant that has been directly removed and intended to be returned, the system must meet: ● Moisture 50 parts per million (PPM) by weight; R-134a and its oil have a much higher affinity for water and are harder to keep dry ● Refrigerant oil: 500 ppm by weight ● Noncondensable gases (air) 150 PPM by weight ■■ J2844–Standard of Purity for Recycled R-1234yf ■■ J2912 R-1234yf (HFO-1234yf ) Refrigerant Identification Equipment standard Contaminated or cross-contaminated refrigerant can cause system and equipment damage as well as present diagnostic problems if you are not aware of the contamination. Cross-contamination can cause reduced system performance, lubrication problems, and chemical breakdown within the system, which may contribute to an acidic condition within the system, leading to component failure. In the event that the recovery/recycling equipment is contaminated with cross-contaminated refrigerant, the unit will have to be cleaned out; the recovery tank will have to be sent out to a refrigerant reclamation station; and the filters and dehydrators will have to be replaced. The Environmental Protection Agency (EPA) prohibits the venting of any automotive refrigerant

Shop Manual Chapter 7, page 236

Contaminated is a term generally used when referring to a refrigerant cylinder or system that fails a purity test and is known to contain foreign substances, such as other ncompatible or hazardous refrigerants. Cross-contaminated refrigerant is a refrigerant that contains some refrigerant other than the type designated on the system service label.

FIGURE 7-2  A typical refrigerant analyzer.

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SNAP stands for Significant New Alternative Policy program and sets Environmental Protection Agency (EPA) guidelines for the use of alternative refrigerants and recovery/recycling equipment.

into the atmosphere, even if the refrigerant is not identifiable by the service facility. The EPA maintains a list of “Refrigerant Reclaimers” that can be ordered at no charge from the EPA Stratospheric Ozone Protection Hotline at 1-800-296-1996 or through the EPA Web site at www.epa.gov/ozone/title6/609. Besides the cost of servicing the unit, there is also the lost time involved while waiting for the recovery tank to be returned after reclamation or the purchase of a spare recovery tank. The bottom line is, if you suspect system contamination and your facility plans on servicing contaminated systems, you must have a dedicated recovery-only unit for recovering contaminated refrigerant to be sent out for reclamation later. Remember to never fill the DOT-approved recovery tank beyond 60 percent of its gross weight capacity. Also, consult local and state regulations on the storage of hazardous or combustible materials. Statistics on refrigerant contamination indicate that: ■■ 63 percent of the systems that are contaminated involve R-12 systems that are contaminated with R-134a. This is generally due to the backyard mechanic who can purchase 1-pound cans of R-134a in a retrofit kit; is not required to obtain a Section 609 license to purchase R-134a; and has no way of removing the old refrigerant. ■■ 18 percent of the contaminated R-12 systems are contaminated with R-22. ■■ 17 percent of the contaminated R-12 systems are contaminated with three or more ­refrigerants, including hydrocarbons. ■■ 2 percent of the contaminated R-134a systems are contaminated with three or more refrigerants, including hydrocarbons. ■■ There are 50 percent more contaminated R-134a systems seen each year. It was once thought that contamination was likely to occur only in the older R-12 systems, but recent evidence indicates that the occurrence of R-134a system contamination is occurring at an alarming rate. This is due in part to the fact that the Significant New Alternative Policy (SNAP) program rule does not apply to R-134a replacement refrigerants. When purchasing refrigerant identification equipment, ensure that it meets the standards set by SAE J1771. Manufacturers are required to label their equipment, stating the unit’s level of accuracy. The Society of Automotive Engineers (SAE) has set purity standards for recycled R-12 and R-134a refrigerants so that they provide proper system performance and longevity. The purity standard for R-134a is J2099 and specifies a limit in parts per million (ppm) for moisture (15 ppm by weight), noncondensable gases (air) (330 ppm by weight), and refrigerant oil (4,000 ppm by weight). The purity standard for R-12 is J1991 and specifies a limit in parts per million (ppm) for moisture (15 ppm by weight), noncondensable gases (air) (150 ppm by weight), and refrigerant oil (500 ppm by weight).

Sealant Contamination Shop Manual Chapter 7, page 241

Refrigerant sealants for small refrigeration system leaks have become a popular remedy when compared to the cost and labor involved with some component replacement. The sealant is added to the system through the high or low side of the system, depending on manufacturer recommendations. The sealant travels through the system with the refrigerant. There are two types available, seal swellers and stop leak. Seal swellers do just what the name implies; they contain chemicals that soften and swell O-rings and seals. Stop-leak sealers work by sealant chemical interaction with moisture. When the sealant begins to leak out of the system, it reacts with the moisture in the air and forms an epoxy, thus sealing the leak. Unfortunately, some sealant contamination has been identified as a major cause of system performance problems and recovery/recycling equipment failures. Damage caused by the use of sealants is not covered by manufacturer warranties. Refrigerant identifiers do not detect the presence of sealants in the refrigerant system. You must use a sealant identifier product specifically designed for this purpose (Figure 7-3). One company, Neutronics Inc., produces one model called QuickDetect™ Sealant Detector, which quickly identifies the presence of stop-leak

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FIGURE 7-3  A simple-to-se Neutronics Inc. refrigerant system sealant identifier will determine whether an air-conditioning system has been contaminated by sealant.

sealants. Once you have determined that sealant is not present in the system, the refrigerant can be safely recovered. In addition to damage to equipment, if the refrigerant system contains excess amounts of moisture, the sealant can become activated inside the system, causing restriction in refrigerant system components including but not limited to the expansion valve, FOT, evaporator, and condenser. Systems should be checked for the presence of refrigerant sealants prior to attaching any other air-conditioning equipment, including refrigerant identification equipment.

Noncondensable Gas A noncondensable gas cannot condense into a liquid. Air in the refrigerant system is considered a noncondensable gas because at no time are refrigerant system pressures great enough or temperatures low enough to cause air (78 percent nitrogen, 21 percent oxygen, and 1 percent other inert gases) to condense into a liquid. Noncondensable gas takes up space in the refrigerant system condenser, which in turn effectively reduces the condenser surface area. This in turn will increase system operating pressure on the high side of a thermostatic expansion value (TXV) system and possibly both high- and low-side pressures on an FOT system. A system is considered contaminated if it contains 150 ppm by weight for R-134a or 330 ppm by weight for R-12. Refrigerant system air contamination may be caused by: ■■ Refrigerant system low-side leak ■■ Improper system evacuation or insufficient evacuation time ■■ Weak evacuation pump Anytime that a system is open for repair service, there is the possibility that air may enter the system. Also, air will enter a closed system if the ambient air pressure is greater than the system refrigerant pressure. For example, assume that an air-conditioning system is low on refrigerant due to a leak on the low side of the system. If the low-pressure cutoff switch is defective or there is a problem that permits the low-side pressure to fall below zero gauge (ambient) pressure, air may enter the system at the same location that the refrigerant leaks

Shop Manual Chapter 7, page 265

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out of the low side. To remove air from an air-conditioning system, it must be leak free and thoroughly evacuated with a quality vacuum pump. To remove air from recovered refrigerant, follow the equipment manufacturer’s instructions included with the recovery/recycle equipment. If the refrigerant system is contaminated with a noncondensable gas, poor refrigerant system cooling and performance will result. An air-contaminated system will cause static (system off and stabilized) system pressure to be higher than that of one containing a pure charge of refrigerant (R134a or R-12). Air contamination will cause the operating pressure on the high side of the refrigerant system to be higher than normal, and the high-side gauge may fluctuate or flutter slowly. This is caused by the fact that air takes up space in the condenser and will occupy even more space when heated. A recovered tank of refrigerant may be checked for excess air contamination by comparing tank pressure to a standard temperature-pressure chart (Figure 7-4). Prior to testing the recovery tank, it must be out of direct sunlight and at a stable temperature above 658F (18.38C) for at least 12 hours. If the recovery tank is suspected STANDARD TEMPERATURE-PRESSURE CHART FOR R-134a

METRIC TEMPERATURE-PRESSURE CHART FOR R-134a

8F

PSI

8F

PSI

8F

PSI

8F

PSI

8F

PSI

8C

kPa

8C

kPa

8C

kPa

65

69

77

86

89

107

101

131

113

158

18

476

29

676

40

945

66

70

78

88

90

109

102

133

114

160

19

483

30

703

41

979

67

71

79

90

91

111

103

135

115

163

20

503

31

724

42

1007

68

73

80

91

92

113

104

137

116

165

21

524

32

752

43

1027

69

74

81

93

93

115

105

139

117

168

22

545

33

765

44

1055

70

76

82

95

94

117

106

142

118

171

23

552

34

793

45

1089

71

77

83

96

95

118

107

144

119

173

24

572

35

814

46

1124

72

79

84

98

96

120

108

146

120

176

25

593

36

841

47

1158

73

80

85

100

97

122

109

149

26

621

37

876

48

1179

74

82

86

102

98

125

110

151

27

642

38

889

49

1214

28

655

39

917

75

83

87

103

99

127

111

153

76

85

88

105

100

129

112

156

STANDARD TEMPERATURE-PRESSURE CHART FOR R-12

METRIC TEMPERATURE-PRESSURE CHART FOR R-12

8F

PSI

8F

PSI

8F

PSI

8F

PSI

8F

PSI

8C

kg/cm 2

8C

kg/cm 2

8C

kg/cm 2

65

74

75

87

85

102

95

118

105

136

18

5.2

28

7.0

38

9.0

66

75

76

88

86

103

96

120

106

138

19

5.3

29

7.1

39

9.2

67

76

77

90

87

105

97

122

107

140

20

5.5

30

7.2

40

9.4

68

78

78

92

88

107

98

124

108

142

21

5.6

31

7.5

41

9.6

69

79

79

94

89

108

99

125

109

144

22

5.8

32

7.7

42

9.9

70

80

80

96

90

110

100

127

110

146

23

6.0

33

7.9

43

10.0

71

82

81

98

91

111

101

129

111

148

24

6.1

34

8.1

44

10.4

72

83

82

99

92

113

102

130

112

150

25

6.3

35

8.3

45

10.7

73

84

83

100

93

115

103

132

113

152

26

6.6

36

8.5

46

10.9

74

86

84

101

94

116

104

134

114

154

27

6.8

37

8.7

47

11.0

FIGURE 7-4  Standard temperature-pressure charts for both R-134a and R-12 can be used to determine whether a refrigerant system is contaminated.

208 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

to be contaminated, a manifold gauge may be connected to the tank; the pressure in the tank will be higher for a given temperature than the chart pressure listed for that temperature. For example, if the tank pressure is 100 psig at 808F, the tank is contaminated. A refrigerant identifier may also be used to detect the presence of noncondensable gases. One common mistake that causes air to be left in the refrigerant system after a repair is improper evacuation. The most common mistake is not opening both service port fittings during the evacuation process. To ensure proper system evacuation, both service valves must be open so that both the high and low side of the refrigerant system is put under a vacuum at the same time.

Moisture and Moisture Removal Moisture is a small quantity of diffused or condensed liquid. Actually, any substance that is not “dry” may be considered “moist.” Moisture in an air-conditioning system is one of its greatest perils. Even a slight amount of free moisture, i.e., a water (H 2 O) vapor, in an air-conditioning system can play havoc. When it is heated and mixed with refrigerant and oil, it can cause sludge and can form harmful acids that erode system components. Atmospheric air contains moisture (humidity), and this moisture can enter the refrigerant system during service. The higher the humidity level, the greater the moisture content for any given quantity of air. Moisture removal, however, is not as simple as air removal. To remove all moisture from a system, one must use a vacuum pump capable of achieving and maintaining a deep vacuum for several hours. Any time the refrigerant system is opened for service, extreme care must be taken to limit the system’s exposure to atmospheric air. Systems should never be left empty and open for longer than is necessary to complete a repair. In a deep vacuum, moisture will boil off and be carried out of the system as a vapor. The length of time required depends on three major factors: the amount of moisture in the system; the ambient temperature; and the efficiency of the vacuum pump, which relates to the amount of vacuum that will be applied to the air-conditioning system. Assuming sea-level atmospheric pressure, an air-conditioning system evacuation should be conducted when the ambient temperature is 608F (15.68C) or above. Moisture will boil at this temperature in a vacuum of 29.4 in. Hg (2.3 kPa absolute) or better. A temperature-vacuum chart is given in Figure 7-5 for moisture removal at various vacuum levels. The average service facility may not possess or maintain equipment capable of achieving a sufficient vacuum for complete moisture removal. Because of this, if a high level of moisture is suspected in an automotive air-conditioning system, the general remedy is to replace the accumulator or receiver-drier that contains a desiccant and then evacuate the system to remove excess moisture. Periodic maintenance of the vacuum pump is essential to ensure maximum performance. The vacuum pump lubricant should be changed at frequent intervals recommended by the manufacturer. New refrigerant is considered to be moisture free. The moisture content of new refrigerant should not exceed 10 ppm. This information is given on the label of the refrigerant container. The SAE purity standards for recycled refrigerant set the maximum allowable moisture content levels to ensure that the refrigerant provides proper system performance and longevity. Standard J2099 states that the maximum allowable of moisture content for R134a is 15 ppm by weight, and standard J1991 states that the maximum allowable moisture content for R12 is 15 ppm by weight. Every time a component is removed from the system for repair or replacement, air is inadvertently introduced into the system. As a result, there is always the danger of moisture entering the system. Refrigerant and refrigeration oil, particularly R-134a and its oil, absorb moisture readily when exposed to air. To keep the system as moisture-free as possible, all

The term virgin refrigerant is used to identify new refrigerant as opposed to recovered refrigerant. To absorb is to take in or suck up; to become a part of.

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PRESSURE/BOILING POINT RELATIONSHIPS Boiling Point of Water ( 8F)

Inches of Vacuum

Microns

Pressure (PSI)

212

0.00

759,968

14.696

205

4.92

535.000

12.279

194

9.23

525.526

10.162

176

15.94

355,092

6.866

158

20.72

233.660

4.519

140

24.04

149,352

2.888

122

26.28

92.456

1.788

104

27.75

55,118

1.066

86

28.67

31,750

.614

80

28.92

25.400

.491

76

29.02

22,860

.442

72

29.12

20,320

.393

69

29.22

17,780

.344

64

29.32

15,240

.295

59

29.42

12,700

.246

53

29.52

10, 160

.196

45

29.62

7.620

.147

32

29.74

4,572

.088

21

29.82

2,540

.049

6

29.87

1,270

.0245

224

29.91

254

.0049

235

29.915

127

.00245

260

29.919

25.4

.00049

270

29.9195

12.7

.00024

290

29.9199

2.54

.000049

FIGURE 7-5  The table illustrates the boiling point of water (H2 O) under a vacuum. Use the table to determine the level of evacuation needed based on ambient air temperature.

The oil used with R-134a(HFC-134a) is very hygroscopic.

Hydrochloric acid (HCl) is a corrosive acid produced when water (H2O) and R-12 are mixed, as occurs within an automotive ­air-conditioning system.

automotive air-conditioning systems have an accumulator or a receiver-drier that contains desiccant, a drying agent (Figure 7-6). Desiccants are chemicals that are capable of absorbing and holding moisture. Any moisture introduced into the system in excess of the amount that the desiccant can handle is free in the system. Even one drop of free moisture (H 2 O) cannot be controlled and may cause irreparable damage to the internal parts of the air conditioner. Moisture in concentrations greater than 20 ppm may cause serious damage. For an idea of how small an amount 20 ppm is, consider one small drop of water in a system having a capacity of 6 lb. (0.94 mL) of refrigerant. That one small drop amounts to 20 ppm, or twice the amount that is desired. Refrigerants react chemically with water (H 2 O) to form hydrochloric acid (HCl). Heat, which is generated in the system, is an aid in the acid-forming process. The greater the concentration of moisture in the system, the more concentrated are the corrosive acids that are formed. Hydrochloric acid (HCl) corrodes all the metallic parts of the system, particularly those made of steel. Iron (Fe), copper (Cu), and aluminum (Al) parts are damaged by the acid as well. The corrosive process also creates oxides that are released into the refrigerant as particles of

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Sight glass

In

Out

Pickup tube

Dessicant

Strainers

Fusible plug FIGURE 7-6  Cutaway of receiver-drier showing construction details.

metal to form a sludge. Further damage is caused when oxides plug the fine-mesh screens in the metering device, compressor inlet, and the drier or accumulator. There are commercially available “remedies” that claim to prevent moisture freeze-up problems. There is also a notion that system freeze-up can be avoided by adding 0.07 oz. (0.002 mL) of alcohol per pound (0.03 mL) of refrigerant. However, the addition of alcohol to the system may cause even greater damage. The drier seeks out alcohol even more than moisture and, in doing so, releases all of its moisture to the system. This can cause severe damage to the system components. Once a system is saturated with moisture, irreparable damage is done to the inside of the system. If the moisture condition is neglected long enough, pinholes caused by corrosion appear in the evaporator and condenser coils and in any metal tubing used in the system. Any affected parts must be replaced. Additives, which are marketed under various trade names, are available that make the claim of increasing the cooling effect and/or stopping leaks. Most additives have a negative effect on the performance of an air-conditioning system, however, and are not recommended.

The average automotive air-conditioning system contains 3 lb. (1.42 mL) or less of refrigerant.

An additive may cause more problems than it will solve.

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Pump down is the process of evacuation whereby a liquid is changed to a vapor by lowering pressure exerted on the liquid, thus lowering its boiling point.

Do not remove the protective caps from the accumulator or receiver-drier until it is to be installed.

Shop Manual Chapter 7, page 250

Pressure below atmospheric is referred to as a vacuum.

Whenever there is evidence of moisture in the system, a thorough system cleanout is recommended. Such a cleanout should be followed by the installation of a new receiver-drier or accumulator and a complete system pump-down evacuation using a vacuum pump, charging station, or recovery system.

Prevention The automotive air-conditioning service technician can prevent unwanted debris and m ­ oisture from entering a system by following a few basic rules: ■■ Always install the receiver-drier or accumulator last. ■■ Always immediately cap the open ends of hoses and fittings. ■■ Do not work around water, outside in the rain, or in very humid locations. ■■ Do not allow new refrigerant or refrigeration oil to become contaminated. ■■ Keep the refrigeration oil container capped when it is not being used. ■■ Develop clean habits: Do not allow dirt to enter the system; keep all service tools clean; and never charge a unit with refrigerant without first ensuring that all air and moisture have been removed.

Evacuating the Refrigeration System (Moisture Removal) As discussed earlier, many problems can arise due to moisture in an automotive air-­ conditioning system. After any repairs have been made to the system, it must be “pumped down” (evacuated) to remove any moisture that may have entered during the process. Moisture removal from a system can cause serious problems for the service technician who is not properly equipped. A vacuum pump is an essential tool for air-conditioning service. Other methods may be used, but the vacuum pump is by far the most efficient means of moisture removal. Typical vacuum pumps suitable for automotive service are shown (Figure 7-7). A pressure below 0 lb. (0 psig) or 0 kiloPascal (0 kPa) gauge pressure is referred to in terms of inches of mercury (in. Hg) on the English scale or kiloPascals absolute (kPa absolute) on the metric scale. Moisture is removed from the air-conditioning system by creating a vacuum. In a vacuum, the moisture within the system boils. The action of the vacuum

FIGURE 7-7  A typical two-stage vacuum pump.

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pump then pulls the moisture in the form of a vapor from the system. When the pressure is increased on the discharge side of the pump, the vapor again liquifies. This process usually occurs inside the pump. A minimum of 30 minutes is required to ensure moisture removal with a compressor speed of about 1,500 revolutions per minute (rpm or r/min.). The compressor is lubricated by refrigeration oil in its pump. Some of the oil is picked up in the refrigerant vapor. If the compressor runs dry of oil when it is operated as a vacuum pump, it may be seriously damaged. A good vacuum pump is capable of pumping a vacuum pressure of 29.76 in. Hg (0.81 kPa absolute) or more. At this pressure, water boils at 408F (4.448C). In other words, if the ambient temperature is 408F (4.448C) or higher, moisture will boil out of the system. At 0 in. Hg (101.3 kPa absolute) at sea level, water boils at 2128F (1008C). To find the ­boiling point of water in a vacuum (absolute pressure), use the table in Figure 7-5. Note that the boiling point is lowered only 1128F (62.28C) to 1008F (37.78C) as the pressure is decreased from 0 in. Hg (101.3 kPa absolute) at sea level to 28 in. Hg (0.98 kPa absolute). However, the boiling point drops by 1208F (66.68C) as the pressure decreases from 28 in. Hg (0.98 kPa absolute) to 29.91 in. Hg (0.30 kPa absolute). The degree of vacuum and the amount of time the system is under a vacuum determines the amount of moisture removed. When evacuating a refrigerant system, it is important to apply the proper vacuum level for the ambient temperature that exists. To determine the minimum vacuum levels required to remove moisture from a refrigerant system refer to the chart in Figure 7-8. The deeper the vacuum or the longer the time, the more moisture is removed. The removal of moisture from a system can be compared to the boiling away (vaporization) of water in an open saucepan on a hot burner. It is not sufficient to cause the water to boil; time must be allowed for it to boil away. The recommended minimum pumping time is 30 minutes below 29 in. Hg. If time allows, however, a four-hour pump down achieves much better results. Vacuum pump manufacturers’ specifications and recommendations should be followed for proper maintenance. For example, changing oil on a regular basis is essential to ensure maximum efficiency. If a system is suspected of being extremely contaminated with water that has caused expansion valve icing or if the evaporator exhibited a whistling noise caused by ice restriction, the evacuation process may be made more efficient by increasing the temperature of the components to which the moisture is suspected to have migrated (in other words, expansion valve, evaporator core). Start the vehicle and allow it to reach operating temperature. Once at operating temperature, turn the blower motor on high, select the Recirculation mode, set the temperature control to hot, and close all windows and doors. Begin the evacuation process. This procedure will increase the evaporator temperature to above 1508F and greatly reduce the evacuation time. The most accurate method for measuring the effectiveness of system evacuation is with the use of a thermistor vacuum gauge or micron meter. A thermistor vacuum gauge measures 29.00 in. Hg 229.9199 (the last inch of vacuum) with extreme accuracy in very small increments called microns. An inch of vacuum contains 25,400 microns. A refrigerant system is considered under a deep vacuum when it is evacuated down to 700–300 microns ­(Figure 7-4). When all the water is removed from the system, you will achieve the lowest evacuation vacuum possible. The ultimate goal is to achieve the deepest possible vacuum to ensure that 100 percent of the water is removed. The refrigerant system should hold a minimum of a 700-micron vacuum for three minutes after turning off the vacuum pump and isolating the system if all the moisture and air has been removed. If the gauge pressure rises above 700 microns, the evacuation process must be repeated. The most efficient evacuation pumps are dual-stage 6 or 8 cubic feet per minute (cfm) vacuum pumps, which will produce vacuums as low as 20 microns. The larger the vacuum

Refrigeration oil is hygroscopic and will absorb moisture.

Contaminated vacuum pump oil can reduce the efficiency of the vacuum pump by 10 percent or more.

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BOILING TEMPERATURES OF WATER AT CONVERTED PRESSURES Temperature in ( 8F)

Inches in Vacuum

Microns

Pounds Sq. in (Pressure)

2128

000

759,968

14,696

2058

5.00

535,000

12,279

1948

9.81

525,526

10,162

1768

16.02

355,092

6,866

1588

20.80

233,680

4,519

1408

24.12

149,352

2,888

1228

26.36

92,456

1,788

1048

27.83

55,118

1,066

868

28.75

31,750

.614

808

29.00

25,400

.491

768

29.10

22,860

.442

728

29.20

20,320

.393

698

29.30

17,780

.344

648

29.40

15,240

.295

598

29.50

12,700

.246

538

29.60

10,160

.196

458

29.70

7,620

.147

328

29.82

4,572

.088

218

29.90

2,540

.049

68

29.95

1,270

.0245

248

29.99

254

.0049

358

29.99.5

127

.00245

FIGURE 7-8  Refer to chart to determine the minimum vacuum levels required to remove moisture from a refrigerant system for a given temperature.

pump, the shorter the evacuation time. As a rule, you cannot buy too large a vacuum pump. This is one area where you should not cut costs.

Moisture Removal at High Altitudes The information given for moisture removal by a vacuum pump applies to normal atmospheric pressures at sea level, 14.696 (14.7) psig (101.3 kPa absolute). At higher altitudes, the boiling point must be reduced to a point below the ambient temperature. Moisture (H 2O) boils at a lower temperature at higher altitudes. However, it must be pointed out that vacuum pump efficiency is reduced at higher altitudes. For example, the altitude of Denver, Colorado, is 5,280 ft. (1,609.3 m) above sea level. Water (H 2O) will boil at 206.28F (96.788C) at this altitude. The maximum efficiency of a vacuum pump, however, is reduced at this altitude. A vacuum pump that can pump 29.92 in. Hg (0.27 kPa absolute) at sea level will pump only 25.44 in. Hg (15.44 kPa absolute) at this altitude. Note in Figure 7-10 that water (H2O) boils at about 1308F (54.48C) at this pressure. 214 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

The English formula for determining vacuum pump efficiency at a given atmospheric pressure is: APL /APS 3 PRE 5 APE where APL 5 atmospheric pressure in your location APS 5 atmospheric pressure at sea level PRE 5 pump rated efficiency APE 5 actual pump efficiency Assume that a vacuum pump has a rated efficiency of 29.92 in. Hg at sea level (0.27 kPa absolute) and that the atmospheric pressure at Denver is 12.5 psia (86.18 kPa absolute). To determine the actual efficiency at this location, the formula is: 12.5 3 29.92 5 25.44 in. Hg 14.7 The metric formula for determining vacuum pump efficiency at a given atmospheric pressure is: Atmospheric Pressure at Sea level

Atmospheric

Original Actual 2 Pressure in 1 5 Efficiency Efficiency Your Location

Assuming the same conditions previously mentioned, the formula is applied in the ­following manner: 101.32 2 86.18 1 0.27 5 15.41 kPa absolute In this example, the ambient temperature must be raised above 1308F (54.448C) if the vacuum pump is to be efficient for moisture removal. To increase the ambient temperature under the hood, the automobile engine can be operated with the air conditioner turned off. The compressor, condenser, and some of the hoses may be heated sufficiently; however, some other parts, such as the evaporator and the receiver-drier, will not be greatly affected. Do not overheat components containing refrigerant. Hydrostatic pressure can build up rapidly and rupture the component. Evacuating an automotive air-conditioning system when the ambient temperature is below, say, 608F (168C) is generally very inefficient. To remove moisture at this temperature, the vacuum pump must pull a minimum of 29.4 in. Hg (2.03 kPa absolute). Unless well maintained, many shop vacuum pumps will not reach the level required for adequate moisture removal at low temperatures. Another method of moisture removal is the sweep or triple evacuation method. Although this method cannot remove all the moisture, it should be sufficient to reduce the moisture to a safe level if the system is otherwise sound and a new drier is installed.

Mixed Refrigerant Types It is not uncommon to find that R-134a has been added to an R-12 system or vice versa. ­Sometimes it is found that a blend refrigerant has been added to an R-12 or R-134a system. If this is the case, the refrigerant must be recovered, and the system should be evacuated and charged with the proper refrigerant. It is not possible to separate the refrigerants with currently available equipment. Recovery should be made using equipment dedicated to contaminated refrigerant and stored in a dedicated cylinder also designated for contaminated refrigerant. In addition to the flammable refrigerants, identified below as hazardous, the following refrigerants are NOT approved for automotive use under the SNAP program rule of the 215 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

EPA. R-176 contains R-12 and, therefore, is inappropriate as an R-12 substitute, and R-405A ­contains perfluorocarbons, which have been implicated in global warming.

Hazardous Refrigerant A refrigerant identifier must be used to ensure the purity of the refrigerant before service is performed on the vehicle. Hazardous refrigerants are generally those that contain an excessive amount of a flammable substance and are therefore not approved by the SNAP program. If a system is known or suspected to contain a flammable substance, it must be recovered in a manner consistent with the specific instructions provided with the particular recovery equipment used. At the present time, flammable blend refrigerants that are NOT approved for automotive (or any other) use include OZ-12®, HC-12a®, and Duracool 12a®.

Leak Detectors A cold leak is generally the most difficult to locate.

Shop Manual Chapter 7, page 245

A sudsing liquid detergent may also be used undiluted. Halogen refers to any of the five chemical elements-astatine (At), bromine (Br), chlorine (Cl), fluorine (F), and iodine (I)-that may be found in some refrigerants.

There are two general types of automotive air-conditioning system leaks: cold leaks and hot leaks. A cold leak occurs when the system is not at its operating temperature and pressure, such as when it is parked overnight. A hot leak occurs at periods of high pressure, such as when the vehicle is moving slowly in heavy traffic. The methods of detecting leaks in an air-conditioning system range from using an ­inexpensive soap solution to using an expensive self-contained electronic instrument.

Leak Detection Using a Soap Solution A soap solution is an efficient method of locating small pinhole-sized leaks. Leaks often occur in areas of limited access where it is impractical or unhandy to use a halide or Halogen leak detector. If a commercial soap leak detector solution is not available, mix one-half cup of soap powder with water to a thick consistency. The mixture should be just light enough to produce suds when applied with a small brush. When the mixture is applied to the area of a suspected leak, bubbles will reveal the leak (Figure 7-9).

FIGURE 7-9  Bubbles reveal the point of the leak.

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Leak Detection Using Visible Dye To locate a difficult leak, it may be desirable to inject a dye solution into the system. The dye approved for automotive air-conditioning system use is available in either yellow or red. When it is used properly, it will not affect the overall performance of the system. After injection, the automobile is driven for a few days. The leak can then be visibly detected by the dye trace at the point of the leak. Once a dye is introduced into the system, it will remain there until the system is completely cleaned out, the oil changed, and the accumulator or receiver-drier replaced. Even then, a slight residue may be noticed in the sight glass. One manufacturer, E. I. DuPont de Nemours and Company, produced Refrigerant-12 with a red dye. Called Dytel®, this refrigerant is charged into the system in the same manner as any other refrigerant. It is soon to become scarce, however, as supplies dwindle due to the CFC phaseout. It is important to note that most leak detector dye solutions are compatible only with certain systems. For example, a dye solution intended for an R-12 system is not satisfactory for use in an R-134a system. Conversely, R-134a dye should not be introduced into an R-12 system. When retrofitting a system that contained dye, it is important that all residual dye be flushed out of the system. Before using a dye solution, be sure to determine that it is approved for such use and will not affect air-conditioning system performance or any vehicle warranty conditions. This assurance generally should be given in writing by the product manufacturer.

Shop Manual Chapter 7, page 247

CFCs are no longer manufactured, as of 1995. To inject is to insert by force or pressure.

Fluorescent Leak Detectors There are several manufacturers of fluorescent leak detectors. A metered amount of ultraviolet-sensitive dye is injected into the system (Figure 7-10). The air conditioner is operated for a few minutes to allow time for the dye to circulate. An ultraviolet lamp is then used to pinpoint the leak. When the ultraviolet light beams come in contact with the dye that has leaked out of the system, the dye will give off a fluorescent glow. It is advisable to first wash the engine compartment before installing dye into the system. In addition, it is easier to detect the dye if ship light levels are low. Though it is not inexpensive, the ultraviolet method of leak detection is most effective for locating small, difficult-to-find leaks. Some automobile manufacturers add fluorescent dye, called scanner solution, to factoryinstalled air conditioners. The refrigerant identification label under the hood will identify the presence of a leak-detecting agent installed in the system. Ford Motor Company started this practice in 1996. Many technicians add scanner solution to systems being serviced for future

One-half oz. (0.015 mL) per year is equal to 1 lb. (0.472 mL) in 32 years.

FIGURE 7-10  A typical fluorescent leak detector.

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troubleshooting. As with any additive, it is important to use the proper scanner solution to ensure system compatibility. More critical than type of refrigerant is the type of lubricant in the system. The scanner solution has either mineral, alkyl benzine, PAG, or polyol ester base stock to match the system lubricant. Using the improper scanner solution can contaminate an otherwise healthy system. Just 0.3 oz. (0.89 mL) is sufficient to treat a system with a refrigerant capacity up to 2.9 lb. (1.21 L). The average system, however, requires 0.5 oz. (14.79 mL) of scanner solution. This is sufficient for a system with a capacity up to 4.9 lb. (2.33 L) of refrigerant. Ultraviolet Leak Detection: Stability and Compatibility Criteria of Fluorescent Refrigerant Leak Detection Dyes for Mobile R-134a and R-1234yf (HFO-1234yf ) Air-Conditioning Systems must meet J2297 standards (revised 2/2011). Because the scanner solution is soluble in the lubricant, the refrigerant is recyclable and is accepted by most manufacturers and reclaimers. If retrofitting a system, be sure that all trace of the scanner solution is removed with the lubricant before introducing a new refrigerant.

Electronic (Halogen) Leak Detectors

Shop Manual Chapter 7, page 247

The electronic (halogen) leak detector is the most sensitive of all leak detection devices. The initial purchase price of a halogen leak detector, however, exceeds the cost of most fluorescent leak detectors. In addition, this more sophisticated device requires routine maintenance in order to maintain accuracy. Electronic leak detectors must be capable of detecting a refrigerant loss rate of 0.15 oz (4g) per year. This value corresponds to one part of refrigerant in 10,000 parts of air or 100 parts per million (ppm). Electronic leak detectors are either corded or cordless (Figure 7-11). The corded leak detector operates on 120 volts (V), 60 hertz (Hz). The cordless leak detector is portable and operates from a rechargeable battery. Both units are simple to operate and easy to maintain. When the halogen leak detector comes in contact with refrigerant vapor, the audible click noise emitted from the device will become more rapid. If the unit is also equipped with an LED light bar, additional lights will illuminate. The halogen leak detector also allows the technician to diagnose the leak the same day the vehicle is in for the repair. This saves the customer both time and money and avoids the aggravation involved to both you and the customer of having to make a return visit. A popular portable halogen leak detector is the model 5750 manufactured by TIF Industries (Figure 7-12). This instrument, which is powered by two “C” cell alkaline batteries,

A

B

FIGURE 7-11  Two types of electronic leak detector: (A) cordless and (B) corded.

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FIGURE 7-12  A portable electronic leak detector that may be used for R-12 or R-134a.

requires no warm-up period and may be used to detect CFCs, HCFCs, or HFCs (R-12, R-22, or R-134a). In addition, this instrument calibrates itself automatically while in use to ignore ambient concentrations of gas and pinpoint leaks much more easily. An important consideration in the selection of an electronic (halogen) leak detector is that it complies with current SAE standards and EPA regulations. Beginning 2008 SAE J2791 standard for R134a leak detecting equipment went into effect. This SAE standard was created to improve leak detection equipment sensitivity requirements to a sensitivity level of 0.15 oz/ year (4g/Yr). It was created in response to the need to reduce refrigerant HFC-134a emissions and to establish minimum performance criteria for handheld electronic leak detection equipment. Leak detectors that meet this standard will have at least three sensitivity scales that can be selected manually: (A) 0.15 oz/year (4g/Yr), (B) 0.25 oz/year (7g/Yr), and (C) 0.5 oz/year (14g/Yr). It must be calibrated to detect a refrigerant leak with two seconds from a distance of 3/8 in (9.5 mm) moving at a rate of 3 in. (75 mm) per second and must be able to self clear itself with two seconds once moved away from the leak. In addition, the leak detector must not false trigger in the presence of engine oil or transmission oil. This is a great improvement over earlier refrigerant leak detection equipment. Equipment produced prior to 2008 was required to meet SAE standard J1627 which stated that equipment had to be capable of detecting a leak at the rate of 0.5 oz/year (14g/Yr) or less per year. Make sure you are using the correct equipment for the vehicle you are working on. Please note that some older electronic leak detection equipment manufactured under the SAE J1627 regulation was build to a sensitivity level that already meets the SAE J2791 standard.

A BIT OF HISTORY The halide leak detector (Figure 7-13) was once one of the most popular tools for locating R-12 refrigerant leaks. Today, though, the halide leak detector is considered an obsolete and potentially unsafe tool for ­refrigerant detection by the ­air-conditioning industry.

Burner Detector unit

Search hose Valve

Cylinder

FIGURE 7-13  A typical halide leak detector for CFC-12 (R-12).

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Refer to individual equipment specifications data sheets for older equipment to see if equipment updating is required. With the advent of R-1234yf, a new standard for electronic leak detection equipment was developed. The new standard is SAE J2913 and went into effect in 2011. Leak detectors meeting this standard are able to differentiate between a 4 gram per year (high sensitivity), 7 gram per year (medium sensitivity), and 14 gram per year (low sensitivity) (0.141, 0.247, and 0.5 oz). Combination electronic leak detectors are available that meet both J2913 and J2791 and can be used to detect either R-134a or R-1234yf.

Other Types Any leak, regardless of how slight, emits an inaudible noise.

Several other types of leak detectors, such as ultrasonic units, are available. Space does not permit the description of each type in this text. The technician should contact local refrigeration suppliers for additional information. This will allow a comparison of the different makes and models before purchase. When making a selection, do not overlook the commercial refrigeration parts supply houses. They often have a greater variety to choose from than the automotive parts supply houses. Regardless of what type of leak detection device you are using, you need to take a systematic approach to detecting leaks. This means you should test the system when it is cold, having sat for several hours or overnight, and again when it is at operating temperature. You need to begin by looking at the most likely areas for a leak to occur. These areas include connection points of lines and components, as well as areas that contain gaskets and seals (Figure 7-14). Suction tube Suction tube Liquid tube

Suction hose

Liquid tube Expansion valve Receiver Compressor Condenser

Evaporator Liquid tube

Discharge hose Discharge hose

Suction hose

Discharge hose

FIGURE 7-14  First check connection points of fittings for signs of refrigerant leakage.

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Recovery/Recycling/Recharging Systems There are many manufacturers of refrigerant recovery/recycling/recharging (R/R/R) systems, each of which produces several models. When considering recovery equipment, there are three terms to become familiar with: recover, reclaim, and recycle.

Recover

To recover refrigerant is to remove it in any condition and store it in an external container without necessarily processing it further. Under certain conditions, this refrigerant is returned to the system from which it was removed. It may also be sold to a reclamation center where it is processed to new product specifications.

Reclaim

To reclaim refrigerant is to remove it from a system and reprocess it to new product specifications (ARI 700-88 standards). Analytical testing is required. This is an off-site procedure by a laboratory equipped to run such tests.

Recycle

To recycle refrigerant is to remove it from a system and reduce contaminants by oil separation and filter drying to remove moisture, acid, and particulate. This is an on-site procedure, and analytical testing is not required. One of the major points of the Clean Air Act was to ensure recovery and recycling of refrigerants, specifically R-12, instead of allowing it to be vented into the atmosphere. A service facility that services mobile air-conditioning systems must have the proper recovery/ recycling equipment under the EPA Clean Air Act, or it will be charged with “Intent to Vent.” The SAE, in conjunction with the EPA, has established guidelines for the recovery and recycling of both R-134a and R-12 refrigerants. ■■ Effective January 1, 1992, no service facility could service mobile air-conditioning systems unless it acquired approved recovery/recycling equipment and trained and certified service personnel performing said services. ■■ Recovery of R-134a became mandatory in November 1995. ■■ Recycling of R-134a became mandatory on January 29, 1998. Beginning in 1992, R-134a was phased into new vehicle production air-conditioning systems. With the 1994 model year, all vehicles sold in the United States contained the ozone friendly refrigerant R-134a. ■■ Must have dedicated recovery/recycling equipment for each alternative refrigerant serviced. Refrigerants may not be mixed, and the term drop-in refrigerant used by some alternative refrigerants should not imply refrigerants can be mixed. The EPA does not allow the mixing of any refrigerant. ● Contaminated refrigerant must also be recovered into a dedicated recovery unit for future redemption. ■■ Beginning on June 1, 1998, refrigerant blends may be recycled, provided that recycling equipment meets Underwriter’s Laboratories (UL) standard and refrigerant is returned to the vehicle from which it was removed. ■■ Beginning December 2007 SAE J2788 standard for R134a recovery/recharge equipment went into effect. This standard requires that any new equipment produced must do a better job at evacuating and recovering refrigerant from the system being serviced. This new equipment must be capable of measuring and displaying the amount of refrigerant recovered to an accuracy of 1/21 oz. In addition, this standard also requires that the recharge accuracy level must be 1/20.5 oz. This regulation is especially important since many systems today are much smaller and contain much less refrigerant when fully charged. It is not unusual to see refrigerant system volumes of less than one pound.

To recover is to remove refrigerant in any condition from a system and transfer it to an external storage container without necessarily testing or processing it in anyway. To reclaim is to process used refrigerant to new product specifications by means that may Include distillation. This process requires that a chemical analysis of the refrigerant be performed to determine that appropriate product specifications are met. This term implies the use of equipment for processes and procedures usually available only at a reprocessing facility. To recycle is to clean refrigerant for reuse by oil separation and pass it through other devices such as filter-driers to reduce moisture, acidity, and particulate matter. Recycling applies to procedures usually accomplished in the repair shop or at a local service facility.

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091 9 7 9 0 8 5 9 8 4 8

Use caution

Label part number

Caution moving parts

Flammable refigerant

Requires registered technician for service

R-1234yf 485g (1.069 lbs)

PAG Refrigerant oil type

Refrigerant type System charge capacity

SAE J639 J2842 J2845

Applicable SAE standards FIGURE 7-15  The R-1234yf decal.

■■

SAE J2788H is specified for recovery equipment intended for use on hybrid vehicles that use high-voltage (HV) electric air-conditioning compressors, the “H” suffix denotes hybrid. It is imperative that a high-voltage-driven compressor oil is not cross contaminated during service since the HV compressor uses a nonconductive dielectric POE oil compared to a PAG oil that is conductive in a conventional belt-driven R-134a system. WARNING: R-1234yf is a mildy flammable refrigerant, never smoke or expose refrigerant to an open flame, hot surface, high-energy ignition source, sparks, or secondary ignition components. This warning is also on the underhood label as is indicated by the flammability symbol (Figure 7-15).

Recovered refrigerant should not be used in another application unless it is first reclaimed.

R-1234yf refrigerant recovery/recycling/recharge (R/R/R) equipment must meet SAE J2843, charging accuracy with 1/2 ½ oz, automatic oil drain, automatic air purge, and integrated internal J2927 refrigerant identifier (Figure 7-16) or external J2912 refrigerant identifier plugged in. The standard requires that the vehicle’s air-conditioning system be analyzed for purity prior to refrigerant recovery or transfer. The equipment must have either a built-in identifier or be inoperable if one is not connected, generally through a USB connector. An acceptable reading that must be received prior to recovery/recycling is 98 percent pure or greater. If an unacceptable reading is detected, such as contamination by another gas (R-134a), the refrigerant is considered contaminated and the equipment will not allow recovery to proceed. If a system is contaminated, a separate recovery-only machine must be used to recover and store the contaminated refrigerant for either reclamation or disposal at an EPA-approved facility. Before the recovery/recycling/recharge equipment can recharge a vehicle’s refrigerant system, it must first pass an automated precharge leak test to detect the possibility of a gross system leak greater than 0.3 g/s before the system is charged. During the pressurized portion of the test, the technician must turn the vehicle’s HVAC system blower motor to high, turn off the A/C, and set air distribution to floor discharge. Next, the technician must use a J2913-compliant leak detector set to low sensitivity (14 g/year) into the center duct of the floor discharge. Once the technician has set up the vehicle and leak detection equipment, the R/R/R machine will install 15 percent of the programmed charge into the vehicle’s refrigerant system. The technician must then monitor the leak detector for the next 5 minutes or until a leak is detected, whichever comes first. After 5 minutes, the sytem will ask a series of questions: 1. Was the leak test performed? Y/N 2. If yes, Was a leak found? Y/N. If the technician answers yes then the machine will only allow recovery and evacuation.

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Courtesy of Robinair, Bosch Automotive Service Solutions

FIGURE 7-16  The R-1234yf recover/recycle/recharge equipment must meet SAE J2843 and looks very similar to a conventional R-134a machine but has an integrated refrigerant identifier that meets SAE J2927.

3. If no, Is there an auxiliary evaporator? If no, then the machine will allow the recharge procedure to continue and will complete the system recharge. If the technician answered yes, then the machine will instruct the technician to perform a rear evaporator leak test as was performed for the front evaporator. 4. Next, was an auxiliary evaporator leak test performed? If yes, was a leak found? Again, if a leak was noted then only recovery and evacuation will be allowed. If no, then the machine will complete the system recharge. The J2843 equipment is a little more time-consuming to use but it is intended to be as environmentally conscious as possible and force technicians to follow proper protocol. The make and model of the equipment selected for recovering and recycling refrigerants should be based on the needs of the service facility. For example, if the air-conditioning service is occasional, a simple recovery unit like the one shown in Figure 7-17 should suffice. This inexpensive unit can recover about 0.5 lb. (0.236 mL) per minute. A separate recovery unit, pictured in Figure 7-18, frees up the service technician for other service work while a system is being evacuated. This unit costs about twice as much as the first unit and removes about 0.78 lb. (0.368 mL) per minute. Neither system, however, can be used for recycling. Many recovery systems are designed to be used for CFC and HCFC recovery only. Some recovery systems may be used for both CFC and HFC refrigerant. These systems have special provisions to prevent mixing the refrigerants. The automotive service technician is primarily concerned with two refrigerants: R-12, a CFC, and R-134a, an HFC. For full service, if a CFC/HFC combination system is not available, the service facility must have two recovery systems: one dedicated for R-12 service (Figure 7-19) and another dedicated for R-134a service (Figure 7-20). This may seem to be an expensive investment, but considering the high cost of refrigerants, an early payback may be realized.

Most service centers impose a recovery fee in addition to their regular charges.

Shop Manual Chapter 7, page 254

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FIGURE 7-17  A mechanical refrigerant pump used to recover refrigerant.

FIGURE 7-18  A typical recovery unit.

FIGURE 7-19  An R-12 recovery unit suitable for automotive service.

FIGURE 7-20  An R-134a Recovery/Recycle/Recharge unit that meets suitable for servicing today’s refrigerant systems.

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Most systems manufactured for automotive air-conditioning system service are used for recovering, evacuating, recycling, and recharging. Current recover–recycle–recharge systems automatically control the functions of the equipment. This eliminates the need for personal attention and the requirement for a separate vacuum pump and charging station. Current equipment also has automatic air purge capabilities to detect and vent air from the storage cylinder. A single-pass recycling machine cleans and filters refrigerant as it is being recovered. A  multipass recycling machine recovers the refrigerant in one operation and recycles it through multiple filters, driers, and separators in another operation. It is important that the manufacturer’s maintenance and operational instructions be ­followed for optimum equipment performance and service. Improper start-up procedures, for example, may induce unwanted air into the system.

Record Keeping Requirements The EPA has established that service shops must maintain records of the name and address of any facility to which refrigerant is sent. In addition, if refrigerant is recovered and sent to a reclamation facility, the name and address of that facility must be kept on file. Service shops are also required to maintain records (on-site) showing that all service technicians are properly certified. Service shops must certify to the EPA that they have purchased or acquired and are properly using approved refrigerant recovery equipment for both R-12 and R-134a. This is accomplished by sending a form to the EPA certifying that the shop owns the equipment. This only has to be done once, and it is not required if additional equipment is purchased. Shops must also certify that each person using the equipment has been properly trained and that technicians who repair or service R-12 and R-134a have been certified by an EPA-approved organization. Additional information regarding EPA regulations and how they relate to the mobile air-conditioning industry may be found at the EPA Web site, www.epa.gov/ozone/title6/609.

PDA Diagnostics A personal digital assistant (PDA) has become as common as the cell phone, and today PDAs are also part of the automotive diagnostic industry. There are programs and interfaces that allow you to use them as onboard diagnostic scan tools, digital storage oscilloscopes, and as air-conditioning system diagnostic and testing tools. The PDA tool is not intended to replace the other air-conditioning service equipment that you have but is just one more tool to aid you in quickly and accurately diagnosing and repairing air-conditioning problems. One advantage of these tools is that they take a systematic approach to testing and analyzing an air-conditioning system. A systematic approach generally only comes with years of experience, and even then no two technicians approach a problem in the same way. One of these systems is produced by Neutronics and is called the Master A/C System Technician (Figure 7-21). This is an all-in-one tool for identifying refrigerant and checking the system pressures. It also provides a PDA interface with updatable cartridges for step-by-step diagnostic procedures. Author’s Note: Being a service technician today involves more than just staying up to date on current service trends and technology. It also involves knowing what changes are occurring at both the state and federal levels and how these changes affect your ability to perform certain services on vehicles. To stay in tune with changes in our industry, you must read trade journals and join trade organizations. Two good organizations to look into are Society of Automotive Engineers (SAE), www.sae.org and Mobile Air Conditioning Society (MACS), www.macsw.org.

Higher than normal high-side pressure does not necessarily indicate an overcharge of refrigerant.

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FIGURE 7-21  A simple-to-use Neutronics Inc. PDA-based Master A/C System Technician is a diagnostic tool designed to analyze refrigerant system pressures and temperatures to determine the most likely cause of system malfunctions.

Charging the System with Refrigerant

Shop Manual Chapter 7, page 264

Charging the air-conditioning system with the correct type and quantity of refrigerant is, perhaps, the most important service procedure that the technician will perform. Proper operation and durability of the system may be directly linked to this procedure. An improperly charged system not only results in less than maximum performance but also leads to inaccurate diagnosis that may result in unnecessary repairs. Before charging an air-conditioning system, determine the type of refrigerant. An undercharged system will: ■■ Result in inadequate cooling under high load conditions. ■■ Cause the compressor to cycle rapidly due to the action of the clutch cycling pressure switch (if equipped). ■■ Aid in early compressor failure. An overcharged system will result in: ■■ Higher than normal high-side pressures. ■■ Reduced cooling capacity under any load condition. ■■ Improperly operating pressure controls. ■■ Early compressor failure. Even a minor error in refrigerant charge level (weight) can affect air-conditioning system performance. This is particularly true of small capacity systems, those under 1.5 lbs. of refrigerant. Air-conditioning systems today are smaller than ever before and more efficient and still offer outstanding performance. In addition, systems manufactured today are much less susceptible to leaks and can go five years or longer on the original factory charge. To address the issue of small capacity refrigerant systems, the EPA adopted SAE standard J2788 effective December 2007, covering the accuracy level of future refrigerant recovery,

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recycling, and recharging equipment. Standard J2788 supersedes the previous standard J2210. Refrigerant recovery, recycling, and recharging equipment must now be certified J2788 compliant. This equipment must be capable of measuring and displaying the amount of refrigerant recovered to an accuracy level of 61 oz. When recharging a refrigerant system with an SAE J2788-compliant machine, it must charge a system with 60.5 oz. of accuracy. It should be noted that refrigerant service equipment built prior to the SAE J2788 standard taking effect may have displays down to a tenth of a pound, but this does not mean that they are ­accurate to a tenth of a pound. Always consult the specifications information for the model and ­manufacturer of the equipment you are using, especially if it was manufactured prior to 2008. There are several generally accepted methods of charging an automotive air-conditioning system. Not all methods, however, are recommended for all systems. The manufacturer’s specifications and procedures should be followed to avoid problems. The air-conditioning system may be charged by weight, chart or graph, low-side and high-side pressure, and superheat. The correct charge is critical for an R-134a system. Many recommend initially undercharging by 5 to 10 percent, testing system performance, then adding refrigerant if necessary. A better choice would be to phase out older equipment in the shop build to meet the older SAE J2210 standard and replace it with recovery/recycling/recharging equipment that meets or exceeds the current SAE J2788 standard for accuracy. Even on a very small 0.8 lbs. system J2788 equipment would charge the system within 1/2 3.9% of the recommended amount of refrigerant and a 2 lbs. system would be charged within 1/2 1.5% of the recommended amount of refrigerant.

Diagnosis Air-conditioning problems may often be diagnosed quickly simply by checking the function of the components of the system. The following should be on the basic checklist for quick diagnosis: ■■ Belt tension ■■ Clutch operation ■■ Radiator/condenser fan operation ■■ Evaporator blower operation ■■ Proper airflow from registers ■■ Observe sight glass, R-12 systems ■■ Refrigerant charge ■■ Suction line ■■ Liquid line ■■ Service valves/ports ■■ Lines, hoses, and connections ■■ Inspect for debris in front of condenser

Belt Tension

Is the belt tight? A loose belt will slip under the heavy heat loads of the air-conditioning system. Also, if it is a serpentine belt (Figure 7-22), another defective accessory component, such as the alternator, may cause the belt to slip. This is also a good opportunity to check the belt for wear, cracks, and glazing, a sign of early failure.

Clutch

With the engine running and the air-conditioning controls set for maximum cooling, make sure that the clutch is fully engaged. If it does not engage or if it slips, check for low voltage at the clutch coil. Other problems that could affect clutch operation are: ■■ Outside ambient air temperature that is too cold ■■ Open high-pressure switch

Determine whether the clutch is engaged but slipping, or whether the belt is slipping on the clutch. Both appear nearly the same.

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Compressor

Idler Alternator

Belt Water pump Power steering Air pump Crankshaft FIGURE 7-22  Routing of a typical serpentine belt.

Open low-pressure switch Low refrigerant charge ■■ Excessive clutch air gap ■■ Thermostat that is out of adjustment Also, note the condition of the clutch mating surfaces. If they are covered with grease or oil, a defective compressor shaft seal may be indicated. ■■ ■■

Radiator-Condenser Fan

On car lines equipped with water-pump-mounted direct-drive fans, the fan should turn when the engine is running. If it does not, the belt may be slipping due to a defective (seized) water pump. Whatever the reason, the problem must be corrected. On some car lines equipped with an electric fan (Figure 7-23), the fan will operate any time the compressor clutch is engaged. On others, the fan only operates during high-temperature conditions. If the fan does not operate as required, check for: ■■ A blown fuse or open circuit breaker ■■ A defective high-pressure switch

FIGURE 7-23  A typical electrical cooling fan.

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An inoperative relay (some models) A defective wiring or connector An inoperative fan may result in serious problems associated with high head pressure at slow and idle engine speeds, such as compressor lockup (seizure) or hose rupture. ■■ ■■

Blower Operation

The blower motor should operate any time the air-conditioning system controls are in the ON position. If it does not, the cause of the problem must be located and corrected. If it operates, make sure that it operates in all speeds. Most have at least an HI-MED-LO speed, whereas some have two or more MED speeds. A typical blower and motor assembly is shown in Figure 7-24. A more detailed description of blower motor operation and diagnosis will be covered in Chapter 10.

Airflow

Check to be sure that the air is flowing from the proper registers (Figure 7-25) in all modes. Refer to Chapter 9 of this manual for a description of the proper airflow for the different modes of operation.

Blower housing Blower and motor assembly

Motor Blower

FIGURE 7-24  A typical blower motor assembly.

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Fresh air

Defrost

Dash panel outlet

Front foot duct

Foot well outlet

Rear door

Rear foot duct

Foot door

Heater core Evaporator

Blower motor

Rear ventilator ducts

Defroster door Defroster ducts

Side

Ventilator door

Ventilator ducts Center

Air mix door

Intake doors

Side

FIGURE 7-25  Details of a typical case and duct system.

Sight Glass

The sight glass, if present, may be a part of the receiverdrier or it may be found in the liquid line.

A sight glass is a window into the high-side liquid line of the refrigerant system. It is generally located on top of the receiver-drier or in the high-side liquid line. The sight glass should be clear when the compressor clutch is engaged and the system is operating properly. This check may be made on many, but not all, R-12 systems. Seldom is a sight glass (Figure 7-26) included in an R-134a system because the properties of the oil will erroneously indicate a low charge. Continuous bubbles in the sight glass generally indicate air trapped in the system. Continuous foam indicates that the charge is low, and oil streaks indicate no liquid refrigerant in the system. When the compressor clutch cycles off and on, it is normal to observe bubbles for a short period of time, particularly when the compressor clutch cycles off.

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Flow

(A)

Flow

(B)

Flow

(C)

FIGURE 7-26  Conditions found in a sight glass: (A) clear, (B) foamy or bubbly, and (C) cloudy.

System Leaks

Visually inspect all hoses, tubing, components, fittings, and service ports for refrigerant leaks. Generally, but not always, a leak will be marked by a trace of refrigeration oil.

Suction Line

The suction line is the hose or line that connects the evaporator outlet to the compressor inlet. It should feel cool to the touch when the air-conditioning system is in operation. If it does not feel cool, install the manifold and gauge set to perform a performance test.

Liquid Line

The liquid line connects the condenser or receiver-drier outlet to the evaporator or metering device inlet. It should be warm or even hot to the touch. If it is not warm, install a manifold and gauge set and perform a performance test. It must be noted, however, that on some car line models the metering device is at the outlet of the condenser. The orifice tube is located at the condenser outlet to reduce or eliminate a hissing noise problem caused by refrigerant passing through it. The line between the metering device outlet and the evaporator inlet, in this case, will be cool.

Service Ports

Service valve ports (Figure 7-27) are often a problem area for leaking. They are often neglected when leak testing because hoses are generally connected to them. The hose(s) should be disconnected to ensure that no refrigerant is leaking past a defective valve seat. The Schrader-type valve may be replaced if it is found to be leaking. Note that there is a distinct difference in the service port used for R-12 as compared with R-134a. In an R-12 system, the low- and high-side ports will be the same size or the high-side port will be smaller. The opposite is true for an R-134a system, which has a larger high-side service port.

A second suction line may be found between the evaporator outlet and the accumulator inlet. A second liquid line may be found between the metering device outlet and the evaporator inlet. Learn to recognize the difference in the two types of fittings.

Hoses and Fittings

Throughout the years of automotive air-conditioning system service, refrigerant hoses have been the greatest cause of refrigerant leakage problems. Since the introduction and requirement of barrier-type refrigerant hoses, however, the problem has been greatly reduced. The problem of leaks still exists at the fittings (Figure 7-28). This is particularly true for hoses equipped with spring lock couplers. When replacing fittings, gaskets, or O-rings, be sure to use the proper component. For example, an O-ring may have a round, oval, or square profile. Also, there may be one or two O-rings used on a particular fitting. It must also be noted that some O-rings are refrigerant specific: an R-12 O-ring may not be used on an R-134a system and vice versa. There are O-rings available, however, that are compatible with both refrigerants. 231 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 7-27  A typical R-134a service valve port cap.

FIGURE 7-28  A leak at a line fitting detected with the use of a soap solution.

Refrigeration Oil The moving parts of a compressor must be lubricated to prevent damage during operation. Oil is used on these moving parts and on the seals and gaskets throughout the system as well. In addition, oil is picked up by the refrigerant, which circulates through the system. This refrigerant and oil combination also helps to maintain the thermostatic expansion valve in a proper operating condition. The oil that must be used in an automobile air-conditioning system is a nonfoaming sulfur-free grade specifically formulated for use in certain types of air-conditioning systems. This special oil is known as refrigeration oil, and it is available in several grades and types 232 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 7-29  Several types and grades of oil are used in automotive air-conditioning systems.

(Figure 7-29). The grade and type to be used are determined by the compressor manufacturer and the type of refrigerant in the system. To replace oil that may be lost due to a refrigerant leak, pressurized oil is available in disposable cans. Generally, this container contains two fluid oz. (59 mL) of oil and a like measure of refrigerant. The refrigerant provides the necessary pressure required to force the oil into the system. Mineral oil, used in R-12 air-conditioning systems, is clear to light yellow in color. Some synthetic oils used in R-134a air-conditioning systems may be blue or some other color. An impurity in refrigeration oil can cause a color change ranging from brown to black. Mineral oil is practically odorless, and a strong odor indicates that the oil is impure. Some synthetic oils, on the other hand, have a pungent odor though not impure. In either case, to ensure optimum system protection and performance, impure oil must be removed and replaced with clean, fresh oil. The receiver-drier or suction accumulator should also be replaced and a good pump down (system evacuation) performed before the air-conditioning system is recharged.

Lubricants for HFC Refrigerants

Some of the substitute automotive refrigerants are compatible with conventional mineral oil or alkyl benzene lubricants. However, R-134a refrigerant is not miscible with conventional mineral oil or alkyl benzene lubricants. Lack of miscibility can lead to system operational problems due to insufficient lubrication. When the two fluids are miscible, the lubricant is carried back to the compressor. When not miscible, however, the lubricant can accumulate in the various components of the air-conditioning system. Lubricant that accumulates in the condenser can reduce heat transfer and restrict the flow of liquid refrigerant. This condition can cause vapor pockets to form in the liquid stream as it flows through the metering device into the evaporator. Lubricant that accumulates in the evaporator will reduce heat transfer and restrict refrigerant vapor flow. Poor lubrication return to the compressor often leads to excessive wear of the compressor due to lubricant starvation. Always select the correct lubricant and amount for the system being serviced. The amount of refrigerant oil contained in a refrigerant system varies according to the design and size of the system. As a rough guideline the distribution of oil throughout the refrigerant system is 50 percent in the compressor, 10 percent in the condenser, 10 percent in the fluid container (receiver dryer/accumulator), 20 percent in the evaporator, and 10 percent in the suction hose (Figure 7-30). When a refrigerant component is replaced always refer to the service information for the recommended amount of oil that should be added to the system.

Miscible refers to the mixing ability and compatibility of two products.

Author’s Note: In addition to remembering to add the recommended amount of oil to the refrigerant system after component replacement, do not forget to pay attention to the amount of oil removed from the system during the refrigerant recovery process that also has to be added back to the system.

233 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Fluid container 10%

Evaporator 20%

Compressor 50%

Condenser 10%

Suction hose 10% FIGURE 7-30  The pie chart roughly represents the distribution of oil throughout the refrigerant system.

When servicing the hybrid electric vehicle refrigerant system do not assume that it takes the same refrigerant oil as the nonhybrid vehicle refrigerant system. When servicing a hybrid vehicles refrigerant system, it is imperative that the correct refrigerant oil be used. The hybrid electric vehicle uses insulated refrigerant oil designed to minimize the conductivity of electricity through the compressor case in the event of a circuit failure. Many Toyota hybrid electric vehicles call for ND-11 refrigerant oil. In addition, it is even more critical than ever to properly evacuate the refrigerant system after service to the required vacuum levels for proper moisture removal. Always refer to vehicle manufacturers recommendations for correct refrigerant oil. Synthetic Lubricants.  Two different types of synthetic lubricant—polyalkylene glycols (PAG) and neopentyl polyol esters (POE)—are available for use with HFC refrigerants. Though first used in automotive air-conditioning in 1992, PAG is not a new lubricant. It has been used for years in compressors for natural gas production and compressors handling other “­difficult” gases. Polyalkylene Glycol (PAG).  PAGs are extremely hygroscopic and can absorb several ­thousand parts per million (ppm) of water when exposed to moist air—100 times more than mineral oil, which generally contains less than 100 ppm of water. High water content causes corrosion and copper plating problems in some refrigeration systems when PAG lubricants are used. PAG is also sensitive to chlorine-containing contaminants such as residual R-12 remaining in a system that has been converted. PAG, however, was selected in 1992 as the lubricant of choice for automotive air-­ conditioning systems in which R-134a is used as the refrigerant. This selection was based on previous success and due to deadline time constraints to phase out R-12. PAG lubricant is available in low- and high-viscosity grades. Always follow the manufacturer’s specifications when adding or changing compressor lubricant. R-1234yf refrigerant systems use specially formulated PAG oil and previous PAG oils formulated for R-134a systems should not be used. Polyol Ester (POE).  Neopentyl POEs are a group of organic esters that have an application in systems having a wide operating temperature range where good lubricating characteristics are desired. These lubricants also possess good miscibility with HFCs. Various POE compositions enhance miscibility with HFCs and their resistance to copper plating in refrigeration systems. They also have excellent thermal stability, low volatility, low deposit-forming tendencies, high flash points, and high auto-ignition temperatures. 234 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

On the downside, POEs are also hygroscopic, susceptible to hydrolysis, and incompatible with certain elastomers. These esters can absorb several thousand parts per million of water; however, they are less absorbent than most PAGs. Therefore, like PAGs, POEs must be handled so excess moisture does not enter the refrigeration system. POE should only be used in automotive air-conditioning systems that specifically require this type lubricant. A few vehicle manufacturers, for example, recommend POE lubricant be used in specific R-12 air-conditioning systems that are being retrofitted to R-134a. Some hybrid electric vehicles specify POE (ester oil) in their refrigerant systems. These POE oils have a lower conductivity of electricity than PAG oils and offer proper insulation between the compressor housing and the high-voltage compressor drive motor. Over time, an air-conditioning system may be exposed to moisture contamination during service. Although PAG oil is more hygroscopic (absorbs water) than ester oil, moisture remains suspended in PAG oil. This further emphasizes the need to evacuate the air-conditioning system beyond the minimum of 30 minutes. One disadvantage of ester oil is that under certain conditions (excess moisture contamination), moisture can drop out of ester oil to form small droplets of water that can cause corrosion and possible freeze-up in the expansion device. Remember, less than one drop exceeds the allowable moisture content in most refrigerant systems.

Hydrolysis is a chemical reaction in which a substance reacts with water to form one or more other substances, such as hydrochloric acid, in an ­airconditioning system.

Safety

Personal protection equipment—such as rubber- or PVC-coated gloves or barrier creams and safety goggles—should be worn when handling lubricants. Prolonged skin contact or any eye contact can cause irritations and discomfort, such as stinging and burning. One should avoid breathing the vapors produced by these lubricants, and they should only be used in a wellventilated area. Keep them in tightly sealed containers to prevent moisture contamination by humidity and to ensure that their vapors do not escape.

The Classification of Refrigeration Oil

The classification of refrigeration oil is based on three factors: ■■ Viscosity ■■ Compatibility with refrigerants ■■ Pour point Viscosity.  The viscosity rating for a fluid is based on the time, in seconds, required for a measured quantity of the fluid to pass through a calibrated orifice when the temperature of the fluid is 1008F (37.88C). The resistance to flow of any fluid is judged by its viscosity rating. The higher the viscosity number, the thicker the fluid. Compatibility.  Refrigeration oil must be compatible with the refrigerant with which it is to be used. It should be noted that refrigeration oil now used in an R-12 system is a mineral oil designated YN-9. This oil cannot be used in an R-134a system. Conversely, a poly-alkylene glycol oil, designated YN-12, for an R-l34a system with a reciprocating compressor, may not be used in an R-12 system. A second polyalkylene glycol oil is used in systems with a rotary compressor. There may be as many as three polyalkylene oils, each formulated for a particular application. Incompatible oil mixtures may cause serious damage to the air-conditioning system. The Saybolt Universal Viscosity (SUV) is defined as the time, in seconds, required for 60 cubic centimeters (cm) of oil at 1008F (37.88C) to flow through a standard Saybolt orifice. Refrigeration oil, to be compatible with the refrigerant used in the system, must be capable of existing (remaining an oil) when mixed with the refrigerant. In other words, the oil is not changed or separated by chemical interaction with the refrigerant. The compatibility of a refrigeration oil with a refrigerant is determined by a test called a floc test F. This test is performed by placing a mixture containing 90 percent oil and 10 percent refrigerant in a sealed glass tube. The mixture is then slowly cooled until a waxy substance appears. The temperature at which the substance forms is recorded as the floc point. 235 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Do not mix oils.

Compatible: Capable of forming a mixture that does not separate and is not altered by chemical interaction.

Pour Point.  The temperature at which an oil will just flow is its pour point. This temperature is recorded in degrees Fahrenheit. The pour point is a standard of the American Society for Testing Materials (ASTM). The pour point temperature for oil and lubricant used in high-temperature refrigeration systems, such as automotive air-conditioning, is between 2408F (2408C) and 2108F (223.38C), depending on grade and type. The following is a list of manufacturers and the popular compressors used with the ­recommended type of refrigerant oil. Always refer to specific vehicle service information for proper lubricant selection and quantity. OEM

Compressor Manufacturer

OEM-Recommended Oil

Acura

Nippondenso

ND8

Nippondenso

ND8

46

Sanden

SP10

46

Nippondenso

ND8

46

Sanden

SP10

46

Alfa Romeo Audi

Zexel (Diesel ZXL100 Kiki, Tama) BMW Chrysler/Jeep

Ford

Honda Hyundai

Infiniti

46

46

Nippondenso

ND8

46

Seiko-Seiki

SP20

100

Mitsubishi

PAG-56

46

Nippondenso

ND8

46

Sanden

SP20

100

Sanden

SP10, SP15

46

Ford

YN-12a, YN-12b

Harrison

UCON-488

Nippondenso

ND8

46

Sanden

SP20

100

Sanden

SP10

Harrison

UCON-488

Panasonic

General Motors

ISO PAG Viscosity

46 133 46 46 133

Nippondenso

ND8

46

Nippondenso

ND9

150

Sanden

SP20

100

Nippondenso

ND8

46

Sanden

SP10

46

Ford

YN-12a, YN-12b

46

Nippondenso

ND8

46

Sanden

SP20

46

Sanden

SP10

100

Calsonic

PAG S (ZXL 100)

46

Zexel

PAG S

46

Zexel

PAG E

100

Isuzu

Zexel

ZXL200

100

Jaguar

Harrison

UCON-488

133

Nippondenso

ND8

Sanden

Ester

Sanden

Ester

Land Rover Mazda

46

Nippondenso

ND8

46

Nippondenso

ND9

150

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OEM

Mercedes-Benz

Mitsubishi Nissan

Compressor Manufacturer

OEM-Recommended Oil

ISO PAG Viscosity

Panasonic

DS-83P

Sanden

SP20

46

Zexel

ZXL100PG

46

Harrison

UCON-488

133

100

Nippondenso

ND8

46

Sanden

SP10

46

York

Ester

Mitsubishi

PAG-56

46

Nippondenso

ND8

46

Atsugi

Type R

100

Calsonic

PAG S

46

Ford

FS10, FX15, VF2

PD46

46

Peugeot

Sanden

SP20

100

Sanden

SP10

46

Porsche

Nippondenso

ND8

46

Rover

Nippondenso

ND8

46

Sanden

SP20

100

Sanden

SP10

46 46

Saab

Nippondenso

ND8

Sanden

Ester

Seiko-Seikl

SP20

100

Saturn

Zexel

ZXL200PG

100

Subaru

Calsonic

PAG R

100

Sanden

SP20

100

Zexel

ZXL200PG

100

Zexel

ZXL100

46

Nippondenso

ND8

46

Nippondenso

ND9

150

Sanden

SP10

46

Sanden

SP20

100

Toyota Volkswagen

Volvo

Zexel

ZXL100

Harrison

UCON-488

Sanden

Ester

York

Ester

Zexel

Ester

46 133

Servicing Tips

The oil level of the compressor should be checked each time the air conditioner is “opened” for service. Always check the manufacturer’s recommendations before adding oil to the airconditioning system. When the oil is not being used, the container must remain capped. Always be sure that the cap is in place and tightly secured. Refrigeration oil is very hygroscopic; it absorbs moisture. Moisture is very damaging to the air-conditioning system. It should be noted that polyalkylene glycol oil is 100 times more hygroscopic than mineral oil. It is also ten times more expensive. For these reasons, it is suggested that refrigeration oil be purchased in small c­ ontainers ­(Figure 7-31). Refrigeration oil is packaged in 1 qt. (0.946 L), 1 gal. (3.785 L), 5 gal. (18.925 L), and larger containers.

Hygroscopic: Readily taking up and retaining moisture.

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FIGURE 7-31  Refrigeration oil is packaged in several container sizes.

Do not refill disposable cylinders.

In conclusion, the properties of a good refrigeration oil are low wax content, good thermal and chemical stability, low viscosity, and a low pour point. A few simple rules are listed here for handling refrigeration oil: DO ■■ Use only approved refrigeration oil. ■■ Be sure that the cap is tight on the container when not in use. ■■ Replace oil if there is any doubt of its condition. ■■ Avoid contaminating the oil. ■■ Dispose of used oil in a proper manner. ■■ Always use safety goggles and gloves when handling lubricants. ■■ Avoid breathing the fumes of lubricants. DO NOT ■■ ■■ ■■ ■■

■■

Terms to Know Absorb Contaminated Cross-contaminated Halogen Hydrochloric acid (HCl) Inject Moisture Pump down Reclaim Recover Recycle Significant New Alternative Policy (SNAP)

■■

Transfer oil from one container to another. Return used oil to the container. Leave the oil container uncapped, Use a grade or type of oil other than that recommended for the air conditioner being serviced. Dispose of used oil in an improper manner. Overfill an air-conditioning system with oil. Author’s Note: Compressor input shaft seals are a source of refrigerant ­leakage causing a low system charge level. It is a common practice for technicians to slip a note card in the air gap between the compressor clutch hub and pulley to see whether oil is detected. Oil on the card indicates that the shaft seal is leaking.

SUMMARY ■■ ■■

■■

The least expensive method of leak testing is using a commercially available soap solution. Moisture collects in an air-conditioning system during service procedures and improper or careless service. Moisture mixed with refrigerant and oil forms corrosive acids and sludge in the system.

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■■ ■■

■■

Refrigerant must be recovered, not vented, as prescribed by the EPA. Manufacturers’ procedures and specifications should be followed when charging an ­air-conditioning system with oil or refrigerant. Many system malfunctions can be diagnosed by visual inspection.

REVIEW QUESTIONS Short-Answer Essays 1. Explain how moisture enters the system. 2. Describe one type of commonly used leak detector. 3. Is it important to maintain a moisture-free system? Why? 4. Explain the key difference between the load and unloaded air-conditioning system performance test? 5. How is the temperature-pressure chart used for system diagnosis? 6. What is the acceptable method of adding dye to the system? 7. Briefly describe how a halogen leak detector will react when it comes in contact with raw refrigerant. 8. What is a noncondensable gas and how does it affect air-conditioning system operation? 9. What does SAE standard J2788 apply to and what are the details of this standard? 10. Describe the process of removing moisture by vacuum.

Fill in the Blanks 1. A _______________ type of leak warrants the use of a dye trace solution. 2. An air-conditioning system _______________ is an ­initial test that determines whether the refrigerant ­system is operating as designed. 3. The maximum moisture content allowable in new refrigerant is _______________. 4. When evacuating a refrigerant system it should be placed under a _______________ for a minimum of _______________ minutes to ensure moisture removal from the system. 5. A _______________ acid is formed by the chemical combination of refrigerant and moisture. 6. The symbol _______________ (English) is used to denote a vacuum pressure. 7. The sensitivity of the electronic leak detector is _______________ per year.

8. _______________ or _______________ refrigerant can cause system and equipment damage and present problems if you are not aware of its presence. 9. In Denver, Colorado, water (H 2O) boils at a ­temperature of _______________ . 10. Air in the refrigerant system is considered a _______________ because at no time are refrigerant system pressures great enough or temperatures low enough to cause air to condense into a liquid.

Multiple Choice 1. Vacuum pump efficiency is being discussed. Technician A says that vacuum pump efficiency is greatest at sea level. Technician B says that altitude has little or no effect on vacuum pump efficiency. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 2. Fluorescent leak detector scanner solution is being discussed: Technician A says once introduced into the system, it cannot be removed. Technician B says a ultraviolet light is required for detecting a leak. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 3. Technician A says that a sight glass is often found in an R-12 system. Technician B says that a sight glass is seldom found in an R-134a system. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 4. Technician A says that service ports may be a source of leaks. Technician B says that hose connections are sometimes a source of leaks. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 239

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5. Technician A says that an overcharged system will result in lower than normal low-side pressures. Technician B says that an overcharged system will result in a slight increase in cooling capacity, but only under low load conditions. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

8. Moisture removal from a refrigerant system is being discussed. The length of system evacuation time required depends on all of the major factors listed below except: A. The amount of moisture in the system. B. The ambient temperature. C. The efficiency of the vacuum pump. D. The amount of oil in the system.

6. Refrigerant system air contamination may be caused by: A. Refrigerant system low-side leak. B. Improper system evacuation or insufficient ­evacuation time. C. Weak evacuation pump. D. All of the above.

9. The most accurate method for measuring the effectiveness of system evacuation is with the use of a: A. Kelvinometer. B. Micrometer. C. Thermistor vacuum gauge. D. Mercury (Hg) vacuum gauge.

7. An R134a recovery tank pressure is determined to be 115 psig at 858F. What does this temperature-pressure relationship indicate? A. The recovery tank is contaminated with moisture. B. The recovery tank is contaminated with air. C. The recovery tank is overcharged. D. The recovery tank is at normal operating pressure.

10. To address the issue of small capacity ­refrigerant ­systems, the EPA adopted a new SAE standard ­effective December 2007, covering the accuracy level of future refrigerant recovery, recycling, and ­recharging equipment. The SAE number for this new standard is: A. J1850 C. J2210 B. 2197 D. J2788

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Chapter 8

Diagnosis of the Refrigeration System Upon Completion and Review of this Chapter, you should be able to: Identify differences between R-12 (CFC-12) and R-134a (HFC-134a) systems.

Diagnose six system malfunctions by gauge readings.

■■

Identify the low and high side of the air-conditioning system.

■■

■■

Read and understand temperature-pressure charts.

■■

Understand the proper handling of refrigerants.

■■

Discuss temperature-pressure relationships.

■■

Understand the proper handling of refrigeration oil.

■■

■■

Identify differences between thermostatic expansion valve (TXV) and fixed orifice tube (FOT) systems.

Introduction Study the air-conditioning system diagram (Figure 8-1), and note the dividing line between the high side and low side of the system and the manifold and gauge set connected into the system. As illustrated, any condition (translated to pressure) that occurs in the low side of the system will be indicated on the low-side (compound) gauge. At the same time, any condition in the high side of the system will be indicated on the high-side (pressure) gauge. There is a direct relationship between the pressure and temperature of refrigerant. For any given pressure, there is a corresponding temperature. For example, if the pressure of the low side of the system is 35 psig (241 kPa), the temperature of the evaporating refrigerant will be 388F (3.38C) for Refrigerant-12 and 408F (4.48C) for Refrigerant-134a. This is the temperature of the refrigerant, not the temperature of the air passing through the evaporator. Actual air temperature will be several degrees warmer. For convenience of illustration, a typical temperature-pressure chart is given in Figure 8-2.

System Diagnosis Knowing the temperature of the ambient air entering the condenser, the normal high-side pressure can be determined by referring to Figure 8-3. This assumes that an unloaded refrigerant system performance test, described in Chapter 6, is being performed. For example, if the system is operating properly and the ambient air temperature is 858F (29.48C), the proper high-side pressure should be approximately 180 psig (1241 kPa) for an R-134a system. Allowances must be made in all readings to provide for slight errors in thermometers and gauges, as well as relative humidity. The diagnostic process starts with a systematic approach to the customer complaint, followed by a detailed rational analysis to assure that the fault is corrected (Figure 8-4). One

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4

High-side gauge

Low-side gauge

Vapor: low pressure and temperature

Vapor: high pressure and temperature

Manifold Hose set

Refrigerant, changing from liquid to vapor. Removes heat from the passenger compartment Accumulator in the evaporator.

Flow

1

Refrigerant, changing from vapor to liquid. Gives up heat to the outside air in the condenser.

Compressor Evaporator

Clutch

Condenser

Flow Liquid: low pressure and temperature

Orifice tube Orifice tube system

3

Liquid: high pressure and temperature

2

A

High-side gauge

Low-side gauge

4 Vapor: low pressure and temperature

Hose set

Flow Remote bulb

Clutch

Flow

3

Thermostatic expansion valve

Refrigerant, changing from vapor to liquid. Gives up heat to the outside air in the condenser.

Compressor

Evaporator

Liquid: low pressure and temperature

Vapor: high pressure and temperature

Manifold

Refrigerant, changing from liquid to vapor. Removes heat from the passenger compartment in the evaporator. Flow

1

Condenser

Receiver/drier Sight glass Expansion valve system

Liquid: high pressure and temperature

2

B FIGURE 8-1  Typical automotive air-conditioning system: (A) orifice tube; and (B) expansion valve.

There are no valid temperature– pressure relationships for a malfunctioning system, such as an undercharge of refrigerant.

of the first steps is to establish a baseline before you perform any repairs. The initial airconditioning performance test can serve as this baseline because it records system pressures, ambient air temperature, vent temperature, and relative humidity levels. In addition to being able to verify a repair with this baseline, you will be in a position to give a customer some relative facts after the repair is completed. An example would be telling a customer: “Your airconditioning system had a vent temperature of 708F (218C) in the shop, where the temperature was 858F (29.48C). Your system refrigerant pressure was determined to be low. A leak at the condenser inlet line was located. After the leak was repaired, the system was recharged with the proper amount of refrigerant. The outlet temperature from your car’s dash ventilation ducts is now down to 388F (3.38C).”

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TEMPERATURE-PRESSURE CHART

TEMPERATURE-PRESSURE CHART

TEMPERATURE °F °C

CFC-12 PRESSURE PSIG KPA

HFC-134A PRESSURE PSIG KPA

–30 –25 –20 –15 –10 –5 0 5 10 15 20 25 30 35 40 45 50

*5.5 *2.3 0.6 2.4 4.5 6.7 9.2 11.8 14.6 17.7 21.0 24.6 28.5 32.6 37.0 41.7 46.7

*9.7 *6.8 *3.6 *0.2 2.0 4.2 6.5 9.1 11.9 15.3 18.4 22.0 26.1 30.4 35.1 40.1 45.5

–23.3 –31.7 –28.9 –26.1 –23.3 –20.6 –17.8 –15.0 –12.2 –9.4 –6.7 –3.9 –1.1 1.7 4.4 7.2 10.0

37.9 15.9 4.1 16.5 31.0 46.2 63.4 81.4 100.7 122.0 144.8 169.6 196.5 224.8 255.1 287.5 322.0

66.9 46.9 24.8 1.4 13.8 29.0 44.8 62.7 82.1 105.5 126.9 151.7 180.0 209.6 242.0 276.5 313.7

TEMPERATURE °F °C

CFC-12 PRESSURE PSIG KPA

55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130

52.1 57.7 63.8 70.2 77.0 84.2 91.8 99.8 108.3 117.2 126.6 136.4 146.8 157.7 169.1 180.0

12.8 15.6 18.3 21.1 23.9 26.7 29.4 32.2 35.0 37.8 40.6 43.3 46.1 48.9 51.7 54.4

359.2 397.8 439.9 484.0 530.9 580.6 633.0 688.1 746.7 808.1 872.9 940.5 1,012.2 1,087.3 1,166.0 1,241.1

HFC-134A PRESSURE PSIG KPA 51.3 57.3 64.1 71.2 78.7 86.8 95.3 104.4 114.0 124.2 135.0 146.4 157.5 171.2 184.6 198.7

353.7 395.1 442.0 490.9 542.6 598.5 657.1 719.8 186.0 856.4 930.8 1,009.4 1,086.0 1,180.4 1,272.8 1,370.0

FIGURE 8-2  A typical temperature-pressure chart for R-12 and R-134a in English and metric values.

320 300 280 260 240 High-side 220 pressure 200 180 (psig) 160 140 120 100 80 60

65

70

75

80 85 90 95 100 Ambient temperature (˚F)

105

110

115

120

50

45 Center vent temperature 40 (˚F) 35 32 10

15

20 25 Low-side pressure (psig)

30

FIGURE 8-3  This unloaded performance test data chart for an R-134a systems high- and low- side refrigerant pressures is an example of the type of chart provided by manufacturers for refrigerant system analysis.

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Confirm customer complaint, symptoms Perform a visual inspection of system and related systems

System pressures incorrect (compressor clutch engaged)

Recheck air blend doors and recirculation door; also heater control valve, if so equipped

Perform air-conditioning system baseline performance test

System pressure correct (compressor clutch engaged)

System (static) pressure incorrect (compressor clutch not engaged)

System static pressure correct (compressor clutch not engaged)

Leak test system

Perform A/C electrical and system control circuit inspection and diagnosis

Perform pressure diagnosis Repair source of leak after recovery of refrigerant

Repair fault or replace component

Repair fault Evacuate and recharge refrigerant system Confirm repair with airconditioning performance test

FIGURE 8-4  Starting air-conditioning system diagnosis by following a logical sequence such as this will improve diagnostic results.

Malfunction refers to a component’s failing to work as designed.

There are seven basic conditions for the automotive air-conditioning system: one condition indicates normal operation, and six conditions indicate a system malfunction. Following is a brief description of system function or malfunction for each of the seven conditions. We will assume that the outside ambient air temperature is 908F (328C).

Temperature and Pressure Relationships of R-12 (CFC-12)

Evaporator coil temperature must be maintained above 328F (08C).

R-12 (CFC-12) was a desirable refrigerant for automotive use because the temperature on the Fahrenheit scale and English system pressure values in the 20–70 psig range are very close to the corresponding temperatures of 208F2708F . There is only a slight variation between the temperature and pressure values of the refrigerant in the 20–70 psig range (Figure 8-5). In this range, the assumption for R-12 is made that for each pound of pressure recorded, the temperature is the same. For example, for a pressure of 23.8 psig, the corresponding temperature is 248F (Figure 8-6). This value, however, is the temperature of the evaporating refrigerant, not the temperature of the outside surface of the evaporator coil or the air passing over it. Unfortunately, this close correlation does not exist in the metric system (Figure 8-7). The objective in automotive air-conditioning is to allow the evaporator to reach its coldest point without icing. Because ice forms at 328F (08C), the fins and cooling coils of the evaporator must not be allowed to reach a colder temperature. Because of the temperature rise through the walls of the cooling fins and coils, the temperature of the refrigerant may be several degrees cooler than that of the air passing through the evaporator. For example, a pressure gauge reading of 28 psig (193.06 kPa) in an R-12 system means that the evaporating temperature of the refrigerant is about 308F (21.18C). Because of the

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FIGURE 8-5  English temperature–pressure chart for R-12 (CFC-12).

FIGURE 8-6  A pressure of 23.8 psig corresponds to a temperature of 248F.

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FIGURE 8-7  Metric temperature–pressure chart for R-12 (CFC-12).

temperature rise through the fins and coils, the air passing over the coil is more on the order of about 348F or 358F (1.18C or 1.78C).

Temperature and Pressure Relationships of R-134a (HFC-134a) The performance characteristics of R-134a and R-12 refrigerants are very similar. R-134a refrigerant has a lower normal low-side pressure than R-12 and a higher normal high-side pressure than R-12 refrigerant. The power consumption of R-134a is slightly higher, but the refrigerant capacity is 3 to 5 percent less than an R-12 system. The vapor pressure of both systems is essentially equal under normal operating temperatures. Like R-12, R-134a has its own unique temperature and pressure relationship, as shown in Figure 8-8. The metric equivalent is given in Figure 8-9. Note that the evaporating temperature and pressure of R-134a is reasonably close in the 10 2 408F (212.2 2 14.48C) range. In fact, the temperature and pressure is nearly the same at 158F (29.48C). A pressure gauge reading of 26 psig (179 kPa) means that the evaporating temperature of the refrigerant in the evaporator is about 308F (21.18C). This may be favorably compared with the temperature and pressure relationship of R-12.

Temperature and Pressure Relationships of R-1234yf (HFO-1234yf) Current research has shown that R-1234yf and R-134a refrigerants have similar performance characteristics, in fact even closer than the similarity in pressure seen between R-134a and R-12. Refrigerant R-1234yf has a slightly higher normal low-side pressure than R-134a and a slightly higher normal high-side pressure than R-134a refrigerant, but they are so close that 246 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 8-8  English temperature–pressure chart for R-134a (HFC-134a).

FIGURE 8-9  Metric temperature–pressure chart for R-134a.

most technicians will probably not notice the difference. The vapor pressure of both systems is essentially equal under normal operating temperatures. Technicians that are used to working on R-134a systems will find that there will be very little difference in working on and diagnosing an R-1234yf system other than the service warning that it is a mildly flammable refrigerant. The temperature–pressure relationship of R-1234yf is shown in Figure 8-10. A pressure gauge reading of 28 psig (193 kPa) means that the evaporating temperature of the refrigerant in the evaporator is about 288F (22.28C). This is very similar to the R-134a pressure–temperature relationship.

Condition One: Normal Operation (Figure 8-11)

Low-side gauge: Normal pressure R-134a (HFC-134a): 30–31 psig (207–214 kPa) ●● R-12 (CFC-12): 32–33 psig (221–228 kPa) ■■ High-side gauge: Normal pressure ●● R-134a (HFC-134a): 204–210 psig (1,407–1,448 kPa) ●● R-12 (CFC-12): 185–190 psig (1,276–1,310 kPa) Results from a performance test should be compared to an air-conditioning performance table for the type of refrigerant in the vehicle’s air-conditioning system. Figure 8-12 shows the normal operating pressure ranges for R134a under various ambient air temperature and humidity levels, and the performance table in Figure 8-13 shows the normal operating pressure ranges for R1234yf under various ambient air temperature and humidity levels. When a refrigerant system is operating as designed, the normal flow of refrigerant in a thermostatic expansion valve (TXV) system is as shown in Figure 8-14; Figure 8-15 shows the normal flow of refrigerant in a fixed orifice tube (FOT) system. Assuming a cycling-clutch system, the desired “average” temperature of the evaporator should be about 358F (1.78C). To achieve a “theoretical average” temperature, the thermostat should cycle the compressor clutch OFF at about 278F (22.88C) and back ON ■■

●●

Average is a single value that represents the median. 247

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R-1234yf Fahrenheit Pressure/Temperature Chart 77 80 83 86 89 92 96 99 102 106 110 113 117 121 125 129 133 137 142 146 148 150 155 160 164 169 174 179 184 190 195

200 206 212 218 223 229 236 242 248 255 261 268 275 282 289 296 304 311 319 326 334 342 351 359 368 376 385 394 403 413

0 4 8 12 16 17 18 22 23 24 28 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70

72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 102 104 106 108 110 111 112 114 116 118 120 122 124 126 128 130

132 134 136 138 140 142 144 146 148 150 152 154 156 158 160 162 164 166 168 170 172 174 176 178 180 182 184 186 188 190

°C

kPa

°C

kPa

°C

-18 -16 -14 -12 -10 -8 -6 -4 -2 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

544 562 581 601 620 641 661 682 704 726 748 771 794 818 842 866 891 917 943 970 997 1024 1052 1081 1110 1140 1170 1201 1232 1264 1297 1330

23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54

1363 1398 1432 1468 1504 1541 1578 1616 1654 1694 1733 1774 1815 1857 1900 1943 1987 2032 2078 2124 2171 2219 2267 2317 2367 2418 2523 2631 2743 2859 2979

55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 82 84 86 88 90

Condenser

9 11 14 16 19 19 20 23 24 25 28 31 33 35 37 38 40 42 44 47 49 51 53 56 58 61 63 66 68 71 74

62 75 90 105 120 137 155 174 194 214 225 236 248 260 272 284 297 309 323 336 350 364 379 394 409 425 440 457 473 490 508 526

Evaporator

PSIG °F

Condenser

PSIG °F

Evaporator

PSIG °F

R-1234yf Celsius Pressure/Temperature Chart kPa

FIGURE 8-10  R-1234yf pressure/temperature chart.

CFC-12

HFC-134a

FIGURE 8-11  Manifold gauge reading 1; system normal.

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Refrigerant Service Port Pressure Relative Humidity

Low Side

High Side

Maximum Center Discharge Air Temperature

558F 2 658F (13 2 188C)

0–100%

22–29 psi (151–199 kPa)

129–168 psi (888–1,157 kPa)

438F (68C)

668F 2 758F (19 2 248C)

Below 40%

22–28 psi (151–192 kPa)

149–215 psi (1,026–1,481 kPa)

438F (68C)

Above 40%

22–34 psi (151–234 kPa)

152–210 psi (1,047- 1,446 kPa)

468F (78C)

Below 35%

22–32 psi (151–220 kPa)

179–220 psi (1,233–1,515 kPa)

488F (88C)

35–50%

22–33 psi (151–227 kPa)

179–225 psi (1,233–1,550 kPa)

508F (138C)

Above 50%

24–37 psi (165–254 kPa)

179–212 psi (1,233–1,460 kPa)

558F (138C)

Below 30%

24–36 psi (165–248 kPa)

202–241 psi (1,391–1,660 kPa)

558F (138C)

30–50%

25–38 psi (172–261 kPa)

202–238 psi (1,391–1,639 kPa)

658F (188C)

Above 50%

28–40 psi (192–275 kPa)

200–235 psi (1,378–1,619 kPa)

668F (198C)

Below 20%

28–40 psi (192–275 kPa)

231–270 psi (1,591–1,860 kPa)

648F (178C)

20–40%

29–42 psi (199–289 kPa)

231–267 psi (1,591–1839 kPa)

668F (198C)

Above 40%

31–43 psi (213–296 kPa)

228–270 psi (1,570–1,860 kPa)

708F (218C)

Ambient Air Temperature

768F 2 858F (25 2 298C)

868F 2 958F (30 2 358C)

968F 2 1058F (36 2 418C)

FIGURE 8-12  An example of an air-conditioning performance table of the normal operating ranges for R134a under various ambient temperature and humidity levels.

A/C Performance Table High Side Service Port Pressure

Maximum Left Center Discharge Air Temperature

Ambient Temperature

Relative Humidity

Low Side Service Port Pressure

13 2 188C (55 2 658F)

0–100%

199–261 kPa (29–38 psi)

1233–1481 kPa (179–215 psi)

108C (508F)

19 2 248C (66 2 758F)

Less than 35%

241–316 kPa (35–46 psi)

1419–1639 kPa (206–238 psi)

128C (528F)

Greater than 40%

227–310 kPa (33–45 psi)

1336–1612 kPa (194–234 psi)

138C (558F)

Less than 35%

241–316 kPa (35–46 psi)

1419–1639 kPa (206–238 psi)

138C (558F)

35–60%

254–323 kPa (37–47 psi)

1460–1667 kPa (212–242 psi)

148C (578F)

Greater than 60%

254–344 kPa (37–50 psi)

1481–1729 kPa (215–251 psi)

178C (618F)

Less than 30%

261–337 kPa (38–49 psi)

1522–1750 kPa (221–254 psi)

158C (598F)

30–50%

268–358 kPa (39–52 psi)

1550–1798 kPa (225–261 psi)

178C (618F)

Greater than 50%

282–385 kPa (41–56 psi)

1591–1860 kPa (231–270 psi)

188C (648F)

Less than 20%

275–351 kPa (40–51 psi)

1632–1853 kPa (237–269 psi)

178C (618F)

20–40%

289–378 kPa (42–55 psi)

1646–1901 kPa (239–276 psi)

188C (648F)

Greater than 40%

310–399 kPa (45–58 psi)

1688–1949 kPa (245–283 psi)

208C (688F)

Less than 20%

296–372 kPa (43–54 psi)

1743–1949 kPa (253–283 psi)

188C (648F)

Greater than 20%

310–399 kPa (45–58 psi)

1770–1998 kPa (257–290 psi)

208C (688F)

Below 30%

330–406 kPa (48–59 psi)

1867–2080 kPa (271–302 psi)

28C (708F)

25 2 298C (76 2 858F)

30 2 358C (86 2 958F)

36 2 418C (96 2 1058F)

42 2 468C (106 2 1158F)

47 2 498C (116 2 1208F)

FIGURE 8-13  An example of an air conditioning performance table of normal operating ranges for R-1234yf under various ambient temperatures and humidity levels.

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Evaporator

Temperature sensing tube

Remote bulb

From condenser

Condenser

Internal equalizing passage (Equalized by evaporator inlet pressure)

Compressor

Receiver-drier

Radiator

High-pressure gas

Low-pressure liquid

High-pressure liquid

Low-pressure gas

To evaporator

FIGURE 8-14  The normal state of refrigerant in a TXV system.

Accumulator

Evaporator

Orifice tube

Condenser

Compressor

Radiator

High-pressure gas

Low-pressure liquid

High-pressure liquid

Low-pressure gas

FIGURE 8-15  The normal state of refrigerant in a FOT system.

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at about 398F (3.98C). According to the R-12 temperature-pressure chart, the gauge reading should be a low of 26 psig (179 kPa) and a high of 36 psig (248 kPa). For R-134a systems, the off cycle should be at 24 psig (165 kPa) and the on cycle at 37 psig (255 kPa). It should be noted that the theoretical average is seldom accomplished in actual operation. Therefore, it is suggested that manufacturers’ specifications be consulted for the operating range of any particular vehicle. Actually, the concern is with air temperature, not with refrigerant temperature. A low of 14–15 psig (96.5–103.4 kPa) and a high of 40–50 psig (275.8–344.7 kPa), then, is a more realistic indication for the low-side gauge. The high-side gauge should indicate pressure shown in the temperature-pressure chart for any given ambient temperature, plus or minus a few psig (kPa).

Moisture in the system causes harmful acids.

Condition Two: Insufficient Cooling (Figure 8-16)

Low-side gauge: Low pressure ●● R-134a (HFC-134a): 0–12 psig (83 kPa) ●● R-12 (CFC-12): 0–15 psig (103 kPa) ■■ High-side gauge: Normal to slightly low pressure ●● R-134a (HFC-134a): 208 psig (1,434 kPa) ●● R-12 (CFC-12): 190 psig (1,310 kPa) There are three major possible causes for this condition. They are as follows: 1. A thermostat that is improperly adjusted (temperature), out of adjustment (mechanical), or defective 2. A restriction in the low side of the system 3. Moisture in the system The TXV control thermostat may be defective or improperly adjusted. It must be adjusted so its electrical contacts will open at the desired low temperature to allow the clutch to cycle off. The differential must be adjusted so the clutch will cycle back on after a predetermined temperature rise. A defective thermostatic expansion valve that limits refrigerant flow will cause evaporator refrigerant starvation (Figure 8-17), resulting in insufficient cooling. Similarly, a restricted FOT that limits refrigerant flow will also cause evaporator refrigerant starvation (Figure 8-18). Another indication of a defective thermostat is that the evaporator coil may be icing over. Ice on the coil blocks the flow of air passing through it. If the system works fine for a while ■■

A restriction is a blockage in the air-conditioning system caused by a pinched line, foreign matter, or moisture freeze-up.

A control thermostat is a temperatureactuated electrical switch used to cycle the compressor clutch on and off, thereby controlling the air-conditioning system temperature.

HFC-134a FIGURE 8-16  Manifold gauge reading indicating insufficient cooling due to improperly adjusted temperature control, restriction of the low side, or moisture in the system.

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Evaporator

Accumulator

Evaporator Remote bulb

Orifice tube

Condenser

Condenser Compressor

Compressor

Receiver-drier

Radiator

High-pressure gas

Low-pressure liquid

High-pressure liquid

Low-pressure gas

Radiator

FIGURE 8-17  Defective thermostatic expansion valve, which limits refrigerant flow, will cause evaporator refrigerant starvation.

A metering device is a component that regulates the proper amount of refrigerant in the evaporator. The two common types for automotive applications are the TXV and the FOT.

High-pressure gas

Low-pressure liquid

High-pressure liquid

Low-pressure gas

FIGURE 8-18  Restricted FOT, which limits refrigerant flow, will cause evaporator refrigerant starvation.

and then becomes warmer, there may be moisture in the system. If reduced airflow is also noted, the evaporator freeze-up is indicated. If evaporator freeze-up is suspected, check for a frozen evaporator line or the compressor clutch not cycling. Causes for this condition are: 1. A defective cycling clutch switch that is stuck in the ON position. 2. An improperly positioned evaporator core sensor (fin sensor) that is not touching the evaporator core or not inserted into the fins. There may be a restriction in the low side of the system (Figure 8-19) between the metering device outlet and the compressor inlet. The screen at the inlet of the metering device may be clogged. If there is excess moisture in the system, it will collect and freeze in the screen at the inlet of the metering device. Refer to Figure 8-1a; restriction will be located in quadrant 3 or 4. Flow

B

Suction line Discharge line

Compressor Evaporator

Condenser

Clutch Accumulator A

Fixed orifice tube Liquid line Flow

FIGURE 8-19  Look for a restriction in the low side of the system between the metering device outlet (A) and the compressor inlet (B).

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Outlet

Inlet

Screen

FIGURE 8-20  Inlet screen of thermostatic expansion valve.

FIGURE 8-21  Orifice tube showing inlet screen.

This condition may be checked by carefully feeling the receiver-drier or condenser outlet, along the liquid line, and finally the metering device inlet. All should be warm. If any part is cool, a restriction is indicated at that point. Only the inlet of the metering device should be warm; the outlet should be cool. In fact, the outlet of the metering device is perhaps the coolest part of the system under normal operating conditions. If the inlet screen of the expansion valve (Figure 8-20) is found to be the problem, it may be cleaned. After cleaning the screen, the receiver-drier must be replaced. Also, the receiver-drier must be replaced if the restriction proves to be at its outlet. This is true even though the liquid line and expansion valve inlet screen may be clean. If the screen on an orifice tube (Figure 8-21) is found to be the problem, the orifice tube and the accumulator should be replaced. A temperature change at the outlet of the accumulator is expected and does not indicate a problem. Another problem that can cause the symptoms of Condition Two is moisture in the system. If there is moisture in the system that is not absorbed by the desiccant in the receiverdrier or accumulator, it may freeze at the metering device inlet. The inlet may then become very cold, the same symptom indicated by a clogged inlet screen. To determine whether moisture is the problem, turn the air conditioner off for 10 to 15 minutes, then turn it back on. If the gauge reading immediately goes to an abnormal condition, the screen is probably clogged. If the gauge reading is normal for a few minutes, then goes to abnormal, there is probably excess moisture in the system. This condition is corrected by replacing the receiverdrier or accumulator. Before condemning a component, though, make sure the system is fully charged with refrigerant. A slightly low system charge will cause rapid cycling of the air-conditioning compressor clutch when the engine speed is raised. On noncycling-clutch systems (variable displacement compressors), the low side will be low (15–30 psig for R-134a) and the high-side will also be low (110–150 psig for R-134a). You may also notice foamy bubbles in the sight glass, if so equipped, and the evaporator outlet line will be warm.

A restriction in the system is generally “marked” by a temperature difference.

Condition Three: Insufficient Cooling or No Cooling (Figure 8-22) ■■

Low-side gauge: Very low pressure to low pressure R-134a (HFC-134a): 15 psig (103 kPa) ●● R-12 (CFC-12): 18 psig (124 kPa) ●●

■■

High-side gauge: Low pressure R-134a (HFC-134a): 139–144 psig (958–993 kPa) ●● R-12 (CFC-12): 130–135 psig (896 kPa) ●●

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CFC-12

HFC-134a

FIGURE 8-22  Manifold gauge reading indicating insufficient or no cooling due to undercharge of refrigerant, clogged metering device inlet screen, defective metering device, or excessive moisture in the system.

If there is a loss of refrigerant, there is a leak in the system.

Shop Manual Chapter 8, page 294

Shop Manual Chapter 8, page 304

If the low-side gauge pressure is moderately low, the most probable cause is an undercharge of refrigerant. If the low-side gauge pressure is very low, possibly in a vacuum, there are four other possible causes, all relating to the metering device: 1. Clogged inlet screen 2. Defective valve or tube 3. Moisture in the system 4. High-side restriction Loss of refrigerant resulting in an undercharge is usually caused by a leak. This condition may also be noted by bubbles in the sight glass, if so equipped. To correct this condition, the cause of the leak must be located and repaired. The system must then be properly evacuated and charged with refrigerant. The effects of an undercharged thermal expansion valve refrigerant system may be seen in Figure 8-23. Similar refrigerant undercharge effects in an orifice tube system may be seen in Figure 8-24. Symptoms of an undercharged refrigerant system may include poor cooling, compressor cycling rapidly, and warm evaporator outlet line. The screen in the metering device may be clogged or there may be moisture in the system, as outlined in Condition Two. An expansion valve may be defective and completely closed. The most probable cause for this condition is that the remote sensing bulb may have lost its charge of volatile gas. If this is the cause, the valve will not regulate (open), and it must be replaced. If the problem still cannot be found, look for a restriction in the high side before the metering device. Refer to Figure 8-1. The restriction will be located in quadrant 2 or 3. It should be noted that the gauge reading may be high if the restriction is found shortly after the low-side service fitting.

Condition Four: Insufficient Cooling or No Cooling (Figure 8-25) ■■

Low-side gauge: Low pressure R-134a (HFC-134a): 20 psig (138 kPa) ●● R-12 (CFC-12): 22 psig (152 kPa) ●●

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Evaporator

Remote bulb

Condenser Compressor

Receiver-drier

Radiator

High-pressure gas

Low-pressure liquid

High-pressure liquid

Low-pressure gas

Lower high-pressure liquid below pickup tube

FIGURE 8-23  Effects of refrigerant undercharge on a thermal expansion valve refrigerant system.

Accumulator

Evaporator

Orifice tube

Condenser Compressor

Radiator

High-pressure gas

Low-pressure liquid

High-pressure liquid

Low-pressure gas

FIGURE 8-24  Effects of refrigerant undercharge on a fixed orifice tube refrigerant system.

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CFC-12

HFC- 134a

FIGURE 8-25  Manifold gauge reading indicating insufficient or no cooling due to a restriction in the high side of the system, such as a bent or kinked tube.

High-side gauge: High to extremely high pressure R-134a (HFC-134a): 281 psig (1,937 kPa) ●● R-12 (CFC-12): 250 psig (1,724 kPa) The most probable cause of this condition is a restriction in the high side of the system. The restriction may be anywhere from the compressor outlet to the receiver-drier or fixed orifice tube inlet. The closer to the compressor, the higher the high-side gauge pressure will be. Refer to Figure 8-1. The restriction will be located in quadrant 1 or 2. A moderately high high-side pressure may indicate a clogged receiver-drier (Figure 8-26) or liquid line. An extremely high pressure may indicate a restriction, such as a bent tube in the condenser closer to the compressor. The probable location of high-side restrictions is shown in Figure 8-27. In any event, the restriction must be located and corrected. Often, a marked temperature change will be noted at the point of restriction. The upstream side of the restriction will be very hot while the downstream side will be cooler. High-side restrictions can cause extremely high temperatures. Be careful to avoid personal injury. If the high-side pressure is abnormally high and the high-side lines and hoses are vibrating or pulsating, the refrigerant system may be overcharged with refrigerant oil. This will also be accompanied by high duct temperatures and poor cooling performance. This condition is difficult both to diagnose and to repair. In excess, oil in the refrigerant system acts as a heat insulator and takes up space. Too much refrigerant oil in the system will cause the compressor to work harder to displace it and in the process increase system temperatures and pressures. Typically the high-side gauge will read a higher pressure than a static temperature-pressure chart would indicate. In a system that contains an excess amount of oil, the outside temperature of the high-side line will be cooler than the static temperature-pressure chart would indicate, but the pressure will be higher than the measured temperature would indicate on the static temperature-pressure chart. To repair a system that is overcharged with oil, the refrigerant must first be recovered; then the compressor must be removed and drained, and the evaporator, condenser, lines, and hoses should be drained or flushed. In addition the receiver-drier/accumulator must be replaced. After reassembly, the system must be evacuated, filled with the proper type and amount of oil, and recharged with the proper amount of refrigerant.

■■

●●

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Evaporator

Remote bulb Very high pressure Condenser Compressor

Radiator

Receiver-drier Restriction

High-pressure gas

Low-pressure liquid

High-pressure liquid

Low-pressure gas

FIGURE 8-26  Effects of partially restricted receiver-drier on a thermal expansion valve refrigerant system.

FIGURE 8-27  A damaged return bend at the condenser inlet will result in very high high-side pressure.

Condition Five: Insufficient Cooling or No Cooling (Figure 8-28) ■■

Low-side gauge: High pressure R-134a (HFC-134a): 43 psig (296 kPa) ●● R-12 (CFC-12): 44 psig (303 kPa) High-side gauge: Low pressure ●● R-134a (HFC-134a): 150 psig (1,034 kPa) ●● R-12 (CFC-12): 140 psig (965 kPa) ●●

■■

A mechanical malfunction can cause an electrical malfunction.

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CFC-12

HFC-134 a

FIGURE 8-28  Manifold gauge reading indicating insufficient or no cooling due to a defective clutch coil or temperature control. The condition may also be caused by a defective clutch or compressor.

Shop Manual Chapter 8, page 295

Determine whether the system is TXV or FOT equipped before diagnostics.

This problem may be caused by either an electrical or a mechanical condition. It may be caused electrically by a defective clutch coil or a defective thermostat. Also, inspect for these defective components: 1. Cycling switch 2. Pressure switch(es) 3. Ambient air temperature switch 4. Evaporator temperature sensor (fin sensor) Mechanically, this condition may be caused by either of the following two problems: 1. A defective clutch 2. A defective compressor a. Valve plate(s) b. Head gasket(s) c. Broken piston ring The symptoms for no or poor compressor action for a TXV system (Figure 8-29) and an FOT system (Figure 8-30) are similar and include poor to no cooling, warm evaporator outlet, and all lines warm to touch. In addition, the low- and high-side pressures will equalize quickly after the air-conditioning system is turned off. To determine whether the problem is due to electrical or mechanical defects, if the air conditioner is operational, visually inspect the clutch center bolt to determine whether the compressor crankshaft is turning properly. If it is turning properly, the problem is probably a defective compressor or valve plate assembly. If the compressor is turning erratically, disconnect the clutch wire and connect it to a digital multimeter (Figure 8-31). If there are at least 10.8 volts present required for proper clutch operation, the problem may be a defective clutch coil or clutch assembly. First, however, check to ensure that the clutch coil is properly grounded. If the multimeter does not indicate at least 10.8 volts, the probable cause is a defective relay, electrical control device, or loose wire. Also, listen for compressor noise, which is an indication of a defective compressor. If the problem is determined to be the compressor, the valve plate or gaskets may be defective. In either case, it will be necessary to remove the compressor head and valve plate assembly to determine and repair the cause or to replace the compressor.

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Evaporator

Remote bulb

Condenser Compressor

Receiver-drier

Radiator

Medium-pressure liquid Medium-pressure gas FIGURE 8-29  No or poor compressor action on a thermal expansion valve refrigerant system. Symptoms include poor or no cooling, warm evaporator outlet, and all lines warm to touch.

Accumulator

Evaporator

Orifice tube

Condenser Compressor

Radiator

Medium-pressure liquid Medium-pressure gas FIGURE 8-30  No or poor compressor action on a fixed orifice tube refrigerant system. Symptoms include poor to no cooling, warm evaporator outlet, and all lines warm to touch.

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FIGURE 8-31  Checking for voltage at the clutch coil connector.

Condition Six: Insufficient Cooling (Figure 8-32) ■■

Low-side gauge: High pressure R-134a (HFC-134a): 38 psig (262 kPa) ●● R-12 (CFC-12): 40 psig (276 kPa) High-side gauge: Normal pressure ●● R-134a (HFC-134a): 184 psig (1,269 kPa) ●● R-12 (CFC-12): 170 psig (1,172 kPa) ●●

■■

CFC-12

HFC-134a

FIGURE 8-32  Manifold gauge reading indicating insufficient cooling due to a defective thermostatic value or mispositioned remote bulb.

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Evaporator

Remote bulb

Condenser Compressor

Radiator

Receiver-drier

High-pressure gas

Low-pressure liquid

High-pressure liquid

Low-pressure gas

FIGURE 8-33  A TXV that is stuck in the open position or is slow to respond to temperature changes will result in poor system performance. Symptoms include poor to fair cooling and evaporator outlet warm to the touch.

This condition is found only in systems equipped with a TXV. The condition, then, is caused by a defective expansion valve. Unlike expansion valve problems of Conditions Two and Three, however, this indication is that the expansion valve is stuck in the open position or is not closing because the remote bulb is not making proper contact with the evaporator outlet tube or has lost its charge (Figure 8-33). A similar condition could occur on a FOT system if the orifice tube was missing (removed) from the system. First, make sure that the remote bulb and the evaporator outlet tube are clean and that the two mating surfaces make good mechanical contact with each other. A small piece of cork (nodrip) tape wrapped around the remote bulb and the outlet tube helps to ensure good “sensing” conditions. This tape also acts as an insulator for the remote bulb, preventing it from sensing and being influenced by ambient air. If the remote bulb is securely fastened to the outlet tube and the condition is not corrected, the expansion valve is probably defective and must be replaced. One method for determining whether the internally regulated thermostatic expansion valve is functioning correctly is to cool it externally with low pressure CO 2. With the use of a low pressure CO 2 regulator, allow the gas from a discharge line to be bled directly over the expansion valve. This will chill the valve, causing both a pressure and an evaporator temperature change. If the TXV proves to be functioning properly and the problem still exists, check the heater control valve and the blend air door. A defective heater control valve may let heated coolant flow through the heater core, thereby creating an environment that promotes a higher than normal low-side pressure. Though not as likely, the blend air door, if mispositioned, may create a similar environment.

A remote bulb is a sensing device connected to the expansion valve by a capillary tube. This device senses the evaporator outlet temperature and transmits pressure to the expansion valve control diaphragm for proper operation.

If air or excessive refrigerant is in the system, recover, evacuate, and recharge the system.

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Shop Manual Chapter 8, page 296

When cleaning air-conditioning components in a charged system, use cool or warm water only.

Condition Seven: Insufficient or No Cooling (Figure 8-34)

Low-side gauge: High pressure R-134a (HFC-134a): 37 psig (255 kPa) ●● R-12 (CFC-12): 42 psig (290 kPa) ■■ High-side gauge: High to extremely high pressure ●● R-134a (HFC-134a): 263 psig (1,813 kPa) ●● R-12 (CFC-12): 235 psig (1,620 kPa) There are several possible causes for this condition: 1. Air in the system 2. An overcharge (excess) of refrigerant 3. An overcharge (excess) of oil 4. Condenser air passages (fins) clogged 5. Defective cooling fan(s) 6. An overheating engine 7. Incorrect refrigerant 8. Contaminated refrigerant The symptoms of a system overcharged with refrigerant include poor to fair cooling, evaporator outlet warm to cool, and poor to no cooling during stop and go traffic, but highway driving may be okay. The compressor clutch may frequently cycle on/off as the high-pressure switch detects high high-side pressure. Too much air in the system may also cause these symptoms. In addition, when the air-conditioning system is turned off on a system with air contamination, the pressure will drop 30 psig quickly but then falls gradually until high- and low-side pressures equalize. The effects of an overcharged thermal expansion valve refrigerant system may be seen in Figure 8-35. Similar effects of a refrigerant overcharge occur in an orifice tube system and may be seen in Figure 8-36. A visual inspection of under-the-hood conditions should determine whether the problem of Condition Seven is due to clogged condenser air passages or an overheating engine. If the problem is determined to be an excess of refrigerant, oil, or air in the system, it is most difficult to determine which of these is the cause. ■■

●●

CFC-12

HFC-134a

FIGURE 8-34  Manifold gauge reading indicating insufficient or no cooling due to air in the system, overcharge of lubricant or refrigerant, clogged condenser, defective cooling fan(s), or an overheating engine.

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Evaporator

Remote bulb

Condenser Compressor

Radiator

Receiver-drier

High-pressure gas

Low-pressure liquid

High-pressure liquid

Low-pressure gas

FIGURE 8-35  Effects of refrigerant overcharge on a thermal expansion valve refrigerant system include high low-side and extremely high highside pressures resulting in poor to no cooling and evaporator outlet warm to the touch.

If the condenser air passages are clogged, heat cannot be carried away. This will result in moderately high pressures and insufficient cooling. Condenser clogging is generally caused by dirt, leaves, bugs, or other foreign material lodged in the fins. The condenser may be cleaned with a strong stream of detergent and water (H 2 O) such as may be found at a do-it-yourself car wash. Whenever possible, if space between the radiator and condenser permits, clean the condenser in the opposite direction of the airflow. Take care not to damage the delicate tubes and fins of the radiator. Use warm, not hot, water. A defective or inoperative coolant fan can give the same symptoms as a blocked condenser in shop conditions. At road speeds, however, ram air may suffice for heat removal. High head pressure may also be caused by a kinked hose or a restriction. The high-side restriction may be anywhere between the compressor outlet and receiver-drier or metering device inlet. See also Condition Four. An overheating engine causes an additional heat load (ambient conditions), which in turn will cause high head pressure conditions. Overheating engines may be caused by: ■■ Loss of coolant ■■ Slipping belts ■■ Improper engine timing ■■ A defective water pump ■■ A defective thermostat or radiator cap Engines and engine service are covered in Delmar Learning’s Today’s Technician series Automotive Engine Repair & Rebuilding, 5th edition, and Automotive Engine Performance, 6th edition (Figure 8-37).

Head pressure is the pressure of the refrigerant from the compressor discharge port to the metering device.

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Accumulator

Evaporator

Orifice tube

Condenser Compressor

Radiator

High-pressure gas

Low-pressure liquid

High-pressure liquid

Low-pressure gas

FIGURE 8-36  Effects of refrigerant overcharge on a fixed orifice tube refrigerant system include high low-side and extremely high high-side pressures, resulting in poor to no cooling and evaporator outlet warm to the touch.

FIGURE 8-37  Engine service and engine performance are covered in the Today’s Technician series.

This condition may be caused by air in the system, which can result, for example, through a low-side leak. If the low side goes into a vacuum while running, ambient air will be drawn into the system. Many systems have a low-pressure switch to prevent the system operation in a vacuum. Improper evacuation or failure to evacuate the system before 264 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

charging with refrigerant can also result in air contamination, as can using improperly recycled refrigerant. This condition may also be caused by an overcharge of refrigerant. Excess refrigerant may be bled off using the standard practice procedures for recovering refrigerant. Because it is almost impossible to determine whether the cause is air or excess refrigerant, it is advisable to recover, evacuate, and recharge the system. Another cause for this condition is excessive oil in the compressor. If no oil has been added, however, this is not likely to be the problem.

Shop Manual Chapter 8, page 296

Moisture Contamination If a refrigerant system is contaminated with moisture, the pressure in the system will swing between a vacuum to normal on the low-side gauge and between low to normal on the high-side gauge. The air-conditioning system may operate normally at first, but as the system runs, a nocooling condition may exist. This condition is often described as intermittent air-conditioning operation by the driver. The moisture in the system freezes in the TXV or FOT and causes a temporary blockage. After the blockage occurs, the evaporator warms up and the ice melts, returning the system to normal until the process repeats itself. If moisture in the refrigerant system is suspected, the old refrigerant must be recovered and the receiver-drier/accumulator must be replaced. The system must then be evacuated to 700 microns or less to ensure that the moisture has been removed from the system before recharging it with a new refrigerant.

Restriction Diagnosis Diagnosing the effects of restrictions in a refrigerant system based on gauge readings is sometimes difficult and misleading because of the location of the refrigerant system service ports. It is important to keep in mind where the service ports are in relation to the compressor discharge and suction ports, and the normal restriction created by the TXV or FOT.

High-Side Restrictions

A restriction on the high side of the system will have different pressure effects depending on where the restriction is. The closer the restriction is to the compressor, the higher the pressure will be. The high-side gauge, however, will not indicate the high-pressure condition if the restriction is before the high-side service port (Figure 8-38); in fact, the gauge reading will be lower than normal. By also looking at the low-side gauge reading, clues can be gained. The low-side gauge may indicate normal or slightly low pressure, or a vacuum, depending on how severe the high-side restriction is. If the high-side restriction is after the service valve, the high-side gauge reading will be higher than normal (Figure 8-39). This is often the case with a restriction at the TXV or FOT. Additional information will be gained by measuring component temperatures with a thermocouple. The line temperature will be higher than normal before the restriction and will be lower than normal after the restriction. An increase in pressure raises the temperature before the restriction, which then acts like an orifice, allowing for a pressure differential as refrigerant flows through; this causes some boil- off to occur, lowering the temperature.

Low-Side Restrictions

A restriction on the low side of the refrigerant system is not as likely because of the larger diameter of the lines and hoses. But it is still possible for restrictions to occur in the evaporator core if the system is contaminated, and if the system has an accumulator, the desiccant may have failed. If a low-side restriction occurs, the low-side gauge reading will be low or even a vacuum, depending on where the service fitting is located in relation to the restriction (Figure 8-40). If the compressor is not able to circulate the refrigerant because of the low- side restriction, the high-side gauge reading will also be low. Finding the restriction by looking 265 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Suction Discharge Low-side High-side (Blue gauge) (Red gauge)

Temperature higher than normal

Restriction

Temperature lower than normal

Restriction

FIGURE 8-38  The high-side pressure gauge reading may be lower than normal if the high-side restriction is before the high-side service port.

FIGURE 8-39  The high-side pressure gauge reading will be higher than normal if the high-side restriction is after the high-side service port. A temperature differential will be detectable before and after the restriction.

Restriction

FIGURE 8-40  The low-side pressure gauge reading will be lower than normal or possibly even a vacuum.

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for temperature differentials before and after the low-side restriction is still possible, but the temperature differential on either side will not be as great, and some temperature difference between the evaporator inlet and outlet is expected.

Preventive Maintenance Preventive maintenance (PM) pays off in the long run. Whenever servicing an automotive air-conditioning system, potential problems can sometimes be discovered before they occur. A thorough visual check of the mechanical and electrical system is well worth the time invested.

Mechanical

Check the air-conditioning system for damaged hoses (Figure 8-41) and connections that may be caused by rubbing or chafing. Slight oil staining may indicate a refrigerant leak. With the engine off, inspect the belt(s) for glazing and cracking. Heavy glazing may indicate a slipping belt. Some glazing, however, is acceptable. Inspect the hoses and hose connectors. Soft or brittle hoses are an indication that they are deteriorating and should be replaced. Do not neglect the heater hoses. A slight leak in a heater hose is often overlooked.

Electrical

Check for loose connections and frayed (Figure 8-42) or broken wires. If the problem is a “blown” fuse or circuit breaker, it is possible that a bare wire is intermittently “shorting” to ground due to vibration. The blower motor can sometimes give an indication of other problems. If, for example, the blower speed increases when the engine is revved up, the battery may be undercharged; a defective voltage regulator may cause overcharging; or the battery ground cable may be corroded or poorly connected. A slipping compressor clutch may be an indication of improper adjustment or low voltage supplied to the coil. The fuse, circuit breaker, and fusible links are provided for protection against an electrical fire. Never bypass a circuit protection device simply because it “blows” frequently. If it blows, there is a reason. To prevent further damage, locate the problem and correct it. Never take chances—if in doubt, disconnect the battery cable. Always disconnect the battery ground (—) cable, not the positive (1) cable (Figure 8-43). If the wrench grounds out while disconnecting the ground cable, no harm is done. If, however, the wrench grounds out while disconnecting the positive cable (with the ground cable attached), the electrical system is “shorted” and may be damaged.

A fully charged automotive battery has a surface charge of 12.8–13.2 volts.

FIGURE 8-41  Check for defective hoses.

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FIGURE 8-42  Check for frayed or broken wires.

FIGURE 8-43  Always disconnect the battery ground (2) cable.

A fully charged 12V automotive battery is capable of delivering very high current. In a matter of seconds, a shorted electrical system can cause extensive damage to the automobile’s wiring harness. From the information given related to system conditions, it should now be obvious that the manifold and gauge set is a very important tool in air-conditioning service. It is not only used to service the system, but also as a diagnostic tool.

Advanced Diagnostic Tools As was noted in Chapter 7, software-based system diagnostics have become integrated into the automotive air-conditioning service industry. One of these tools, the Neutronics Inc. Master A/C System Technician (Figure 8-44), attaches to the high-side and low-side pressure service fittings and uses a temperature sensor to check ambient air temperature and component temperature. The technician follows the diagnostic steps listed and inputs requested information, such as component temperatures. Using the FlexTemp’s™ temperature probe to check component temperature differences, the software uses the Delta T method, low-and high-side pressures, as well as look-up tables to calculate charge levels on FOT systems. On 268 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 8-44  Air-conditioning system electronic analyzer used to diagnose system performance.

thermostatic expansion valve systems, it bases its calculations on the temperature of refrigerant leaving the condenser and high-side line pressure to determine system charge levels. Temperature and pressure comparisons are a standard practice to determine superheat, subcooling, and system change levels and performance. On an FOT system, the outlet line from the evaporator should be 38F–108F (28C268C) colder than the evaporator inlet line temperature on a properly charged system. If the evaporator outlet line is warmer than the inlet line, the system is low on refrigerant. If the evaporator outlet line is colder than 108F (28C268C), the system may be overcharged. If you do not own a sophisticated diagnostic tool, you can use two contact thermometers and a manifold gauge set to perform a Delta T system charge level test. Run the engine at 1,000 rpm and, if equipped with a cyclingclutch switch, jump the connector so the compressor will run continuously. Check both the evaporator inlet and outlet line temperatures simultaneously. Compare your results to a Delta T chart for the manufacturer and type of vehicle you are working on. By checking both superheat and subcooling, you can gain information above and beyond what your pressure gauges are telling you. When you adjust the system charge based on superheat, you are charging the system based on the amount of air passing over the evaporator. You should not, however, base your refrigerant charge levels on superheat results for thermal expansion valve systems. TXV systems control superheat by automatically adjusting to evaporator refrigerant temperature. Superheat will help you to determine whether the TXV is working, though. A method for determining the superheat capacity of the refrigerant is to: 1. Check the low-side pressure reading of the system and convert it to a temperature based on the type of refrigerant in the system. An example of a pressure-to-temperature comparison chart was given in Figure 8-2. 2. Place the blower fan on high speed setting. 3. Next, check the temperature of the low-side (suction) line about 6 in. before the compressor. 4. Now calculate the difference between the low-side line temperature and the saturation temperature based on the chart (low-side line temperature minus saturation temperature). 269 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

5. If the ambient air temperature is 758F–858F (23.898C–29.448C), the superheat should be 128F–158F ( 211.118C to 29.44 8C). If the ambient air temperature is above 858F (29.448C), the superheat should be 88F–128F (213.338C to 211.118C). Example for an R-134a system: Low-side line temperature is 458F (7.228C) Low-side line pressure is 30.4 psig, saturation temperature will be 358F (1.68C) 458F (7.228C) 2 358F (1.678C) 5 108F (12.228C) superheat 6. If superheat is low, then the evaporator may be flooded, and if the superheat is high, then the evaporator may be starved for refrigerant. Do not adjust charge levels until subcooling has been tested.

Subcooling

7. To determine subcooling, check the high-side pressure reading of the system and convert it to a temperature based on the type of refrigerant in the system (saturation temperature). 8. Next, check the high-side liquid-line temperature as close to the evaporator as possible, but before the metering device (in other words, FOT or TXV). 9. Now calculate the difference between the high-side liquid-line temperature and the saturation temperature based on the chart (saturation temperature minus high-side temperature). The subcooling temperature should be 128F–158F (211.118C to 29.448C). It should be noted that the temperature of the liquid line at the condenser outlet and the temperature of the liquid line at the metering device inlet should be within 28F (216.678C) of each other. If not, there could be a restriction in the liquid line. Example for an R-134a system: High-side liquid line temperature is 1958F (90.558C) High-side liquid line pressure is 198.7 psig; saturation temperature will be 1808F (82.228C) 1808F (82.228C) 2 1958F (90.558C) 5 158F (9.448C) subcooling Using the information gained from both the superheat and the subcooling test, we will have some idea of how the system is operating. 1. If both the superheat and subcooling are low, the TXV is stuck open or the wrong orifice tube is installed (too large). 2. If both the superheat and subcooling are high, look for a restriction at the metering device, evaporator, or refrigerant line. 3. If the superheat is low and subcooling is high, the system may be overcharged. 4. If the superheat is high and subcooling is low, the system may be undercharged. Another method for determining system performance and charge levels is to compare the on and off times of the compressor clutch. The charts in Figure 8-45 represent typical on and off times of the compressor clutch on a cycling-clutch system compared to ambient air temperature. The charts in Figure 8-46 depict the typical duct discharge temperature and the expected high- and low-side system pressure for a typical R-134a system at various ambient temperatures. The system should operate within the shaded areas. More detailed information is given in Chapter 8 of the Shop Manual.

Leaks

Service valves and protective caps (Figure 8-47) are among the most common causes of refrigerant leaks. The high- and low-pressure service (Schrader) valves are not perfect seals and may leak a small amount of R-134a. The level of leakage may not exceed 0.25 ounces per year. The service valve cap and O-ring are the primary seal, and the Schrader valve is considered the secondary seal. It is imperative that the service valve cap seal be in good condition. When servicing a refrigerant system, the initial untorquing of the service cap may release a short wisp 270 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Seconds 30 20

Normal clutch on-time

Total clutch cycle time 100 80

25

60

15

40

10 5

20 60

80 70 90 100 Ambient temperatures (°F)

Seconds 30 25

60

Normal clutch off-time

80 70 90 100 Ambient temperatures (°F)

Seconds

Normal clutch cycle rate per minute

3

20

2

15 10 5

1

60

80 70 90 100 Ambient temperatures (°F)

60

80 70 90 100 Ambient temperatures (°F)

FIGURE 8-45  Typical diagnostic and testing chart for cycling clutch systems.

CONDITIONAL REQUIREMENTS FOR CYCLING CLUTCH SYSTEM

Normal Clutch Cycling versus Refrigerant System Pressure

Stabilzed pressure Stabilized in-car temperatures 70°F to 80°F (21°C to 27°C) Maximum blower speed Maximum A/C (Recirculation) Compressor clutch engaged

kPa PSI 230 1400 1200

1500 Engine RPM Normal center discharge outlet temperatures C F 10 8 6 4 2

50 45

25

0 60 15

100 F 90 80 70 35 20 25 30 C Ambient temperatures

170

1000 140 800 600 400 200 100 50

40

200

110 80 50 20 0 60 15

100 F 90 80 70 35 20 25 30 C Ambient temperatures

FIGURE 8-46  Typical duct discharge temperature and expected high- and low-side system pressures of a typical R-134a system.

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FIGURE 8-47  Service valve with protective cap removed.

FIGURE 8-48  Service valves with hoses connected are often neglected when leak testing.

of refrigerant. On systems with fluorescent leak dye, installed dye may be present in the service fitting. Because the caps are the final seal, this is normal as long as it is not excessive. Always verify with an electronic leak analyzer after blowing out the service fitting with low pressure shop air. As much as a pound (0.45 kg) of refrigerant per year can escape from the service valve if the cap is missing or the O-ring is defective. Leak testing the service valve is often neglected because the service hoses are generally connected to them (Figure 8-48). Service valves should be leak tested with the caps and the service hoses removed. System integrity should not depend on the sealing power of a protective cap. The primary purpose of the cap is to keep debris out of the service valve. If found to be leaking, the service valve should be repaired or replaced as applicable. Often, a new Schrader assembly is sufficient to stop most leaks. An insufficient refrigerant charge, for any reason, will cause oil to become trapped in the evaporator. Oil also leaks out with refrigerant at the point of a leak. Any oil loss due to any reason can result in compressor seizure. The compressor circulates a small amount of oil through the system with the refrigerant. Oil pumped out of the compressor in small quantities is mixed with the refrigerant in the condenser. This oil enters the evaporator with the refrigerant, and if the evaporator is properly flooded with refrigerant, passes to the compressor through the low-pressure line. Some of the oil passes to the compressor in small droplets. Most of the oil, however, is swept along the walls of the refrigerant lines by the velocity of the refrigerant vapor. This oil is returned to the compressor as a mist. If the evaporator is starved of refrigerant, oil will not return to the compressor in sufficient quantity to keep it properly lubricated. The major cause of premature compressor failure is a lack of lubricant. The tendency of a customer to have refrigerant added to the system “every few months or so” is a sure sign that the compressor is doomed. If the system is leaking refrigerant, it is a good bet that it is also leaking lubricant, and compressor failure is sure to follow.

High Pressure

The top of the condenser is often the highest point of the system; air, lighter than refrigerant, seeks the highest point.

As refrigerant pressure increases in an air-conditioning system, its temperature also increases. The resulting high temperature quickly accelerates the failure of a contaminated system. An increase in temperature of only 158F (88C) doubles the chemical reaction rate in the system. High temperature starts a chain of harmful reactions even in a clean system. Contamination, resulting from high temperature, may cause seizure of the compressor bearings. High heat may also cause the refrigerant in the system to decompose or break down. High heat can cause synthetic rubber parts to become brittle and susceptible to cracking and breaking. As temperature and pressure in an air-conditioning system increase, stress and strain on compressor discharge valves increase. If this condition is not corrected, the discharge reeds in the valve plates may fail.

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High pressure and the accompanying high temperature can be caused by air in the airconditioning system. Air can enter the system through careless or incomplete service procedures. Systems that have been opened to the atmosphere during service procedures must be properly evacuated. If the system is not properly evacuated, the results, most surely, will be an air-contaminated system. A system with air contamination does not operate at full efficiency. Air in the airconditioning system can cause oil to oxidize. Oxidized oil forms gums and varnishes that coat the inside walls of the tubes, reducing the efficiency of the heat transfer process. Still more damaging, air usually carries moisture into the system in the form of humidity. When an air-conditioning system is operated with a low-side pressure below atmospheric pressure (14.696 psig at sea level), air will be drawn into the system through the leak. This occurs when a noncycling system is low on refrigerant; the low side often operates below atmospheric pressure in a vacuum. If a system contaminated in this way is recharged without proper evacuation procedures, high temperature and pressure conditions will result. Air, a noncondensable gas, has a tendency to collect in the condenser during the off cycle.

Connections If there is an O-ring compression fitting, avoid overtightening. Overtightening can cause O-ring damage, resulting in a leak or early failure. Before assembly, inspect the fitting for burrs, which may cut the O-ring. It is important that the proper O-ring be used for the type of refrigerant and the type of fitting. It is also important to follow the manufacturer’s recommendations for selecting O-rings. When a connection is made with an O-ring compression fitting, place the gaskets or O-ring over the tube before inserting it into the connection (Figure 8-49). Use a torque and backing wrench to ensure a proper connection. Again, follow the manufacturer’s specifications for proper torque requirements.

Restrictions Most restrictions are caused by dirt, foreign matter, or corrosion. Corrosion is generally due to excess moisture in the system. Contaminants can lodge in filters and screens and can block the flow of refrigerant through the system. Filters are found in the receiver-drier and suction line accumulator, usually as a means to hold the desiccant in place. Screens are generally found: ■■ At the metering device inlet ■■ In the receiver-drier or accumulator ■■ At the compressor inlet A restriction in the system can cause a “starved” evaporator. This can result in reduced cooling, poor oil return, and eventually, if not corrected, compressor seizure.

A contaminated system may have both a strainer and a drier.

O-ring

FIGURE 8-49  Place the O-ring over the fitting before inserting it into the connection.

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FIGURE 8-50  A supplemental liquid line filter/drier.

Supplemental aftermarket liquid-line filters are available for installating in airconditioning systems that have been contaminated (Figure 8-50). The filter should be installed in the system: 1. After repeated metering device plugging 2. When a seized compressor has been replaced The liquid-line filter contains a screen and a filter pad. It does not contain a desiccant. The fine-mesh screen catches larger particles and holds the filter in place. The filter catches smaller particles and filters the refrigerant oil. The filter is installed in the liquid line between the condenser outlet and the evaporator inlet. Filters are available with or without an expansion tube orifice. The filter without an orifice is generally preferred. This type can be installed anywhere in the liquid line, preferably close to the metering device. A filter with an orifice is required when the installation is to be made in the low-pressure side of the system beyond the original expansion tube location. This installation, which is usually found on General Motors vehicles, requires that the original expansion tube be removed from the system.

Contamination Contamination by foreign matter has many sources, including: ■■ Failed desiccant ■■ Preservative oils ■■ Lint ■■ Soldering or brazing fluxes ■■ Loose corrosion flakes Any of these materials in the air-conditioning system can cause: ■■ Compressor bearings to seize ■■ Metering device failure ■■ Corrosion of metal parts ■■ Decomposition of refrigerant ■■ Breakdown of the oil Corrosion and the by-products of corrosion can clog metering device screens, ruin compressor bearings, and accelerate the failure of compressor discharge valves. Moisture is the primary cause of corrosion in the air-conditioning system. 274 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

In fact, the greatest enemy of an air-conditioning system is moisture. When combined with the metals found in the system, moisture causes the formation of iron hydroxide and aluminum hydroxide. When combined with refrigerant, moisture can form three acids: 1. Carbonic (H 2 CO 3 ) 2. Hydrochloric (HCl) 3. Hydrofluoric (HF) Avoid contact with hydrochloric and hydrofluoric acids; both are very poisonous. Moisture also causes metering devices to freeze up. As the operating temperature of the evaporator is reduced to the freezing point, moisture collects in the metering device orifice and freezes. This, in turn, restricts the flow of refrigerant into the evaporator. The result is an erratic or poor cooling condition of the evaporator. High temperature and foreign matter are responsible for many refrigerant system difficulties. In most cases, it is the presence of moisture that accelerates these conditions. The acids that result from the combination of high pressure, moisture, and refrigerant cause damaging corrosion.

Carbonic acid is a weak solution generally found in solutions of carbon dioxide in water.

SUMMARY ■■ ■■ ■■ ■■ ■■ ■■

■■

■■

■■

There are but six basic abnormal conditions for air-conditioning system diagnosis. The evaporator coil temperature is kept above 328F (08C) to prevent freeze-up. A misadjusted or defective thermostat may cause evaporator freeze-up. An undercharge of refrigerant is an indication of a leak in the system. A restriction in the high side of the system will cause high high-side pressure. A defective thermostatic expansion valve (TXV) can cause the same symptoms as a lowside restriction. Air in the system can cause the same symptoms as an overcharge of refrigerant or oil. An overheated engine can cause high high-side pressure. The proper cure for an undercharged system is to first repair the leak, then recharge the system. Observe all safety practices when handling refrigerants.

Terms to Know Average Control thermostat Head pressure Malfunction Metering device Remote bulb Restriction

REVIEW QUESTIONS Short-Answer Essays 1. What effect would a low-side restriction have on a system and how would it be detected? 2. How can moisture in the system cause a problem? 3. How does one determine whether a problem is due to electrical or mechanical failure?

6. Why must the temperature of an evaporator be kept above 328F (08C)? 7. What is the symptom of a refrigerant system that is overcharged with refrigerant? 8. What does current research indicate about R-1234yf and R-134a refrigerants, performance characteristics?

4. How does one clean a dirty condenser?

9. What effect would an overcharge with refrigerant oil have on a system and how would it be detected?

5. How is a baseline used in a refrigerant system diagnosis test?

10. What effect would a high-side restriction have on a system and how would it be detected? 275

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Fill in the Blanks 1. _______________ on the evaporator coil _______________ the flow of air through it, resulting in poor or _______________ cooling. 2. Very low low-side pressure may be caused by a _______________ screen in the metering device _______________. 3. A high low-side pressure is an indication that the thermostatic expansion valve (TXV) _______________ restricting the flow of _______________. 4. High high-side pressure may be caused by excessive _______________, oil, or _______________ in the system. 5. _______________ is the primary cause of corrosion in the air-conditioning system. 6. Most restrictions are caused by _______________, or _______________. 7. By checking both ______________ and ______________, you can gain information above and beyond what your pressure gauges are telling you. 8. If a low-side restriction occurs, the low-side gauge reading will be _______________ or even a _______________. 9. If a refrigerant system is contaminated with moisture, the pressure in the system will swing between a _______________ to _______________ on the low-side gauge and between _______________ to on the high-side gauge. 10. The _______________ and _______________ _______________ is an important tool for airconditioning service.

Multiple Choice 1. Technician A says that a gauge reading of 21 psig (145 kPa) corresponds to an R-12 evaporator temperature of about 208F (26.78C). Technician B says that a gauge reading of 21 psig (145 kPa) corresponds to an R-134a evaporator temperature of about 23.58F (24.78C). Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 2. Technician A says that if R-134a evaporating temperature is 308F (21.18C), the gauge pressure should be about 26 psig (179 kPa). Technician B says that a low-side gauge pressure of 26 psig (179 kPa) indicates a refrigerant evaporating temperature of 278F (22.88C) in an R-12 system. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

3. During a refrigerant system performance test the following results are recorded: outside ambient temperature of 908F, high-side gauge reading of 145 psi, and low pressure gauge reading of 14 psi. What is indicated by these results? A. Faulty refrigerant compressor B. Normal refrigerant system operation C. Low refrigerant levels D. A restriction on the high side of the refrigerant system 4. A customer complains of poor air-conditioning cool ing performance. During a system performance test, the low-side gauge reading is 50 psig; the high-side gauge reading is 310 psig; and the ambient air temperature is 818F (27.228C). What is the least likely cause of the above results? A. Restricted airflow through condenser B. Refrigerant overcharge C. Refrigerant undercharge D. Overcharge of refrigerant oil 5. Temperature and pressure comparisons are a standard practice to determine all of the following, except: A. System change levels B. Superheat C. Subheat D. Subcooling 6. During a refrigerant system performance test, the high-side pressure instantly goes over 370 psig when the compressor is engaged. Which of the following is the most likely cause? A. An overcharged system B. An undercharged system C. Moisture in the system D. Expansion valve stuck open 7. An R-134a thermal expansion valve system contains the proper refrigerant charge. During a system performance test, the low-side gauge reading is 40 psig and the high-side gauge reading is 140 psig with an ambient air temperature of 878F (30.558C). Which of the following is the most likely cause of these results? A. An overcharged system B. A restricted evaporator C. A restricted condenser D. An expansion valve stuck open 8. During a system performance test, the low-side gauge is reading a vacuum. Which of the following is the most likely cause? A. An overcharged system B. Incorrectly connecting the gauge hoses to the wrong service ports C. An expansion valve stuck open D. A restricted expansion valve

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9. During a system performance test, the low-side gauge reading and the high-side gauge reading are about the same. Which of the following is the most likely cause? A. An overcharged system B. Moisture in the refrigerant system C. A malfunctioning compressor D. A restricted expansion valve

10. An R-134a thermal expansion valve system contains the proper refrigerant charge. During a system performance test, the low-side gauge reading and the highside gauge reading are in the high range and the system has poor cooling performance. Which of the following is the most likely cause? A. A restricted airflow across the evaporator B. A restricted airflow across the condenser C. An expansion valve stuck open D. A malfunctioning compressor

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Chapter 9

Compressors and Clutches

Upon Completion and Review of this Chapter, you should be able to: ■■

State the purpose and describe the function and operation of a magnetic clutch in an air-conditioning system.

■■

Compare fixed and variable displacement compressors.

■■

Discuss electric motor–driven compressors. Kilometer is the metric conversion for the English mile, and liter (litre) is the metric conversion for the English quart or gallon. Auxiliary components are those such as the rear evaporator in a dual air-conditioning system, which is often referred to as an “auxiliary evaporator.”

■■

■■

■■

Discuss and explain the operating principles of a reciprocating compressor. Discuss and explain the operating principles of a scroll compressor. Discuss and explain the operating principles of a rotary compressor.

Introduction There are many different types, makes, and models of compressors used for automotive airconditioning applications. A prime consideration for new compressor design is to help to reduce overall vehicle weight. Overall vehicle weight is decreased by reducing the weight of individual components. A reduction in overall (gross) vehicle weight provides greater economy or more miles per gallon (kilometers per liter) of fuel. The compressor, as well as other auxiliary components, must also be designed to be efficient and durable to withstand long hours of heavy use. Chapter 5 of this manual generally covered the refrigeration system, and Chapter 6 considered other basic components of the system. If necessary, refer to these chapters to review the compressor’s role in a vehicle air-conditioning system.

The low-pressure condition exists in an air-conditioning system from the metering device outlet to the compressor inlet.

Function

Low pressure is a relative term used to describe normal pressure in the low side of an airconditioning system.

One function, creating a low-pressure condition at the compressor inlet, aids in the removal of heat-laden refrigerant vapor from the evaporator. This low-pressure condition is essential to allow the refrigerant metering device to admit the proper amount of liquid refrigerant into the evaporator (Figure 9-1).

The compressor in an automotive air-conditioning system serves two important functions. It creates a low-pressure condition within the system, and it compresses refrigerant vapor from a low pressure to a high pressure, thereby increasing its temperature. It is important that these two functions be accomplished at the same time.

Low-Pressure Condition

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Refrigerant picks up 10°F (5.5°C)

Low pressure 30 PSIG (207 kPa)

Superheat

Flow 44°F 6.7°C

34°F 1.1°C 34°F 1.1°C 34°F 1.1°C 34°F 1.1°C

Blower High pressure 190 PSIG (1310 kPa) psig kPa °F °C

-

34°F 1.1°C Flow

pounds per square inch, gauge KiloPascal degrees Fahrenheit degrees Celcius

Refrigerated air

Evaporator 10 percent (flash) gas, 90 percent liquid Metering device 100 percent liquid

FIGURE 9-1  The intake stroke of the compressor creates a low-pressure condition to draw refrigerant into the evaporator.

Compress Refrigerant

The second function of the compressor is to compress the low-pressure refrigerant vapor into a high-pressure refrigerant vapor. This increased pressure raises the heat content of the refrigerant. High pressure with high heat content is essential if the refrigerant is to condense, giving up its heat, in the condenser. It is in the condenser that the refrigerant vapor is changed to a liquid. While it is a slightly lower temperature, it is still at a high pressure until it again reaches the metering device, generally at the inlet of the evaporator. Failure of either function of the compressor will result in a loss or reduction of the circulation of refrigerant within an air-conditioning system. Without proper refrigerant circulation in the system, the air conditioner will not function properly or may not function at all.

Design Several types of compressors are used in automotive air-conditioning systems. Regardless of the type, however, with few exceptions, most compressors are basically of the reciprocating piston design. Reciprocating means that the piston moves up and down, to and fro, or back and forth (Figures 9-2 and 9-3). Multicylinder compressors have a set of valves for each piston. A set consists of one suction and one discharge valve. The suction and discharge valves operate conversely of each other. Discharge pressure (piston on the upstroke) forces the suction valve closed and the discharge valve open. In a two-cylinder compressor, for example, when piston one is on the upstroke, the other piston is on the downstroke. Piston two is then forcing the suction valve open while the high pressure behind the discharge valve is holding it (discharge valve) closed.

High pressure is a relative term used to describe refrigerant pressure in the high side of an airconditioning system. The high-pressure condition exists from the compressor outlet to the metering device inlet. The suction valve is on the low-side suction port (intake) of the refrigerant compressor. It is a mechanical one way check valve that only allows refrigerant to flow into the compressor. The discharge valve is on the high-side discharge port (pressure) of the refrigerant compressor. It is a mechanical one-way check valve that only allows refrigerant to flow out of the compressor.

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A crankshaft is the part of a reciprocating compressor to which the wobble plate or connecting rods are attached. It is splined to the clutch plate and receives reciprocating power from the drive pulley assembly when the clutch is engaged.

FIGURE 9-2  The piston(s) moves down (top to bottom) during the suction (intake) stroke.

An axial plate is the part of an automotive air-conditioning compressor piston assembly that rotates as a part of the drive shaft. Swash plate is another term used for a wobble plate. A wobble plate is a type of offset concentric plate attached at an angle. It is found on some compressor crankshafts and is used to move the pistons up and down as the shaft is turned. Another term used for a wobble plate is a swash plate. Rotary compressors use vanes attached to a rotor assembly and are driven by the input shaft to compress refrigerant.

FIGURE 9-3  The piston(s) moves up (bottom to top) during the compression (discharge) stroke.

Two basic methods of driving the piston of a reciprocating compressor are by crankshaft or axial plate. The axial plate is often called a swash plate or wobble plate. The exceptions, rotary and scroll compressors, found on a limited number of car lines beginning in the early 1990s, are discussed later in this chapter.

Crankshaft

Driving the piston of a reciprocating compressor by crankshaft (Figure 9-4) is an operation that is very similar to that of an automobile engine. The main difference is that a compressor crankshaft drives the piston, whereas in an engine, the piston drives the crankshaft. The compressor crankshaft is driven directly or indirectly off the engine crankshaft by means of pulleys and belts (Figures 9-5, 9-6, 9-7, and 9-8).

Axial Plate

The other method of driving the piston of a reciprocating compressor is by an axial plate pressed on the main shaft, providing a reciprocating motion of the piston (Figure 9-9). The axial plate is driven directly or indirectly by the main shaft off the engine crankshaft by means of pulleys and belts.

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Water pump

Alternator

Compressor Air pump

Power steering Crankshaft

Crank type

FIGURE 9-5  A four-belt system. The compressor is driven off the crankshaft pulley via the water pump pulley.

FIGURE 9-4  Details of a piston driven by action of the crankshaft in a compressor.

Alternator pulley

Power steering pump pulley

A scroll compressor is a spiral corkscrew design compressor used in limited applications to produce a more continuous, steady supply of refrigerant pressure. Turning the crankshaft causes a to-fro, fore-aft, or up-down action of the piston(s). Turning the axial plate will create the same conditions as turning a crankshaft. Other terms used for V-rib or serpentine belt are poly-rib and microgroove.

AC compressor pulley Water pump pulley

Air pump pulley Crankshaft pulley

FIGURE 9-6  A three-belt system. The compressor is driven off the crankshaft pulley with the alternator used for belt tensioning.

Shop Manual Chapter 9, page 335

Clutch All belt-driven automotive air-conditioning compressors have an electromagnetic clutch attached to the crankshaft or main shaft (Figure 9-10). The clutch provides a means of turning the compressor on and off. An idler pulley or tensioner is provided to adjust belt tension. Most compressors are driven off the crankshaft by a single belt, along with such other accessories as the power steering pump, alternator, and water pump. This system is known as a serpentine drive. This serpentine belt is tensioned by a spring-loaded or manually adjustable idler pulley assembly, which generally rides on the back (flat) side of the belt. Refer to Figure 9-8 shown earlier.

A serpentine belt is a flat or V-grooved multiribbed design that winds through all of the engine accessories to drive them off the engine crankshaft pulley.

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Idler pulley Power steering pulley Water pump pulley Alternator pulley

Compression clutch pulley Crankshaft pulley Air pump pulley

FIGURE 9-7  A two-belt serpentine drive system. The compressor is tensioned by a manually adjusted idler pulley.

Alternator pulley

Belt cross section

Idler pulley

Power steering pump pulley

AC compressor pulley

Water pump pulley Air pump pulley Crankshaft pulley FIGURE 9-8  A single-belt drive system. The belt is tensioned by a spring-loaded idler pulley.

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Double-ended piston Shaft Axial plate

FIGURE 9-9  The piston(s) is moved back and forth or to and fro by an axial plate.

The three main parts of the compressor clutch assembly are the coil magnet, the pulley and idler bearing, and the clutch plate (shoe) (Figure 9-11). The clutch drive plate is splined to the input shaft of the compressor. The compressor clutch is a large electromagnet that, when energized, draws the clutch plate into the clutch pulley. The magnetic field holds the clutch plate tightly against the clutch pulley as long as current is supplied to it. This in turn engages the drive pulley to the compressor input shaft, causing the shaft to spin. When the compressor clutch is not engaged, 283 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Field coil (magnetic)

Rotor/pulley

Hub/armature (Drive hub) Bearing Compressor shaft

Shim Shaft nut

Shaft key

FIGURE 9-10  An electromagnetic clutch provides a means of turning the compressor on and off.

Shaft seals

Felt dust seal

Clutch hub Snapring

Shims

Snapring Compressor

Field coil

Clutch pulley

FIGURE 9-11  The three mains parts of the compressor clutch assembly are the field coil, clutch pulley, and the clutch hub.

the input shaft of the compressor does not spin and the drive pulley freewheels on a sealed bearing assembly. If a noise is heard when the clutch is not engaged, it is generally an indication of a faulty bearing, which in many cases can be serviced without the replacement of the entire compressor assembly. If, however, the noise is only heard when the compressor clutch is engaged, this may indicate that there is an internal problem with the air-conditioning compressor. 284 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

The operation of the air-conditioning clutch today is controlled by the heater control head and often uses a solid-state control module. The power train control module (PCM) is also integrated into the system. The PCM controls compressor clutch engagement when: ■■ The low-pressure switch senses pressure below 25 psig. ■■ The high-pressure switch senses pressure above 450 psig. ■■ Coolant temperature is above 2308 F (1108 C). ■■ Engagement is delayed for 5–10 seconds when the engine is first started. ■■ Engine speed is below 400 rpm. ■■ The throttle is opened above 80 percent. When the air-conditioning switch on the climate control head assembly is first turned to the on position, the PCM runs a logic loop to check the operation of its sensors to make sure they are within operational parameters prior to allowing the compressor clutch to engage (Figure 9-12). The PCM will also look at the air-conditioning system high- and low-pressure transducers to verify that the system contains the proper refrigerant charge before allowing the compressor to engage. The idle speed will also be raised to compensate for the added load on the engine. Most air-conditioning compressor clutch circuits also use a clamping diode placed across the clutch coil to prevent unwanted electrical spikes as the clutch is disengaged, which could damage control modules and relay contacts. The air-conditioning clutch can generate a voltage

A BIT OF HISTORY Battery

Ignition Junction block

PDC

Compressor relay

Compressor clutch

Throttle position sensor Coolant temperature sensor Crankshaft position sensor Transmission oil temperature sensor

IC

Ambient temperature sensor

A/C request

A/C

FIGURE 9-12  When an air-conditioner clutch request is made, the PCM will process the request after input sensor data and refrigerant system pressure are analyzed.

Early automotive airconditioning systems did not have a convenient driver-operated means of engaging and disengaging the compressor. Most compressors were beltand pulley-driven off the crankshaft or accessory device. If one wished to disable the compressor for the winter months, the belt was removed. It was then replaced for the warm months. In-car temperature was controlled by means of a hot gas bypass valve. The compressor operated any time the engine was running and the hot gas bypass valve simply routed the unwanted gas from the compressor discharge back to the suction side of the system. This inefficient method of temperature control has not been used for automotive service since the mid-1960s. 285

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A zener clamping diode is a semiconductor rectifier diode oneway voltage gate that allows current to flow when voltage levels increase above its threshold voltage. The hot gas is no longer used as a method of temperature control in automotive air-conditioning systems. The suction side is another term used to describe the low side of the refrigerant system. Chrysler Air-Temp manufactured the only V-type compressor for automotive use. It is now discontinued.

spike of over 200 volts, and the diode provides a path back through the coil assembly for this unwanted voltage. The diode is wired in parallel with the air-conditioning compressor clutch and may be part of the field coil assembly, or it may be located in the engine wiring harness near the clutch. Other systems use a bidirectional zener clamping diode that turns on at voltages above the 60-volt level. Use a digital volt ohmmeter (DVOM) set to diode testing to inspect the integrity of the diode. In addition, clutch coil resistance and amperage draw should be measured and compared to the manufacturer’s specifications. When servicing compressor clutches, be sure to properly set the air gap of the clutch plate to the pulley hub to the manufacturer’s specifications (generally 0.020 in. [0.50 mm]), using a nonmagnetic feeler gauge. If the air gap is set too loose, the clutch may not engage or may slip. If the air gap is set too tight, the clutch may drag, causing noise and leading to overheating of the clutch coil. Air-conditioning compressor clutches can fail for many reasons. They may slip if improperly adjusted or if the proper current is not supplied. Coil assembly may develop a short or an open. The bearing may fail; a noise may develop; or the clutch may drag due to weak return springs, to name a few failures.

Types of Compressors According to a leading compressor rebuilder, there are currently over 160 makes and models of remanufactured compressors readily available for use in mobile air-conditioning systems. The various types include reciprocating piston (Figure 9-13), scroll (Figure 9-14), rotary vane (Figure 9-15), and scotch yoke (Figure 9-16).

Reciprocating (Piston-Type) Compressors Reciprocating, piston-type mobile air-conditioning compressors, depending on their design, may have one, two, four, five, six, seven, or ten pistons (cylinders). Tecumseh manufactured a single-cylinder compressor for use with aftermarket air-conditioning systems in compact imports. A two-cylinder V-type compressor was manufactured by Chrysler Air-Temp but was discontinued due to its heavy weight. Two-cylinder, in-line reciprocating compressors manufactured by Nippondenso, Tecumseh, and York may be found on some early model vehicles, as well as some heavy duty and off-road equipment.

FIGURE 9-13  A typical reciprocating piston compressor details.

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Scroll mechanism FIGURE 9-14  Scroll compressor details.

Case temperature switch Discharge port Vane

Suction port

Check valve Bearing

Rotor Discharge Bearing valve Electromagnetic clutch

Front seal

FIGURE 9-15  A typical rotary vane compressor details.

FIGURE 9-16  A typical scotch yoke compressor details.

A four-cylinder, radial-design scotch yoke reciprocal compressor, manufactured by Harrison (Frigidaire) as their model R-4, is available in either standard or lightweight versions. A similar compressor, model HR-980 by Tecumseh, was produced through the late 1980s. A version of the radial scotch yoke reciprocating compressor design was produced by Keihin in Japan for use on some Honda automobiles. 287 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 9-17  The Calsonic V-5 compressor.

Author’s Note: In order to understand what can physically go wrong in an air-conditioning system, you must know how an air-conditioning compressor is built and how it functions. Even if you never intend to overhaul the assembly, diagnosing a system failure will be all but impossible without this level of understanding. Shop Manual Chapter 9, page 364

The intake stroke of the compressor creates a negative pressure that draws refrigerant in from the low side of the system. The compression stroke of the compressor creates a positive pressure greater than that contained on the high-side hot gas line leaving the compressor, and it thus forces refrigerant under pressure through the system when the exhaust valve is opened.

Sanden (Sankyo), Harrison (Frigidaire), and Calsonic manufacture a five-cylinder compressor. The Sanden compressor is a positive displacement compressor; the Harrison V-5 and Calsonic V-5 (Figure 9-17) compressors are of a variable displacement design. Six six-cylinder axial design compressors are currently available. The Harrison model A-6 was manufactured for over 20 years, from 1962 through the mid-1980s. This compressor was superseded by a lighter version, model DA-6, in 1982. Two more changes soon followed: the “Harrison Redesigned” HR-6 and the “High Efficiency” HR6HE version. Ford and Chrysler also have models of a six-cylinder compressor similar to one developed originally by Nippondenso. A six-cylinder variable displacement compressor by Calsonic, model V-6, is very similar in appearance to Calsonic’s model V-5 compressor. Honda Air Device Systems (HADS) manufactures a seven-cylinder compressor (Figure 9-18) for use with refrigerant R-134a air-conditioning systems. Harrison manufactures a seven-cylinder variable displacement compressor (Figure 9-19).

Action

Low-pressure refrigerant vapor is compressed to high-pressure refrigerant vapor by action of the pistons and valve plates. For each piston, there is one intake (suction) valve and one outlet (discharge) valve mounted on a valve plate. For simplicity of understanding, a single-cylinder (piston) compressor is discussed. By action of the crankshaft, the piston travels from the top of its stroke to the bottom of its stroke during the first one-half revolution. On the second one-half revolution, the piston travels from the bottom of its stroke to the top of its stroke. The first action, top to bottom, is called the intake or suction stroke; the second action, bottom to top, is called the compression or discharge stroke.

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Wobble plate

Relief valve

Pistons Field coil

Pressure plate

FIGURE 9-18  Honda Air Device Systems (HADS) compressor details.

FIGURE 9-19  Harrison’s seven-cylinder variable displacement compressor.

The piston is fitted with a piston ring to provide a seal between the piston and the cylinder wall. This seal helps to provide a negative (low) pressure on the down or intake stroke, and a positive (high) pressure on the up or exhaust stroke.

The Intake Stroke.  During the intake stroke, a low-pressure area is created atop the piston and below the intake (suction) and exhaust (discharge) valves. The higher pressure atop the intake valve, from the evaporator, allows this valve to open, admitting low-pressure heat-laden refrigerant vapor into the compressor cylinder chamber. The discharge valve is held closed during this time period. The much higher pressure atop this valve, as opposed to the low pressure below it, prevents it from opening during the intake stroke. The Discharge Stroke.  During the compression stroke, a high-pressure area is created atop the piston and below the intake and exhaust valves. This pressure becomes much greater than that above the intake valve and closes that valve. At the same time, the pressure is somewhat greater than that above the exhaust valve. The pressure difference is great enough to cause the exhaust valve to open. This allows the compressed refrigerant vapor to be discharged from the compressor.

Exhaust is the final stage that occurs as the piston is moving up on the compression stroke and pressures exceed the preset calibration on the exhaust valve, forcing refrigerant in the high side of the system.

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Compression action is repeated over 6,000 times each minute at road speeds in an R-4 compressor.

Shop Manual Chapter 9, page 361

Continuous Action.  This piston action is repeated rapidly—once for each revolution of the crankshaft; perhaps 600 times each minute at curb idle. At over-the-road speeds, the action may be repeated 1,500 or more times each minute for each cylinder of the compressor.

Rotary Vane Compressors The rotary vane compressor, by design, provides the greatest cooling capacity per pound of compressor weight. It has no pistons and only one valve: a discharge valve. The discharge valve actually serves as a check valve to prevent high-pressure refrigerant vapor from entering the compressor through the discharge provisions during the off cycle, or when the compressor is not operating. The function of the rotary vane compressor is the same as that of the piston- or reciprocating-type compressor. Its operation, however, is entirely different. The concept and use of rotary-type compressors for refrigeration service is not new. Two basic types of rotary vane compressors have been available for nonautomotive refrigeration use for many years: rotating vane and stationary vane. York was first to introduce this compressor to the automotive marketplace in the early 1980s. Only about 50,000 rotary vane compressors were manufactured by York before being discontinued, however. With some exceptions, a rotary vane compressor was also found on some Geo Prism and Toyota Corolla and Tercel car lines as early as 1989. In 1993, Panasonic manufactured a rotary compressor that was introduced on some Ford car lines. The Zexel rotary compressor was also used on Nissan’s Altima.

Operation of Rotary Compressors

Follow the illustration shown (Figure 9-20) for a brief description of the operation of a rotary vane compressor. ■■ The compressor shaft turns a rotor assembly that has vanes that extend to the wall of the cylinder block. Suction intake begins

Suction port

Suction intake continues

Cylinder

Rotor Suction intake ends

1

3

Vane

New suction cycle

Exhaust begins

2 Exhaust port

4

FIGURE 9-20  The operational sequence of a rotary vane compressor.

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■■ ■■ ■■

■■

This forms a compression chamber, or several chambers if there is more than one vane. The rotating vanes then draw in refrigerant vapor through the suction ports. Compression of the refrigerant starts after the vanes have crossed the suction ports, increasing the refrigerant pressure and temperature. The hot vapor is then forced out through the discharge valves to the condenser.

Scroll Compressors Although the scroll compressor was first patented in 1909, it did not meet practical application until it was introduced by Copeland Corporation in 1988 for use in home air conditioners and heat pumps. Sanden introduced the scroll compressor to the automotive marketplace in 1993. Its unique design is considered by many to be a major technological breakthrough in compressor design and its use has expanded. A scroll compressor is composed of two scrolls: one is a fixed scroll and the other is a moveable scroll attached to the rotating input shaft. When combined, they create a spiral configuration with the moveable scroll orbiting eccentrically without rotating inside the fixed scroll, thereby trapping and pumping refrigerant (Figure 9-21). The compressor housing forms the fixed scroll, and the compressor input shaft attaches to the orbiting scroll (Figure 9-22). The design of the two scroll halves creates a varying volume of space between them that allows for the suction and compression of the refrigerant. A scroll compressor has only one cylinder with a compression stroke (output) for every 360 degrees of rotation. If you look closely at Figure 9-23, you will notice that a new intake chamber forms after each 360 degrees of rotation. In other words, for every 360 degrees of rotation, a new compression chamber is formed and a discharge pulse occurs. Thus a scroll compressor is a one-cylinder compressor. Follow the illustration shown (Figure 9-23) for a brief description of the operation of a scroll compressor. ■■ Compression in the scroll compressor is achieved by the interaction of a orbiting scroll and a stationary scroll. ■■ Refrigerant vapor enters the compressor suction port and an outer opening of one of the orbiting scrolls.

A rotary vane compressor has fewer moving parts than does a reciprocating compressor. A scroll compressor has only one moving part, the scroll. The scroll compressor was first introduced by Copeland Corporation for use in residential heat pump systems.

Discharge port Fixed scroll Suction port

Shaft

Orbiting scroll

Discharge port

FIGURE 9-21  A scroll design refrigerant compressor.

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Fixed scroll

Orbiting scroll

Belt-driven scroll

Discharge valve Belt-driven A/C clutch

Bearing Fixed scroll

Discharge port

FIGURE 9-22  The compressor housing forms the fixed scroll, and the compressor input shaft attaches to the rotating scroll.

Gas

Gas

1. Compression in the scroll is created by the interaction of an orbiting spiral and a stationary spiral. Gas enters an outer opening as one of the spirals orbits.

Gas

Compression

4. By the time the gas arrives at the center port, discharge pressure has been reached.

Discharge

Suction

2. The open passage is sealed off as gas is drawn into the spiral.

Gas

3. As the spiral continues to orbit, the gas is compressed into an increasingly smaller pocket.

FIGURE 9-23  The operational sequence of a scroll compressor.

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This open passage allows refrigerant vapor to be drawn into the passage of the scroll, which is then sealed off. ■■ As the scroll continues to orbit, the passage becomes smaller and the refrigerant vapor is compressed. ■■ As the refrigerant pressure increases, the discharge valve is pushed open when the pressure in the scroll passage rises above both the valve spring tension and the discharge line pressure (pressure differential is greater in the compressor than in the high-side port), and the refrigerant flows into the discharge port and the high-side discharge line. ■■ Refrigerant gas is discharged from the compressor once every shaft rotation. So, if the shaft is rotating at 2,000 rpm, there are 2,000 pump pulses every minute, generating a virtually continuous flow of refrigerant through the system. ■■ As the refrigerant vapor is discharged from the compressor discharge port, its temperature and pressure have been increased. This brief explanation is of just one vapor passage of the scroll. During actual operation, all vapor passages of the scroll are in various stages of compression at the same time. This provides a nearly continuous suction and discharge pressure at all times. ■■

Scotch Yoke Compressors In a scotch yoke compressor (Figure 9-24), opposed pistons are pressed into opposite ends of a yoke riding upon a slider block located on the shaft eccentric. Rotation of the shaft moves the yoke, with attached pistons, in a reciprocating motion. Counterweights are used to balance the rotating assembly. A suction reed valve is located at the top of each piston, and a discharge valve plate is located at the top of each cylinder. Like all reciprocating compressors, low-pressure refrigerant is drawn into the cylinder through the suction valve on the intake stroke and is forced out through the discharge valve on the exhaust stroke at a high pressure.

Discharge valve

Piston Suction valve

Shaft Yoke FIGURE 9-24  A typical scotch yoke compressor details.

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Variable Displacement Compressors

Operation of the control valve is dependent on differential pressure, known as delta p ( Dp).

Harrison first introduced a variable displacement compressor in 1985. A variable displacement compressor is designed to match any automotive air-conditioning load demand under all conditions. This is accomplished by varying the displacement of the compressor by changing the stroke (displacement) of the pistons. The axially oriented pistons are driven by a variableangle wobble (swash) plate. The angle of the wobble plate is changed by a bellows-activated control valve located at the rear of the compressor in the suction port (low-pressure) side and is opened and closed in response to changes in low-side pressure (Figure 9-25). The internal pressure of the crankcase is controlled by the operation of the control valve. The angle of the wobble plate is determined by the pressure differential between the crankcase’s internal pressure and the piston cylinder pressure. When air-conditioning demand is high, with an increased heat load, the refrigerant pressure on the low side will increase. In this situation, the suction pressure will be above the control point, and the control valve bellows will compress to open the low-pressure side valve and close the high-pressure side valve, which will maintain a bleed from the compressor crankcase to the suction side (Figure 9-26). In this case, the crank-case’s internal pressure will be equal to the pressure on the suction port side. The internal pressure in the cylinder will be greater than the crankcase pressure, and the wobble plate will be at the maximum angle, providing greatest piston travel (stroke) and displacement (Figure 9-27). Conversely, when the air-conditioning demand is low, such as when the passenger compartment or ambient air temperature is low or during high-speed driving, the suction pressure will also be low. In this situation, the suction pressure will be below the control point, and the control valve bellows will expand to close the low-pressure side valve and open the high-pressure side (discharge port) valve, which will bleed high pressure into the compressor crankcase (Figure 9-28). In this case, the crankcase internal pressure will trigger a pressure differential between the internal pressure in the cylinder and the crankcase, and the wobble plate will move to its minimum angle, providing the least piston travel (stroke) and displacement (Figure 9-29).

Compressor discharge pressure

Crankcase pressure feed Crankcase pressure return

Bellows

Compressor suction pressure

FIGURE 9-25  Variable displacement compressor control valve assembly.

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Discharge port

Cylinder pressure

High pressure valve - open

Crankcase pressure

Spring pressure

Crankcase

FORCES NEEDED TO DECREASE STROKE

Suction port

FIGURE 9-26  Variable displacement compressor control valve in position to lower compressor crankcase pressure and provide maximum wobble plate displacement angle.

Swash plate

Suction valve

Rear head

Piston

Piston rod

Socket plate

Drive lug

Discharge chamber

MAXIMUM SWASH PLATE ANGLE (maximum displacement)

Discharge valve

Control valve

MINIMUM SWASH PLATE ANGLE (minimum displacement)

Shaft Cylinder

Front head

Magnetic clutch assembly

Discharge control

Discharge capacity cm 3 (cu in)

Piston stroke length mm (in.)

Minimum

10.5 (0.641)

1.6 (0.053)

Maximum

184 (11.228)

28.6 (1.126)

FIGURE 9-27  Variable displacement compressor at maximum displacement.

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Discharge port

Cylinder pressure

High pressure valve - open

Crankcase pressure

Spring pressure

Crankcase

FORCES NEEDED TO DECREASE STROKE

Suction port

FIGURE 9-28  Variable displacement compressor control valve in position to increase compressor crankcase pressure and provide minimum wobble plate displacement angle.

Piston

Wobble plate

Control valve bellows Control valve

Pressures Crankcase Piston Stroke

Low pressure Discharge

FIGURE 9-29  Variable displacement compressor at minimum displacement.

The angle of the wobble plate is actually controlled by a force balance on the pistons. Only a slight increase of the crankcase-suction pressure differential is required to create a force on the pistons sufficient to result in a movement of the wobble plate. Temperature, then, is maintained by varying the capacity of the compressor, not by cycling the clutch on and off. This action provides a more uniform method of temperature control and at the same time eliminates some of the noise problems associated with a cycling clutch system. 296 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Electronic Variable Displacement Compressor

An electronic variable displacement compressor design is based on a swash plate design, but it is able to change piston stroke in response to the cooling capacity required (Figure 9-30). The piston stroke is changed by the tilt of the swash (wobble) plate, which changes refrigerant discharge volume. A typical discharge volume for an electronic variable displacement compressor varies from 0.885 to 11.228 cu. in. (14.5 to 184 cm3). It is similar in design to the V-5 compressor but uses an electronic high-pressure control valve pulse–width–modulated solenoid, which replaces the conventional control valve and is often used with an automatic temperature control climate control system. The electronic control valve solenoid’s magnetic coil receives a duty cycle signal from the refrigerant control system air-conditioning amplifier. The duty cycle signal regulates the amperage applied to control the high-pressure control valve lift amount. By changing the high-pressure valve lift, the high-pressure electronic control valve is able to vary compressor volume by routing more or less pressure to the rear chamber of the compressor, which in turn changes the angle of the wobble plate. The compressor output can be varied from 1 to 100 percent. With this wide range of outputs it optimizes the air-conditioning system’s efficiency while lowering CO2 emissions, improving fuel economy, and improving engine performance.

Electronic control valve solenoid Shoe

Piston

Link

Discharge control Hinge ball

Maximum

Electronic control valve capacity cm 3 (cu in) 171 (10.4)

Piston stroke length mm (in.) 30.5 (1.20)

Swash plate Drive shaft

Thrust flange

FIGURE 9-30  The variable displacement compressor piston stroke is changed by the tilt of the swash (wobble) plate, which changes refrigerant discharge volume based on a pulse width–modulated signal to the electronic control valve.

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A broken discharge valve plate will set up a mini-vibration sufficient to “shake” the compressor loose enough to cause belt slippage.

For maximum cooling, the high-pressure control valve solenoid is closed by the magnetic field (amperage) applied to the electronic coil at the electronic control valve solenoid (Figure 9-31). The climate control module increases the duty cycle (on time) during high heat load conditions based on evaporator temperature sensor data and other system inputs (Figure 9-32). This creates a pressure balance between inside the crankcase (by lowering crankcase pressure) and the suction line, causing the swash plate to move to the maximum stroke position. To reduce compressor output, the electrical signal to the electronic control valve solenoid is turned off and the high pressure control valve is opened by spring force (Figure 9-33). The climate control module decreases the duty cycle (on time) during low heat load conditions based on evaporator temperature sensor data and other system inputs (Figure 9-34). At this point, the suction-line pressure is still low (maximum output), which enables the suction

Crankcase

Suction port

High-pressure valve closed

Cylinder pressure

Low-pressure valve open Diaphragm

Crankcase pressure

Spring pressure FORCES NEEDED TO INCREASE STROKE

V DC

Solenoid + Duty Cycle = 87%

13.34 volts

FIGURE 9-31  For maximum cooling, the high-pressure control value solenoid is closed by the magnetic field applied to the electronic coil at the electronic control valve solenoid, opening the pressure passage from the suction port to the crankcase.

A DC 20

1.317

Solenoid Current = 0.8A

0 volts

1.717

0.917

0.517

0.117

High Heat Load – Greater Duty Cycle Command to Solenoid (87%). Solenoid Currect = 0.8A FIGURE 9-32  As the duty cycle is increased to the variable displacement compressor, control solenoid amperage increases, creating a strong magnetic field opening the solenoid.

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Crankcase

Suction port

High-pressure valve open Low-pressure valve closed Diaphragm

Cylinder pressure

Crankcase pressure

Spring pressure FORCES NEEDED TO DECREASE STROKE

Solenoid + Duty Cycle = 43%

V DC

12 volts

FIGURE 9-33  To reduce compressor output, the high-pressure control valve solenoid is turned off. This allows discharge pressure to enter the crankcase.

A DC 20

0 volts

1.717

1.317

0.917

Solenoid Current = 0.4A

0.517

0.117

Low/Medium Heat Load – Medium Duty Cycle Command to Solenoid (43%). Solenoid Currect = 0.4A FIGURE 9-34  As the duty cycle is decreased to the variable displacement compressor, control solenoid amperage also decreases, creating a weak magnetic field and allowing the solenoid to close.

port to close and the discharge port to open. This in turn allows high pressure to enter the crankcase. This increased crankcase pressure is applied to the swash plate, creating a pressure difference between the pistons and the crankcase, which changes the angle of the swash plate and reduces displacement. During diagnosis, if the compressor is not producing adequate pressure after the system refrigerant has been recovered and recharged with the proper amount of refrigerant, be sure to check that the climate control module is sending the correct duty cycle signal to the compressor. An unplugged solenoid will cause the compressor to default to minimum displacement. Always check for both powertrain and climate control system stored trouble codes, which could inhibit proper system operation. Inaccurate climate control sensor inputs such as inaccurate evaporator, ambient or cabin temperature sensor readings, or pressure sensors could cause the wrong displacement command to be sent. 299 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

On belt-driven applications there is no need for an electromagnetic clutch, but some design applications do use one. The compressor output can be lowered to almost zero output pressure when there is no command for air conditioning. The compressor shaft turns continuously whenever the engine is running, so lubrication is critical. It is essential that the system be properly charged with both oil and refrigerant at all times to maintain adequate compressor lubrication and avoid failure. The clutchless system is designed to keep the oil charge circulation going even when the air conditioning is turned off. There is a vibration damper built into the compressor pulley to absorb engine torque fluctuations. The pulley is also designed with a spoke limiter mechanism attached to the compressor drive shaft that will break away in the event the compressor locks up, allowing the pulley to free-wheel and continue to rotate. This is a safety feature that allows the compressor to be driven by a common drive belt without the fear of belt system failure due to compressor failure.

Diagnosing Problems and Making Repairs Shop Manual Chapter 9, page 340

Broken discharge valves in compressors (Figure 9-35) are not uncommon. Broken suction valves and piston rings are less often encountered, but lead to the same diagnosis. Broken valves or rings are easier to diagnose in one- and two-cylinder reciprocating compressors than in multicylinder compressors. The manifold and gauge set is the diagnostic tool most often used to determine valve plate condition. The first indication of failure is a higher than normal low-side (suction) pressure accompanied by a lower than normal high-side (head) pressure. Valve and ring failures, however, are not as easily diagnosed in four-, five-, and six-cylinder compressors. The first indication of valve or ring failure in these compressors is that the belt(s) will not remain tightened. One defective discharge valve plate in a six-cylinder compressor, for example, sets up a vibration that, when not otherwise detected, literally shakes the belt(s) loose. This is true regardless of how well the adjustment provisions are tightened. Many simple compressor repairs are usually a routine service provided by the automotive air-conditioning technician. These repairs include checking and adding oil, replacing the crankshaft seal, and, in many units, replacing the valve plate assembly. More complex repairs are often “shopped out” to a specialty shop that has the facilities for semi-mass-rebuilding procedures. Because of the general high cost of labor, one-on-one compressor rebuilding is not usually economically feasible.

Broken reed

FIGURE 9-35  Broken reed in valve plate.

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Compressor Failure

Compressor failure, representing almost 30 percent of all vehicle air-conditioning system repairs, is the leading cause of system failure according to a survey conducted in the late 1990s by the Mobile Air Conditioning Society Worldwide. The principal cause of compressor failure was found to be leaks, followed by internal mechanical problems. Clutch problems were the least common reasons for compressor failure. It should be noted that repeat compressor failures are often caused by a restricted condenser that went undiagnosed after the initial compressor failure. Many of today’s honeycomb design condensors cannot be flushed and should be replaced if a restriction is suspected or a catastrophic compressor failure has occurred with particles present in the compressor oil. The survey revealed that over half of the reported compressor failures were to R-134a airconditioning systems in vehicles that had been retrofitted to avoid using R-12 refrigerant. This is probably because many older compressors designed for R-12 simply will not withstand the rigors of R-134a’s higher operating pressures. The lack of proper lubrication is also implicated as a problem with vehicle air-conditioning system compressors and is generally due to not properly changing the lubricant during retrofit procedures or not checking lubricant during repair procedures. Most compressors are designed to function with a compression ratio between 5:1 and 7:1. One may make a quick check of a compressor’s operating compression ratio by dividing high-side psia by low-side psia. Note that these are absolute pressures, so one must add 15 to both low-side and high-side gauge readings. The formula is: Compression Ratio 5

Shop Manual Chapter 9, page 343

High-Side Pressure 1 15 Low-Side Pressure 1 15

For example, assume that the low-side pressure is 30 psig and the high-side pressure is 220 psig. When 15 is added to these values, they become 45 psia and 235 psia, hence: 235 5 5.2 45 Pressure ratios above 7.5:1 can cause early compressor failure because of the added load on bearings, pistons, and seals. Also, higher operating temperatures generated by the higher operating pressures can cause lubrication breakdown, which results in harmful deposits on the compressor’s internal assembly.

Electric Motor–Driven Compressors Electric motor–driven air-conditioning compressors used on current production hybrid vehicles enable air-conditioning operation even when the internal combustion engine is not running. The system uses a humidity sensor to improve the efficiency of passenger compartment dehumidification. The electric air-conditioning compressor is driven by an integrated electric motor (Figure 9-36). The compressor motor runs on three-phase alternating current (AC) power at 2001 volts supplied by the hybrid AC inverter. The electric compressor is a scroll design compressor driven by a brushless electric motor. The basic construction of the compressor is the same as a standard belt-driven scroll-type compressor. Special compressor oil is used to insulate the compressor housing from the high voltage components inside the compressor. Always refer to the manufacturer’s specifications for proper oil selection; currently 2004 and later model Toyota electric compressors use ND11 compressor oil with a high insulation value. Because the compressor electric motor is powered by over 200V AC, special high-voltage circuit safety precautions must be followed. Always read and understand manufacturer high-voltage safety procedures prior to working on or near any high-voltage circuits or components.

Shop Manual Chapter 9, page 372

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FIGURE 9-36  Electric air-conditioning compressor is driven by an integrated 200-volt electric motor.

The compressor utilizes an oil separator that reduces the circulation of compressor oil through the system. As the refrigerant gas and oil leave the compressor discharge port, they flow around a cylindrical pipe in the oil separator. The centrifugal force that is created by the rotation of the refrigerant gas and oil causes the oil to separate out due to the difference in specific gravity between the two. The lighter refrigerant gas passes out the discharge port, while the heavier compressor oil is discharged into an oil storage reservoir. From the reservoir, the oil travels back to the inside of the compressor and the process is repeated. Other than the compressor, the rest of the air-conditioning system operates and is diagnosed in the same way as in a conventional system. Never work on the high-voltage systems of a hybrid electric vehicle until you have completed a hybrid electric training program. The following are basic hybrid electric vehicle warnings that should be adhered to: ■■ Never assume that a hybrid electric vehicle is shut off, because they are silent. ■■ Always verify that the Ready indicator is off. ■■ Remove the service plug and wait at least 5 minutes before touching any of the highvoltage wires, connectors, or components. ■■ Always wear insulated electrical (lineman) gloves before coming in contact with any high-voltage system wiring or components, to prevent electrocution. ■■ Never damage, cut, or open any orange high-voltage power cables or components. ■■ Always test circuit for voltage with a digital multimeter to ensure that a 0 volt reading is obtained before touching any high-voltage terminals. ■■ Special electrically insulating refrigerant oil is used to keep voltage from conducting from the electric drive motor to the compressor case. Toyota specifies ND-11 compressor oil. Always refer to the specific manufacturer’s recommendations for proper compressor oil usage for the application in question. Some manufacturers warn that a diagnostic trouble code may be set or a complete hybrid electric system shutdown could occur due to the addition of even a small amount of the wrong lubricating oil being added to a system. They also warn that if the wrong lubricant is added and circulated through the system that all major refrigerant system components (evaporator, compressor, condenser, storage container, etc.) must be replaced. Honda hybrid electric vehicles use a dual-scroll air-conditioning compressor design. It is actually two compressors in one. It has a conventional belt-driven 75 cc scroll compressor and 302 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

a smaller 15 cc scroll compressor driven by a 3-phase high voltage electric motor. Depending on conditions and the demand on the air-conditioning system the compressor can be switched from belt drive to electric drive or engage both. During idle stops the air-conditioning compressor operates in electric-only mode unless cooling demand is high and the internal combustion motor is operating or if the high voltage battery pack state of charge is low in which case the internal combustion engine would be commanded on. It is predicted that eventually the belt-driven air-conditioning compressor on all platforms will be replaced by a high-voltage electric motor–driven compressor, which is more reliable and less prone to leakage. But this will have to wait until high-voltage power generation is available on more platforms.

Stretch to Fit Belts

Provided by The Gates Corporation

Ford, General Motors, and Subaru began using stretch to fit belts to drive their air-conditioning compressors and other single-drive belt accessories on some models beginning in 2008. Stretch to fit belts were designed by Gates, a global supplier of OE belts and hoses, as an alternative to adjustable micro-V belts. The belt is very similar in appearance to a conventional micro-V belt. The difference is the use of a reinforcing cord made of polyamide material, which is more elastic than traditional aramid or polyester fibers used in traditional designs that makes them self-tensioning. The polyamide fibers and elastic backing compound allow the belt to stretch and then retract to maintain proper tension throughout its lifetime without the need for a manual or automatic belt tensioner. The micro-V belt ribbed drive surface is still made with EPDM for long service life that resists cracking. Out of the package they are shorter than their actual working length, but once installed they automatically tension, providing optimum load-carrying capacity. A stretch to fit belt may be identified by looking at the part number; if the last letters are “SF,” as in K030195SF (Figure 9-37), then it is a stretch to fit

FIGURE 9-37  A stretch to fit belt can be identified by looking at the last two letters of the part number; if the number ends in “SF” then it is a stretch to fit belt.

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belt requiring special service instruction for replacement. General Motors has indicated that these are one-time use belts and once removed should be replaced, meaning that if you find it necessary to remove an air-conditioning compressor driven by a stretch to fit belt, the belt must be replaced to maintain optimal load-carrying capacity. Terms to Know Auxiliary Axial plate Compression Crankshaft Discharge valve Exhaust High pressure Intake Low pressure Rotary Scroll Serpentine Suction Suction valve Swash plate Wobble plate Zener clamping diode

SUMMARY ■■

■■

■■

■■

Reciprocating compressors have a piston or pistons that draw low-pressure heated refrigerant vapor into a chamber, increases its heat content and pressure, and “pumps” it out as a high-pressure high-temperature vapor. A scroll compressor draws low-pressure heated refrigerant vapor through its suction port into a continuously moving scroll where the vapor’s pressure and temperature are increased and then forced out through its discharge port as a high-pressure high-temperature vapor. In a rotary compressor, a rotating vane draws in low-pressure heated refrigerant vapor through the suction port and increases its temperature and pressure before forcing it out through the discharge port. It is discharged as a high-temperature high-pressure vapor. An electromagnetic clutch is used to engage and disengage (turn on and off ) a compressor, as desired, in present applications of automotive air-conditioning systems.

REVIEW QUESTIONS Short-Answer Essays

9. What are the two primary functions of a compressor?

1. Describe the operating principles of a reciprocating compressor.

10. Why is the scroll compressor considered to be the most efficient?

2. Why is low pressure important?

Fill in the Blanks

3. What are other terms used to describe an axial plate? 4. What type of refrigerant compressor designs are used on hybrid electric vehicles? 5. Explain the operation of an electronic variable displacement compressor. 6. Describe the function of a variable displacement compressor. 7. Describe the operating principles of a rotary compressor. 8. What is the purpose of a magnetic clutch: a. In a fixed displacement compressor system? b. In a variable displacement compressor system?

1. In-car temperature is controlled in a variable displacement compressor system by varying the capacity of the _______________, not by cycling the _______________ on and off. 2. Compression in a scroll compressor is achieved by the interaction of a orbiting _______________ and a stationary _______________. 3. A _______________ compressor is designed to match any automotive air conditioning _______________ demand under all conditions. 4. Electric motor–driven air conditioning _______________ used on current production hybrid vehicles enable air-conditioning operation even when the _______________ is not running.

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5. A _______________ compressor has only one cylinder with a compression stroke (output) for every _______________of rotation. 6. A single belt driving all accessories is often called a _______________ drive system. 7. The compressor serves two important functions, to create a _______________ condition within the system, and it _______________ refrigerant vapor from a low pressure to a _______________, thereby increasing its_______________. 8. An electromagnetic clutch is used to turn the _______________ on and off. 9. If a compressor clutch _______________ is set too loose, the clutch may not engage or it may slip, if too tight the clutch may _______________. 10. A _______________ _______________ compressor is designed to match any automotive air-conditioning load demand under all conditions.

Multiple Choice 1. The electronic variable displacement compressor is based on what type of compressor design? A. Rotary compressor design B. Swash plate compressor design C. Scroll compressor design D. Vane compressor design 2. Electric motor–driven air-conditioning compressors used on hybrid vehicles are based on what compressor design? A. Wobble plate compressor design B. Swash plate compressor design C. Scroll compressor design D. Rotary compressor design 3. An air-conditioning compressor clutch failed due to overheating. What is the most likely cause of the failure? A. A low refrigerant charge B. A faulty compressor clutch diode C. High resistance in the compressor D. A loose drive belt clutch circuit 4. The compressor pumps refrigerant as a A. liquid. B. liquid that changes to a vapor. C. vapor that changes to a liquid. D. vapor. 5. The methods used to drive a compressor are being discussed: Technician A says that automotive air-conditioner compressors have an electromagnetic clutch.

Technician B says that a serpentine belt system is often used to drive a compressor clutch. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 6. A technician finds an air-conditioning clutch will not engage. Upon initial testing the compressor is receiving both proper power and ground at the compressor clutch electrical connector; in addition the compressor input shaft turns freely by hand. Which of the following is the most likely cause? A. A faulty pressure cycling switch. B. Low refrigerant level. C. A locked-up compressor. D. Compressor clutch air gap too large. 7. All of the following statements about variable displacement compressors are true, except: A. Variable displacement compressors control evaporator pressure by varying their pumping capacity. B. Variable displacement compressors have a cycling clutch. C. Variable displacement compressors do not have a cycling clutch. D. Variable displacement compressor piston stroke is adjusted by an internal pressure valve. 8. Reciprocating compressors are being discussed. Technician A says that the suction valve is opened to allow refrigerant vapor to enter due to a differential in pressure above and below the valve. Technician B says that the discharge valve is opened to allow refrigerant vapor to leave due to a differential in pressure above and below the valve. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 9. The function of a scroll compressor is being discussed. Technician A says that its function is to create a low pressure condition in the system. Technician B says that its function is to increase the temperature and pressure of refrigerant vapor. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 10. The following are automotive air-conditioning system compressor types, except: A. Rotary C. Centrifugal B. Swash plate D. Scroll

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Chapter 10

Case and Duct Systems

Upon Completion and Review of this Chapter, you should be able to: ■■

Identify types of case/duct systems.

■■

Understand and control unpleasant HVAC odor.

■■

Discuss air distribution through the case/duct system.

■■

Identify the need for and location of cabin air filters.

Understand the airflow through the case/duct system for defrost mode, heat mode, and cool mode.

■■

■■

The heater coolant flow control valve is generally found outside the case/ duct system for ease of service.

The evaporator core is often easier to service in a split case system.

Hybrid means that no particular system is in mind—that the illustration is representative of any system.

Understand Mode Door Actuator operation: cable, vacuum, and electric.

Introduction This chapter is intended to provide a basic understanding of the automotive heater/airconditioner case/duct system for factory-installed heater/air-conditioning systems. The system discussed in this unit should be considered typical. It is not representative of any particular automotive case/duct system. A typical automotive heater/air-conditioner case/duct system (Figure 10-1), at first glance, may seem to be a complicated maze of passages and doors. Actually, it is much simpler than it first appears (Figure 10-2). The case/duct system serves two purposes. First, it houses the heater core and the airconditioner evaporator. Second, it directs fresh or recirculated conditioned air into the vehicle. This air is directed through selected components into the passenger compartment via selected outlet provisions, such as panel registers, a floor outlet, and defroster outlets. The supply air may be either fresh (outside) or recirculated (in-car) air, depending upon the system mode selected. After air is heated or cooled (conditioned), it is delivered to either the floor outlet, dash (panel) outlets, or the defrost (windshield) outlets.

Mode is the manner or state of existence of something, for example, heat or cool, open or close. FIGURE 10-1  A typical case and duct system may seem like a maze at first glance.

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Front ducts Rear ducts

Heater

Evaporator Blower

Fresh air Defrost

Intake

Dash outlet

Dash ducts

Foot well outlet

Mode control motor

Recirculation control motor Blower Resistor

Inlet duct temperature sensor Blower unit components

A/C filter Air mix control motor

Evaporator components

FIGURE 10-2  A typical case and duct system showing both exterior and interior view.

Two basic types of case assemblies are used to house the heater core and air-conditioner evaporator: the independent case assembly and the split case assembly. The independent case, which is used on compact and small cars, may have an upstream blower (Figure 10-3) or a downstream blower (Figure 10-4). Either an upstream integral blower (Figure 10-5) or an independent blower (Figure 10-6) is used on split case systems. The split case system, which is used on larger cars, is located on both sides of the engine firewall. The independent case system is usually located under the dash, on the inside of the firewall. For simplicity of understanding, a typical hybrid case/duct system is illustrated in this unit. Also, for the purposes of explanation, this system is theoretically divided into three Shop

To defrost is to remove frost. It also refers to the vent position where warm outlet air is directed to the windshield.

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Heater

Heater-defrost door

Evaporator Blower

To floor Outside air

Blend door

To defroster

Recirulate A/C defrost To panel door

Outside/ recirculate door

FIGURE 10-3  An independent case/duct system with an upstream blower.

Blend door

Evaporator

Outside air

Blower A/C defrost door

To defroster Outside/ recirculate door Recirculate

Heater

To A/C registers A/C heat door

To floor

Restrictor air door

FIGURE 10-4  An independent case/duct system with a downstream blower.

Restrictor door Heater

A/C heat door To A/C registers

Blower

Outside air

Outside door

Blend door

Recirculate door Recirculate

To defroster

Heat-defrost door

Evaporator

To floor

FIGURE 10-5  A split case system with an upstream blower.

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Blend door

Bypass door

Evaporator

Outside air Blower Panel-defrost door

To A/C registers Outside/ recirculate door Recirculate

Heater To defroster

Shop Manual

Blower High-low door

Chapter 10, page 397 To floor

FIGURE 10-6  A split case system with an independent blower.

The plenum is an area filled with air at a pressure that is slightly higher or lower than the surrounding air pressure, such as the chamber just before the blower motor.

Manual sections (Figure 10-7): the air intake, heater core and air-conditioning evaporator (plenum), and air distribution. Each will be studied, first individually, then as a complete system. Remember, however, that this discussion is of factory-installed or original equipment manufacturer (OEM) installation. There are many considerations involved in the design of an automotive air-conditioning system and the volume of airflow requirements of the case and duct system. The interior passenger compartment soak temperatures of the vehicle are affected by many factors. Temperatures are affected by both exterior and interior surface colors and tint versus nontint windows. Heat load on the air-conditioning system varies with the number of passengers in the vehicles, due to both body heat and breath temperatures, which are typically 408F2608F above ambient air temperatures. The temperature of the interior surfaces due to the radiant heat of the sun can range from 508F21008F above ambient air temperatures. All of these factors and more affect the overall performance of the heating and air-conditioning system.

This test also assumes that the heating system is in proper working order.

A

F

C

H G

D

C B

E

B A A— B— C— D—

Fresh air inlet Recirculate air inlet To floor outlets To defrost outlets

B

E — To A/C (panel) outlets F — Heater core G — Evaporator core H — Motor and blower assembly

FIGURE 10-7  Three sections, right to left: (A) air intake section; (B) plenum section; and (C) air distribution section.

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Motor and blower assembly

Fresh (outside) air inlet

Fresh/recirc. door Recirculate (inside) air inlet FIGURE 10-8  Air intake (inlet) section.

Shop Manual Chapter 10, page 398

Understanding how the entire system functions is essential to proper diagnosis of the system as a whole.

Air Intake To recirculate is to reuse, to circulate over and over again. Fresh air intake is generally through vents provided just in front of the windshield, often hidden by the hood cowl. The blend door is a door in the duct system that controls temperature by blending heated air and cool outside air. A Bowden cable is a wire cable inside a metal or rubber housing used to regulate a valve or to control a remote device.

Shop Manual Chapter 10, page 402

The air intake or inlet section (Figure 10-8) consists of a fresh (outside) air inlet, a recirculate (inside) air inlet, and a fresh-recirculate blend-air door. The outlet of this section is to the blower inlet. The fresh air inlet provides the system with fresh outside air; the recirculate air inlet provides a recirculated in-car air. The position of the fresh-recirculate door depends on the system mode. Generally, in all modes except maximum cooling (MAX A/C), the air supply is from the outside ambient. In MAX A/C, the air supply is from the inside (recirculated). Even in the MAX A/C mode, some systems provide for up to 20 percent fresh air. This is to provide for a slightly positive in-vehicle pressure. A slightly positive pressure must be maintained inside the vehicle to prevent the possibility of the entrance of dangerous exhaust gases that could produce a hazardous, if not lethal, in-vehicle atmosphere when all the windows are tightly closed.

Core Section The core section, more appropriately called the plenum section, is the center section of the system. It consists of the heater core, the air-conditioning evaporator, and a blend door. The blend door may be operated by a Bowden cable or, on many systems today, it is operated by an electric or vacuum actuator and provides a full range control of the airflow either through or around the heater core. All air passes through the air-conditioning evaporator. It is in this section that full-range temperature and humidity conditions are provided for in-car comfort. A description of how this is accomplished follows.

Heating

The heater coolant valve is open to allow hot engine coolant to flow through the heater core. Cool outside fresh air is heated as it passes through the heater core. In the heating mode, the air conditioner is not operational; therefore, it has no effect on temperature as the air first passes through the evaporator. The desired temperature level is achieved by the position of the blend door. This allows a percentage of the cooler outside air to bypass the heater core, tempering the heated air. The heated and cool air are blended in the plenum to provide the desired temperature and humidity level before passing to the air distribution section.

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Cooling

If all other conditions are correct, the compressor is turned on in the cooling mode. In maximum cooling (MAX A/C), recirculated air passes through the air-conditioner evaporator and is then directed back into the vehicle. In other than MAX A/C, fresh outside air passes through the air-conditioning evaporator and is cooled before delivery into the vehicle. The desired in-vehicle temperature level is achieved by the position of the blend door. The blend door allows a percentage of cooled air to pass through the heater core to be reheated. The cooled air passing through the evaporator and the reheated air passing through the heated core are blended in the plenum to provide the desired temperature level. This tempered air is then directed to the air distribution section.

Distribution Section The air distribution section directs conditioned air to be discharged to floor outlets, defrost outlets, or dash panel outlets. Depending on the position of the mode doors, conditioned air may be delivered to any combination of these outlets. There are two mode (blend) doors in the air distribution section: the HI/LO door and the DEF/AC door. The HI/LO door provides 0–100 percent full-range conditioned air outlet control to the HI (dash) and LO (floor) outlets. The DEF/AC door provides conditioned air outlet control either to the defrost (windshield) outlets or to the dash panel outlets.

Combined Case The combined case/duct system provides full-range control of air circulation through the heater core and air-conditioner evaporator. Figure 10-9 shows 100 percent recirculated air through the air-conditioner evaporator and out through the panel outlets. This may typically represent mode and blend door positions when maximum cooling (MAX A/C) is selected during high in-car ambient temperature conditions. Figure 10-10 shows 100 percent fresh air circulation through the heater core and out through the floor outlets. This may typically represent the mode and blend door positions when heat is selected during low in-car ambient temperature conditions. A variation (Figure 10-11) shows some of the heated air diverted to the defrost outlets. This would be the typical application to clear the windshield of fog or light icing conditions.

Evaporator

Defroster outlet

Panel registers

A full flow of refrigerant in the evaporator core provides maximum cooling at all times. The bi-level control is sometimes referred to as the HI/LO door or control. Mode doors are diverters within the duct system for directing air to various locations.

Blower Outside air (in)

Heater core Floor outlet

The coolant flow control may allow from partial to full flow of coolant based on the temperature selected by the operator.

Even on Recirculate, up to 20 percent fresh air may be brought in to maintain a positive in-car pressure.

Blower motor

Firewall

Some may refer to the core section as the mixing section; it is in this section that heated and cooled air are mixed.

Recirculate air (in)

FIGURE 10-9  All recirculated air through the evaporator and out the panel registers (outlets).

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Blower motor Evaporator

Firewall

Defroster outlet

Blower Outside air (in)

Heater core Floor outlet

Recirculate air (in)

Panel registers

FIGURE 10-10  All fresh air flows through the heater core and out the floor outlets. Though air flows through the evaporator, the compressor is not running and there is no cooling effect.

Blower motor Evaporator

Firewall

Defroster outlet

Bi-level is a condition whereby air is delivered to two levels in the vehicle, generally the floor and dash outlets. In MAX cooling, the heater coolant control valve is closed if the system is equipped with one.

Outside air (in)

Heater core Floor outlet

Shop Manual Chapter 10, page 412

Blower

Panel registers

Recirculate air (in)

FIGURE 10-11  The same condition as illustrated in Figure 10-10, but with some air diverted to the defroster outlet.

Air Delivery In addition to OFF, there are six selections for the condition of the air to be provided to the passenger compartment of the car. Some may require recirculated air, and others may require fresh air. While the select conditions may differ slightly from one car model to another, they typically are MAX, panel, panel/floor (bi-level), floor, floor/defrost, and defrost. Following are some of the typical duct door routings of conditioned air for the various selections available at the driver control panel.

MAX

In MAX (maximum) cooling (Figure 10-12), the compressor is running and the outside/ recirculate air door is closed to ambient air. Flow is from in-car air, through the evaporator, and out through the panel registers. Bi-level, which will provide some air to the floor outlet (Figure 10-13), may be selected.

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Blower motor Evaporator

Firewall

Defroster outlet

Blower Outside air (in)

Heater core Floor outlet

Recirculate air (in)

Panel registers

FIGURE 10-12  In MAX cooling, airflow is from in-vehicle, through the evaporator, and out the panel outlets.

Blower motor Evaporator

Firewall

Defroster outlet

Blower Outside air (in)

Heater core Floor outlet

Panel registers

Recirculate air (in)

FIGURE 10-13  MAX cooling with BI-LEVEL selected.

If MAX heating (Figure 10-14) is selected, the compressor is not running and the heater coolant valve is open, if the system is equipped with one. Airflow is from in-car, through the evaporator and heater core, and out the floor outlet. If bi-level is selected (Figure 10-15), some air is directed to the panel registers. A small amount of air in either condition is directed to the windshield to prevent fogging.

Panel (Norm)

If normal (panel) cooling is selected, the air-conditioner compressor is running. Airflow is from outside ambient, through the evaporator, and out the panel registers (Figure 10-16). For humidity control, some air may be directed through the heater core (Figure 10-17) as well. If normal (panel) heating is selected, the air-conditioning compressor is not running and the coolant control valve is open, if the system is equipped with one. Airflow is from the outside ambient, through the heater core, and out the floor outlets (Figure 10-18).

The “panel” registers are those visible on the dash assembly.

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Blower motor Evaporator

Firewall

Defroster outlet

Blower Outside air (in)

Heater core Floor outlet

Recirculate air (in)

Panel registers

FIGURE 10-14  Airflow when MAX heating is selected.

Blower motor Evaporator

Firewall

Defroster outlet

Blower Outside air (in)

Heater core Floor outlet

Recirculate air (in)

Panel registers

FIGURE 10-15  MAX heating with BI-LEVEL selected.

Blower motor Evaporator

Firewall

Defroster outlet

Blower Outside air (in)

Heater core Floor outlet

Panel registers

Recirculate air (in)

FIGURE 10-16  Normal cooling (air conditioning) is selected.

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Blower motor Evaporator

Firewall

Defroster outlet

Blower Outside air (in)

Heater core Floor outlet

Recirculate air (in)

Panel registers

FIGURE 10-17  Airflow when humidity control is required with normal cooling.

Blower motor Evaporator

Firewall

Defroster outlet

Blower Outside air (in)

Heater core Floor outlet

Panel registers

Recirculate air (in)

FIGURE 10-18  Airflow when normal heating is selected.

In either condition, cooling or heating, a small amount of conditioned air is directed to the defrost outlets as an aid to prevent windshield fogging (Figure 10-19).

Panel/Floor (Bi-level)

Bi-level air in the cooling mode can be selected (Figure 10-20) to provide some conditioned air to the floor outlet. Bi-level air may also be selected in the heating mode to provide some air through the panel registers (Figure 10-21). The bi-level setting simply means that conditioned air may be provided at two outlets, panel and floor, as desired by some vehicle occupants. In some systems, this is referred to as HI-LO or PNL/FLR. This condition is similar in operation to MIX.

Vent

The vent brings in unconditioned, ambient air when neither heating nor cooling is desired. The compressor is not running, and the heater coolant valve is not open if the system is equipped with one. Air passage is from ambient air through the heater or evaporator core to

Floor outlets are not generally visible from the seated position. ATC is a recognized acronym for automatic temperature control. MIX is a term used to describe the bi-level or HI/LO mode position. To vent is to introduce fresh outside air into the vehicle.

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Blower motor Evaporator

Firewall

Defroster outlet

Blower

Outside air (in)

Heater core

Floor outlet

Recirculate air (in)

Panel registers

FIGURE 10-19  Some conditioned air is directed to the defroster outlets to prevent windshield fogging.

Blower motor Evaporator

Firewall

Defroster outlet

Blower Outside air (in)

Heater core Floor outlet

Recirculate air (in)

Panel registers

FIGURE 10-20  Airflow in the cooling mode when BI-LEVEL is selected.

Blower motor Evaporator

Firewall

Defroster outlet

Blower Outside air (in)

Heater core Floor outlet

Panel registers

Recirculate air (in)

FIGURE 10-21  Airflow in the heating mode when BI-LEVEL is selected.

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Blower motor Evaporator

Firewall

Defroster outlet

Blower Outside air (in)

Heater core Floor outlet

Recirculate air (in)

Panel registers

FIGURE 10-22  Airflow when VENT is selected in the bi-level condition.

the selected outlets—floor outlets and panel registers. Figure 10-22 shows the vent setting selected with bi-level air delivery.

Heat/Cool

A temperature control is generally provided to select in-car temperature. There are two methods: manual/semiautomatic and automatic (Figure 10-23). Temperature and mode are manually selected in the manual/semiautomatic temperature control (SATC) system. In the automatic temperature control (ATC) system, the selected temperature and mode are a fully automatic function of a digital microprocessor. The microprocessor compares data

SATC stands for semiautomatic temperature control. ATC stands for automatic temperature control.

AC

HIGH

LOW

Shop Manual Chapter 10, page 413

MAX OFF

COLD

HOT

HI MED LOW

Cold

Blend

Blend

FAN

AC

MAX

OFF

Hot

HIGH

AC MAX OFF

LOW

COLD

HOT

FIGURE 10-23  Typical air-conditioner/heater controls.

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Blower motor Evaporator

Firewall

Defroster outlet

Blower

Outside air (in)

Heater core

Floor outlet

Recirculate air (in)

Panel registers

FIGURE 10-24  Airflow when DEFROST is selected.

Blower motor Evaporator

Firewall

Defroster outlet

Blower

Outside air (in)

Heater core

Floor outlet

Panel registers

Recirculate air (in)

FIGURE 10-25  With DEFROST selected, some air will be diverted to the floor outlets.

from designated sensors to maintain the desired in-car temperature. These sensors will be discussed in greater detail in Chapter 11, System Controls.

Defrost

In the defrost position (Figure 10-24), outside ambient air passes through the heater core and is directed to the defroster outlets. A slight amount of heated air is directed to the floor outlets (Figure 10-25). If the outside ambient air temperature is above 508F (108C), the compressor may operate to temper the heated air for humidity control.

MIX

MIX may be selected on some models. Generally, those with a MIX select do not have a bi-level (HI-LO) select provision. When in the MIX position, the floor/defroster door opens halfway (Figure 10-26). In this selection, conditioned air is delivered to the floor and defrost outlets. In-car temperature is controlled by adjusting the temperature control lever. 318 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Blower motor Evaporator

Firewall

Defroster outlet

Blower

Outside air (in)

Heater core

Floor outlet

Other settings for MIX are HI/LO and BI-LEVEL.

Recirculate air (in)

Panel registers

FIGURE 10-26  Airflow when MIX or BI-LEVEL is selected.

The compressor will operate if in-car temperature conditions warrant. The compressor will also operate if outside ambient air temperature is above 508F (108C) as an aid for in-car humidity control.

Dual-Zone Duct System The dual-zone duct system found in some cars has a separate driver- and passenger-side duct system (Figure 10-27). Both sides have a defrost/air-conditioning outlet door and a heater/ floor outlet door that operate together. The passenger has control of the passenger-side temperature door only. The dual-zone duct air distribution system can be controlled by either a manual or automatic climate control system and has a separate temperature control for the passenger. The passenger may adjust the temperature of the air at the outlet vents on the passenger side in an automatic climate control system only within the limits set by the driver—generally up to 308F (16.78C) cooler or warmer than that selected by the driver. Passenger control on a manual climate control system is not usually restricted by the driver’s temperature selection.

Driver windshield air

Driver floor air

Heater core

Evaporator core

Blower and motor

Driver panel air Fresh air

Passenger panel air Passenger windshield air

Passenger floor air

Recirculate air

FIGURE 10-27  A typical dual-duct system.

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Driver windshield air

Driver floor air

Heater core

Evaporator core

Blower and motor

Driver panel air Fresh air

Passenger panel air Passenger windshield air

Passenger floor air

A

Recirculate air

FIGURE 10-28  A typical dual-zone duct system with passenger-side full hot selected (A).

Driver windshield air

Driver floor air

Heater core

Evaporator core

Blower and motor

Driver panel air Fresh air

Passenger panel air B Passenger windshield air

Passenger floor air

Recirculate air

FIGURE 10-29  A typical dual-zone duct system with passenger-side full cold selected (B).

The passenger manually controls the position of the passenger-side temperature air door, controlling the discharge temperature of the passenger-side air outlets between full hot (Figure 10-28) and full cold (Figure 10-29). The actual passenger-side temperature depends on the general operation of the system. The passenger controls do not engage or disengage the compressor, change blower speed, or reposition the passenger mode door.

Rear Heat/Cool System Some trucks and vans may be equipped with a rear air distribution system to provide rear heating, cooling, or a combination of both. The rear air distribution system is often referred to as an auxiliary air-conditioning system (Figure 10-30). Depending on design, it may have the following major components: blower and motor, temperature door, evaporator core with metering device, heater core with flow control, outlet mode door, control panel(s), and controller. The rear auxiliary system that provides only heating or cooling does not require an outlet or temperature mode door. The heat-only control panel has a blower speed control accessible to the rear-seat passengers. The rear blower master control for the cooling-only system is generally in the front control panel. The switch in the REAR position permits the rear blower switch to select the speed of the rear blower. 320 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Overhead air Left belt line air

Heater core

Right belt line air Evaporator core Blower and motor

Diverter door Air in Left floor air

Right floor air

FIGURE 10-30  A typical rear (auxillary) heat-cool system duct.

Systems that provide both heating and cooling have an outlet mode door to direct outlet air to the upper or lower vents (Figures 10-31 and 10-32). Some systems may have a temperature door controlling outlet air temperature, while others are controlled by the front master control. The heat/cool system generally has both front and rear control panels for controlling the rear air distribution system. The control panels allow selection of the blower speed, the mode door, and in some systems the temperature door position. Because the rear system is connected in parallel to the front system, the rear controls cannot override the master controls, such as to energize or de-energize the compressor or heater control valve. The rear system can only provide cooling or heating when cooling or heating is selected in the front system. It should be noted that in some minivans rear heat/cool temperature control is determined by the driver’s temperature control setting and only offers heating or cooling to the rear compartment. This is considered a two-zone system (front driver/passenger separate zones), with

Overhead air Left belt line air

Heater core

Right belt line air Evaporator core Blower and motor

Diverter door Air in Left floor air

Right floor air FIGURE 10-31  Air diverted to upper vents.

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Overhead air Left belt line air

Heater core

Right belt line air Evaporator core Blower and motor

Diverter door Air in Left floor air

Right floor air

FIGURE 10-32  Air diverted to lower (floor) vents.

the rear compartment only able to control the fan speed in order to control the temperature. The driver must slide the temperature control past the 75 percent point toward full hot position in order for the rear compartment to be heated or past the 25 percent full cold position in order for the rear compartment to be cooled (Figure 10-33). If the midpoint on the driver’s temperature control is selected, the rear compartment will receive full heating or full cooling; depending on the last position selected by the driver, no temperature blending is available to the rear compartment. True three-zone systems have a rear HVAC duct system with full blend features, as depicted in Figures 10-30, 10-31, and 10-32. Overhead outlets Side Evaporator

Center

Recirculate air

Side Rear blower motor Mode door— only full hot or full cold positions available

Floor outlets

Heater core

FIGURE 10-33  Typical rear HVAC system on two-zone system with driver in control of temperature control.

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Case/duct Evaporator Firewall

Drain tube

Floorboard

FIGURE 10-34  An evaporator drain extends through the floorboard of a vehicle.

FIGURE 10-35  An evaporator drain hole hose extending from the bottom of a vehicle.

Evaporator Drain Moisture extracted from the air in the evaporator is readily expelled from the evaporator case through a drain tube that extends through the floorboard of the vehicle. To prevent insects from entering the evaporator through this tube, it has a molded, accordion shape (Figure 10-34). The weight of the moisture, as it collects, overcomes the rigidness of the tube closure and allows the water to pass. Over time, however, airborne debris and dust may restrict the tube to the point that causes water to back up inside the case. This is sometimes evidenced by water droplets exiting the dash outlets with the air or dripping onto the floor mats in the passenger compartment. There have even been reports of drivers getting a cold, wet right foot when making a hard right turn. If this becomes a problem, it is necessary to clean out the drain tube to ensure that it will open to allow water to pass. This is best done from under the vehicle (Figure 10-35). For obvious reasons, do not stand immediately under the tube while cleaning it.

Odor Control During the normal operation of the passenger comfort heating/ventilation/air-conditioning (HVAC) system, moisture can accumulate in the ductwork and collect on the evaporator core surface. Under normal operation, most of this moisture will drain out of the case drain, causing no problems. Air that enters the passenger compartment contains microscopic contaminants and bacteria that will stick to the moisture on the evaporator and case. During periods of high humidity or when the recirculation mode is used extensively, this becomes an ideal

HVAC stands for heating/ventilation/ air conditioning and is generally used when referring to the system as a whole.

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Shop Manual Chapter 10, page 407

environment for odor-causing mold, bacteria, and mildew to grow. When these environmental conditions arise, a musty odor develops and becomes very pronounced when the HVAC system is first turned on. The industry has developed commercially available treatments to combat this problem by chemically coating the evaporator core and duct with an antimicrobial deodorizer and disinfectant product to eradicate these contaminants. These products generally offer protection for three cooling seasons or more under normal air-conditioning use. They are applied using a siphon-type sprayer (Figure 10-36). In addition to chemically treating the HVAC system, the case drain vent must be checked to be sure that it is not plugged and will properly drain the system of excess moisture. Some manufacturers have also integrated a feature into their HVAC systems that leaves the blower motor on for a brief period of time after the air conditioner is turned off to allow the evaporator core and ducts to dry even after the vehicle has been turned off. There are also kits

2 Or, loosen blower motor at flange, and apply between motor and case.

Evaporator housing

Blower motor housing

1 Apply at seam between blower motor case and evaporator housing.

Spray antimicrobial deodorizer onto evaporator fins and tubes. SIPHON TYPE SPRAYER

FIGURE 10-36  A typical siphon-type sprayer for the application of antimicrobial deodorizer to eliminate musty odors.

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available to add this delay timer feature to other vehicles. Some manufacturers have sent out service bulletins recommending the installation of a blower delay feature on troublesome HVAC systems and have developed specific kits for specific models. General Motors calls their system Electronic Evaporator Dryer (EED), and it is not polarity sensitive, which means it may be installed on any GM vehicle without the need for a special harness. The EED pulses the blower motor in 10-second bursts, and it also incorporates an ambient temperature sensor that automatically disables the EED if the ambient temperature drops below 608F (15.568C) due to low levels of microbial growth at low temperatures. In addition, many makes and models of vehicles today offer cabin air filters to trap these microscopic contaminants and bacteria before they enter the HVAC system. The next section will discuss this topic in more detail.

Cabin Air Filters The cabin air filter is another feature of many vehicles today. It is a passenger compartment filter medium installed in the duct system to filter out pollen and dust particles, which would otherwise enter the interior of the vehicle. The introduction of the air filters in the automotive air-conditioning system of domestic vehicles has been slow. The first occurrence was found in the 1938 Nash; the next occurrence was not until more than 35 years later in Oldsmobile’s 1974 Toronado and 88. They were first introduced across major car lines in European vehicles during the mid-1980s but have since become a feature on many vehicles produced both in the United States and abroad. It is expected that the popularity of cabin filters will grow, and some estimates indicate that 85 percent of the cars and light trucks sold in the United States contain one or more cabin filters. As a vehicle travels down the road or is sitting in traffic, the air outside the vehicle (which may contain high levels of dust and pollen as well as other impurities) is drawn in through the fresh air intake system even when the blower motor is not on. The cabin filter is placed in the fresh air intake ductwork (Figure 10-37) and is designed to reduce pollens, bacteria, dust, exhaust gases, and mold spores, as well as other tiny airborne allergens that may enter a vehicle’s ventilation system. Mold spores are the main contributor to the musty, stale smell that may be emitted from the ventilation system. Most cabin air filters have the ability to remove up to 95 percent of all particles that are 3 microns or larger. There are two main filter designs used today: the particle filter and the absorption filter. The particle filter is designed to remove solid particles larger than 3 microns (less than one millionth of an inch in diameter) such as dust, pollen, soot, and mold spores. The filter element is made of a special paper or nonwoven microfiber fleece. The filter material may also be electrostatically charged to improve its efficiency. The absorption filter is designed to remove odor-causing particles and gases. It uses activated charcoal to remove these particles. Activated charcoal is a carbon substance that has been treated with oxygen to open up millions of tiny pores, which increases its surface area. As the impurities pass by the

Ventilation air filter

Shop Manual Chapter 10, page 414

Fresh air

Purified air

Recirculation air

Evaporator

Blower

FIGURE 10-37  Many vehicles have a cabin air filter.

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activated charcoal’s surface, they are attached to the charcoal surface and trapped, much like a magnet attracts and holds metal particles. Because activated charcoal attracts and holds impurities, it will eventually become saturated and require replacement. The combination filter (or two-stage filter) combines both the particle filter and the absorption filter into one assembly. The cabin air filter is part of routine maintenance and is generally changed every 15,000 miles (24,000 km), but you should refer to specific vehicle service schedules for manufacturers’ recommendations. If the filters are not serviced regularly, they will eventually cause an airflow restriction as they become clogged. The cabin air filter is generally located at the fresh air intake under the hood (Figure 10-38) or under the dash (Figure 10-39) on the passenger side of the vehicle. Consult the manufacturer’s service information for exact locations and service procedures. A clogged filter can create an air pressure drop, placing a greater demand on the blower motor and, perhaps, leading to an early failure. Because it restricts airflow, a clogged filter will also affect air-conditioning, heating, and defroster performance. Some systems that are equipped with a cabin air filter are also equipped with an airborne pollutant (air-quality) sensor (Figure 10-40). It is located in the intake air plenum chamber and is tasked with detecting pollutants in the ambient air. The sensor signal is used by the climate control module for the automatic air recirculation mode. In this mode if the sensor detects pollutants in the fresh air intake, it will automatically switch to the air recirculation mode. These systems are used in conjunction with a combination cabin air filter that combines a particle filter (dust and pollen) and activated charcoal to cleanse the air of some chemical contamination. The sensor is designed to detect oxidizable and reducible gases such as carbon monoxide and nitrous oxides and as such is not designed to detect all odor-causing agents. Once the pollution concentrations drop below a calibration threshold for the system, the fresh air mode door is opened to once again to draw fresh air from outside of the vehicle into the passenger compartment. The sensor determines the average pollutant concentrations and sends this information as a digital square-wave signal to the climate control module (Figure 10-41). During initial system activation phase, when automatic mode is first turned on, the sensor takes approximately 30 seconds to initialize. The climate control module uses this information to determine when and for how long it should select the recirculation mode. The control module only selects recirculation mode during peak pollution levels and only for a set period of time depending

Glove compartment

FIGURE 10-38  Typical location of an under-hood cabin air filter.

FIGURE 10-39  Typical location of an under-dash cabin air filter.

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Combination filter

Air quality sensor

SO2 NOx CS2

H2S C6H14

Airborne pollutants

Signal to operating and display unit

CO C6H6

FIGURE 10-40  Some automatic temperature control systems are equipped with and airborne pollutant sensor in the fresh air intake plenum and are used to automatically activate the recirculation mode.

Air quality sensor

Air conditioner control unit

M Positioning motor for air recirculation mode Ambient temperature

Air pollution level

Air recirculation

> +2˚C

Low rise

Yes min. 25 sec.

> +2˚C

Low

No

+2˚C - –5˚C

Higher rise

Yes

< –5˚C

Higher rise

max.15 sec.

ECON mode compressor off

max.15 sec.

Defrost mode

No

Warm-up phase of sensor appox. 30 sec.

No

FIGURE 10-41  The airborne pollutant (air quality) sensor sends a digital square- wave signal to the climate control (air conditioning) module if airborne pollutants are detected.

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on ambient air temperature and air pollution levels. The system will not remain in the recirculation mode for extended periods of time in heavily polluted areas. This automatic function is not available in all mode ranges, such as defrost mode or during the warm-up phase of the sensor, or in manual mode. Many systems will also switch to the recirculation mode when the wash/wipe system is activated to clear the windshield. The sensor is a mixed oxide sensor (oxide mixed with tin or tungsten) utilizing semiconductor technology with platinum and palladium as a catalyst and an operating temperature of 6628F (3508C), but with a very low power consumption of 0.5 watts. The material in the mixed oxide sensor changes its electrical properties (resistance) when it comes in contact with reducible or oxidizable gases (Figure 10-42). From an internal operational standpoint, if the internal resistance of the sensor rises, oxidizable gases are present, and if the resistance falls, reducible gases are present. Because of the nature of the chemical and physical properties of a mixed oxide sensor it is able to detect both gases simultaneously. The system is automatically calibrating and self-learning and if the sensor fails, the automatic recirculation mode is no longer available and a trouble fault code is set.

Measuring pollution in oxidisable gases

Properties of oxidisable gases

Oxide mixed with tin

Sensor electronics

Sensor electronics

CO Oxidation

CO2

Oxygen Tin

Oxygen Oxidisable gas

Carbon

Measuring pollution in reducible gases

Properties of reducible gases

Oxide mixed with tin

Sensor electronics

Sensor electronics

H2O Reduction

N2O2

Oxygen

Oxygen

Tin

Reducible gas Nitrogen FIGURE 10-42  The airborne pollutants (air quality) is a mixed oxide sensor that changes its electrical properties (resistance) when it comes in contact with reducible or oxisable gases.

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The Air Door Control System The air door control system uses vacuum-operated or electrically powered motors to position the air doors, also referred to as mode doors, to provide the desired in-vehicle air delivery conditions. These generally include OFF, MAX, VENT, BI-LEVEL, HTR, BLEND, and DEF. The airflow pattern for each of these conditions is given in Chapter 8 of the Classroom Manual. There are basically three types of control systems: vacuum, rotary vacuum, and vacuum solenoid and electric motor.

Vacuum Control

In the vacuum control system, vacuum actuators, also called vacuum motors, are used to position the air doors and valves. This system relies on a vacuum signal from either the engine manifold or an onboard vacuum pump. Vacuum is applied to the selected actuator by a rotary vacuum valve (RVV) or a vacuum solenoid in the main control panel.

Rotary Vacuum Valve

When a rotary vacuum valve system (Figure 10-43) is used to control air doors and valves, the master control head selector rotates a vacuum switch that aligns the vacuum passages in the valve to direct a vacuum signal to the appropriate vacuum actuator(s) for the mode selected.

A/C OFF

Vacuum source

HOT

COLD

2 1

3 45

6 7

2 1

34

5 6 7

Defroster valve actuator Heater outlet

Defrost outlets

45 2 3 6 7 1

2 1

34

Heater core

A/C outlets

A/C evaporator core

56

7

2 1

3 45

6 7

Outside air inlet Air inlet valve actuator

Recirculation air inlet

FIGURE 10-43  Typical rotary vacuum valve system.

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Vacuum Solenoids

When vacuum solenoids (Figure 10-44) are used to control doors and valves, the master control head selector contains electrical circuits that provide a ground path for the selected vacuum solenoid. The selected (energized) solenoid allows vacuum to be applied to the selected actuator. An automatic air distribution system often uses vacuum solenoids that are located inside the programmer to control the position of the mode doors. The programmer controls the electrical ground side of the solenoids to establish a ground path to the selected vacuum solenoid. When the ground path is removed, the vacuum actuator is allowed to vent.

Electric Actuator Motors

Many vehicles today use electric actuator motors to control air distribution mode doors and temperature blend doors. Electric actuators may be used alone or in combination with cable or vacuum control, with some doors operated by electric actuators and others controlled by cables. There are several types in use as electric mode door actuators. The two-position type either fully opens or fully closes a mode door; the fresh air/recirculation door is often this type. Another type is the variable-position actuator, which can position the mode door at any point from fully open to fully closed; temperature blend doors are typically of this design. The manual control head (HVAC dash control assembly) on many of these systems does not directly control the actuators. The manual control head is instead wired to the body control module (BCM) or a separate HVAC control module that is connected to the actuators

Vacuum source

VENT BI-LEVEL HTR NORM BLEND MAX OFF DEF

VENT HTR BLEND DEF

Defrost solenoid

BI-LEVEL NORM MAX OFF

VENT HTR BLEND DEF

BI-LEVEL NORM MAX OFF

A/C solenoid

Heater solenoid

VENT HTR BLEND DEF

BI-LEVEL NORM MAX OFF

VENT BI-LEVEL HTR NORM BLEND MAX DEF OFF

Bi-level solenoid

Recirculation solenoid

Hot in run

Defroster valve actuator

A/C valve actuator Bi-level valve actuator

Heater outlet

Defrost outlets

Heater core

A/C outlets

Outside air inlet

A/C evaporator core

Air inlet valve actuator

Recirculation air inlet

FIGURE 10-44  A typical vacuum solenoid control.

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and controls their position in response to inputs from the control head. Many of these systems use a multiplexed switch in the control head to control air distribution mode door position, meaning they only use one wire to communicate to the control module by using a different resistance value in the switch for each function. The control module interprets this information by dropping a voltage through the circuit (Figure 10-45). Most temperature selectors use a potentiometer to command the temperature blend door. Mode door actuators all perform the same function. They position the mode doors based on driver input to the control head assembly. Electric mode door actuators may be five-wire, three-wire, or two-wire controlled. Both the two-wire and the five-wire actuators (Figure 10-46) generally use a driver circuit in the control module to control their movement. The control module will supply 12 volts to one driver circuit and ground the other driver circuit, thus giving bidirectional control depending on the polarity of the two wires to move the motor in one direction or the other. Which driver is negative and which is positive controls the rotational direction of the motor. When both sides of the actuator motor are power or ground, the motor stops (it is electrically balanced). The control module determines door position through feedback circuits. On the two-wire actuator, the control module counts the actuator commutator pulses to determine door position. On the five-wire actuator, the control module determines mode door position through the potentiometer feedback voltage signal, which is built into the actuator assemblies. The three-wire actuator (Figure 10-47) generally has an external 12-volt supply and ground. Control of the actuator is through a logic module built in to the actuator—in essence, a smart motor. The three-wire actuators are

Shop Manual Chapter 10, page 415

HVAC dash control head assembly Temperature control

20A ign. fuse

Temperature selection signal HVAC control module (or BCM)

Ground for sensors

A/C

Mode switch signal 0–5 volt signal

Mode selection

FIGURE 10-45  A typical wiring schematic for a multiplexed HVAC control system.

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Actuator motor Driver

Common driver Control module

Five-wire actuator

5V ref. Signal Ground

Actuator motor Driver

Two-wire actuator

Control module Driver

FIGURE 10-46  Typical wiring diagrams for both five-wire and two-wire bidirectional mode door actuators.

Ignition

Position

Hot Cold

Ground Logic Control head Actuator FIGURE 10-47  Typical mode door motor schematic for a three-wire actuator motor.

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self-calibrated. Remember when checking a three-wire actuator that the 12-volt power and ground circuits are constants, and the input line from the control head is the position control (command) circuit. Electric mode door actuators are not adjustable and must be replaced if faulty. It is also necessary to initialize a calibration procedure in order for the control module to relearn mode door position if the actuator or control module is replaced or otherwise loses its memory. Consult the manufacturer’s service information for exact procedures on recalibrating the systems.

Control System Faults An inoperative vacuum motor could be due to a loss of vacuum signal at the appropriate time. This could be the fault of the vacuum source, vacuum switch, check valve, reserve tank, hose, restrictor, or vacuum motor. To determine the cause, disconnect the suspected vacuum motor (Figure 10-48) and substitute another vacuum source, such as the vacuum pump. If the motor is inoperative, it should be replaced. If it is operative, check further for the source of the problem. If an inoperative fresh air door or mode door is the problem, a fault in the vacuum control system is again indicated. Most older systems use vacuum motors with a vacuum selector valve at the control head to control the operation of these doors. Some vehicles have vacuum motors controlled by electric solenoids, whereas others use electric motors at the doors. There are also systems in which all the mode doors have electric motor control (Figures 10-46 and 10-47). Generally, a vacuum system problem can be traced to a cut, kinked, crimped, or disconnected vacuum hose. A faulty selector valve, vacuum actuator, storage tank, or check valve may also be the problem. In an electric solenoid or electric motor system, an electrical system defect may be responsible for improper mode door operation. Because these systems function electrically, it is wise to consult the appropriate manufacturer’s service manual for specific troubleshooting procedures. One must be extremely careful when troubleshooting electrical systems under the dash. Just one improper test point could cause serious damage to one of the onboard computers. The area under the dash is cramped and congested—filled with wires, vacuum hoses, and ducts, as well as various electrical and mechanical components and assemblies. It is not, therefore, easy to gain access to any of the components, especially those associated with the vacuum control system. The control panel on many vehicles, however, may be pulled out far

FIGURE 10-48  A typical vacuum motor.

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enough from the dash to gain access. Extreme caution must be exercised when gaining access to any under-dash component. Failure to do so could trigger the air bag restraint system.

Visual Inspection When addressing a customer complaint for poor or insufficient heating or cooling, the first step is to make a visual inspection. The following should be included in the inspection: ■■ Is the case and ductwork sound? Check for cracks or broken or disconnected ducts. ■■ Are the vacuum hoses sound? Check for disconnected, split, damaged, or kinked vacuum hoses. ■■ Is the airflow restricted? Check to ensure that mode doors are opening. Check for leaves or other debris that may block airflow, such as at the fresh air inlet screen located at the base of the windshield. Is the cabin filter clean, if so equipped? ■■ Are the cables secure? Check for loose, broken, or binding mode door control cables. Author’s Note: When checking electric actuator circuits, use only highimpedance multimeters. Never use a test light that could overload the circuits in the microprocessor. Always follow the manufacturer’s recommended diagnostic procedures.

Mode Door Adjustment A BIT OF HISTORY No company has an exclusive patent on HFC-134a, and the industry-wide availability of it allowed for the rapid introduction of R-134a as the industry replacement for R-12, which began in 1992.

A cable or vacuum actuator is used to position one or more of the mode doors in the duct system. The cable-operated system (Figure 10-49) consists of a steel cable encased in a plastic, nylon, or steel housing. It is used to connect the mode door to the control panel. Adjustments are made on the mode door end of the cable by repositioning the cable housing in its mounting bracket. The cable is usually held in place with a clip or a retainer secured in place with a hex-head screw. The only adjustment possible for a vacuum actuator (Figure 10-50) is in the linkage, if there are adjustment provisions. If the problem proves to be a defective vacuum motor, however, it must be replaced. First, ensure that there is a vacuum signal at the vacuum motor indicating that the vacuum system is sound. More information on troubleshooting and servicing of the vacuum-operated and electrically operated actuators can be found in Chapter 11 of this manual as well as in Chapters 10 and 11 of the Shop Manual.

Defrost actuator Cable housing

Air outlet changeover door lever

Retaining clip

FIGURE 10-49  A typical cable-operated mode door.

Register actuator

Plenum

Floor actuator FIGURE 10-50  A typical vacuum-operated mode door.

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SUMMARY ■■

■■ ■■ ■■

Terms to Know

There are many variations of mode and blend door positions, as well as many case/duct system designs. Doors may be electric, vacuum, or cable operated. Some doors are either fully opened or fully closed; others are infinitely variable. Because of the many different applications and methods of control (Figures 10-51 and 10-52), it is necessary to consult a particular manufacturer’s manual for specifications and testing procedures.

Fresh air Defrost

Dash panel outlet

Foot ducts Foot well outlet

Defroster door

Defroster ducts

Side

Foot door

Heater core Evaporator

Ventilator door

Ventilator ducts Center

Air mix door

Automatic Temperature Control (ATC) Bi-level Blend door Bowden cable Defrost Heating/ventilation/air conditioning (HVAC) MIX Mode Mode doors Plenum Recirculate Semiautomatic temperature control (SATC) Vent

Blower motor

Intake doors

Side

FIGURE 10-51  One type of case and duct system. Compare with Figure 10-52.

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Ventilator ducts Side

Defroster ducts Fresh air

Outlet doors

Inlet door

Center Recirculate air

Blower motor

Air mix door

Side Evaporator

Heater core

Foot ducts FIGURE 10-52  Another type of case/duct system. Compare with Figure 10-51.

REVIEW QUESTIONS Short-Answer Essays

Fill in the Blanks

1. What is one of the two purposes of the case/duct system?

1. Mode doors may be _______________, cable, or _______________ operated.

2. Why do some case and duct systems develop a musty odor?

2. The MIX selection on some models is basically the same as the _______________ selection on other models.

3. Where is the air taken from that is to be “conditioned” for MAX cooling? 4. What is the purpose of maintaining a slightly positive pressure in the vehicle’s interior? 5. Explain how the programmer controls the movement of the electronic actuated blend door. 6. How are pollen and dust particles stopped from entering the passenger compartment? 7. Where is air directed in the distribution section? 8. Describe the airflow through the case/duct system when DEFROST is selected. 9. How does the blend door create the desired in-vehicle temperature and how is the air tempered to maintain a desired humidity? 10. Define the term bi-level.

3. Some systems that are equipped with a cabin air filter are also equipped with an _______________ airborne _______________ sensor. 4. A small amount of conditioned air may be directed to the _______________ outlets to prevent windshield _______________. 5. The compressor may operate in the heat mode to help maintain in-vehicle _______________. 6. Cooled air is generally delivered into the passenger compartment through the _______________ vents. 7. Heated air is generally delivered into the passenger compartment through the _______________. 8. The _______________ duct system found in some cars has a separate driver- and passenger-side _______________ system.

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9. There are two types of blower system: an upstream blower and a _______________. 10. The case system provides a _______________ for the components, whereas the duct system provides a for the airflow.

Multiple Choice 1. A vehicle is brought into the shop with a complaint of weak airflow from all the dash vents. Which of the following is the most likely cause? A. A blend door stuck in the heat position B. The recirculation mode door stuck in the recirculation position C. A dirty cabin air filter D. A mode door stuck in the floor vent position 2. The rear evaporator duct is cooling properly on a vehicle with a rear heating and cooling system, but the front evaporator duct temperature is too warm. What is the most likely cause of this condition? A. An undercharged refrigerant system B. A misadjusted front blend door C. An overcharged refrigerant system D. A stuck open rear thermal expansion valve 3. When the air-conditioning system is first turned on, a musty odor comes from the vents. What is the most likely cause for this? A. An undercharged refrigerant system B. A misadjusted front blend door C. Mold formation on the evaporator core D. Ice formation on the evaporator core 4. The following statements about a typical system set to MAX cooling are true, except: A. The compressor clutch is engaged. B. The blower motor is running. C. The outside/recirculate door is in recirculate position. D. Return air is from vehicle exterior.

6. In the MIX/BILEVEL position, conditioned air is delivered to the _______________ outlet. A. Panel C. Floor B. Defrost D. Both B and C 7. An inoperative vacuum motor could be caused by all of the following, except: A. Defective vacuum switch B. Kinked vacuum hose C. Mode door cable misadjustment D. Leaking vacuum reserve tank 8. The airflow path in the case/duct system illustrated in Figure 10-52 is being discussed: Technician A says that airflow is also through the heater core in the cooling mode. Technician B says that airflow is also through the evaporator in the heating mode. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 9. Technician A says that up to 20 percent of fresh air provides a means to maintain a positive in-vehicle pressure when the windows are closed. Technician B says this positive pressure is necessary to provide a proper balance of air pressure within the air delivery system. Who is correct? A. A only C. B only B. Both A and B D. Neither A nor B 10. In the case and duct system the air distribution mode doors may be operated by all of the following except: A. Vacuum motors B. Cable C. Electrically powered motors D. Potentiometers

5. During normal air-conditioning system operation, the position of the system mode doors: A. Is fully opened. B. Is fully closed. C. Is partially opened (or closed). D. Depends on the mode selected.

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Chapter 11

System Controls

Upon Completion and Review of this Chapter, you should be able to: ■■

■■

■■

■■

■■

■■

■■

Understand the requirements of fuses and circuit breakers for electrical circuit protection.

■■

Understand the role of the manual master control assembly in a HVAC system.

■■

Discuss the operation and function of the temperature control thermostat.

■■

Explain the role of the low- and high-pressure cutoff switches.

■■

Compare the function of gauges versus lamps for engine coolant temperature.

■■

Discuss vacuum control devices and understand their function as well as vacuum system diagrams. Discuss and compare the differences of automatic temperature control systems that use various pressureand temperature-actuated controllers and recognize the components.

A fuse is an electrical device used to protect a circuit against accidental overload or unit malfunction. A circuit breaker is a bimetallic electrical device used to protect a circuit against accidental overload or unit malfunction. It automatically resets once it cools down.

■■

Explain the operation and role of refrigerant pressure sensors. Discuss the operation of various climate control system input sensors. Discuss the role of the automotive scan tool in adding in the diagnosis of HVAC system failures. Discuss the various body and network codes associated with the operation of the HVAC system. Describe the operation of the Controller Area Network (CAN) protocol and climate control local area network (LAN) systems. Discuss the operation and role of heated and climate controlled seats (CCS).

Introduction The automotive air-conditioning control system can be as simple as that found in aftermarket installations or as complex as that found in computer-controlled automatic factory-installed systems. The simple system usually consists of a master on/off switch, blower control, thermostat, blower motor, clutch coil, and fuse or circuit breaker. Note in the schematic (Figure 11-1) that only one wire is shown from the battery. The other side of the battery, as well as the blower motor and clutch coil, terminate to ground. The vehicle chassis, body, and all metal parts are common (ground) in 12-volt, direct-current (DC) automotive electrical systems. A separate ground wire circuit is not required unless the car has fiberglass or other nonconducting body components. An electrical symbol (Figure 11-2) is used to indicate a ground connection. Examples of other wiring diagram symbols are shown in Figure 11-3. The schematic for a factory-installed heater/air-conditioner control system is more ­complex (Figure 11-4). Actually, the schematic in this illustration has been condensed so that

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B+ Main fuse 100A Heater 40A

Ign fuse 40A

IP Fuse Panel

A/C switch

Ignition switch Blower motor relay

To ECM Blower motor

2 34 1 Off

Blower switch

FIGURE 11-1  A typical air-conditioner/heater system schematic.

FIGURE 11-2  Electrical symbols used to identify a ground connection.

it can be shown on one page. Many schematics of factory-installed heater/air-conditioning systems require several pages in the shop service manual for illustration. The air-conditioning and heater electrical systems are integral and often share fuses or circuit breakers. The blower motor serves both the heater and air conditioner in factoryinstalled systems. Electrical circuits associated with the heating and cooling system, such as those used to warn of engine overheating conditions, may also be a part of the electrical system schematic.

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SYMBOLS USED IN WIRING DIAGRAMS Positive Negative

Diode

Ground

Zener diode

Fuse

Motor

Circuit breaker

C101

Connector 101

Condenser

Male connector

Ohm

Female connector

Fixed value resistor

Splice

Variable resistor

S101

Splice number

Series resistors

Thermal element

Coil

Multiple connectors

Open contacts

Digital readout

Closed contacts

Single filament bulb

Closed switch

Dual filament bulb

Open switch

Light emitting diode

Ganged switch (N.O.)

P

Temperature switch

T

T

Thermistor

Single-pole double-throw switch

PNP bi-polar transistor

Momentary contact switch

NPN bi-polar transistor

Pressure switch

Gauge

Battery

Wire Crossing FIGURE 11-3  Typical schematic symbols.

Manual Master Control The master control is the primary or main control. A rheostat is a wirewound variable resistor with one input and one output wire. A multiwound motor is also referred to as a tapped motor.

The manual master control (Figure 11-5) generally includes the blower speed control provisions. The variable (infinite) speed control, also known as a rheostat (Figure 11-6), is generally found on aftermarket systems. Also used are four- or five-position blower speed controls. The four-speed five-position control (Figure 11-7) has three resistors to provide selected blower motor speed. The first position is OFF. The second position, LOW, supplies current to the motor through all three resistors. This provides maximum reduced voltage for low-speed operation. The next position, (M1), supplies current to the motor through two resistors to provide medium-low speed. Current is supplied to the motor through one resistor in the fourth position, (M2), to provide medium-high blower speed. The fifth position, HIGH, supplies full battery voltage to the motor to provide high-speed operation of the blower. Some multiposition blower speed control switches (Figure 11-8) do not have resistors. These switches provide full battery voltage to either of several windings in the motor. The blower motor speed control may be a part of the master ON/OFF control ­(Figure 11-9). The blower switch, in either ON position, provides full battery voltage to the control ­thermostat. In this arrangement, the compressor clutch does not engage unless the blower motor is running.

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Fusible link

Ignition switch

25A Blower motor relay

25A

OFF

ICA 13A

ON

Cooling fan motor

Dual pressure control

M

ON OFF

Blower speed resistor

Blower motor

M

LO OFF

ML

MH

ON OFF

Cooling fan motor relay

HI

OFF LO

ML

Clutch relay

HI MH

Blower switch

Engine control module

OFF

Clutch coil

A/C ECO

A/C Switch

A/C control unit

Air inlet sensor

Air thermo sensor

FIGURE 11-4  A typical climate control system electrical diagram.

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Rheostat OFF REAR COLD

HOT

Heater control

A/C

FIGURE 11-6  A rheostat is a two-wire variable resistor with no feedback signal wire, common on dashlight dimmer circuits.

OFF REAR COLD

HOT

Manual A/C control FIGURE 11-5  Typical master controls.

B+

Hot in run

IP Fuse Panel HVAC 20A

Junction block

Mode selector

LO M1

Evaporator pressure control switch

M2

Blower switch

Blower motor

HI

Blower motor relay

A/C clutch

FIGURE 11-7  Wiring diagram for typical multispaced blower motor.

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Hot in run

Fuse block

Climate Control Panel (CCP)

Fuse 7 25 A

solid state Do not measure resistance

Outside temp

Data input/ output

Off

Econ

Cooler

Warmer

Lo

Hi

Auto

5V

5V Data input/ output

Fusible link

B+

Blower feedback

Body Computer Module (BCM) solid state Do not measure resistance

Electronic Climate Control (ECC) solid state power module Do not measure resistance

Blower motor FIGURE 11-8  Wiring schematic showing a pulse width modulated motor control circuit and feedback circuit to the BCM.

FIGURE 11-9  A master control panel.

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Shop Manual Chapter 11, page 448

Some thermostat capillary tubes are inserted into a well provided in the suction line immediately after the evaporator. The capillary tube is often filled with the same fluid used in the system, either R-12 or R-134a.

Thermostat An electromagnetic clutch is used on the compressor of all automotive air-conditioning systems to turn it on when cooling is desired and off when cooling is not desired. The clutch is often used to provide a means of in-vehicle temperature control. One way to accomplish this is to control the compressor operation with a temperature-sensitive switch known as a thermostat (Figure 11-10). Another method, control with a pressure-sensitive switch, is covered later in this chapter. The thermostat may be located in the evaporator, where it senses the temperature of the air being delivered into the vehicle, or it may be mounted in such a manner that its remote bulb is immersed into a well in the outlet tube (suction line) of the evaporator (Figure 11-11). The thermostat cycles the clutch on-off at the selected setting. This in turn controls the average in-vehicle temperature. The thermostat senses the temperature of the evaporator core air or of the vapor leaving the evaporator. A temperature above that selected closes the thermostat contacts to provide current to the clutch coil. The clutch is energized and the compressor operates. A temperature

Warmer

Cooler

FIGURE 11-10  Typical thermostat adjustment.

Thermostat

H-valve To Evaporator Liquid line

Suction line

Capillary tube Well FIGURE 11-11  A typical thermostat location on an H-valve.

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Accumulator Pivoting frame

To clutch coil

Bellows

Insulator

Capillary tube From master control

Cold control

Remote bulb

FIGURE 11-12  Thermostat capillary tube shown with points open.

at or below that selected opens the thermostat switch to interrupt current to the clutch coil. The clutch then de-energizes and compressor operation stops. Thermostats generally have an OFF position so that the clutch can be turned off regardless of the temperature. In this way, the blower motor can be operated without a refrigerating effect.

Thermostat Construction

A capillary tube connected to the thermostat is filled with a temperature-sensitive fluid or vapor. The capillary is attached to a bellows within the thermostat (Figure 11-12). This bellows, in turn, is attached to a swinging frame assembly. Two electrical contact points are provided. One contact is fastened to the swinging frame through an insulator, and the other electrical contact is fastened to the body of the unit, again through an insulator.

Thermostat Operation

As the inert gas in the capillary tube expands, a pressure is exerted on the bellows. The bellows, in turn, closes the electrical contacts (Figure 11-13). The temperature selection is provided by a cam that is connected to the swinging frame via a shaft to an external control knob. When the knob is turned clockwise, the spring tension is increased against the bellows. If more pressure is required to overcome the increased spring tension, more heat is necessary. Because it is heat that is being removed from the evaporator, a lower temperature is required to open the points. On a temperature rise, the heat again exerts pressure on the bellows to close the points and allow for cooling. A second spring in the thermostat regulates the temperature interval that the points are open. This interval usually represents a temperature rise (delta T or ∆T) of 128F (6.68C), providing sufficient time for the evaporator to defrost.

A bellows is an accordion-type chamber that expands and contracts as its interior pressure is increased or decreased to create a mechanical action, such as in a thermostatic expansion valve. An insulator is a nonconductive material, such as the covering on electrical wire.

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Clutch Points

Battery

Pivoting frame Bellows Insulator

Capillary

Fuse Cold control Motor

Remote bulb

Switch FIGURE 11-13  Thermostat operation: points closed.

Thermostat Installation and Handling

As with any device containing a capillary tube, care must be exercised when handling a thermostat. There should be no sharp bends or kinks in the capillary. When a bend must be made, it should be no sharper than can be formed around the end of a thumb. For best results, the end of the capillary tube should be inserted into the evaporator core between the fins to a depth of about 1 in. (25.4 mm). The capillary should not be inserted all the way through the fins because it may interfere with the blowers, which are often mounted behind the core. If a remote bulb prevents insertion, the remote bulb should be fastened against the evaporator core (Figure 11-14). If the capillary is damaged and has lost its charge of inert gas for any reason, the t­ hermostat must be replaced. When there is no fluid in the capillary, the unit has no ON cycle. The ­capillary cannot be recharged using standard equipment. Many thermostats are adjustable.

FIGURE 11-14  Thermostat remote bulb inserted into the evaporator core.

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Pressure Cutoff Switch Some systems have a low- and high-pressure cutoff switch as part of the clutch circuit. These switches, which are normally closed (nc), are sensitive to system pressure and open in the event of abnormally low or high pressure. This in turn interrupts electrical current to the clutch coil to stop the compressor. The low pressure switch serves two purposes on some systems: temperature control and system protection. Some pressure switches (Figure 11-15) can be replaced without having to remove the refrigerant from the system. Others, however, require that the refrigerant be recovered before the old switch can be removed. Those that do not require refrigerant removal have a valve depressor located inside the threaded end of the pressure switch (Figure 11-16). This pin presses on the Schrader-type valve stem as the switch is screwed on and allows system pressure to be expressed on the switch.

Cycling pressure switch

Accumulator Schrader type valve

Shop Manual Chapter 11, page 455

The clutch-cycling low-pressure switch is often found on the accumulator. A pressure cycling switch may open (close) on low or high pressure depending on application.

Electrical connector FIGURE 11-15  Some pressure switches can be replaced without removing the refrigerant.

FIGURE 11-16  A valve depressor located inside the threaded portion of the pressure switch.

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Low-Pressure Switch

A pressure switch is an electrical switch that is actuated by a predetermined low or high pressure. A pressure switch is generally used for system protection.

Many cycling clutch orifice tube systems and fixed orifice tube cycling clutch systems use a pressure switch instead of a thermostat. The pressure cycling switch, which is mounted on the accumulator, senses low-side pressure to cycle the clutch off at about 24226 psig (1652179 kPa) and cuts back in at about 40242 psig (2762290 kPa). These pressures correspond to temperatures of 248F2278F (24.48C222.88C) and 438F2458F (6.18C27.28C), respectively, for R-12. They correspond to 27.58F2308F (22.58C221.18C) and 458F2478F (7.28C28.38C), respectively, for R-134a. This maintains a cold evaporator while controlling for freeze-up. The pressure–temperature relationships for R-12 and R-134a in the evaporating range is given in Figure 11-17. The low-pressure cutoff switch (Figure 11-18) may be found in the system anywhere between the evaporator inlet and the compressor inlet. In the event of an abnormally low ­pressure of 8–10 psig (55.2–68.9 kPa), the switch will open to stop the compressor. This

PRESSURE

TEMPERATURE ˚F 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

˚C –6.7 –6.1 –5.6 –5.0 –4.4 –3.9 –3.3 –2.8 –2.2 –1.7 –1.1 –0.6 0.0 0.6 1.1 1.7 2.2 2.8 3.3 3.9 4.4 5.0 5.6 6.1 6.7 7.2 7.8 8.3 8.9 9.4 10.0

CFC-12 psig 21.0 21.7 22.4 23.2 23.9 24.6 25.4 26.1 26.9 27.7 28.4 29.2 30.1 30.9 31.7 32.6 33.4 34.3 35.2 36.1 37.0 37.9 38.8 39.8 40.7 41.7 42.6 43.6 44.6 45.7 46.7

kPa 144.8 149.6 154.4 160.0 164.8 169.6 175.1 180.0 185.5 191.0 195.8 201.3 207.5 213.1 218.6 224.8 230.3 236.5 242.7 248.9 255.1 261.3 267.5 274.4 280.6 287.5 293.7 300.6 307.5 315.1 322.0

HFC-134a psig 18.4 19.2 19.9 20.6 21.4 22.0 22.9 23.7 24.5 25.3 26.1 26.9 27.8 28.7 29.5 30.4 31.3 32.2 33.2 34.1 35.1 36.0 37.0 38.0 39.0 40.1 41.1 42.2 43.3 44.4 45.5

kPa 126.9 132.4 137.2 142.0 147.6 151.7 157.9 163.4 168.9 174.4 180.0 185.5 191.7 197.9 203.4 209.6 215.8 220.0 228.9 235.1 242.0 248.2 255.1 262.0 268.9 276.5 283.4 291.0 298.6 306.1 313.7

FIGURE 11-17  Low-side pressure–temperature chart for R-12 and R-134a, English and metric.

348 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

A

B

FIGURE 11-18  Low-pressure cutoff switch: (A) male thread; and (B) female thread.

prevents further reduction of system pressure to protect the system from the possible entrance of air or moisture, as would be the case with a low-side leak.

High-Pressure Switch

The high-pressure cutoff switch is found on some General Motors, Chrysler, and Subaru car lines. This switch is found in the system anywhere between the compressor outlet and the condenser inlet. In the case of an abnormally high pressure of 300–500 psig (2,068.5–3,447.5 kPa), the switch will open, stopping compressor action. This prevents system damage or ­rupture that may be caused by a further increase in pressure. The high-pressure switch is normally closed (nc) and opens if the air-conditioning system pressure exceeds 425–435 psig (2,930–2,953 kPa). It closes when the system pressure drops to below 200 psig (1,379 kPa). This switch provides for system safety if, for any reason, pressures exceed safe limits. Unlike the low-pressure switch, the high-pressure switch does not provide data to the microprocessor. This switch is usually in series with the compressor clutch circuit.

Compressor Discharge Pressure Switch

Many factory systems use a compressor discharge pressure switch to disengage the c­ompressor clutch electrical circuit if the refrigerant charge in the system is not adequate enough to provide sufficient circulation. The compressor discharge pressure switch is also called a no-charge switch, ambient low-temperature switch, or a low-pressure cutoff switch. The switch is designed to open electrically to shut off the compressor when high-side system pressure drops below 37 psig (255 kPa). This switch also performs the secondary function of an outside ambient air temperature sensor. When outside ambient air temperature falls below 408F (4.48C), the reduced corresponding refrigerant pressure, 36.9 psig (254.4 kPa), keeps the switch open. The compressor discharge pressure switch (Figure 11-19), which is located in the compressor housing or the high-pressure discharge line from the compressor or receiver-drier, cannot be repaired. If it fails in service, it must be replaced with a new unit. Its function is to protect the compressor. That function should not be defeated, such as by bypassing it with a jumper wire.

Conditions such as a defective condenser fan motor may cause excessive high-side pressure.

The compressor discharge pressure switch is actually a low-pressure switch.

Factory-Installed Wiring The electrical schematic illustrated earlier in Figure 11-4 is typical of any of the hundreds that illustrate the wiring of factory-installed air-conditioning (cooling and heating) systems. When servicing a particular system, it is necessary to consult the appropriate service manual for specific information and schematic details. As previously discussed, it must be noted that various 349 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 11-19  A compressor discharge pressure switch.

methods of temperature control are used: thermostat, pressure control, variable ­displacement compressor, and blend air (warm and cool).

Coolant Temperature Warning System Shop Manual Chapter 11, page 456

When operating, the automotive air-conditioning system places a high demand and an additional heat load on the engine cooling system. The condenser is located upstream (in front) of the radiator. Air intended to remove heat from the engine coolant in the radiator first passes through the condenser. A malfunctioning air conditioner will often affect engine coolant temperature. Conversely, an overheated engine will affect air-conditioning performance. To monitor the engine coolant condition, a dash light or a dash gauge (Figure 11-20) is used. Either type has a sending unit located in the engine coolant system.

Most telltale lamp systems have one lamp: HOT. The telltale lamp is often referred to as an “idiot light.”

Lamps

There are two types of engine coolant lamp systems: the one-lamp system and the two-lamp system. The one-lamp system (Figure 11-21) warns that the engine has overheated and that immediate attention is required.

FIGURE 11-20  A typical engine coolant temperature gauge.

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Lamp

Fuse 12V Sending unit FIGURE 11-21  A one-lamp coolant warming system.

The two-lamp system has one lamp to indicate cold and another lamp to indicate hot. In the two-lamp system, the cold switch is closed until the engine coolant temperature reaches its normal operating temperature, usually about 1808F (82.28C). In both the one- and two-lamp systems, the hot contacts of the sending unit close when engine coolant temperature reaches about 2508F (121.18C). The actual temperature at which this switch closes depends upon the engine design. The main disadvantage of the telltale light system is obvious: the hot lamp generally is not illuminated until after there is a problem. This is probably why the telltale light is sometimes referred to as an “idiot light.”

Gauges

T/GA

The coolant temperature gauge system (Figure 11-22) consists of two parts: the dash (gauge) unit and the engine (sending) unit. The sending unit contains a sintered material known as a thermistor. A thermistor changes resistance in relation to its temperature.

C-11

79

Y-L C-110

8

(F)Y-L 1

FIGURE 11-22  Engine coolant temperature gauge schematic.

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The higher the temperature of a thermistor, the lower its resistance. Negative refers to any pressure less than atmospheric; positive refers to any pressure above atmospheric.

Delta P (∆p) is a term used when referring to a difference in pressure. Atmospheric pressure is reduced by about 0.4912 psia (3.3868 kPa) per 1,000 ft. (304.8 m) of elevation.

This material, which is sealed in a metal bulb, is screwed into a coolant passage of the engine. It has a high resistance when cold and a low resistance when hot. The varying resistance of the sending unit regulates the amount of current passing through the coil of the dash gauge and moves the pointer accordingly.

Control Devices Many controls used in automotive air-conditioning systems are either negative (vacuum) or positive (pressure) actuated. Others are mechanically, electrically, or electronically actuated.

Vacuum Circuits

To understand vacuum circuits, it is first essential that the term vacuum be defined and understood. Vacuum is defined as a space that is devoid of matter. Because all things contain matter in some form, it would seem that there is no such thing as a vacuum. For all practical purposes, therefore, a vacuum is better thought of as a portion of space that is partially devoid of matter. For a clearer understanding, consider that a vacuum is a space in which pressure is below atmospheric pressure. A good example of a vacuum is demonstrated by a person drinking through a straw (Figure 11-23). As the person sucks on the straw, a slight vacuum is created in the straw. Atmospheric pressure, which is greater than the vacuum pressure, is exerted against the surface of the liquid. This difference in pressure, known as delta P (∆p), forces the liquid up the straw. Atmospheric Pressure.  Atmospheric pressure at sea level is 14.696 psia (101.328 kPa ­absolute). For all practical purposes, this value is usually rounded off to 14.7 psia (101.4 kPa absolute) or 15 psia (103.4 kPa absolute). At sea level, then, a pressure of 14 psia (96.5 kPa absolute) is a vacuum. Traditionally, English system vacuum pressure values are given in inches of mercury (in. Hg).

A

B

FIGURE 11-23  A person drinking through a straw: (A) vacuum pressure; and (B) atmospheric pressure.

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Vacuum Terms.  Most automotive manufacturers’ manuals give vacuum value ­requirements and specifications using the term inches only. In this manual, references to vacuum values are given in the English and metric absolute scales of pressure. The conversion chart in ­Figure 11-24 may be used as an aid for comparison of inches to psia and kPa absolute.

Vacuum-Operated Devices

Many vacuum-operated devices, such as heater coolant valves and mode doors, are activated with a vacuum pot, also called a vacuum motor or vacuum power unit.

Single-Chamber Pot.  The exertion (force) of atmospheric pressure on one side of a ­diaphragm causes the diaphragm to move toward the lower (vacuum) pressure side ­(Figure 11-25). This moves the device that is to be controlled through a lever, arm, or rod linkage. Dual-Chamber Pots.  Dual-chamber vacuum pots (motors) operate below atmospheric ­pressure based on a pressure differential (Ap) from one side to the other. A higher pressure on either side will move the diaphragm to the side with a lower pressure. This provides a push or pull effect on the vacuum pot.

Inches of Mercury (in. Hg) 28.98 27.96 26.94 25.92 24.90 23.88 22.86 21.83 20.81 19.79 18.77 17.75 16.73 18.71 14.69 13.67 12.65 11.63 10.61 9.59 8.57 7.54 6.52 5.50 4.48 3.46 2.44 1.42 0.40

Pounds per Square Inch Kilopascals Absolute Absolute (psia) (kPa absolute) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.0

3.45 6.89 10.34 13.79 17.24 20.68 24.13 27.58 30.03 34.47 37.92 41.37 44.82 48.26 51.71 55.16 58.61 62.05 65.50 68.95 72.40 75.84 79.29 82.74 86.19 89.63 93.08 96.53 99.98 103.42

A vacuum pot is a device designed to provide mechanical action by the use of a vacuum signal. A vacuum pot is also called a vacuum motor or vacuum power unit. Changes in atmospheric pressure do not affect the operation of dual-chamber vacuum motors.

FIGURE 11-24  Conversion chart: absolute scale versus atmospheric scale.

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A

B

FIGURE 11-25  Movement of a singlechamber vacuum motor: (A) no vacuum applied; and (B) full vacuum applied.

Vacuum Source

The vacuum reserve tank and check valve prevent erratic operation of the vacuum motors.

Shop Manual Chapter 11, page 457

When running, the automobile engine provides a ready source of vacuum. This source is usually taken off the intake manifold and routed to the various components through smalldiameter synthetic rubber, plastic, or nylon hoses. The engine vacuum supply source can vary from 0.01 in. Hg (14.7 psia or 101.4 kPa absolute) to 20 in. Hg (4.89 psia or 33.7 kPa absolute), or more. Actual vacuum conditions depend on certain engine conditions. The reason for the vacuum variation is not important in this discussion. It is important, however, to be aware that engine vacuum does vary. Because of this vacuum variation, a reserve tank and check valve are used (Figure 11-26). This combination of devices provides the means to maintain maximum vacuum values to properly operate air-conditioning and heater vacuum controls under all engine operating conditions. It should be noted that more than one reserve tank or check valve may be found in the air-conditioning and heating system vacuum circuit. It may also be noted that the vacuum system may serve other components, such as the power brake booster. Reserve Tank.  Vacuum reserve tanks are provided in a variety of sizes and shapes. Some early tanks, which are made of metal, resemble a large juice can (Figure 11-27). Others (Figure 11-28) are made of plastic and resemble a sphere. Vacuum reserve tanks generally require no maintenance, but they sometimes develop pinhole-sized leaks due to exposure to the elements. When a vacuum tank is found to be leaking, it may be repaired. If the reservoir fails to hold a vacuum, the mode doors may operate sporadically or not at all. The default or normal position for the mode door when no vacuum is applied is typically in the defrost mode, supplying air to the windshield on many vehicles. This is done for safety so that the windshield will stay clear even with a system failure.

Check valve To vacuum source Reserve tank

Tee To vacuum system

FIGURE 11-26  Reserve vacuum tank and check valve.

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FIGURE 11-27  An early vacuum reserve tank.

FIGURE 11-28  A plastic vacuum reserve tank.

Spring

To vacuum tank

To intake manifold

Seat

Disc valve

FIGURE 11-29  A typical vacuum check valve.

Check Valve.  Many types and styles of check valves are used in the automotive vacuum circuit. Essentially, a check valve (Figure 11-29) allows the flow of a fluid or vapor in one direction and blocks the flow in the opposite direction. Many systems use a check valve between the engine manifold supply vacuum hose and the reservoir tank. This ensures a consistent supply of vacuum and a source of vacuum if manifold vacuum decreases (such as under a load). Restrictor.  Some vacuum systems have a restrictor to provide a delay or to slow the operation of a device. Restrictors have a small orifice that sometimes becomes clogged with lint or other airborne debris. Attempts to clean a restrictor usually prove unsuccessful, and replacement is suggested. To test a restrictor, simply use a vacuum pump and gauge setup.

Vacuum System Diagrams The vacuum system diagram in Figure 11-30 must be considered to be typical only because it is a composite of one of hundreds of variations. The manufacturer’s vacuum system diagram for a specific year/model car must be followed. Basically, the vacuum system is used to open, close, or position the heater coolant valve and mode doors to achieve a desired preselected temperature and humidity level. Pressure differentials provide a source of power to perform the mechanical movement of devices.

Vacuum signal legend includes “pv” for partial vacuum, “nv” for no vacuum, and “v” or “fv” for full vacuum.

Shop Manual Chapter 11, page 410

A BIT OF HISTORY In 1964, Cadillac introduced the first automatic air-conditioning climate control system. This was one of the most significant advancements in available options for the luxury car market.

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Restrictor Defroster YELLOW

YELLOW

BLUE

BLUE WHITE

WHITE

DRK GREEN DRK GREEN

LT GREEN VIOLET

VIOLET ORANGE

BLACK

BLACK TAN

RED vacuum tank

TAN

Upper door

Lower door

GRAY

Water valve FIGURE 11-30  A typical vacuum system diagram.

Shop Manual Chapter 11, page 458

The average person is comfortable at a temperature of 788F to 808F with a relative humidity (RH) of 45–50 percent.

Automatic Temperature Controls Many different types of semiautomatic and automatic temperature control systems are used today—so many that it is not possible to cover each system individually in this manual. S ­ ystems are modified or changed from year to year and from car model to car model. Many solid-state components are so sensitive that even the 1.5-volt battery used in an analog ohmmeter may destroy them. A digital ohmmeter, then, must be used whenever a ­manufacturer’s specifications suggest that component resistance measurements be taken. Some components and circuits are so sensitive to outside influence, however, that some ­schematics are labeled “Do not measure resistance.” Heed this caution when it is noted to avoid damage to delicate electronic components. Though systems differ in many respects, all are designed to provide in-car temperature and humidity conditions at a preset level (within system limitations), regardless of the temperature conditions outside the car (Figure 11-31). The temperature control also functions to hold the relative humidity within the car to a healthy level and to prevent window fogging. For example, if the desired temperature is 758F (23.898C), the automatic control system will maintain an in-car environment of 758F (23.898C) at 45–55 percent humidity, regardless of the outside weather conditions. In even the hottest weather, a properly operating system can rapidly cool the automobile interior to the predetermined temperature (758F or 23.898C). The degree of cooling then cycles to maintain the desired temperature level. In mild weather conditions, the passenger compartment can be held to this same predetermined temperature (758F or 23.898C) without resetting or changing the control. During cold weather, the system rapidly heats the passenger compartment to the ­predetermined 758F (23.898C) level and then automatically maintains this temperature level. Automatic climate control systems have a range of functions from FULL AUTO mode to semi auto and manual override control. To select FULL AUTO mode, the AUTO button

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on the climate control panel is selected. On some systems, the fan control knob must be set to the AUTO position. Cabin temperature is determined by the temperature control dial or increase/decrease temperature buttons (Figure 11-31). The system is designed to select the appropriate mix of volume (fan speed) and temperature of cooled or heated air in order to get the passenger cabin to the temperature selected as quickly as possible. On very cold days, the system may not run the blower motor until the heater core has reached a preset temperature, to avoid blowing frigid air on the occupants. The exception to this is if defrost is selected, in which case the blower motor will run to direct air to the windshield. On many systems, if the temperature selected is the lowest limit or the highest limit, the system will produce maximum cooling or heating respectively. At these positions, the ­system will no longer regulate interior temperature, but instead produce maximum output. The ­system only regulates interior temperature when the temperature control knob is set between the maximum and minimum limits. When the AUTO mode is selected, the automatic climate control system allows the ­vehicle occupant semiautomatic mode control of various functions manually, while still maintaining preset cabin temperature. These features vary among manufacturers but generally allow for driver- and passenger-side temperature control and air discharge selection, as an example. Often selecting recirculation or changing fan speed will disengage FULL AUTO control. Temperature Control Different ambient temperatures Constant interior temperature

through

Automatic flop control and switching the air conditioner on and off

A

B

C

FIGURE 11-31  The AUTO feature on the climate control head allows the driver to select and maintain a desired temperature setting.

357 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

In-car comfort may dictate a temperature setting other than that determined to be ideal for the average person.

The intent of this text is to give an overall understanding of the components of the v­ arious systems, not to cover any particular system in detail. These components include but are not limited to: ■■ Coolant temperature sensor ■■ In-car temperature sensor ■■ Outside temperature sensor ■■ High-side temperature switch ■■ Low-side temperature switch ■■ Evaporator thermistor ■■ Low-pressure switch ■■ High-pressure switch ■■ Vehicle speed sensor ■■ Throttle position sensor ■■ Sun load sensor ■■ Power steering cutout switch Many automotive electronic temperature control systems have self-diagnostic test provisions whereby an onboard microprocessor-controlled subsystem will display a code. This code (number, letter, or alphanumeric) is displayed to tell the technician the cause of the malfunction. Some systems also display a code to indicate which computer detected the malfunction. The manufacturer’s specifications must be followed to identify the malfunction display codes. It is possible for the air-conditioning system to malfunction even though self-check testing indicates there are no problems. It is then necessary to follow a manufacturer’s step-by-step procedure to troubleshoot and check the system.

Control Panel

The control panel is found in the instrument panel at a convenient location for both driver and front-seat passenger access. Two types of control panels (Figure 11-32) may be found: manual and push-button. All serve the same purpose: to provide operator input control for A

Pwr

B

CLIMATE CONTROL

DRIVER

Pwr

PASS

CLIMATE CONTROL COLD

HOT

C Pwr

DRIVER

D Pwr

PASS

HI AUTO LO

66

65

66

DRIVER

REAR

PASS

REAR SYSTEM OFF AUTO FRONT

REAR

FRONT

REAR CONTROL

Infrared temperature sensor FIGURE 11-32  Examples of typical control panels for HVAC systems: (A) a typical single-one system; (B) a typical zone system; (C) a typical three-zone system; and (D) a typical three-zone system with automatic temperature control (ATC).

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the air-conditioning and heating system. Some control panels have features that other panels do not have, such as provisions to display in-car and outside air temperature in English or metric units. Provisions are made on the control panel for operator selection of an in-car temperature, generally between 658F (47.28C) and 858F (56.68C) in one-degree increments. Some have an override feature that provides for a setting of either 608F (42.28C) or 908F (72.28C). Either of these two settings will override all in-car temperature control circuits to provide maximum cooling or heating conditions. A microprocessor is usually located in the control head to input data to the programmer, based on operator-selected conditions. When the ignition switch is turned off, a memory circuit will remember the previous setting. These conditions will be restored each time the ignition switch is turned on. If the battery is disconnected, however, the memory circuit is cleared and must be reprogrammed. Some dual systems also have a control panel in the rear of the vehicle (Figure 11-33) for the comfort and convenience of the rear-seat passengers. A mini-microprocessor is found in the control head to input temperature and humidity data selected by the operator to the programmer. Most electronic temperature control heads have provisions for self-testing, known as onboard diagnostics (OBD). This system provides a number, letter, or alphanumeric code to give the technician information relative to the problem. Manufacturers’ charts must be consulted to interpret a particular code. For example, Ford’s “09” or “88,” a no-trouble code, corresponds to General Motors’ “70.” Another example, code “14,” indicates “control head defective” in a Ford system, whereas “36” indicates “ATC head communications failure” in a Chrysler system. Note too that some electronic climate control (ECC) programmers (Figure 11-34) have an “ECC diagnostic connector” provision for the connection of an external readout. Many others use the onboard OBD II 16 pin-data link connector (DLC) to access diagnostic information, codes, and system data streams. Comfort of those in the passenger compartment is maintained by mixing cooled and ambient or heated air in the plenum section of the heater/air-conditioning duct system. In the AUTO mode, the operator sets the desired comfort level, often humidity as well as temperature. Both the quality as well as the quantity of air delivered to the passenger compartment is then controlled automatically. The blower speed and air delivery can, however, be manually controlled if desired. The control panel in Figure 11-32D is typical for an automatic temperature control (ATC) system. The control panel may be used to select a predetermined temperature level that will automatically be maintained at all times. If desired, the operator can override the automatic

A programmer is the part of an automatic temperature control system that controls the blower speed, air mix doors, and vacuum or electrical actuators. Dual systems usually refers to systems with two evaporators in an air-conditioning system, one in the front and one in the rear of the vehicle, driven off a single compressor and condenser system.

FIGURE 11-33  A typical rear control panel.

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Hot at all times

Hot in run

IP Fuse Panel HTR-A/C 25A

Junction block

HVAC controller TEMP Hot in run or start

Under-hood fuse-relay center

LED

Compressor logic

AC

DEFROST

Ign fuse 10A

A/C fuse 10A

Compressor clutch relay LO M1

Fan switch

Cycling switch

M2 HI

A/C clutch

High pressure cutoff switch

AC enable

Blower motor

Blower motor relay

PCM

FIGURE 11-34  A typical electronic climate control system schematic.

provisions of the control head by selecting MAX A/C or MAX heat. Manual modes are also available for selecting BI-LEVEL, DEF, VENT, and DEFOG operation. Check the heater and A/C function test chart (Figure 11-35) for the proper system response for the various control settings.

Electronic Temperature Control Systems Many types of electronic temperature control systems are in use. The flowcharts shown in Figure 11-36 illustrate two typical systems. The following information relates to many of the components found in an electronic temperature control system. Not all components, however, are found in all systems.

High-Side Temperature Switch

The high-side temperature switch is located in the air-conditioning system liquid line between the condenser outlet and the orifice tube inlet (Figure 11-37). Though it is a temperaturesensing device, it provides air-conditioner system pressure data to the processor. System temperature is determined by system pressure based on the temperature–pressure relationship of the refrigerant. 360 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

SYSTEM RESPONSE

CONTROL SETTINGS

Defrost A/C Remarks outlets outlets

STEP

Mode control

Temp control

Fan control

Blower speed

Heater outlet

1

OFF

60

Does not function

OFF

No airflow

No airflow

No airflow

A

2

AUTO

60

LO

LO

Min. airflow

Airflow

No airflow

A

3

AUTO

60

LO to HI

LO to HI

Small airflow

4

BI-LEVEL

60

LO to HI

LO to HI Airflow

No airflow Airflow Small airflow

5

AUTO

90

HI

HI

Airflow

6

DEF FRT

90

HI

HI

Small airflow

7

DEF REAR

90

Airflow

Small No airflow airflow No Airflow airflow

Does not change system response

D A,D A,B,C,D A,D A

REMARKS: A. The word “AUTO” must appear in L/H upper corner of display when in automatic mode. Mode arrows in display must indicate flow from appropriate outlet. LEDs must light above mode buttons when selected. B. Listen for air noise reduction as recirculation door closes. C. During transition from air-conditioner outlets to heater outlets, there will be a period of time when one half of the air will be directed from the defroster outlets. D. Check for airflow at side window defogger outlets in all modes but OFF. FIGURE 11-35  A typical heater and air-conditioning function test chart.

Low-Side Temperature Switch

The low-side temperature switch is located in the air-conditioning system line between the orifice tube outlet and the condenser inlet. Its purpose is to sense low-side refrigerant pressure and to provide this information to the microprocessor.

Refrigerant Pressure Sensors

Many air-conditioning systems today are equipped with a refrigerant pressure sensor, also called a pressure transducer, on both the high-pressure and low-pressure sides of the refrigerant system. The pressure sensors provide the climate control module, body control module (BCM), and ECM/PCM with refrigerant pressure data. The pressure sensor is an electromechanical sensor and it appears physically similar to other refrigerant pressure cutoff switches, with the exception that it has three wires connected to it. Like many other computer sensors, the three circuits are the 5-volt reference circuit, a ground circuit, and a signal circuit, all connected to the control module (Figure 11-38). The typical voltage signals are 0.1 volts at 0 psig to 4.9 volts at 450 psig or above. With the use of a scan tool, both high-side and low-side refrigerant system pressures can be monitored without the need for a manifold and gauge set. One possible system code that can be stored related to this sensor is P0530—air-conditioner pressure sensor circuit. 361 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

A

B FIGURE 11-36  Electronic temperature control flowcharts with five inputs (A) and nine outputs (B).

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Lowpressure switch

Compressor

Condenser

Accumulator Evaporator

Orifice tube

Low-side temperature switch

High-side temperature switch

FIGURE 11-37  Location of the low- and high-side temperature switch.

5V

5V

PCM

A/D converter To MAP and TPS

A/C pressure transducer FIGURE 11-38  The AC pressure transducer monitor high- and low-side pressure in the air-conditioning system and sends this data to the ECM/PCM or the BCM and climate control module, depending on system design.

Shop Manual Chapter 11, page 468

Refrigerant pressure sensors also protect the air-conditioning system from excessively high or low pressures. If the high-pressure sensor detects excessively high pressure on the high side of the system, this voltage information is sent to the ECM/PCM or climate control module. If a high-pressure condition is detected that is above manufacturer specifications, which are typically in the range of 431 psig (2972 kPa), the control module turns off the air-conditioner compressor clutch relay until pressure drops to a safe level. Many systems will also disable the compressor if discharge pressure is too low, typically below 29 psig (203 kPa). As was discussed earlier, the refrigerant system is also protected by a high-pressure relief valve that is located in the rear cylinder head of the compressor (Figure 11-39). If pressure in the refrigerant system reaches an unusually high level that will cause serious damage to system components (generally above 500 psig), the pressure release valve will open, releasing refrigerant into the atmosphere.

363 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Evaporator

Expansion valve

Pressure relief valve S Condenser D Compressor

Radiator

Receiver/Drier

High-pressure gas

Low-pressure liquid

High-pressure liquid

Low-pressure gas

Refrigerant pressure sensor

FIGURE 11-39  The high-pressure relief valve is located at the rear of the compressor and the high-pressure sensor is located on the high-side line between the compressor discharge port and the restriction device.

Conditions such as a loss of refrigerant may cause abnormally low lowside pressures.

Low-Pressure Switch

The low-pressure switch is located in the low side of the air-conditioning system, usually on the accumulator (Figure 11-40). This normally closed (nc) switch opens when system low-side pressure drops below 2–8 psig (13.8–55.2 kPa). An open low-pressure switch signals the microprocessor to disengage the compressor clutch circuit to prevent compressor operation during low-pressure conditions. Low-pressure conditions may result due to a loss of refrigerant or a clogged metering device.

Pressure Cycling Switch

The pressure cycling switch is found on some systems. It is used as a means of temperature control by opening and closing the electrical circuit to the compressor clutch coil. On cycling clutch systems, this switch usually opens at a low pressure of 25–26 psig (172.4–179.3 kPa) and closes at a high pressure of 46–48 psig (317.2–331 kPa). On some systems, this switch may be in line with the compressor clutch coil. On other systems, it may send data to the microprocessor to turn the compressor on and off.

Input Sensors

A sensor is a general name given to a transducer, which is short for “transfer indicator.” In automotive terms, a sensor is a device that is capable of sensing a change in pressure, temperature, or other controlled variables. The climate control module uses input sensor output voltage data (Figure 11-41) to determine actuator commands that will be required to maintain a selected temperature (Figure 11-42). Climate control system input sensors are generally either a thermistor or a type of diode (in other words, photovoltaic diode). 364 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Ambient sensor

In-vehicle sensor

Sun load sensor

T

Intake sensor

T

T

Controller LAN signal

VACTR

FIGURE 11-40  The low-pressure switch is usually located on the accumulator.

M

M

M

Mode door motor

Air mix door motor

Upper vent door motor

FIGURE 11-41  The most common types of climate control sensors used as either the thermistor or the diode. These input sensors supply data directly to the climate control module or BCM.

INPUTS Outside air temperature sensor 0–5 volt range

Sunlight sensor 0–5 volt range

In-car temperature sensor 0–5 volt range

Evaporator temperature sensor 0–5 volt range

Engine coolant temperature sensor 0–5 volt range

Air mix control motor

Compressor clutch circuit

Climate control unit

Mode control motor

Blower fan control motor

Recirculation control motor OUTPUTS

FIGURE 11-42  The climate control module logic uses input sensor information to determine output actuator control to maintain selected cabin temperature.

365 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

5V Reference

HVAC control module

To aspirator 60°F (15.56°C) A.

Thermistor temperature sensor FIGURE 11-43  Wiring diagram for a typical thermistor.

To aspirator 90°F (32.22°C) B.

To aspirator (40°F (4.44°C) C. FIGURE 11-44  The resistance of a thermistor changes as temperature changes.

Shop Manual Chapter 11, page 462

Although they may vary in physical appearance, all thermistors have the same general operating characteristics (Figure 11-43)—that is, they are extremely sensitive to slight changes in temperature. A thermistor may be one of either two designs, a negative temperature coefficient (NTC) or positive temperature coefficient (PTC) design. As a rule, climate control systems use NTC thermistor designs. In an NTC thermistor, a change in the resistance value of each sensor is inversely proportional to a temperature change (Figure 11-44). For example, when the temperature decreases, the resistance of the sensor increases; and when the temperature increases, the sensor resistance decreases. In Figure 10-59A, one thermistor is installed in an air duct. With air at a temperature of 608F (15.568C) passing through the duct, the resistance value of the thermistor is 94 ohms. Referring to the resistor value given in the chart (Figure 11-45), this thermistor is currently reading correctly. If the temperature in the duct is 908F (32.228C), as in Figure 11-44B, then the resistance of the thermistor decreases to about 45 ohms. If, however, the temperature is decreased to 408F (4.448C), the thermistor resistance is increased to 160 ohms (Figure 11-44C). Even though this value is not on the chart, it appears the thermistor is reacting as designed. A graph of individual sensor values at various temperatures (Figure 11-46) may be compared with the examples given to this point. Note that each sensor has a different value for a particular temperature. Though all NTC thermistors react to temperature changes in the same manner, the specific resistance value for a given temperature varies among sensor types and specific vehicle applications. Always refer to specific vehicle information when trying to determine proper thermistor operation.

Sun Load Sensor

The sun load sensor (Figure 11-47) is usually found atop the dashboard, adjacent to one of the radio speaker grilles. The sun load sensor is a photovoltaic diode that sends an appropriate

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Temperature* 8F 8C

Resistance Ohms

Temperature* 8F 8C

Resistance Ohms

50

10.0

120

66

18.9

83

51

10.6

117.5

67

19.4

81

52

11.1

115

68

20.0

79

53

11.7

112.5

69

20.6

77

54

12.2

110

70

21.1

75

55

12.8

107

71

21.7

73.5

56

13.3

104

72

22.2

72

57

13.9

101.5

73

22.8

70.5

58

14.4

99

74

23.3

69

59

15.0

96.5

75

23.9

67.5

60

15.6

94

76

24.4

66

61

16.1

92.5

77

25.0

64.5

62

16.7

91

78

25.6

63

63

17.2

89

79

26.1

61.5

64

17.8

87

80

26.7

60

65

18.3

85

81

27.2

58.5

*Temperature of ambient air passing across the thermistor FIGURE 11-45  Thermistor values.

signal to the microprocessor to aid in regulating the in-car temperature. The sun load sensor can also be found under the defrost grille at about the center of the windshield. It is a thermistor that is sensitive to the heat load of the sun on the vehicle. As light level increases, the resistance of the photodiode increases. The BCM compares the sun load values with in-car temperature values to determine how much cooling is required in order to maintain selected in-vehicle temperature conditions (Figure 11-48). When sunlight intensity is high, the control module will automatically increase blower fan speed and increase the volume of air flowing to the dash discharge vents. This in turn improves comfort by preventing the passengers from feeling hotter from the effects of direct sunlight increasing the temperature of the upper portion of the body.

Outside Temperature Sensor

The outside temperature sensor (OTC), also called an ambient temperature sensor (ATS), is a negative temperature coefficient thermistor in a protective housing located behind either the front bumper or grille (Figure 11-49). As with an NTC thermistor, when the temperature of the sensor increases, the resistance of the sensor will decrease (Figure 11-50). The climate control module passes a 5-volt reference through the thermistor and measures current flow. The purpose of the OTC is to sense outside ambient temperature conditions to provide data to the microprocessor. Data from the OTC is processed by the BCM and is displayed on the electronic climate control (ECC). Through a rather complicated process, the OTC provides information regarding outside ambient temperature that is essential for the proper operation of an electronic automatic temperature control (EACT) system.

Shop Manual Chapter 11, page 466

367 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

0

TEMPERATURE (°C) 20 30

10

50

40

TEMPERATURE (°F) 30 200

40

50

60

70

90

80

100

110

120

130

180

160

140

OHMS

120

100

80

SE SENS

60

OR #2

NS

OR

#1

40

SENS

OR #

3

20

0

FIGURE 11-46  Individual sensor values graphed.

5 volt reference

Sun load sensor FIGURE 11-47  A typical sun load sensor.

Automatic Temperature Control module

Photodiode

FIGURE 11-48  Typical diagram for a sun load sensor.

368 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Resistance (kV)

12 11 10 9 8 7 6 5 4 3 2 1 14 −10

32 0

50 10

68 20

86 104 ˚F 30 40 ˚C

Temperature

FIGURE 11-49  The outside temperature sensor is located behind the grille.

FIGURE 11-50  Both the OTC and the in-car temperature sensor are negative temperature coefficient thermistors that decrease in resistance with an increase in temperature.

This sensor circuit has several programmed memory features to prevent false ambient temperature data input during periods of low-speed driving or when stopped close behind another vehicle, such as when waiting for a traffic signal. If ambient air temperature is below the minimum preprogrammed level, the control module will not allow the air-conditioning compressor clutch to engage. Air conditioning is not generally required at temperatures below 508F (108C). This is due to the low relative moisture content contained in air at that temperature, even at the saturation point.

In-Car Temperature Sensor

The in-car temperature sensor, also called an in-vehicle sensor (Figure 11-51), is located in a tubular device called an aspirator. A small amount of in-car air is drawn through

An aspirator is a device that uses suction to move air, accomplished by a differential in air pressure.

Shop Manual Chapter 11, page 467

Instrument panel In-car sensor

Aspirator tube

In-car air

Aspirator venturi

Out

In Main airstream

FIGURE 11-51  A typical in-car temperature sensor and aspirator assembly.

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OFF

A/C

A/C

72

MODE AUTO

FAN REAR

AUTO

Off

In-car sensor

FIGURE 11-52  The in-car temperature sensor may be located in a separate louvered housing on the dashboard or climate control panel.

the aspirator across the in-car sensor to provide average in-car temperature data to the microprocessor. The aspirator is a small duct system that is designed to cause a small amount of in-car air to pass through it. The main airstream causes a low pressure (suction) at the inlet end of the aspirator. This causes in-car air to be drawn into the in-car sensor plenum. The in-car sensor, located in the plenum, is continuously exposed to average in-car air to monitor the in-car air temperature. Like the OTC, the in-car temperature sensor is also a negative temperature coefficient thermistor. Some in-car temperature sensors use a small electric fan positioned behind the thermistor to draw in-car air across sensor (Figure 11-52) to maintain accurate in-car ­temperature readings.

Evaporator Temperature Sensor Shop Manual Chapter 11, page 461

The evaporator temperature sensor (Figure 11-53), also called a fin temperature sensor, is used on many systems to control evaporator temperature. It is located at the evaporator and is fitted in between the cooling fins to measure and control evaporator core temperature. The evaporator temperature sensor is another negative temperature coefficient (NTC) thermistor. Evaporator housing

A

B

Thermistor in place

FIGURE 11-53  A typical evaporator thermistor (A) in position; and (B) between evaporator cooling fins.

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Like all other NTC thermistors, when the temperature of the sensor increases, the resistance of the sensor will decrease. The climate control module passes a 5-volt reference through the thermistor and measures current flow. The purpose of the evaporator temperature sensor is to sense evaporator core temperature conditions and provide the data to the controller. By monitoring the core temperature, the microprocessor can determine whether the compressor clutch should be turned on or off to add additional refrigerant temperature regulation. The compressor is turned off when the evaporator core temperature drops to 348F (1.18C). This prevents the formation of frost and ice on the fins of the evaporator. On electronically controlled variable displacement compressors, the output volume of the air-conditioner compressor can be controlled by pulse width modulation of the compressor electronic pressure control valve. In this manner, the compressor output can be varied to complement the actions taken by the thermal expansion valve to maintain the evaporator core at the optimal temperature range for current system demands.

Infrared Temperature Sensor

Some vehicles with automatic temperature control are equipped with an infrared temperature sensor (ITS) to determine passenger compartment temperature. It may be located in the temperature control assembly or near the dash discharge outlets at the center of the dash. Infrared temperature sensors measure surface temperatures rather than air temperature and thus can adjust passenger compartment temperatures based on the perceived temperature (caused by ultraviolet radiation from the sun or evaporative heat loss) of the passenger instead of actual air temperature. The temperature control module interprets the data received by the ITS and evaporator temperature sensor to adjust blower speed and the amount of refrigerant flowing through the evaporator core to maintain the selected temperature level of the passenger compartment. If an infrared sensor is found to be defective, it must be replaced as an assembly.

Shop Manual Chapter 11, page 464

Air Humidity Sensor

Information from the air humidity sensor is used by some hybrid electric platforms to reduce air-conditioning compressor load when in-car humidity levels are low. On some platforms, the sensor is located at the base of the rearview mirror and integrates an air humidity sensor, windshield temperature sensor, and interior temperature sensor. This information is used to permit adaptive control of the automatic defrost function. The air humidity sensor integrates a temperature sensor since determining air humidity is dependent on air temperature. The ability of air to hold moisture is directly proportional to its temperature. The humidity sensor uses a capacitive thin-layer film to measure moisture content of the air. The capacitor uses a special dielectric material that absorbs water vapor. The water absorbed by the capacitance material changes the electrical properties and thus the capacitance of the capacitor (Figure 11-54). By measuring the capacitance and converting this to a voltage signal, air humidity can be measured.

Coolant Temperature Sensor

The engine coolant temperature (ECT) sensor is an NTC thermistor (Figure 11-55) that is located in an engine coolant passage. It provides engine coolant temperature information to various control modules including the climate control module ECM/PCM and BCM. The control unit supplies a 5-volt reference voltage to the sensor, and as the engine temperature increases, the sensor resistance will decrease. As sensor resistance decreases, it creates an easier path to ground, which results in a lower voltage observed at the control module. Based on the information received from the ECT sensor, the climate control module can increase or decrease blower fan operation on some vehicle models. As an example, on a vehicle with FULL AUTO mode climate control, the blower fan will not operate if engine coolant temperature is too low.

Shop Manual Chapter 11, page 465

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Voltage signal

V

V

Sensor electronics

Sensor electronics

Dielectric

Plate capacitor

Water vapor

FIGURE 11-54  The humidity sensor uses a capacitive thinlayer film to measure moisture content of the air. The water absorbed by the capacitance material changes the electrical properties and thus the capacitance of the capacitor.

Thermistor FIGURE 11-55  The ECT sensor is an NTC thermistor located in an engine coolant passage.

This sensor also provides input information to other onboard computers to provide data for fuel enrichment, ignition timing, exhaust gas recirculate operation, canister purge control, idle speed, and closed-loop fuel control. A defective coolant temperature sensor will cause poor engine performance, which will probably be evident before poor air-conditioning performance is noticed.

Vehicle Speed Sensor

The vehicle speed sensor is a pulse generator that is usually located at the transmission output shaft. It provides actual vehicle speed data to the microprocessor as well as other subsystems, such as the electronic control module (ECM).

Throttle Position Sensor

The throttle position sensor is actually a potentiometer with a voltage input from the p ­ rocessor. The processor, then, determines throttle position based on the return voltage signal. At the wide-open throttle (WOT) position, the compressor clutch is disengaged to provide ­maximum power for acceleration. This device is often called the WOT sensor and is most often found on diesel engine–equipped vehicles.

Heater Turn-On Switch

The heater turn-on switch is usually a bimetallic snap-action switch found in the coolant stream of the engine. Its purpose is to prevent blower operation when engine coolant temperature is below 1188F21228F (48.98C2508C), if heat is selected. If cooling is selected, the programmer will override this switch to provide immediate blower operation, regardless of engine coolant temperature.

Brake Booster Vacuum Switch The brake booster vacuum switch is a low-pressure switch.

The brake booster vacuum switch is found on some cars. Its purpose is to disengage the airconditioning compressor whenever braking requires maximum effort. This switch, which is usually in series with the compressor clutch electrical circuit, does not provide data to the microprocessor.

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Power Steering Cutoff Switch

The power steering cutoff switch, which is found on some cars, is used to disengage the air-conditioning compressor whenever power steering requires maximum effort. This switch, on some cars, is in series with the compressor control relay and does not provide data to the programmer. On other applications, this switch is in the electronic control module and provides feedback data to the microprocessor.

The power steering cutoff switch is a high-pressure switch

Analyzing Sensor Input Information

The following is a simplified description of how the electronic climate control system uses input sensor information to control outputs in the FULL AUTO mode automatic climate control mode. The climate control module must analyze data from the in-car temperature sensor, the outside ambient air temperature sensor (Figure 11-56), and the temperature level selected at the control panel before calculating the best position for the recirculation door to optimize system performance. When the climate control module calculates where discharge air should be directed and at what volume, it must analyze data from the in-car temperature sensor, the sun load sensor (Figure 11-57), and the temperature level selected at the control panel. The climate control module then figures the best position for the mode door control motors to optimize system passenger comfort.

IN-CAR TEMPERATURE

Set temperature

OUTSIDE AIR TEMPERATURE

CLIMATE CONTROL UNIT

Recirculation control motor

FIGURE 11-56  The climate control module will weigh various inputs when determining the position for the recirculation mode control door.

IN-CAR TEMPERATURE

Set temperature

SUNLIGHT INTENSITY

CLIMATE CONTROL UNIT

Mode control motor

FIGURE 11-57  The climate control module will weigh various inputs when determining the position for the mode door control motors.

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When the weather is cooler and both heating and dehumidification may be required, the climate control module will determine whether hotter or cooler air is needed in the passenger compartment to maintain the selected preset temperature. It must analyze data from the in-car temperature sensor, the outside ambient air temperature sensor (Figure 11-58), and the temperature level selected at the control panel. The climate control module then calculates the best position for the air mix control motor and heater valve, if equipped to optimize system passenger comfort. At other times, the control module determines the appropriate speed for the blower motor to achieve both a high level of passenger comfort and system performance (Figure 11-59). This can be a complicated process, and the control module must interpret information from the sun load sensor, in-car temperature sensor, evaporator temperature, engine coolant temperature, and, as always, the desired passenger compartment temperature selected. During varying heat load conditions, the climate control module may need to cycle the compressor clutch off to maintain evaporator core temperature and to avoid frost or ice forming on the evaporator cooling fins (Figure 11-60). The control module analyzes data from the in-car temperature sensor, selected passenger compartment temperature, and the evaporator temperature sensor to determine whether the air-conditioning compressor clutch should be engaged or disengaged. The climate control system logic is much more complex than can be fully explained in the examples given here, and often many of the described conditions are occurring simultaneously. These brief examples should improve your understanding of the system complexity and how decisions are arrived at.

IN-CAR TEMPERATURE

Set temperature

OUTSIDE AIR TEMPERATURE

CLIMATE CONTROL UNIT

Air mix control motor/heater valve

FIGURE 11-58  The climate control module will determine the best position for the air mix door, based on both inside and outside temperatures.

SUNLIGHT INTENSITY

COOLANT TEMPERATURE

IN-CAR TEMPERATURE

Set temperature

EVAPORATOR TEMPERATURE

CLIMATE CONTROL UNIT

Blower motor

FIGURE 11-59  The climate control module will determine the best blower motor speed, based on many inputs, to achieve both a high level of passenger comfort and system performance.

374 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

IN-CAR TEMPERATURE

Set temperature

EVAPORATOR TEMPERATURE

CLIMATE CONTROL UNIT

Compressor clutch relay

FIGURE 11-60  The climate control module at times decides whether the airconditioning compressor clutch should be engaged or disengaged.

Scan Tool A scan tool (Figure 11-61) is a microprocessor that is designed to communicate with the vehicle’s computer. When connected to the computer through diagnostic connectors, a scan tool accesses diagnostic trouble codes (DTCs), runs tests to check system operations, and monitors the activity of the system. Both trouble codes and test results are displayed on a light-emitting diode (LED) screen or are printed out on the scanner printer. Today, most scan tools have large screens with many lines of information and graphing capabilities. Many may be interfaced with a laptop or desktop computer for increased data display and graphing, as well as enabling service technicians to store information and create their own data and waveform library. Most scan tools can store the test data in a random access memory (RAM) that can be accessed by a printer, personal computer, or an engine analyzer to retrieve the information. Trouble codes set by the computer help the technician identify the cause of the problem. Most diagnostic work on computer control systems should be based on a description of symptoms to help locate any technical service bulletins that refer to the problem. One can also use the symptom description to locate the appropriate troubleshooting sequence in the manufacturer’s service manuals. Since 1996 and the introduction of OBD II and a standard 16-pin data link connector (DLC), most climate control systems can be accessed through this same connector assembly with a generic OBD II scan tool. Manufacturer-specific and many enhanced generic scan tools also have the ability not only to retrieve data and trouble codes from the climate control module or BCM but also to allow the technician to activate output devices like the

The average person is comfortable at 788F2808F (25.68C226.78C) at a relative humidity (RH) of 45–50 percent.

FIGURE 11-61  A typical handheld scan tool with graphing features.

375 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Shop Manual Chapter 11, page 485

Shop Manual Chapter 11, page 486

air-conditioner compressor clutch when a command is received from the scan tool. This is generally referred to as bidirectional control. The scan tool can also read refrigerant system high-side and low-side operating pressures on systems equipped with pressure transducers. If the air-conditioning system compressor will not engage, a scan tool can be used to verify whether an air conditioner request signal is present when the HVAC control switch is set to AC or DEFROST. Sometimes the air-conditioner compressor clutch will not be commanded on if any of the following conditions are present: ■■ Battery voltage is less than 10.5 volts. ■■ Intake air temperature is too low (below 458F). ■■ Engine coolant temperature is too high (greater than 2608F). ■■ Throttle angle is above 90 percent. ■■ Refrigerant system high-side pressure is above 431 psig (2972 kPa). ■■ Refrigerant system discharge pressure is below 29 psig (203 kPa). It should be noted that these are only examples and that specific vehicle information should be consulted. The following is a list of OBD II codes relevant to HVAC and climate control system diagnostics: Generic OBD-II Body Codes: B1200—Climate control push-button circuit failure B1239—Airflow Blend Door Driver Circuit Failure B1242—Airflow Recirculation Door Driver Circuit Failure B1249—Blend Door Failure B1250—Air Temperature Internal Sensor Circuit Failure B1251—Air Temperature Internal Sensor Circuit Open B1252—Air Temperature Internal Sensor Circuit Short to Battery Power B1253—Air Temperature Internal Sensor Circuit Short to Ground B1254—Air Temperature External Sensor Circuit Failure B1255—Air Temperature External Sensor Circuit Open B1256—Air Temperature External Sensor Circuit Short to Battery Power B1257—Air Temperature External Sensor Circuit Short to Ground B1258—Solar Radiation Sensor Circuit Failure B1259—Solar Radiation Sensor Circuit Open B1260—Solar Radiation Sensor Circuit Short to Battery B1261—Solar Radiation Sensor Circuit Short to Ground B1262—Servo Motor Defrost Circuit Failure B1263—Servo Motor Vent Circuit Failure B1264—Servo Motor Foot Circuit Failure B1265—Servo Motor Cool Air Bypass Circuit Failure B1266—Servo Motor Air Intake Left Circuit Failure B1267—Servo Motor Air Intake Right Circuit Failure B1268—Servo Motor Potentiometer Defrost Circuit Failure B1269—Servo Motor Potentiometer Defrost Circuit Open B1270—Servo Motor Potentiometer Defrost Circuit Short to Battery B1271—Servo Motor Potentiometer Defrost Circuit Short to Ground B1273—Servo Motor Potentiometer Vent Circuit Failure B1273—Servo Motor Potentiometer Vent Circuit Open B1274—Servo Motor Potentiometer Vent Circuit Short to Battery B1275—Servo Motor Potentiometer Vent Circuit Short to Ground B1276—Servo Motor Potentiometer Foot Circuit Failure

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B1277—Servo Motor Potentiometer Foot Circuit Open B1278—Servo Motor Potentiometer Foot Circuit Short to Battery B1279—Servo Motor Potentiometer Foot Circuit Short to Ground B1280—Servo Motor Potentiometer Cool Air Circuit Failure B1281—Servo Motor Potentiometer Cool Air Circuit Open B1282—Servo Motor Potentiometer Cool Air Circuit Short to Battery B1283—Servo Motor Potentiometer Cool Air Circuit Short to Ground B1284—Servo Motor Potentiometer Air Intake Left Circuit Failure B1285—Servo Motor Potentiometer Air Intake Left Circuit Open B1286—Servo Motor Potentiometer Air Intake Left Circuit Short to Battery B1287—Servo Motor Potentiometer Air Intake Left Circuit Short to Ground B1288—Servo Motor Potentiometer Air Intake Right Circuit Failure B1289—Servo Motor Potentiometer Air Intake Right Circuit Open B1290—Servo Motor Potentiometer Air Intake Right Circuit Short to Battery B1291—Servo Motor Potentiometer Air Intake Right Circuit Short to Ground B1849—Climate Control Temperature Differential Circuit Failure B1850—Climate Control Temperature Differential Circuit Open B1851—Climate Control Temperature Differential Circuit Short to Battery B1852—Climate Control Temperature Differential Circuit Short to Ground B1853—Climate Control Air Temperature Internal Sensor Motor Circuit Failure B1854—Climate Control Air Temperature Internal Sensor Motor Circuit Open B1855—Climate Control Air Temperature Internal Sensor Motor Circuit Short to Battery B1856—Climate Control Air Temperature Internal Sensor Motor Circuit Short to Ground B1857—Climate Control On/Off Switch Circuit Failure B1858—Climate Control A/C Pressure Switch Circuit Failure B1859—Climate Control A/C Pressure Switch Circuit Open B1860—Climate Control A/C Pressure Switch Circuit Short to Battery B1861—Climate Control A/C Pressure Switch Circuit Short to Ground B1862—Climate Control A/C Lock Sensor Failure B1946—Climate Control A/C Post Evaporator Sensor Circuit Failure B1947—Climate Control A/C Post Evaporator Sensor Circuit Short to Ground B1948—Climate Control Water Temperature Sensor Circuit Failure B1949—Climate Control Water Temperature Sensor Circuit Short to Ground B1966—A/C Post Heater Sensor Circuit Failure B1967—A/C Post Heater Sensor Circuit Short to Ground B1968—A/C Water Pump Detection Circuit Failure B1969—A/C Clutch Magnetic Control Circuit Failure B2175—A/C Request Signal Circuit Short to Ground B2380—Heater Coolant Temp Sensor Circuit Short to Ground B2381—Heater Coolant Temp Sensor Circuit Open B2428—A/C Post Heater Sensor 2 Circuit Failure B2429—A/C Post Heater Sensor 2 Circuit Short to Ground B2513—Blower (Fan) Circuit Failure B2514—Blower (Fan) Circuit Short to Battery Power B2515—Heater Blower Relay Circuit Failure B2516—Blower Control Circuit Failure B2518—Compressor Over Temperature Fault B2606—A/C Temperature Sensor Out of Range 377 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Generic OBD-II Network Codes: U0164—Lost Communications with HVAC Control Module U0165—Lost Communications with HVAC Control Module, rear U0324—Software Incompatibility with HVAC Control Module U0325—Software Incompatibility with Auxiliary Heater Control Module U0422—Invalid Data Received from Body Control Module U0424—Invalid Data Received from HVAC Control Module U0425—Invalid Data Received from Auxiliary Heater Control Module Though this list is extensive, it is not intended to be comprehensive. Always consult specific manufacturer service information to aid in the diagnostic process. Using a scan tool and following the published diagnostic steps for a specific trouble code will improve your ability to repair HVAC system failures. Though scan tools are a vital tool, not all system failures have set diagnostic trouble codes. You must become familiar with circuit wiring diagrams and the network communication process on the vehicle you are working on. In addition, you must become comfortable in the use of digital multimeters and all the functions available on them. A thorough understanding of automotive electrical systems and electronics is required in today’s world of advanced electrical control devices, along with knowledge of specific system operation.

Electronic HVAC Control Module Self-Diagnosis

Shop Manual Chapter 11, page 477

Some older climate control systems have the ability to perform self-diagnostics without the aid of a scan tool. These systems can run function tests and enter sensor/actuator relearn procedures. In addition, these systems can display trouble codes either in the form of flash coding LEDs on system control buttons or by displaying the code on the climate control screen. To access trouble codes, the system must enter the self-diagnosis mode. The retrieval system varies among manufacturers and even varies between models and years, making it necessary to consult vehicle-specific service information to enter the self-diagnosis mode. In general, the electronic control panel will enter the self-diagnosis mode by pressing a series of buttons on the control panel in a specific sequence. Once the self-diagnosis mode is entered, the control panel will display the code or flash an LED on one of the control panel buttons, with any specific codes stored. In addition, some systems will perform a self-test on all output devices and cycle the HVAC system through all available mode cycles (in other words, operate all mode control doors in the ventilation system). The following is an example of a portion of one manufacturer’s sequence required to access the Self-Diagnostic Mode (Figure 11-62): 1. Turn the ignition switch ON. 2. Within 10 seconds of turning the ignition switch on, press and hold the HVAC control panel OFF button for at least 5 seconds. 3. Check inputs from each sensor circuit for opens or shorts: a. Does code 20 appear on the display? i. Yes—Go to step 4. ii. No—Go to step 13. 4. Check Advance function: a. Push the driver’s side temperature control UP switch. b. Advance to step 5—Mode and intake door motor position switch check. i. Yes—Go to step 6. ii. No—Replace Multifunction control panel assembly (switch malfunction). 5. Check Return function: a. Push the driver’s side temperature control DOWN switch.

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Ignition switch ON Within 10 seconds after starting engine press OFF switch for a least 5 seconds.

Temperature switch (driver side)

Step 2 - Input signals from each sensor are checked. Press temperature control UP switch (driver's side)

Press temperature control DOWN switch (driver's side)

Step 3 - Mode and intake door motor position switch is checked. Press temperature control UP switch (driver's side)

Press temperature control DOWN switch (driver's side)

Step 4 - Actuators are checked.

Press temperature control UP switch (driver's side)

Press temperature control DOWN switch (driver's side)

Display screen Status

OUTSIDE 25˚C

Audio OFF

Passenger

Driver

25.0˚C

DUAL

AUTO

25.0˚C

Ignition switch OFF Self-diagnosis is canceled or AUTO switch ON

Step 5 - Temperature detected by each sensor is checked. Press fan UP + switch Intake switch

Press fan DOWN - switch

Auxiliary mechanism Temperature setting trimmer Foot position setting trimmer Inlet port memory function

Shifting from STEP 5 to auxiliary mechanism is accomplished by means of pressing (Fan) UP switch.

Step 5 - Detects multiplex communication error FIGURE 11-62  An example of a manufacturer’s sequence to access the Self-Diagnostic Mode for the electronic climate control system.

b. Return to step 3—Inputs from each sensor circuit are checked for opens or shorts. i. Yes—Push the driver’s side temperature control UP switch and advance to step 6 again: Mode and intake door motor position switch check. ii. No—Malfunctioning control panel assembly (switch) or control module. 6. Check Mode and intake door motor position switch: a. Does code 30 appear on the display? i. Yes—Go to step 14. ii. No—Go to step 7. This sequence continues for several more steps, but the ­general idea of how the systems work should be apparent.

Controller Area Network If you are going to work on an automatic climate control system, it is necessary to understand the network on which they communicate. The Controller Area Network (CAN) protocol is the latest serial bus communication network used on OBD II systems and offers real-time

Controller Area Network (CAN) A high-speed serial bus communication network. The CAN protocol has been standardized by the International Standards Organization (ISO) as ISO 11898 standard for high-speed and ISO 11519 for lowspeed data transfer.

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Starting in the 2008 model year, the universal communication method or “language” is used for sharing of information between modules on a vehicle network or with a scan tool.

control. The speed of data transmission is expressed in bits per second (bps). The high-speed version, which can operate at 1 megabit per second (Mbps) and is used for power train management systems, performs in virtually real-time data rate transfer speeds. The low-speed version can operate at 125 kilobits per second (Kbps) and is used for body control modules and passenger comfort features. Although the prefix kilo usually indicates a multiplier value of 1,000, in a serial data stream a kilobyte has a value of 1,024 bytes of data. This is the mathematical result of a base two numbering system (ones and zeros) carried to the tenth place. Additionally, a megabyte has a value of 1,048,576 bytes of data, which is one kilobyte (1,024) squared. The CAN system has allowed for improved communication with onboard vehicle systems and is a true multiplexed network. The CAN communication line is divided into three classes or speeds of serial data transfer. Class A is the slowest transmission rate with speeds less than 10 kbps. Class A networks are used for low priority data transmission; generally related to noncritical body control module functions such as memory seats. Class B networks are mid-speed range networks with data transmission speeds between 10 kbps and 125 kbps; generally related to less critical devices such as heating, ventilation, and air conditioning (HVAC); advanced lighting systems; and dash clusters. Class C networks have the fastest data transmission rate with speeds up to 1 Mbps. Class C networks are the most expensive to produce and are used for “mission critical” data transmission that flow at real-time speeds. Examples of Class C data include fuel control and ABS activation activity. The data link connector (DLC) is also connected to the Class C network for improved onboard diagnostics. CAN enables the use of enhanced diagnostics and more detailed DTCs. With CAN, a scan tool is capable of communicating directly with sensors, independently of the PCM. The CAN protocol uses smart sensors. Each component contains its own control unit (microprocessor) called a “node.” Each node on the network has the ability to communicate over a twisted pair of wires or a single wire, called a data bus, with all the other nodes on the network (bidirectional communication) without having to go through a central processing unit (Figure 11-63), unlike other multiplexed systems used in the past for data sharing. Every component on the network is independently capable of processing and communicating data over a common transmission line. Nodes transmit information (messages) with an identifier that prioritizes the message. The messages transmitted from a node are a package of data bits, which include a beginning of message signal, component identifier, message (sensor output signal), and an end of message signal. Because this is a bidirectional communication network, the control module receiving the data will send a signal back that the information was received. In order for this sophisticated communication protocol to function, the data transmission package must be a set size (number of bits) and format, and the information order must be consistent for all devices. When multiple nodes need to send data simultaneously to the control module, the node will first see whether the data bus is busy. The system uses collision detection similar to that of an Ethernet system. But unlike Ethernet, the CAN system can handle high data transmission rates. In essence, the node is looking into traffic to see whether a higher priority node should be allowed to pass. Each CAN node on the network will have its own network unique identifier code, and nodes may be grouped based on function. The data message is then transmitted with its unique identifying code onto the network. Each node and control module on the network will perform an acceptance test of the transmission to determine whether it is relative based on its identifier. Relative information is processed and nonrelative information is ignored. Then the system segments transmissions based on the priority identifier (Figure 11-64) of the data package. The priority is determined by the unique number of the identifier, with lower number identifiers having higher priority. This guarantees higher priority node identifier messages access to the network, and lower priority node messages will be automatically retransmitted in the next available bus cycle based on priority.

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Twisted pair of wires TPS Node

VSS Node

MAF Node

BCM

P.L.

A_CAN

P.L.

C_CAN

A_CAN P.L. = Physical Layer FIGURE 11-64  Each node on the network has its own address and priority identifier. When sending data simultaneously, the CAN system segments data transmissions based on the priority identifier.

PCM

FIGURE 11-63  A twisted pair data bus network with all nodes communicating on a shared line.

Because the CAN protocol technology allows for many nodes on one set of wiring, the overall vehicle wiring harness size is greatly reduced. A twisted pair wired network contains a CAN H (1) and a CAN L (2) wire. The CAN bus is a differential bus system where the data signal from the CAN H (1) wire is a mirror image of the CAN L (2) ­network wire (­ Figure 11-65). The combination of the twisted pair network wiring combined with the differential bus data eliminates the effect of EMF noise on the data transmission. Multiple networks on the vehicle can be linked together by gateways if necessary (Figure 11-66). Class C high-speed data flows on one network, Class B mid-speed data flows on a s­ econd network, while Class A low-speed data flows on a third network. As an example, the coolant

CAN 1 CAN 2

FIGURE 11-65  Waveform of the CAN H (1) and of the CAN L (2) twisted pair data bus network.

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Occupant classification and restraint

CAN B data bus medium speed

60V 120V Central gateway DLC

Climate control

Memory seat and mirror

Smart cluster

Front control module

High-speed CAN C data bus

120V power train control

SKIM/RKE

ABS traction control

FIGURE 11-66  An example of a typical CAN B network and a CAN C network.

temperature (CT) sensor will place its data on the network data bus, allowing any control module on the network direct access to the information without the need for one control module (for example, the BCM) requesting the information from another control ­module (for example, the PCM). The BCM has direct access to information without having to request it from the PCM. In 1996, the Environmental Protection Agency (EPA) specified that all vehicles be able to transmit generic scan tool data. However, proprietary data, any data other than P0 codes and data streams, were free to use any other protocol the manufacturer chose. The CAN PCM will still transmit data to the data link connector (DLC) in SAE’s generic scan tool protocol, as specified by the EPA for generic scan tool data communication, such as generic DTCs. But, in order to access all the functions available, you will need to have a scan tool that is compatible with CAN if that is the vehicle’s network operation system. Unless you have purchased a scan tool since the turn of the century (2000), it will be necessary to upgrade your existing scan tool or replace it with one that is capable of communicating with CAN. The EPA emission regulations for the 2008 model year have specified CAN as the new scan tool communications protocol for all vehicles sold in the United States, providing the repair technician more data for troubleshooting emission failures. With CAN, the industry finally has a single standard for onboard diagnostic communication. The CAN protocol still allows access to the typical DTC information and data streams, but with enhanced DTC detail. A scan tool is also capable of bidirectional communication directly with a smart sensor or actuator node as well as other control modules on the network. In addition, flash calibration for almost all nodes on the network will become commonplace. A smart sensor is capable of reporting the result of internal voltage drops, opens, grounds, and other self-test features. The network has the ability to take faulty sensors off-line and can self-diagnose the difference between a faulty device and a faulty circuit.

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Climate Control Network

The climate control network on a CAN system communicates on a medium-speed CAN B data bus network with data transmission speeds between 10 kbps and 125 kbps. The climate control system uses a small local area network (LAN) between the climate control module and the various mode door and air mix door motors in the system (Figure 11-67). The climate control module and motors are connected by a data transmission line and a power supply line. The data transmission line transmits initial compulsory start signal, component addresses, motor opening angle signals, error-checking messages, and motor stop signals. A local control unit (LCU) is integrated into each mode door motor, air mix door motor, recirculation door motor, and even the climate control module (Figure 11-68). The LCU is responsible for the following network functions: component address, data transmission, motor opening angle signals, motor stop and drive decision, opening angle sensor, and comparison data. The climate control module receives data from each of the system sensors (Figure 11-69) and based on this information will send open/close commands out to the LCUs of the various mode door motors (nodes). Each node is responsible for reading its respective signal according to the address code (Figure 11-70). Next, each node sends position information back to the control module LCU, where the information is compared to the command signal (Figure 11-71). Subsequently, the climate control module can select hot/cold, defrost/vent, fresh air/recirculated air, or any combinations required, and verify that the command was followed. On some vehicles, if the vehicle battery has been disconnected, the climate control module will engage the air-conditioning compressor clutch. A relearn procedure must be performed for all the mode door motors with a scan tool or, on some models, through their self-diagnostic procedure. A scan tool has become a necessary tool for many vehicle diagnostic procedures. Also it is more important than ever to follow manufacturers’ diagnostic steps in the service information published. Power supply line Communication line Climate control module

Air mix door motor (Driver side)

Air mix door motor (Passenger side)

Mode door motor (Driver side)

Mode door motor (Passenger side)

Upper ventilator door motor

Intake door motor

FIGURE 11-67  The climate control system uses a small local area network (LAN) between the climate control module and the various mode door and air mix door motors in the system.

Climate control module

LCU (Local Control Unit)

Communication interface

Air mix door motors, mode door motors, upper ventilator door motor, and intake door motor

LCU (Local Control Unit)

M

PBR

FIGURE 11-68  A local control unit (LCU) is integrated into each mode door motor, air mix door motor, recirculation door motor, and even the climate control module.

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A/C LAN system

• Temperature control switch (Potentio temperature control) • A/C switch • FAN switch • Intake switch • MODE switch • Defroster switch • OFF switch • DUAL switch • AUTO switch • UPPER VENT switch

Mode door motor (Driver side) Climate control module

Ventilator door (Driver side) Max. cool door (Driver side)

PBR (Potentio Balance Resistor)

Defroster door

Mode door motor (Passenger side)

Ventilator door (Passenger side) Max. cool door (Passenger side)

PBR (Potentio Balance Resistor) Air mix door motor (Driver side)

Unified meter and A/C amp. (Microcomputer)

Intake sensor

Ambient sensor

PBR (Potentio Balance Resistor)

Air mix door (Driver side)

Air mix door motor (Passenger side)

Air mix door (Passenger side)

PBR (Potentio Balance Resistor) Upper ventilator door motor

Upper ventilator door

In-vehicle sensor

PBR (Potentio Balance Resistor)

Sun load sensor

Intake door motor

Intake door

PBR (Potentio Balance Resistor) ECM

IPDM E/R

Blower motor Refrigerant pressure sensor

Compressor Engine coolant temperature sensor Vehicle speed sensor

FIGURE 11-69  The climate control module receives data from each of the system sensors and based on this information will send open/close commands out to the LCUs of the various mode door motors.

Transmission data form Start

Address Opening angle data

Error check

Transmitted from unified meter and A/C Amp.

Air mix (Driver side) 0.1 sec

Air mix (Passenger side)

Mode (Driver side)

Mode (Passenger side)

Upper ventilator

Stop signal

Transmitted from door motors

Intake

Air mix (Driver side)

Air mix (Passenger side)

Mode (Driver side)

FIGURE 11-70  The LCU communication data stream contains initial compulsory start signal, component addresses, motor opening angle signals, error-checking messages, and motor stop signals.

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Unified meter and A/C amp.

Air mix door motor (Driver side)

Air mix door motor (Passenger side)

Mode door motor (Driver side)

Mode door motor (Passenger side)

Upper ventilator door motor

Intake door motor

: Opening angle indication signal : Door motor stop signal FIGURE 11-71  Each node sends position information back to the control module LCU, where the information is compared to the command signal.

Heated and Climate Controlled Seating Though not part of the HVAC system on vehicles, both heated seats and climate controlled seats (CCS) are part of the overall passenger compartment comfort package on many vehicles. Seat surface temperature is an important factor for overall customer satisfaction of the entire vehicle climate control system. The average vehicle HVAC system can adjust the cabin air temperature to the occupant’s comfort zone in about 12 to 15 minutes when outside temperature conditions are extreme, hot or cold. Studies have shown that when vehicles are only driven for short distances, the HVAC system does not have enough time to reach optimum performance levels to meet the needs of the passenger compartment comfort level selected. To meet these demands, manufacturers have developed both heated seats and climate controlled seating. Heated seats are generally only offered for the two front passenger seats and are controlled independently from two separate switches typically located on the center console or on the instrument panel center stack (Figure 11-72). The most common design uses two resistive heating elements per seat (Figure 11-73). One is located in the seat back and the other is located in the bottom seat cushion. When electrical current passes through the heated seat element, the resistance of the wire used in the element converts the electrical energy into heat energy. The seats are controlled by a heated seat module that contains the control logic and software for the system. On current systems, the module communicates on the Controller Area Network (CAN) data bus. The following discussion covers the more complicated CAN

OFF

A/C

A/C

72

MODE AUTO

FAN REAR

AUTO

Driver side heated seat switch

Off

Passenger side heated seat switch

FIGURE 11-72  Front passenger heated seats are controlled independently from two separate switches typically located on the center console or on the instrument panel center stack.

FIGURE 11-73  The most common design uses two resistive heating elements, one in the seat cushion and one in the back.

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data bus systems; it should be noted that although the basic design of the systems are similar among manufacturers, specific system operation and diagnosis information for the specific make, model, and year should always be consulted. The resistive element heated seat system operates on battery current that is only received when the ignition switch is in the ON or RUN position, and the heated seats will turn off anytime the switch is moved from this position. The heated seat control module responds to messages sent from both the heated seat switches and the ignition switch status by controlling integrated solid-state relays for the 12-volt output to the heating elements located in each seat. These switches’ inputs send a resistive signal to a controller node, which in turn sends a signal by the CAN data bus to the heated seat module, signaling the module to either energize or de-energize the heating element in the respective seat(s). The individual heated seat switches generally have two settings: one for low temperature (100.48F or 388C) and one for high temperature (107.68F or 428C). In addition, the switches contain an amber LED for both high/low heat setting to indicate to the passenger which setting has been selected. Some systems will supply a boosted heat level for the first few minutes of operation to quickly bring the seat up to temperature when the high temperature switch position is selected and then drop back to normal high-temperature current flow after this initial boost period. Most systems will also automatically shut off after operating for extended periods of time, generally two hours. The system will also shut off if an open or short is detected in the heating element system. The resistive element in the heated seat cushion and back consists of a carbon fiber element with multiple circuits wired in parallel with one another (Figure 11-74). If one or more circuits in the element develop a malfunction, the other circuits will continue to operate and provide heat, though a dead spot (no heat) in the cushion may develop. The carbon fiber element is captured between the leather seat cover and the cushion assembly. The heated seat element cannot be repaired and must be replaced as an assembly if found to be damaged or inoperative. Center cushion heating element

Seat cushion foam Side bolster heating elements FIGURE 11-74  Heated seat resistive elements.

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Lo

Hi

Lo

Hi

Left seat switch

Right seat switch Left seat Left seat switch switch return sense

Right seat Right switch seat return switch sense

Data bus (+)

Data bus (−)

Data bus (+)

Data bus (−)

Switch bank

Cabin compartment node (CCN)

Battery +

Battery feed

Left seat HSD

Left seat cushion

Left seat back

Heated seat module (HSM)

Right seat HSD

Ground

Right seat cushion

Right seat back

FIGURE 11-75  Typical wiring diagram for a resistor element heated seat.

To properly diagnose these systems, a scan tool and the appropriate service information for the specific make, model, and year of the vehicle is required (Figure 11-75). These systems are equipped with a low/high voltage cutoff feature and will shut down if the vehicle voltage drops below 11.1 volts or rises above 15.5 volts as a general rule. Always verify the proper system voltage and that the battery is fully charged prior to any diagnosis of the heated seat system. Heated seats have been around for many years, but climate controlled seating is a relatively new addition to the comfort package. Some early design systems utilized a resistive heating element to heat the seat and cooled air from the vehicle air-conditioning system to cool the seat. Most current production climate controlled seating is self-contained (Figure 11-76) and does not use a standard resistive heating element to heat the seat cushion or rely on the vehicle air-conditioning system. Instead, both the passenger seat heating and cooling modes draw air in from the passenger cabin, and a solid-state thermoelectric device (TED) heat pump rapidly converts electric current into heat or cool air. Then the integrated blower pumps the air through the seat cushions (Figure 11-77). The Amerigon’s Climate Control Seat TM (CCSTM ) system is completely independent of the vehicle’s HVAC system and is one of the most popular self-contained systems being used by most automotive manufacturers in the United States, Japan, and Europe. Each seat has independent electrical controls and greatly improves passenger comfort by focusing the cooling/heating directly on the passenger, independent of cabin air temperature.

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The airflow passes through the grooves on the seat pad surface

Terms to Know Aspirator Bellows Circuit breaker Controller Area Network (CAN) Delta P (Ap) Dual systems Fuse Insulator Master control Pressure switch Programmer Rheostat Vacuum pot

Climate control seat fan FIGURE 11-76  Climate controlled seat with integrated heating and cooling unit as well as selfcontained air ducts and blower assembly.

FIGURE 11-77  Air that has been either heated or cooled, based on driver command, is pumped through the passenger in the seat cushion.

SUMMARY ■■

■■

Many of the components of an automatic temperature control system are covered in this chapter. Because of the complexity of the automatic control system and its number of variations, it is essential that manufacturers’ specifications, manuals, and schematics be consulted for any specific year/make/model car to be serviced.

REVIEW QUESTIONS Short-Answer Essay 1. What is the purpose of the clutch diode? 2. Explain what is meant by this sentence: “The change in resistance value of each sensor is inversely proportional to a temperature change.” 3. What is the relationship of the aspirator to the in-car temperature sensor? 4. Compare the difference between a temperature-­ controlled switch and a pressure-controlled switch. 5. Describe a sun load sensor.

6. On an automatic temperature control system what occurs if the temperature selected is the lowest limit or the highest limit? 7. Describe an air humidity sensor and its relationship to air temperature. 8. Describe the evaporator temperature sensor and the outside temperature sensor and how they are similar. 9. Describe the term input sensor. 10. Briefly describe the climate control network on a CAN bus system.

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Fill in the Blanks

Multiple Choice

1. The climate control network on a _______________ system communicates on a medium-speed _______________ _______________ data bus network.

1. Which of the following is the best description of a pressure switch designated NC? A. It is held closed during normal pressure conditions. B. It is held closed during extreme low-pressure conditions. C. It is held closed during extreme high-pressure conditions. D. It is held open during extreme high-pressure conditions.

2. The control module analyzes data from the _______________ _______________ _______________, selected passenger compartment temperature, and the evaporator temperature sensor to determine whether the air-conditioning compressor clutch should be _______________ _______________ _______________. 3. The climate control module uses input sensor _______________ _______________ _______________ _______________ to determine actuator commands that will be required to maintain selected temperature. 4. On an automatic climate control system with a _______________ _______________ sensor when ­sunlight intensity is _______________, the control module will automatically _______________ blower fan speed and increase the volume of air flowing to the dash discharge vents. 5. The air _____________ sensor integrates a temperature sensor since determining air humidity is dependent on air _____________. 6. The FOTCC system uses a _______________ ­sensitive compressor cycling switch instead of a _______________ sensitive switch. 7. The outside temperature sensor (OTC), also called an _______________ _______________ _______________, is a _______________ temperature coefficient thermistor. 8. Some in-car temperature sensors use a small _______________ _______________ positioned behind the thermistor to draw in-car air across the sensor to maintain accurate in-car _______________ readings. 9. An automatic air-conditioning system should provide selected in-car _______________ and _______________ at all times. 10. Many air-conditioning systems today are equipped with a refrigerant pressure sensor, also called a _______________ _______________, on both the _______________ pressure side and the _______________-pressure side of the refrigerant system.

2. The temperature fluctuates between hot and cold on a vehicle equipped with an automatic temperature ­control system. Which of the following is the most likely cause? A. An open blower motor control relay B. A low refrigerant charge level C. A faulty coolant temperature sensor D. A disconnected in-car temperature sensor aspirator tube 3. All of the following statements are correct, except: A. A low-pressure cutoff switch opens at a predetermined low pressure. B. Atmospheric pressure at sea level is 14.696 psia. C. A clutch coil resistor is used to prevent high voltage spikes. D. A sensor is an electrical input device that may be used to sense temperature or pressure. 4. A vehicle’s automatic temperature control system does not hold the temperature set on the temperature ­control assembly. What operation should the technician perform first? A. Change the in-car temperature sensor. B. Evacuate and recharge the refrigerant system. C. Refer to the appropriate diagnostic fault chart. D. Replace the mix door actuator. 5. The blower motor does not run when the HEAT mode is first selected and the engine is cold on a vehicle that is equipped with an automatic temperature ­control system. Which of the following is the most likely cause? A. The ambient air temperature is open. B. The system is functioning normally. C. There is an excessive voltage drop at the blower motor. D. The coolant temperature sensor is out of range.

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6. When the air-conditioning switch is turned to the OFF position, the compressor clutch stays engaged. Which of the following is the most likely cause? A. The compressor clutch air gap is set too wide. B. An electronic thermostat is out of specification. C. A pressure switch is stuck closed. D. A compressor clutch relay is stuck in the closed position.

7. The blower motor on a four-speed switched system only functions on the high-speed setting. Which of the following is the most likely cause? A. The current draw at the blower motor is too high. B. The resistor block assembly is faulty. C. There is an open blower motor switch. D. The blower motor ground is faulty.

20A Fuse Heater A/C control assembly

LOW HI

M3 M2

M1

R1 R2 R3 Blower motor relay

R4

Fuse 30A

Hot at all times

Blower motor

8. The blower motor in the above figure has blower motor speeds M2, M3, and High, but does not run in either LOW or M1. Which of the faults listed below could be the cause? A. Faulty heater A/C control assembly B. Faulty resistor block C. Faulty blower motor relay D. Faulty blower motor

9. The following may be used to maintain in-vehicle ­temperature, except: A. Evaporator thermistor B. Variable displacement compressor C. Mass airflow sensor D. Pressure cycling switch

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Hot at all times

Hot in run

IP Fuse Panel HTR-A/C 25A

Junction block

HVAC controller TEMP Hot in run or start

A

Underhood fuse-relay center

LED

Compressor logic

B AC

DEFROST

Ign fuse 10A

A/C fuse 10A

Compressor clutch relay LO M1

Fan switch

Cycling switch

M2 HI

A/C clutch

High pressure cutoff switch

AC enable

Blower motor

Blower motor relay

10. In the above figure if a ground is not supplied by the PCM at point “C,” what effect would this have on the circuit shown? A. A/C compressor clutch would always be engaged. B. The blower motor would not have high speed.

C PCM

C. The blower motor would not be turn on. D. A/C compressor clutch would not be turn on.

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Chapter 12

Retrofit and Future Trends (R-12 TO R-134a) Upon Completion and Review of this Chapter, you should be able to: ■■

■■ ■■

Discuss CO2 (R-744) as a refrigerant and why some are still holding out hope for it in the future.

■■

Discuss the various refrigerants approved to replace R-12.

■■

Identify the refrigerant approved to replace R-12 in automotive air-conditioning systems.

Understand the problems associated with contaminated refrigerant. Compare components used in R-134a systems with those used in R-12 systems.

Introduction

Retrofit is the process of modifying equipment that is already in service by installing updated parts and materials made available after the time of original manufacturing. Alternative refrigerant is a refrigerant that can be used to replace an existing refrigerant, such as ozone-friendly R-134a that is used to replace ozonedepleting R-12.

In this chapter, we will first discuss future trends and changes that are taking place or may take place within the refrigerant industry. Only a few years ago, it looked like the industry was going to abandon R-134a in favor of a refrigerant with a lower global warming potential (GWP). In Europe, the switch to R-1234yf has already been taking place. Daimler is one of the manufacturers that is still dedicating research and development money into R-744 CO 2 refrigerant systems, while other European manufacturers are looking at alternative refrigerants similar in system performance to R-134a that can compete with R-1234yf. At the time of this writing, Daimler has decided to continue producing new vehicle platforms using R-134a in violation of the EU requirement to switch to a low-GWP refrigerant beginning in 2013 and fully abandon R-134a by 2017. Daimler contests that their testing indicates that R-1234yf is a flammable refrigerant and as such is unsafe in their vehicle platforms. Ultimately this will be decided in the European court system. In addition, some say do not count R-134a out in the U.S. market due to improvements in system designs, smaller sizes, and decreased lifetime leakage rates. It appears R-134a will be replaced by a refrigerant with a GWP number below 150 by the early 2020s. Some are also predicting that as the industry eventually shifts to fully electric vehicle–powered platforms that gas-based air-conditioning systems will be replaced by a fully electric gasless air-conditioning system, which is yet to be developed for automotive commercial applications. But be sure, whatever the changes are we will be ready to service them when the time comes. When speaking about an automotive air-conditioning system, the term retrofit is used to describe the process of converting an R-12 system to one using an alternative refrigerant. In this text, it will be assumed that the conversion refrigerant is R-134a because the automotive industry worldwide chose this refrigerant to be the replacement in new, as well as retrofitted, automotive air-conditioning systems. Due to the current age of vehicles (pre-1994) that

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require retrofitting, it is becoming a less prevalent procedure. At some point, retrofitting will be limited to vehicles under consideration for restoration or those luxury platforms that retain substantial market value. Regardless of what happens in the future we will not be retrofitting either an R-12 system or R134A to R-1234yf refrigerant. In fact this is not allowed by the EPA. R-134A will continue to be available for servicing systems into the future regardless of the popularity of R-1234yf. Most automobile manufacturers have developed retrofit kits and procedures for some of their late 1980 through early 1990 model vehicles. These kits and information are intended to provide the best level of performance with R-134a refrigerant, with no regard for costs. Vehicle owners, however, generally do not want to pay the high cost for a retrofit and are therefore often the target of the independent technician offering an inexpensive solution—the “magic bullet,” so to speak.

New Refrigerant Systems on the Horizon Air-conditioning systems, which were once considered a luxury, are now considered standard equipment on most passenger vehicles. However, with increased popularity came environmental hazards. We have already discussed the environmental hazards and dangers of an R-12 system, but there are also dangers associated with R-134a. R-134a is not an ozonedepleting refrigerant, but it is a greenhouse gas. The concern in the world community has shifted from the threat of ozone-depleting chemicals to a concern over global warming. In 1997, the U.S. government decided not to sign the Kyoto Protocol, an international agreement that, among other things, set reduction quotas for the production of greenhouse gases that contribute to global warming. The U.S. government did agree with the principle of the agreement and decided to implement a voluntary U.S. policy to limit the production of greenhouse gases. Global warming has become a more pronounced concern, but as of the time of printing this textbook, the United States had not passed any legislation to phase out or ban the use of R-134a refrigerant but is pressuring the industry by incentivizing manufacturers to choose a lower GWP refrigerant with the use of carbon credits. With that said there is ­considerable research taking place to find an alternative to R-134a that will be more environmentally friendly and still offer the passenger comfort levels currently achievable at a reasonable cost and dependability. The front-runner and the one that has gained the most widespread acceptance is HFO-1234yf (R-1234yf), though some are still holding out long-term hopes for CO 2 (R-744) systems, but that appears doubtful at least for now. CO2

(R-744) Refrigerant Systems

Another alternative refrigerant that once held widespread hopes for being the next refrigerant due to its low GWP rating of 1 is carbon dioxide, CO 2 (R-744), a naturally occurring gas. Though most research has been shelved for now, further discussion is warranted to understand why the industry makes the choices that it does and other options that are available though not currently likely. A CO 2 system is similar to today’s systems, but the operating pressures are extremely high, seven to ten times greater than for R-134a systems. Currently, the efficiency of the overall system is much lower than R-134a systems. Less-efficient systems require more power to perform the same job, and because we still rely on the internal combustion engine, the overall benefits of the CO 2 system are negated. As research continues, R-744 systems are becoming more efficient. Carbon dioxide shows potential as a refrigerant because the properties of the gas make it ideal for small portable refrigeration systems. Although technically CO 2 is a greenhouse gas, its release into the atmosphere is harmless because there is enough CO 2 occurring naturally or

R-1234yf is a lowGWP refrigerant developed by Honeywell and Dupont. R-744 is the refrigerant gas designation given to carbon dioxide (CO2 ).

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Adiabatic expansion is a process that occurs without the loss or gain of heat.

obtained through natural chemical reaction that no new CO 2 would have to be created. The new R-744 refrigerant systems could greatly benefit automotive manufacturers, who could, for the first time since R-12 systems, offer a system that cools better than the current R-134a systems and poses no environmental hazard that could affect costs through government regulations, but high costs negate this benefit. One large hurdle that automotive manufacturers must first overcome is the extreme line pressure that the system must operate at. The average high-side pressure will be in the range of 2,000 psig (13789.5 kPa), which means system components like the compressor and lines must be strengthened. On the other hand, the new R-744 systems require about half the refrigerant capacity of current R-134a systems, with better cooling results. There are some differences in the R-744 system compared to the R-134a system. The R-744 system (Figure 12-1) has a gas cooler instead of a condenser to reduce the temperature of the R-744 gas but not condense it. Instead, some of the gas condenses as it passes through the expansion valve as a result of adiabatic expansion. Further cooling occurs by exchanging heat with the inner heat exchanger, which is between the gas cooler and evaporator on the low side of the system. The R-744 system can also serve as a source of heat for the passenger compartment through the use of an integrated heat pump (Figure 12-2), a special heat exchanger that uses the heat created in the air-conditioning system to provide heat for the passenger compartment. This will be a very useful system for both passenger compartment heating and cooling, especially on electric-powered or fuel cell–powered vehicles (which have little or no waste heat). In addition, with smaller, more fuel-efficient internal combustion engines, the need for a supplemental heater is also growing, especially in the compact diesel market. This system will enable both heating and cooling simultaneously by regulating refrigerant gas flow through both expansion valves in the system. One expansion valve will regulate refrigerant flow to the evaporator for cooling, while the second expansion valve will regulate refrigerant flow to the interior gas cooler (heater core) for heating. Compressor Low pressure

High pressure

Expansion device

Gas cooler

Accumulator/internal heat exchanger

Evaporator High-performance heat exchanger

FIGURE 12-1  A typical R-744 (CO 2 ) refrigerant system.

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Bypass valve 2

Accumulator

Exterior gas cooler

Evaporator

Expansion valve 2

Expansion valve 1

Bypass valve 1

Compressor Interior gas cooler

FIGURE 12-2  An R-744 system with heat pump for passenger compartment heating.

As for the near future, we will see more electronics integrated into the automotive airconditioning system. The use of computer-controlled variable displacement compressors will increase, and electric-driven compressors will become commonplace on vehicles with start-stop technology (idle shutoff systems). There will also be an increased use of electronic expansion valves and orifice tubes. The future looks bright and exciting for the automotive air-conditioning industry.

The Inexpensive Retrofit

The procedures for an inexpensive retrofit are relatively simple and generally do not require major component replacements. The process usually only requires removal of the R-12 refrigerant, new fittings, new label, and the addition of the proper lubricant. For many, this simple inexpensive retrofit will provide the owner with an air-conditioning system performance that is comparable to the former R-12 system. Even if the retrofit results in slightly reduced performance, it is usually sufficient for customer satisfaction. The EPA has an ongoing program intended to educate car owners on matters concerning retrofit options. Many car owners, however, rely on their service technician for their education. When recommending a retrofit to a customer, the “three C’s” should be discussed: cost, climate, and components. Cost.  What is the value of the car? How long will the customer continue to drive it? Is it a refrigerant leaker or is this the first time the air-conditioning system has been serviced? How much is the customer willing to spend? Climate.  Does the customer live in the North and require minimal air-conditioning performance because the car is only used for occasional short pleasure trips, or does the customer live in the South and need maximum performance because the car is used five or six days a week for business? 395 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Components.  Are the air-conditioning system components in good working order? Are they compatible with the new refrigerant, R-134a? Are there any indications of leaking hoses, restrictions in the system, or a noisy compressor? If not operational, did the system cool satisfactorily when it was last working? If R-12 system performance is no more than marginally satisfactory, retrofitting will not make it better. To the contrary, owners should be prepared for a slight reduction in system performance.

Retrofit Problems

Crosscontamination is when one refrigerant is contaminated with another. This usually occurs due to improper or incomplete service procedures.

In older cars, it is often necessary that worn air-conditioning system components be replaced. R-134a operates at a higher pressure than R-12 and will put additional stress on system components. Older, somewhat worn components not designed for R-134a service may not withstand the higher pressures and are more likely to fail. There is no such thing as a universal retrofit kit that can be purchased nor is there a set procedure for a technician to follow that will ensure a successful retrofit for every car. Even within a given vehicle model, the retrofit requirements will vary. For example, a vehicle driven 90,000 miles (144,810 kilometers) in southern Florida may require a more extensive retrofit than an identical car driven, say, 25,000 miles (40,225 kilometers) in northern Minnesota. According to EPA regulations, any alternate refrigerant used to replace R-12 requires the following: ■■ Unique service fittings (Figure 12-3) must be used on both the high side as well as the low side of the system. This requirement is intended to reduce the likelihood of crosscontamination of the air-conditioning system or the repair facility’s refrigeration service equipment. ■■ Use of the new refrigerant must be noted on a uniquely colored label (Figure 12-4) to distinguish the type refrigerant and lubrication used in the system. ■■ All R-12 must be properly removed from the system before filling the system with an alternative refrigerant. ■■ To prevent release of refrigerant to the atmosphere, a high-pressure compressor shut-off switch must be installed on any system equipped with a pressure relief device. ■■ Separate, dedicated EPA-approved equipment must be used to recover R-12 refrigerant from the system. ■■ Barrier hoses must be used with alternative refrigerant blends that contain HCFC-22.

FIGURE 12-3  An R-134a system uses unique hose fittings.

FIGURE 12-4  A label identifies the type of refrigerant in the system.

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The Replacement Refrigerant of Choice Several refrigerants in addition to R-134a are now listed by the EPA as acceptable for motor vehicle air conditioner (MVAC) use under their SNAP plan. Others are under SNAP review. The SNAP program tests and evaluates substitute refrigerants for their effect on human health and the environment. SNAP does not test and evaluate refrigerants for performance or durability. Except for R-134a, no refrigerant has been endorsed by vehicle manufacturers for use in MVACs. While some alternate refrigerants are being marketed as “drop-ins,” there is by definition no such thing as a refrigerant that can literally be “dropped in” on top of existing R-12 in a system. The current refrigerant of choice—R-134a—is considered to be one of the safest refrigerants based on toxicity data. Extensive tests indicate that R-134a does not pose cancer or birth defect hazards, is not corrosive on steel, aluminum, or copper samples, and is not ­flammable at ambient temperatures at atmospheric pressure. Service equipment and vehicle air-­conditioning systems, however, should not be pressure or leak tested using compressed air. Some mixtures of air and R-134a have been known to be combustible at elevated pressures. As with any other chemical, R-134a should be handled with respect; work in a wellventilated area, wear adequate personal protection, avoid open flames, and do not inhale any vapor.

System Charge

The amount of R-134a charged into the system should initially be 80–90 percent of the charge of R-12. Most manufacturers provide guidelines regarding the amount of R-134a to be used.

Lubricants

The mineral oil used with R-12 cannot be adequately transported through the system by R-134a. Most, but not all, automobile manufacturers chose polyalkaline glycol (PAG) lubricants for use in new and retrofitted air-conditioning systems charged with R-134a. PAGs are very hygroscopic; they draw water from the atmosphere when exposed to open air. Some specialists choose to use polyol ester (POE) lubricants (Figure 12-5), believing that PAG’s hygroscopic nature limits its lubricating ability and causes corrosion in a system. Although it is less hygroscopic than PAG, care must still be taken with POE to ensure that excess moisture does not enter the system. Personal protection such as PVC-coated gloves or barrier creams and OSHA-approved safety goggles should be used when handling these lubricants. Prolonged skin contact or

FIGURE 12-5  A small container of POE lubricant.

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eye contact can cause irritations such as stinging and burning. Avoid breathing any vapors produced by these lubricants, and only use them in a well-ventilated area. They should be stored in tightly sealed containers to prevent contamination by humidity and to ensure that the vapors do not escape. Flushing.  The amount of mineral oil that can remain in a system after retrofitting without affecting performance is still being debated. The technician should always remove as much of the mineral oil as possible, however. Removal may require draining components such as the compressor and accumulator. Tests have shown that any residual R-12 remaining in the system will not have a significant effect on system performance. If the vehicle manufacturer does not recommend flushing the system during the retrofit procedure, it can be assumed that flushing is not necessary. Hoses and O-Rings.  Tests have shown that lubricant used in an automotive air-conditioning system is absorbed into the hose to create a natural barrier to R-134a permeation. In most cases, R-12 nonbarrier hoses will perform well for R-134a service, provided they are in good condition. Any replacement hose, however, should be of the barrier type. If the fittings were not disturbed during retrofit, replacing them should not be necessary. Most retrofit instructions suggest lubricating replacement green or blue R-134a O-rings with mineral oil to provide protection because the mineral oil also provides a natural barrier.

Viton® is a registered trademark of Dupont Dow Elastomers.

Compressors.  Most compressors that function satisfactorily in an R-12 system will continue to function after retrofitting an R-134a system. When a compressor is first operated with R-12, a thin film of metal chloride forms on bearing surfaces to serve as an antiwear agent. This protection continues even after the system has been retrofitted to R-134a. This may explain why new R-12 compressors often fail when installed in an R-134a system without the benefit of a break-in period with R-12. Some older compressors have seals made of Viton® that are not compatible with R-134a or the new lubricants and must be replaced. Also, any compressor that is not in good working order should be replaced during the retrofit procedure with one designed for R-134a service. Desiccants.  R-12 systems often use silica gel or a desiccant designated XH-5, while R-134a systems use either XH-7 or XH-9. Some recommend replacement during the retrofit procedure of the accumulator or receiver-drier to one having XH-7 or XH-9 desiccant. It is generally agreed, however, that the accumulator or receiver-drier should be replaced if the vehicle has over 70,000 miles (112,630 kilometers), is five years or more old, or is opened up for major repair. Condensers and Evaporators.  It is generally accepted that if an R-12 system is operating within the manufacturer’s specifications, there may be no need to replace the condenser or evaporator. The higher vapor pressures associated with R-134a, however, may result in lost condenser capacity. When planning a retrofit, the technician should consider the airflow and condenser design. A pusher-type cooling fan mounted in front of the condenser often has improved the performance of a retrofitted air-conditioning system. Bent, misshapen, or improperly positioned airflow dams and deflectors also affect performance. Hood seal kits are often recommended for retrofit procedures. Pressure Cutout Switch.  Systems not equipped with a high-pressure cutout switch should have one installed to prevent damage to air-conditioning system parts and to prevent refrigerant emissions. The high-pressure cutout switch will disengage the compressor clutch during high-pressure conditions, thereby reducing the possibility of venting refrigerant and engine cooling system overheating. Metering Devices.  Orifice tubes, thermostatic expansion valves, pressure cycling switches, or other pressure controls may have to be changed during the course of a retrofit.

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With the exception of R-134a, all approved alternate refrigerants are blends; they contain two or more refrigerants. In addition to R-134a, the following alternate refrigerants are available. One must be cautioned that not all are approved by the EPA for use in MVAC and MVAC-like appliances. Some are considered by the EPA to be dangerous, and heavy penalties are imposed on those who use them. The EPA makes no exceptions and its rules are simple: Use it—get caught—pay the penalty. There are no excuses. There are one or more questions in the certification exam that test whether the technician “knows the law.” If there are any doubts, call the Stratospheric Ozone Hotline and ask. Their toll-free number is (800) 296-1996.

Other Refrigerants The Mobile Air Conditioning Society (MACS) has warned on many occasions that several refrigerant products are being offered as substitutes for R-12. Many of these refrigerants contain butane (R-600), ethane (R-170), or propane (R-290). Although they are all refrigerants, they are also very flammable materials. By the close of 1993, 13 states and the District of Columbia had established laws that prohibited the use of any flammable refrigerant in mobile air-conditioning equipment. The first states to enact the law were Arkansas, Connecticut, Idaho, Indiana, Kansas, Louisiana, Maryland, North Dakota, Oklahoma, Texas, Utah, Virginia, and Washington. In early 1994, Florida was first to pass a law to make it illegal to use any flammable refrigerant in an automobile air-conditioning system. It is now a violation of federal law to use any refrigerant, flammable or otherwise, in a mobile air-conditioning system if it has not been approved by a department of the EPA known as the SNAP program (www.epa.gov/ ozone/snap/). Currently, there are five refrigerants that are not approved. Although there are 10 refrigerants that are approved for use, only one, R-134a, has been universally accepted by the automotive industry. All refrigerants used in a mobile air-conditioning system must have unique fittings and be identified by labels. There are also requirements for compressor highpressure cutoff switches to prevent venting to the atmosphere. Everyone is looking for the “magic bullet,” a drop-in replacement for R-12. So far, it does not exist. MACS warns: ■■ Use only R-12 in an R-12-equipped system. ■■ Use only R-134a in an R-134a-equipped system. ■■ Follow retrofit procedures to use R-134a in an R-12 system. ■■ Do not use refrigerants that contain a toxic substance. ■■ Do not use a refrigerant that contains a flammable substance. ■■ The use of unauthorized refrigerants will void the manufacturer’s warranties. ■■ Talk to your customer about prior automotive air-conditioning service. Take no chances with health and safety. Use extreme caution if an unknown refrigerant has been introduced into the system. ■■ Protect yourself, your equipment, and your refrigerant. Use a refrigerant identifier on every job.

Substitute Refrigerants Five of the 10 substitute refrigerants found acceptable for automotive use by the EPA contain HCFC-22 as a main component. The use conditions for these refrigerants—R-406/GHG/ McCOOL, GHG-X4/Autofrost/Chil-it, Hot Shot/Kar Kool, GHG-HP, and GHG-X5—in addition to unique fittings, labels, and compressor shutoff switch, require barrier hoses. The other five refrigerants accepted by the EPA—R-134a, FRIGC FR-12, Free Zone RB-276, Ikon-12, and Freeze-12—have the same use conditions except they do not require barrier hoses.

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Currently, with the exception of R-134a, no vehicle manufacturer approves the use of any of these refrigerants for use in any of their air-conditioning systems as a substitute refrigerant for R-12. There are three refrigerants at present that are not acceptable to the EPA due to their flammability. These refrigerants are OZ-12, HC-12a, and Duracool-12. Also, refrigerant R-176 is not acceptable because it contains R-12, and R-405A is unacceptable because of its potential association with global warming and high stratospheric lifetime. The EPA last accepted a substitute refrigerant in mid-1997. It must be noted that the EPA accepts refrigerant for use in certain applications, such as MVACs. However, this does not mean that the EPA recommends or otherwise endorses any particular refrigerant for any particular use. The agency, however, does recognize that R-134a is currently the accepted refrigerant for vehicle use by the industry. Dedicated service and storage equipment is required by the EPA for each type of refrigerant used in a service facility. For the average facility, that means two systems: one for R-12 and one for R-134a. If one decides to service vehicles using, for example, FREEZE-12, a third set of service and storage equipment must be purchased for use. This is required even though FREEZE-12 contains 80 percent R-134a. The other 20 percent contains HCFC-142b, and it would contaminate the R-134a equipment. For the latest updates and information on refrigerant approval or any other stratospheric ozone issue, one may contact the EPA. Contact information, toll-free numbers, FAX numbers, and Web site addresses are found in the Appendix.

Freeze 12

Freeze 12 (Figure 12-6)—a blend of 80 percent R-134a and 20 percent HCFC-142b—is acceptable for automotive use subject to having proper fittings, labeling, and a compressor shutoff switch. It is not a drop-in replacement for R-12 or R-134a. The high-side service port must be 3/8-24 right-hand thread and the low-side service port must be 716-20 right-hand thread. The label background color is required to be yellow.

Free Zone/RB-276

Free Zone/RB-276 (Figure 12-7)—a blend of 79 percent R-134a, 19 percent HCFC-142b, and 2 percent lubricant—is acceptable for automotive use subject to having proper fittings, labeling, and a compressor shutoff switch. It is not a drop-in replacement for R-12 or R-134a. The high-side service port must be ½-13 right-hand thread and the low-side service port must be 9 -18 right-hand thread. The label background color is required to be light green. 16

Hot Shot/Kar Kool

Hydrocarbons are organic compounds containing only hydrogen (H) and carbon (C).

Hot Shot—a blend of 50 percent HCFC-22, 39 percent HR-124, 9.5 percent HCFC-142b, and 1.5 percent R-600a—is acceptable for automotive use subject to having proper fittings, labeling, barrier hoses, and a compressor shutoff switch. It is not a drop-in replacement for R-12 or R-134a. Although this refrigerant contains hydrocarbons (R-600a, Isobutane), it is not flammable as blended. The high-side service port must be 5 8 -18 left-hand thread and the low-side service port must be 5 8 -18 right-hand thread. The label background color is required to be medium blue.

GHG-HP

This refrigerant is a blend of 65 percent HCFC-22, 31 percent HCFC-142b, and 4 percent R-600a. It is acceptable for automotive use subject to having proper fittings, labeling, barrier hoses, and a compressor shutoff switch. Although it contains hydrocarbons (R-600a, Isobutane), it is not considered flammable as blended. It is not a drop-in replacement for R-12 or R-134a. The required fitting sizes and label background color were undetermined at the time of this writing. Contact the EPA for this information. 400 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 12-6  Typical Freeze 12 containers.

FIGURE 12-7  A Free Zone/RB-276 refrigerant cylinder.

GHG-X4/Autofrost/Chil-It

This refrigerant—a blend of 51 percent HCFC-22, 28.5 percent HCFC-124, 16.5 percent HCFC-142b, and 4 percent R-600a—is acceptable for automotive use subject to having proper fittings, labeling, barrier hoses, and a compressor shutoff switch. Although it contains hydrocarbon (R-600a, Isobutane), it is not flammable as blended. It is not a drop-in replacement for R-12 or R-134a. The high-side service port must be 0.305-32 right-hand thread and the lowside service port must be 0.368-26 right-hand thread. The label background color is required to be red.

GHG-X5

GHG-X5—a blend of 41 percent HCFC-22, 15 percent HCFC-142b, 40 percent HFC-227ea, and 4 percent R-600a—is acceptable for automotive use subject to having proper fittings, labeling, barrier hoses, and a compressor shutoff switch. This refrigerant contains 4 percent Isobutane, a hydrocarbon, but it is not considered flammable as blended. It is not a drop-in replacement for R-12 or R-134a. The high-side service port must be ½-20 left-hand thread and the low-side service port must be 916-18 left-hand thread. The label background color is required to be orange.

R-406A/GHG

This refrigerant is a blend of 55 percent HCFC-22, 41 percent HCFC-142b, and 4 percent R-600a. It is acceptable for automotive use subject to having proper fittings, labeling, barrier hoses, and a compressor shutoff switch. It is not considered flammable as blended, although it contains Isobutane (R600a), a hydrocarbon. It is not a drop-in replacement for R-12 or R-134a. The high-side service port must be 0.305-32 left-hand thread and the low-side service port must be 0.368-26 left-hand thread. The label background color is required to be black. 401 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Ikon-12

This refrigerant was approved for automotive air-conditioning system use in mid-1996. The manufacturer, Ikon Corporation, claims that the composition of this refrigerant is confidential business information. Requirements relating to fitting sizes and label color are not developed at the time of this writing. Nor is it yet known whether barrier hoses are required. Contact the EPA or the manufacturer for more information.

FRIGC FR-12

This refrigerant is a blend of 39 percent HR-124, 59 percent R-134a, and 2 percent R-600. It is acceptable for automotive use subject to having proper fittings, labeling, and a compressor shutoff switch. It is not considered flammable as blended, though it contains a hydrocarbon, Butane (R-600). It is not a drop-in replacement for R-12 or R-134a. The high-side and low-side service ports must be a quick disconnect type, but they are different from the R-134a service ports. The label background color is required to be grey.

OZ-12®

This refrigerant, a hydrocarbon Blend A, is not SNAP-approved by the EPA. The agency claims that it contains a flammable blend of hydrocarbons and that insufficient data was submitted to demonstrate its safety.

R-176

This refrigerant contains R-12, HCFC-22, and HCFC-142b. It is not SNAP-approved by the EPA, which claims that it is not appropriate to use an R-12 blend as an R-12 substitute.

HC-12a®

This refrigerant, a hydrocarbon Blend B, is not SNAP-approved by the EPA, which claims that it contains a flammable blend of hydrocarbons and that insufficient data was submitted to demonstrate its safety.

Duracool 12a

This refrigerant is not SNAP-approved by the EPA. It is identical to HC-12a® in composition, but it is produced by a different manufacturer.

R-405A

This refrigerant is not SNAP-approved by the EPA because it contains perfluorocarbons, which are implicated in global warming.

MT-31

This blend proposed as an R-12 substitute is not approved by the EPA for use in any application because of the toxicity of one of its components.

The Do-It-Yourselfer

Water (H2O), a refrigerant, is unwanted in an airconditioning system.

Although the Clean Air Act (CAA) amendments prevent the sale of small containers of R-12 to the general public, it is not unusual to find small cans of R-134a (Figure 12-8) on the shelves of automotive parts shops. Nor is it at all uncommon for do-it-yourselfers (DIYer) to somehow acquire refrigerant and install it in their personal vehicles. If asked by friends to purchase refrigerant for them, be aware that you may be subject to the wrath of the EPA for doing so, and act accordingly. Some refrigerants are flammable under certain conditions. Refrigerants are not compatible with each other and will contaminate the system.

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FIGURE 12-8  A small container and can tap of both R-12 and R-134a; notice the different style of can taps.

Contaminated Refrigerant Mixing two or more different refrigerants in an air-conditioning system contaminates the refrigerant. The refrigerant is contaminated in that it is no longer “pure” and will not react chemically and physically as intended. Not only will the system not function properly, if it functions at all, but also contaminated refrigerant can damage expensive equipment, such as a recovery/recycle unit. Do not put any additional refrigerant in a recovery cylinder if the present date is five years or more past the test date stamped on the cylinder shoulder or collar. There are no exceptions to the rule that recovery cylinders must be inspected every five years. There is no “grace period.” Using a recovery cylinder beyond the reinspection date can result in heavy penalties. If there is any doubt as to the purity of the refrigerant in the vehicle, do not service the air-conditioning system unless you are properly equipped. With the transition to CFC-free air-conditioning systems, the likelihood of cross-mixing refrigerants is a growing concern. Different refrigerants, as well as their lubricants, are not compatible and should not be mixed. It is possible, however, for the wrong refrigerant to be mistakenly charged into an air-conditioning system or for refrigerants to be mixed in the same recovery tank. Also, because recovery/recycling equipment is generally designed for a particular refrigerant, inadvertent mixing can cause damage to the equipment. A refrigerant identifier tester is far superior to pressure–temperature comparisons because, at certain temperatures, the pressures of R-12 and R-134a are too similar to differentiate with a standard gauge. This is easily noted in the chart shown in Figure 12-9. For example, at 908F (32.28C), both 95 percent R-12 and 95 percent R-134a have about the same pressure—111 and 112 psig, respectively. Given that this chart is accurate to plus or minus 2 percent, there is really no way of determining which type refrigerant is in the air-conditioning system or tank. Also, because other substitute refrigerants and blends may have been introduced into the automotive air-conditioning system, they can contaminate a system or tank and may not be detected by the pressure–temperature method. A refrigerant identifier would conclude the refrigerant in our example to be UNKNOWN. The purity of refrigerants has been set by SAE purity standards for both R-12 and R-134a. The purity standard for recycled R-12 is J1991 and the specified limits are 15 parts per million (ppm) by weight for water, 4,000 ppm by weight for refrigerant oil, and 330 ppm by weight for noncondensable gases (air). The purity standard for recycled R-134a is

The thermometer should be placed in an area where it can “sense” free air.

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AMB TEMP

R-12/R-134a PERCENT BY WEIGHT

°F

°C

100/0

98/2

95/5

90/10

75/25

50/50

25/75

10/90

5/95

2/98

0/100

  65   70   75   80   85   90   95 100 105 110 115 120

18.3 21.1 23.9 26.7 29.4 32.2 35.0 37.8 40.6 43.3 46.1 48.9

64 70 77 84 92 100 108 117 127 136 147 158

67 74 81 88 96 105 114 123 132 142 152 164

71 79 85 93 101 111 119 127 138 147 159 170

74 82 91 99 108 116 126 135 146 156 166 177

83 90 99 107 116 125 135 145 158 170 183 195

84 92 101 110 120 130 140 151 164 176 192 205

78 87 96 105 114 125 135 145 159 173 184 196

73 81 89 98 106 116 126 136 149 164 175 187

70 77 85 95 103 112 122 133 144 157 168 181

67 74 83 92 100 109 119 130 141 152 163 176

64 71 79 87 95 104 114 124 135 146 158 171

CFC-12/HFC-134a Cross-Contamination Chart. All pressures are given in psig. For kPa, multiply psig by 6.895. For example, 100 percent R-12 at 95 °F (35 °C) is 108 psig or 744.7 kPa. FIGURE 12-9  Temperature–pressure chart of R-12 and R-134a mixed refrigerants.

J2099, and the specified limits are 15 parts per million (ppm) by weight for water, 500 ppm by weight for refrigerant oil, and 150 ppm by weight for noncondensable gases (air). Refrigerant should test at least 98 percent pure when tested with a purity tester. If the refrigerant is less than 98 percent pure, it should be considered contaminated refrigerant and treated as such.

Proper Equipment Recovery cylinders must be inspected every five years.

Being properly equipped means that you have access to and use “recovery only” equipment (Figure 12-10) that meets SAE’s J2209 standards. You must also have proper recovery cylinders that meet rigid U.S. Department of Transportation (DOT) specifications. These cylinders should be marked “CONTAMINATED REFRIGERANT” for identification. Only contaminated refrigerant should be recovered into this cylinder. Disposable cylinders, known as DOT 39s (Figure 12-11), must not be used for recovered refrigerant. Federal law prohibits refilling these cylinders.

FIGURE 12-10  A typical refrigerant recovery unit.

FIGURE 12-11  Disposable R-134a cylinder.

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Do Not Take Chances

If there is any doubt about the purity of the refrigerant, question the customer. Ask the customer such questions as: ■■ When is the last time the system was serviced? ■■ Who worked on it? ■■ What parts were replaced? ■■ Do you have a copy of the work order? Remember, under the CAA, anyone performing repairs for consideration (pay) to a motor vehicle air-conditioning system must be certified, must use recovery/recycle equipment, and must comply with all rules and regulations. Be very suspicious if the customer’s response to “Who worked on it?” is something like, “Well, my neighbor works at a shop and he did it over the weekend as a favor to me.” You should then ask, “Where?” Chances are the customer will reply, “At my home.” The good-intentioned neighbor may have simply been trying to do a favor. Whatever the reason, he could have contaminated the system. After all, the air conditioner still does not work. If it worked, your customer would not have brought it to you for service. Do not take a chance. Test a sample of the refrigerant with a purity tester as covered in Chapter 7 of this manual and Chapter 7 of the Shop Manual. If a purity tester is not available and there is even the slightest doubt, turn the vehicle away. An alternative is to keep the vehicle overnight, a period of 12 hours or more, and check for refrigerant purity according to a temperature–pressure chart before attempting repairs.

If in doubt, perform the purity test.

Purity Test A determination of the purity of the refrigerant in the vehicle is possible while allowing for reasonable inaccuracies of the gauge, the thermometer, and the reader. After a 12-hour period, the pressure should nearly match that expected for any given temperature if the refrigerant is pure. There are other factors to be considered, however, when testing refrigerants. For example, if there is air in the system, an accurate reading may not be noted. If there is any doubt, do not run the risk of contaminating a good tank of refrigerant.

Disposal of Contaminated Refrigerant Contaminated refrigerant may be reclaimed to ARI-700-88 standards, or it may be destroyed by fire. This is usually accomplished at an off-site reclamation facility that is equipped to handle such problems. Remember, however, that it is your responsibility to legally dispose of contaminated refrigerant.

Make no attempt to destroy refrigerant without the proper equipment.

Use of Alternate Refrigerants Many new alternative refrigerants marketed for use in motor vehicle air-conditioning systems are being touted by their manufacturers and distributors. Whether employed by a nationwide repair chain or a one-person service facility, the technician should take the time to determine how well an alternative refrigerant will perform and whether it may pose any problems for customers or raise liability issues.

Health and the Environment

The EPA’s SNAP program determines what risks to human health and the environment are posed by refrigerant alternatives. The EPA evaluates the alternative refrigerant’s ozone-depleting potential (ODP), GWP, flammability, and toxicity. The SNAP evaluation, however, does not determine whether the alternate refrigerant will provide adequate performance or whether it will be compatible with the components of the system. 405 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Use Conditions

The EPA places conditions or restrictions on how an alternative can be used. Under SNAP, for example, an R-12 substitute requires the use of a new label and new fittings unique to the alternative. There are no exemptions to the rule for do-it-yourself (DIY) mechanics. Because of the vast range of equipment types and designs, the EPA does not issue retrofit procedures. The manufacturer of the system is the best source of information about how well a given substitute will perform. Additionally, one must determine whether charging a system with a particular “new” refrigerant will void any manufacturer’s warranty.

Clean Air Act (CAA)

The CAA requires that the EPA establish standards for recovery, recycling, and reclamation of refrigerants, including alternatives, accepted under SNAP. If standards have not been published by the EPA for a particular alternative, they may be under development. Ensure that the refrigerant manufacturer intends to work with the EPA to develop uniform methods for extraction, recycling, and reclamation.

Standards

The Air Conditioning and Refrigeration Institute (ARI), a manufacturers’ trade association, develops standards for the industry. ARI’s standard 700 specifies acceptable levels of refrigerant purity for R-12, as well as for certain refrigerant blends. The purpose of the standard is to enable end users to evaluate and accept or reject any refrigerant. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASH-RAE), a trade association, sets many of the standards and guidelines to provide a uniform method of rating refrigerants for toxicity and flammability and to assign refrigerant numbers. In fact, before ARI determines that its standard 700 should apply to a particular refrigerant, it must receive a classification from ASH-RAE. However, ASH-RAE classification is not required for SNAP acceptability.

Flammability

Both ASHRAE and the EPA evaluate refrigerants for flammability. The EPA requires that a new refrigerant be analyzed according to a test of the American Society of Testing Materials (ASTM). This test determines the concentrations in the air at which a substance is flammable at normal atmospheric pressure. Some hydrocarbons, for example, ignite at concentrations as low as 2 percent by volume. If a blend contains a flammable component, the EPA requires leak testing to ensure that the blend does not change and become flammable. If a system is charged with an alternative refrigerant that later becomes unavailable, the system may have to be retrofitted again, a service the customer may feel is unfair and be unwilling to pay for.

Grace Period

A refrigerant manufacturer must submit information on a new refrigerant for SNAP review at least 90 days before marketing. The CAA, however, does not prohibit the sale and use of that refrigerant after the 90-day period. If the agency is still engaged in its review after 90 days, the refrigerant can be sold and used even though it is not formally approved. The EPA may later determine that the refrigerant is unacceptable, and you may be stuck with an inventory of refrigerant that cannot be legally used.

Use versus Sale

The CAA granted to the EPA authority to regulate the use of alternative refrigerants, not the sale of them. If, for example, the EPA determines that an alternative is unacceptable for automotive service, it is still legal to sell it to the automotive trade. Using it in a customer’s 406 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

air-conditioning system, however, is considered illegal, and the technician who serviced the air-conditioning system may be fined $25,000 and have to serve up to five years in prison.

Retrofit Components Following is an overview of some of the problems and conditions associated with components, listed in no particular order, when retrofitting an automotive air-conditioning system from R-12 to R-134a refrigerant.

Access Valves

There is a distinct difference between the access valves used on R-134a systems ­(Figure 12-12) and those used on R-12 systems (Figure 12-13). Adapters (Figure 12-14) are available that are to be used on R-12 fittings during retrofit procedures to make them compatible with R-134a equipment. A special adapter, called a saddle clamp access valve (Figure 12-15), is available for installation where space does not permit the R-134a adapter to convert the R-12 valve.

Accumulator

Accumulators (Figure 12-16) in R-12 systems typically have a desiccant designated as XH5. This desiccant is not compatible with R-134a refrigerant. The desiccant to be used in R-134a systems is designated XH7 or XH9. This desiccant is found in accumulators and receivers designated for R-134a service. General Motors and Ford do not recommend that their accumulator be changed because the desiccant used is compatible with R-134a. Both XH7 and XH9 desiccants are compatible with R-12 as well as R-134a. If a clutch cycling pressure switch (CCPS) is to be changed, however, the accumulator may have to be replaced to accommodate the metric threads found on the switch. In some retrofit packages, an adapter may be included for English-to-metric thread conversion.

Saddle clamp access valves have been used to gain access to domestic “hermetic” air conditioners for many years.

Shop Manual Chapter 12, page 518

Do not attempt to screw a metric fitting into an English fitting.

Compressor

Compressors are being redesigned to withstand the slight increase in pressures associated with R-134a. Most compressor rebuilders are also incorporating these design changes into their rebuilding procedures. When purchasing a new or rebuilt compressor for an R-134a system, make sure that it has been identified for that application. It is not recommended that a compressor be replaced as a matter of course for retrofitting. The compressor should only be replaced if it is defective. Do not replace a compressor simply because the system is being retrofitted.

FIGURE 12-12  Access valve port on an R-134a system.

FIGURE 12-13  Access valve port on an R-12 system hose.

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FIGURE 12-14  Adapter fittings for retrofitting R-12 access valve fittings over to R-134a access valve fittings.

FIGURE 12-15  A saddle clamp access valve.

FIGURE 12-16  A typical accumulator.

Engine performance is often affected by the increased load created by the air conditioner.

Do not overload the circuit by adding a second motor to the original relay.

Condenser

To change any part of an original design is to change the performance of the equipment. This may be especially true for the condenser. The engine cooling system may also be affected by the slight increase in pressure (and temperature) of the condensing R-134a refrigerant. A dam may be considered to reduce the problems. Some manufacturers recommend replacing the condenser assembly during the retrofit procedure with one designed for use with R-134a, or system performance may suffer after retrofitting. Always refer to the manufacturer’s recommendations prior to performing retrofit procedures or quoting the cost of the service to your customer. Dams.  A dam, loosely identified, is the sealing provision located between the radiator and condenser that helps to direct ambient and ram air through both components. It is critical that all condenser and radiator seals be in place. All holes, regardless of how small, that could allow air to bypass either component should be blocked off to ensure maximum airflow. In some installations, the condenser will be changed. Because the mounting space is limited, this usually means a condenser with more fin area or fins per inch (FPI). A higher rpm cooling fan motor may be used to replace the original motor. In other cases, a second motor and fan, a pusher type, may be placed in front of the condenser. The idea is to improve or increase airflow to remove more heat.

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If a fan and motor are added, a relay should also be added. This is to ensure that the electrical system is not overloaded. The coil of the relay may be wired in with the compressor clutch circuit (Figure 12-17) to ensure that the fan is running when the air-conditioning system is turned on. An in-line fuse is included to protect the circuit.

Evaporator

The evaporator is not replaced unless it is found to be leaking. There have been no problems reported when using R-12 evaporators for an R-134a retrofit. Minor changes are necessary for evaporators designated for use with R-134a refrigerant to accommodate the slightly higher pressure that may be expected.

Hoses

Generally, hoses (Figure 12-18) used for automotive air-conditioning service in 1989 and later year/model vehicles need not be replaced when retrofitting from R-12 to R-134a. The exception is if the hose is found to be leaking during retrofit procedures.

O-Rings and Seals

Although O-rings made of epichlorohydrin and designated for R-12 service are not c­ ompatible with R-134a, it is not recommended that they be replaced when retrofitting an air-­conditioning system. The exception is if the fitting is found to be leaking. In that case, use only O-rings and seals (Figure 12-19) designated for the refrigerant being used in the system. Generally, O-rings and seals for R-12 systems are black. Unfortunately, some manufacturers prefer black R-134a O-rings and seals as well. Many, however, color code the O-rings and seals designated for R-134a service. When in doubt, use color-coded neo prene or HSN/HNBR O-rings or seals; they are also compatible with R-12.

If O-rings are to be replaced, use components designated for use with R-134a.

Metering Devices

Metering devices should not be changed as a matter of practice when retrofitting a system. There are two types of metering devices used in the modern automotive air-conditioning system: the thermostatic expansion valve (TXV) and the fixed orifice tube (FOT). Thermostatic Expansion Valve.  The TXV (Figure 12-20) does not have to be replaced when retrofitting a system from R-12 to R-134a. If, however, a TXV is found to be defective, it should be replaced with a model designed for use with the system refrigerant. An R-12 TXV used in an R-134a system will result in higher superheat and improved overall evaporator temperature. An R-134a valve used in an R-12 system will have reduced superheat and will not perform as well. Because superheat has a direct effect on performance, it is not advisable that the superheat be allowed to increase more than 38F (1.78C) over that of the operating R-12 system.

Butyl 12 Volts

Braid

Rubber

Superheat is heat that is added after the refrigerant has vaporized.

Nylon Rubber

Motor

Note 1 Note 1: to existing relay, existing fan motor, or auxilary switch

Relay

FIGURE 12-17  Schematic for adding an auxiliary condenser fan motor.

FIGURE 12-18  Construction detail of a barrier hose.

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FIGURE 12-19  Typical air conditioner O-rings and seals.

FIGURE 12-20  Typical thermostatic expansion valves.

If a new TXV is required, use one that is designed for the specific refrigerant in the system. As a rule of thumb: R-12 valves should not be used on automobiles originally equipped with R-134a systems and, conversely, R-134a valves should not be used on R-12 systems. Orifice Tube.  With the exception of one automobile manufacturer, it is not recommended that the orifice tube (Figure 12-21) be replaced when retrofitting an air-conditioning system. Volvo recommends changing the orifice tube to one that has a 0.002 in. (0.0508 mm) or smaller orifice. If it is changed, however, a slight increase in high-side pressure may be noted.

Pressure Switch Do not bypass system protective switches.

Either or both of two switches may be recommended for change during some retrofit procedures. These switches are the CCPS and the refrigerant containment device. A brief description follows. Clutch Cycling Pressure Switch.  The CCPS (Figure 12-22) may be changed for some R-134a retrofits. The difference is that the R-134a switches are calibrated for slightly lower clutch cycling pressures. Also, the mounting threads are metric to prevent the connection of an English-thread R-12 switch in an R-134a system. Refrigerant Containment Device.  This device, which is new for 1994 and later model/ year vehicles, may also be included in some retrofit kits for earlier model year vehicles. The refrigerant containment device includes models for single- and dual-function refrigerant containment switches and the air conditioner high-pressure transducer.

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Cycling pressure switch

Schradertype valve

Accumulator

Electrical connector FIGURE 12-21  An orifice tube.

FIGURE 12-22  A cycling clutch pressure switch.

Each have their specific applications. The single switch is in general use, controlling the compressor clutch; the dual switch also includes provisions to control the condenser fan. The transducer is in some solid-state temperature control systems.

High-Pressure Switch

The EPA requires the installation of a high-pressure cutout switch, also called a refrigerant containment switch. Its purpose is to interrupt the clutch coil circuit, thereby stopping the compressor before high-side pressure reaches the point at which it would open the highpressure relief valve and release refrigerant into the environment. One such switch designed for retrofit (Figure 12-23) is included with a tee-fitting service valve and is actually a dual-pressure switch. It opens the compressor clutch circuit at a high pressure of about 390–400 psig (2,689–2,758 kPa) and closes the circuit at about 310–315 psig (2,137–2,172 kPa). For low-pressure protection, the switch opens the clutch circuit at a low pressure of about 28 psig (193 kPa), a condition that would not exist on the high side of the system unless the refrigerant had leaked out. This then would prevent the compressor from running when the air-conditioning system is first turned on.

Receiver-Drier

The receiver-drier (Figure 12-24) used in R-12 systems typically has XH5 desiccant. This desiccant is not compatible with R-134a refrigerant. To be sure, the receiver-drier should be replaced during retrofit procedures with a unit designated for R-134a service and PAG or ester lubricants. This desiccant, designated XH7 or XH9, is also compatible with R-12 refrigerant and mineral oils.

A system has an accumulator or a receiver-drier, not both.

Retrofit Labeling Requirements

Once the original refrigerant has been replaced with a SNAP-approved alternative refrigerant, label (Figure 12-25) must be affixed over the old label. The label must contain detailed information about the retrofit installation. The label’s background color is unique for each SNAP refrigerant (Figure 12-26). The label must show: ■■ Name and address of the installer who performed the retrofit ■■ The refrigerant name and identification number (i.e., R-134a) 411 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

■■ ■■ ■■ ■■

The refrigerant charge amount installed The date the retrofit was performed The type of refrigerant oil installed and the part number The amount of refrigerant lubricant (oil) installed

FIGURE 12-24  A typical receiver-drier.

FIGURE 12-23  A high-pressure cutout switch with saddle clamp.

NOTICE: RETROFITTED TO R-134a RETROFIT PROCEDURE PERFORMED TO SAE J1661 USE ONLY R-134a REFRIGERANT AND SYNTHETIC 1 2 OIL TYPE: PN: OR EQUIVALENT, OR A/C SYSTEM WILL BE DAMAGED 3 ESTER

REFRIGERANT CHARGE/AMOUNT: 4 LUBRICANT AMOUNT: PAG RETROFITTER NAME: ADDRESS: 9 CITY:

6

8

STATE:

DATE:

10

ZIP:

1 Type: manufacturer of oil (Saturn, GM, Union Carbide, and so forth).

6 Retrofitter name: Name of facility that performed the retrofit.

2 PN: Part number assigned by manufacturer.

7 Date: Date retrofit is performed.

3 Refrigerant charge/amount: Quantity of charge installed.

8 Address: Address of facility that performed the retrofit.

4 Lubricant amount: Quantity of oil installed (indicate ounces, cc, or mL).

9 City: City in which the facility is located.

5 Kind of oil installed (check either PAG or ESTER).

5

7 11

10 State: State in which the facility is located. 11 Zip: Zip code of the facility.

FIGURE 12-25  A typical retrofit label.

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Refrigerant

Background

CFC-12

White

HFC-134a

Sky blue

Freeze 12

Yellow

Free Zone / RB-276

Light green

Hot Shot

Medium blue

GHG-X4

Red

R-406A

Black

GHG-X5

Orange

GHG-HP

Not yet developed*

Ikon-12 / Ikon A

Not yet developed*

FRIGC FR-12

Gray

SP34E

Tan

R-426A (RS-24, new formulation)

Gold

R-420A

Dark green (PMS #347)

FIGURE 12-26  A unique background color label is required for each SNAP-approved refrigerant.

System Flushing Little is written about flushing because “the jury is still out” on the subject. Some claim that flushing is necessary to “clean” an air-conditioning system, whereas others claim flushing causes more harm than good. There is no need to flush an air-conditioning system to remove refrigerant. Refrigerant removal is accomplished with the use of a proper refrigerant recovery machine. Flushing, then, is only performed in an attempt to clean the system of excess debris and lubricant. Actually, during the flushing procedure, a great deal of the debris will be caught in the screens of the metering device and dehydrator (receiver or accumulator). Also, the lubricant will be trapped in the bottom tank of the evaporator and dehydrator. Little, if anything, will be removed by flushing if the individual components are not removed from the vehicle and flushed individually. General Motors (GM), as a rule, does not recommend flushing an air-conditioning system. There are but two possible exceptions to the rule: a lubricant overfill or lubricant contamination. Even then, GM recommends removing and draining the accumulator in an effort to remove the lubricant before considering flushing the air-conditioning system. If flushing is determined to be necessary, the only flushing chemical approved by GM is the same refrigerant that the air-conditioning system was originally charged with. Accordingly, flushing procedures are not specifically covered in this manual. If it is found, however, that an automotive air-conditioning system needs flushing, one should follow the specific instructions included with the flushing equipment. Several flushing systems are available. Robinair, for example, has air-conditioning flushing kits (Figure 12-27), which include an accessory that connects to their recovery/recycle machines and uses recovered refrigerant as a flushing agent.

An Industry Study A paper sponsored by Elf Atochem, a leading manufacturer of refrigerants, was presented in the winter of 1994 at the International CFC and Halon Alternatives Conference. Written by a staff engineer and a senior technician at Elf Atochem’s fluoro chemicals research and

Flushing is the process of removing solid particles, such as metal flakes or dirt.

A BIT OF HISTORY The time is at hand to seriously consider the retrofit market for automotive air-conditioning systems. According to a report made by the International Trade Commission, the agency that tracks refrigerant production, only about half as much R-12 was produced in 1994 as in 1993. They also caution us that production of all CFCs ended January 1, 1996. That means that the only R-12 now available for automotive use is that which has been recovered and recycled or was produced prior to production being banned by the Clean Air Act. 413

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FIGURE 12-27  Typical flush system.

development center, the paper revealed that retrofitting is simpler than originally believed. The report was the result of a study of a fleet of 17 employee-volunteered vehicles retrofitted in 1993 to R-134a and polyalkaline glycol (PAG) lubricant. In early 1994, 20 more vehicles were retrofitted with R-134a and polyol ester (POE) lubricant. Only refrigerant and lubricant were replaced; no system components were replaced. Some were power flushed to remove as much of the mineral oil as possible; others were simply drained and refilled. The study involved a random selection of both domestic and imported cars and light trucks. Regardless of the procedure, flush or no flush, there was little or no noticeable difference in the performance of any of the vehicles. There were only two reported failures; both lost their complete R-134a charge due to O-ring failure. Another vehicle lost 6 percent of its charge of R-134a due to a leak. The worst “leaker” in the study was actually a control vehicle that had not been retrofitted at all. This vehicle lost 38 percent of its R-12 charge due to a leak. Author’s Note: If after retrofitting a system from R-12 to R-134a the high-side head pressure is excessive, the installation of an auxiliary cooling fan will help lower this pressure. The auxiliary fan should be wired so that it will run continuously when air conditioning is selected.

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SUMMARY ■■

■■ ■■

■■ ■■

■■

■■

The concern in the world community has shifted from the threat of ozone-depleting chemicals to a concern over global warming. In the United States and Asia, manufacturers are not required to phase-out R-134a. Some are still holding out long-term hopes for CO 2 (R-744) systems, but that appears doubtful at least for now. Follow appropriate manufacturer’s retrofit procedures. After retrofit, appropriate decals must be affixed to identify the type of refrigerant in the system. A light blue (the industry color code for R-134a) decal is placed over the current R-12 decal (Figure 12-25). A yellow (the color used for caution) decal may be placed around the hoses at the service fittings.

Terms to Know Adiabatic expansion Alternative refrigerant Cross-contamination Flushing Global Warming Potential (GWP) Hydrocarbons Retrofit R-744

REVIEW QUESTIONS Short-Answer Essay 1. Describe the meaning of the term retrofit. 2. What is the meaning of the term global warming potential? 3. What did the European Union mandate beginning January 1, 2011? 4. Describe the proper disposal of contaminated refrigerant. 5. Are vehicles manufactured or sold in the United States required to phase-out R-134a refrigerant systems? 6. Describe the difference in application for an XH9 drier compared to an XH5 drier. 7. CO 2 is a greenhouse gas, so how could it be used in an air-conditioning system as an environmentally friendly alternative? 8. What is an important consideration for the condenser during retrofit procedures? 9. Describe the conditions under which hoses and O-rings should be replaced during retrofit procedures. 10. Identify and describe either of the components that are included on R-134a systems but are not found on R-12 systems.

Fill in the Blanks 1. The EPA’s _______________ _______________ _______________ program determines what risks to human health and the environment are posed by refrigerant alternatives.

2. Mixing two or more different refrigerants in an airconditioning system _______________ the refrigerant. 3. If a hose is found to be _______________ during retrofitting it should be _______________. 4. _______________ _______________ is a process that occurs without the loss or gain of heat. 5. _______________ _______________ _______________ is when one refrigerant is contaminated with another. 6. R-12 receiver-driers containing _______________ ­desiccant must be replaced with receiver-driers ­containing _______________ or _______________ d­esiccant when retrofitting to R-134a. 7. _______________ is the refrigerant gas designation given to carbon dioxide (CO2). 8. Another alternative refrigerant that once held widespread hopes for being the next refrigerant due to its low GWP rating of 1 is _______________, a naturally occurring gas. 9. _______________ _______________, known as DOT 39s, must not be used for _______________._______________ 10. MACS is an acronym for _______________ _______________ _______________

Multiple Choice 1. All of the following alternate refrigerants are approved for automotive use, except: A. Freeze-12 C. Ikon-12 B. FRIGC FR-12 D. Duracool 12a 415

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2. Replacement of hoses during retrofit procedures is being discussed. Technician A says hoses need not be replaced unless they are the old-style nonbarrier type. Technician B says hoses need not be replaced unless they are equipped with the old-style O-rings and fittings. Who is correct? A. A only C. B only B. Both A and B D. Neither A nor B 3. Refrigerant contamination is being discussed. Technician A says that R-12 with a 5 percent trace of R-22 is considered contaminated. Technician B says that R-12 with a 5 percent trace of R-134a is considered contaminated. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 4. The concern in the world community has shifted from the threat of ozone-depleting chemicals to a concern over which of the following? A. Global cooling C. Global weather B. Global warming D. Global disaster 5. Technician A says that a DOT 39 cylinder may be used to temporarily store contaminated refrigerant. Technician B says that, if they are used, DOT 39s must be marked “CONTAMINATED REFRIGERANT” for identification. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

6. Which of the following desiccants should be used with HFC-134a refrigerant? A. XH5 C. XH9 B. XH7 D. Both B and C 7. A refrigerant retrofit label must contain all of the following except: A. Name and address of the installer who performed the retrofit B. The refrigerant charge amount installed C. The amount of R-12 removed from the system D. The type of refrigerant oil installed and the part number 8. Technician A says that a red label is required to identify R-134a in an automotive air-conditioning system. Technician B says that a yellow label is used to identify R-12 in an automotive air-conditioning system. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 9. The retrofit label’s background color for R-134a refrigerant is: A. White C. Royal blue B. Tan D. Light blue 10. Technician A says that O-rings designated for R-12 service need not be changed for retrofit. Technician B says that O-rings designated for R-134a service may also be used for R-12 service. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

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GLOSSARY GLOSARIO Note: Terms are highlighted in color, followed by Spanish translation in bold. Absolute zero  The complete absence of heat, believed to be

24598F (2273.158C). This is shown as 0 degrees on the Rankine and Kelvin temperature scales.

Cero absoluto  Ausencia completa de calor, lo cual se cree

ser 24598F (2273.158C). Se indica como 0 degrees en las escalas de temperatura Rankine y Kelvin.

Absorb  To take in or to suck up; to become a part of itself. Absorber  Admitir o aspirar; llegar a ser una parte de sí

mismo.

Accumulator  A tank-like vessel located at the outlet

(tailpipe) of the evaporator to receive all of the refrigerant that leaves the evaporator. This device is constructed to ensure that no liquid refrigerant enters the compressor.

Acumulador  Recipiente parecido a un tanque ubicado en la

salida (tubo de escape) del evaporador para recibir todo el refrigerante que sale del evaporador. Dicho dispositivo está diseñado de modo que asegure que el refrigerante líquido no entre en el compresor.

Air conditioning (A/C)  The process of adjusting and

regulating by heating or refrigerating; the quality, quantity, temperature, humidity, and circulation of air in a space or enclosure; to condition the air. Acondicionamiento de aire  Proceso de ajustar y regular al calentar o enfriar, la calidad, cantidad, temperatura, humedad, y circulación de aire en un espacio o encerramiento; para acondicionar el aire. Allotrope  A structurally different form of an element.

For example, though different in structure, the properties of graphite and diamond are the same as the element carbon (C).

Aliotropo  Una forma de un elemento que es diferente

en estructura. Por ejemplo, aunque son diferentes en estructura, las propiedades del grafito y diamante son las mismas del elemento carbón (C).

Alternative refrigerant  A refrigerant that can be used to

replace an existing refrigerant, such as ozone friendly R-134a that is used to replace ozone-depleting R-12.

Additive  A substance added to another substance, expected

Refrierante alternativa  Un refrigerante que se puede usar

Aditivo  Sustancia que se agrega a otra sustancia para

Ambient  All around, surrounding, or encompassing.

to increase its quality or performance. Antifreeze, for example, is an additive that may be added to water (H 2 O) to raise its boiling point and lower its freezing point.

mejorar su cali-dad o rendimiento. Por ejemplo, el anticongelante es un aditivo que puede agregarse al agua (H 2 O) para elevar su punto de ebullición y disminuir su punto de congelación.

Adiabatic expansion  The process of expansion without the

gain or loss of heat.

Expansión adiabiático  El proceso del expansión sin un gano

o pérdida del calor.

Adsorb  To take up and hold a thin layer of vapor or liquid

molecules on the surface of a solid substance.

Adsorber  Recoger y retener una capa delgada de moléculas

de vapor o líquido en la superficie de una sustancia sólida.

Aftermarket  A term generally given to a device or accessory

that is added to a vehicle by the dealer after original manufacturer, such as an air-conditioning system.

Postmercado  Término dado generalmente a un dispositivo

o accesoria que el distribuidor de automóviles agrega al vehículo después de la fabricación original, como por ejemplo un sistema de acondicionamiento de aire.

para reem-plazar un refrigerante actual, tal como el R-134 que no agota el ozono del medio ambiente para reemplazar el R-12 que sí lo agota.

Amblente  El area circundante o los alrededores. Ampere (A)  Ampere or Amperage is the unit for measuring

current. One ampere equals a current flow of 6.28 × 1018 electrons per second.

Amperio (A)  el amperio o amperaje es la unidad de

medición de la corriente. Un amperio equivale a un flujo de corriente de 6,28 × 1018 electrones por segundo.

Antifreeze  A commercially available additive solution

used to increase the boiling temperature and reduce the freezing temperature of engine coolant. A solution of 50 percent water and 50 percent antifreeze is suggested for year-round protection.

Anticongelante  Solución aditiva comercialmente disponible

utilizada para elevar la temperatura de ebullición y disminuir la temperatura de congelación del enfriador del motor. Se sugiere una solución de un 50 por ciento de agua y un 50 por ciento de anticongelante para proveer protección durante todo el año.

Arid Dry. Arido Seco.

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Aspirator  A device that uses suction to move air,

accomplished by a differential in air pressure. Aspirador  Dispositivo que aspira para mover el aire; dicho movimiento se debe a una diferencia en la presión del aire. ATC  Abbreviation for automatic temperature control. ATC  Abreviatura de control automático de temperatura. Atmosphere Air. Atmosfera  El aire. Atom  The smallest possible particle of matter. Atomo  Partícula más pequeña de materia. Automatic  A self-regulating system or device that adjusts to variables of a predetermined condition. Automático  Sistema o dispositivo con regulación automática que se adjusta a estadores variables de una condición predeterminada. Auxiliary  A backup component or system. The rear evaporator in a dual air-conditioning system is often referred to as an “auxiliary evaporator.” Auxiliar  Un componente o sistema auxiliar. El evaporador trasero en un sistema del aire acondicionado muchas veces se refiere como un evaporador auxiliar. Average  A single value that represents the median. Promedio  Un valor único que representa la mediana. Axial  Pertaining to an axis; a pivot point. Axial  Perteneciente a un eje; punto de giro. Axial plate  That part of an automotive air-conditioner compressor piston assembly that rotates as a part of the driven shaft. Placa axial  La parte del conjunto del pistón de un compresor del acondi-cionador de aire automotriz que gira como parte del árbol mandado. Barrier  A term given to something that stands in the way, separates, keeps apart, or restricts; an obstruction. Barrera  Término dado a algo que impide, separa, mantiene separado, o restringe; una obstrucción. Bellows  An accordion-type chamber that expands and contracts as its interior pressure is increased or decreased to create a mechanical action, such as in a thermostatic expansion valve. Fuelles  Cámara en forma de acordeón que se dilata y se contrae cuando su presión interior se aumenta o se disminuye para crear una acción mecánica, como por ejemplo en una válvula de expansión termostática. Bi-level  A condition whereby air is delivered at two levels in the vehicle, generally to the floor and dash outlets. Bilevel  Condición por medio de la cual se envía el aire a dos niveles en el vehículo, generalmente al piso y a las salidas del tablero de instrumentos. Blend air door  A door in the duct system that controls

temperature by blending heated and cooled air.

Puerta de aire mezclado  Puerta en el sistema de conductos

que regula la temperatura al mezclar el aire calentado y enfriádo. Blend door  See Blend air door. Puerta de mezcla  Ver Blend air door [Puerta del aire mezclado]. Block valve  A type of thermostatic expansion valve utilizing an internal sensing bulb. Válvula de bloque  Tipo de válvula de expansión termostática que utiliza una bombilla sensora interior. Bowden cable  A wire cable inside a metal or rubber housing used to regulate a valve or control from a remote place. Cable Bowden  Cable trenzado de alambre que está envuelto por una cubierta de metal o de caucho y que se utiliza para regular una válvula o regulador desde un sitio a distancia. British thermal unit (Btu)  A measure of heat energy; one Btu is the amount of heat necessary to raise one pound of water 18F. Unidad térmica británica (Btu)  Medida de energía calorífica; un Btu es igual al calor necesario para elevar la temperatura de una libra de agua en 18F . Butane  A colorless gas (C 4 H10 ) that is used as a fuel. Butano  Gas incoloro (C 4 H10 ) utilizado como combustible. Bypass  A passage or hose that directs coolant around thermostat when thermostat is closed and back to the water pump. Desviado  Un pasaje o manguera que dirige el refrigerante alrededor del termostato cuando está cerrado y lo dirige a la bomba de agua. Capillary tube  A tube with a calibrated inside diameter and length used to control the flow of refrigerant. In automotive air-conditioning systems, the tube connecting the remote bulb to the expansion valve or to the thermostat is called the capillary tube. Tubo capilar  Tubo cuyo diámetro y longitud interiores son calibrados; se utiliza para regular el flujo de refrigerante. En sistemas automotrices para el acondicionamiento de aire, el tubo que conecta la bombilla a distancia a la válvula de expansión o al termostato se llama el tubo capilar. Case  A thing used to hold, cover, or contain something, such as the evaporator and heater cores of an air-conditioning system. Caja  Cosa utilizada para guardar, cubrir, o contener algo, como por ejemplo los núcleos del evaporador y del calentador de un sistema de acondicionamiento de aire. CCOT  Cycling clutch orifice tube. CCOT  Tubo de onificio del embrague con funcionamiento cíclico. CCPS  Cycling clutch pressure switch. CCPS  Autómata manométrico del embrague con

funcionamiento cíclico.

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CDPS  Compressor discharge pressure switch. CDPS  Autómata manométrico de discarga del compresor. Centrifugal  Moving away from the center or axis; to develop a

force that is progressively away or outward from the axis.

Centrífugo  Moviéndose hace afuera del centro o el eje;

desarollar una fuerza que se mueva progresivamente hacia afuera del eje.

Centrifugal impeller  Rotating water pump impeller that uses

centrifugal force to force water drawn in from the center outward to the outlet passage.

Impulsor centrífugo  Un impulsor giratorio de la bomba

de agua que usa la fuerza centrífuga para forzar el agua proveniente del centro hacia afuera al pasaje de salida.

Centrifugal pump  A type of pump used to circulate coolant by

centrifugal force in an automotive cooling system.

Bomba centrifuga  Tipo de bomba utilizada para la circulación

del enfriante por medio de la fuerza centrífuga en un sistema automotriz para el acondicionamiento de aire.

CFCs  See Chlorofluorocarbon. CFCs  Véase Clorofluorocarbono. Change of state  Rearrangement of the molecular structure of

matter as it changes between any two of the three physical states: solid, liquid, or gas.

Cambio de estado  Reordenamiento de la estructura molecular

de materia al cambiarse entre cualquier de los tres estados f ísicos: sólido, líquido, o gas.

Check valve  A one-way valve that only allows flow in one

direction and restricts flow in the opposite direction.

Válvula de retención  Una válvula de una vía que solo permite

fluir en una dirección y restringe el flujo de la dirección opuesta.

Ley para Aire Limpio  Enmienda Título IV firmado y aprobado

en 1990 que estableció la política nacional relacionada con la reducción y eliminación de sustancias que agotan el ozono.

Clutch  An electromechanical device used to engage and

disengage the compressor in an automotive air-conditioning system.

Embrague  Un dispositivo electromecánico que sirve para

embragar y desembragar el compressor en un sistema del aire acondicionado automotivo.

Clutch diode  A diode placed across the clutch coil to prevent

unwanted electrical spikes as the clutch is engaged and disengaged.

Diodo de embrague  Diodo que cruza la bobina del embrague

para evitar impulsos afilados eléctricos no deseados al engranarse y desen-granarse el embrague.

Clutch field  Consists of many windings of wire and is fastened

to the front of the compressor. Current applied to the field sets up a magnetic field that pulls the armature in to engage the clutch.

Campo del embrague  Consiste de muchos devanados de

alambre y se fija a la parte delantera del compresor. La corriente aplicada al campo produce un campo magnético que tira la armadura para engranar el embrague.

Cold  The absence of heat. Frío  Ausencia de calor. Collector  A tank located in the radiator to collect coolant. Colector  Tanque ubicado en el radiador para acumular

enfriante.

Compression  The act of reducing volume by pressure. Compresión  Acción de disminuir el volúmen por efectos de la

presión.

Chlorine (Cl)  A poisonous greenish-yellow gas used in some

Compression stroke  That part of the compressor piston that

Cloro (Cl)  Gas venenoso de color verdusco amarillo utilizado

Carrera de compresión  Parte del movimiento del pistón del

Chlorofluorocarbon (CFC)  A manufactured compound used

Compressor  A component of the refrigeration system

Clorofluorocarbono  Compuesto sintético utilizado en

Compresor  Componente del sistema de refrigeración que

Circuit breaker  A bimetallic device used instead of a fuse to

Condenser  The component of a refrigeration system in which

refrigerants and known to be harmful to the ozone (O 3 ) layer.

en algunos refrigerantes; conocido como una sustancia nociva al ozono (O 3 ).

in refrigerants such as R-12, more accurately designated CFC-12.

refrigerantes como por ejemplo el R-12; designado con más precisión como CFC-12. protect a circuit.

Disyunto  Dispositivo bimetálico utilizado en vez de un fusible

para la protección de un circuito.

Clean Air Act (CAA)  A Title IV amendment signed into

law in 1990, which established national policy relative to the reduction and elimination of ozone-depleting substances.

travels from the bottom of its stroke to the top of its stroke.

compre-sor desde la posición inferior de su carrera hasta la posición superior de su carrera.

that pumps refrigerant and increases the pressure of the refrigerant vapor. bombea el refrigerante y eleva la presión del vapor del mismo.

refrigerant vapor is changed to a liquid by the removal of heat.

Condensador  Componente de un sistema de refrigeración en

el que el vapor del refrigerante se convierte en un líquido debido a la eliminación de calor.

Conduction  The transmission of heat through a solid. Coducción  Transferencia de calor a través de un sólido.

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Contaminated  Not being of pure form. Refrigerant is

considered contaminated when it contains greater than 2 percent of one or more other gases. Contaminado  El no ser de una forma pura. El refrigerante se considera ser contaminado cuando contiene uno o más gases en una cantidad de 2 por ciento o más. Contamination  A matter rendered unpure due to the production of foreign matter. Contaminación  Una materia hecha impura debido a la introducción de materia extraña. Control thermostat  A temperature-actuated electrical switch used to cycle the compressor clutch on and off, thereby controlling the air-conditioning system temperature. Termostato de control  Un interruptor eléctrico actuado por la temperatura que sirve en los ciclos de apagado y prendido del embrague del compresor, así controlando la temperatura del sistema del aire acondicionado. Control valve  A mechanical, pneumatic, or electric valve used to control the flow of coolant into the heater core. Válvula de regulación  Válvula mecánica, neumática, o eléctrica utilizada para regular el flujo de enfriante al núcleo del calentador. Controller Area Network (CAN)  A high-speed serial bus communication network. The CAN protocol has been standardized by the International Standards Organization (ISO) as ISO 11898 standard for high-speed and ISO 11519 for low-speed data transfer. Red de área de controlador (CAN)  red de comunicaciones de bus serial de alta velocidad. El protocolo CAN ha sido estandarizado por la Organización Internacional de Estandarización (ISO) como la norma ISO 11898 para la transferencia de datos a alta velocidad y la norma ISO 11519 para la transferencia de datos a baja velocidad. Convection  The transfer of heat by the circulation of a vapor or liquid. Convección  Transferencia de calor mediante de la circulación de un vapor o líquido. Coolant pump  A term often used when referring to a water pump. Bomba del enfriante  Término utilizado con frecuencia al referirse a una bomba de agua. Crankshaft  That part of a reciprocating compressor on which the wobble plate or connecting rods are attached to provide for an up-down or to-fro piston action. Cigueñal  Parte de un compresor recíproco sobre la cual se fijan las bielas a la placa oscilante para permitir el movimiento de arriba abajo o el de un lado para otro. Cross-contamination  Contamination that can occur when a system is retrofitted to an alternative refrigerant and the entire original refrigerant is not removed or when one piece of equipment is used for more than one type of refrigerant.

Contaminación cruzada  La contaminación que puede ocurrir

cuando un sistema se equipa después de fabricación para aceptar un refrigerante alternativo y no se remueva todo el refrigerante original o cuando una pieza del equipo se usa para más de un tipo del refrigerante. Cycle  It is one complete on-off occurrence. Including the total on time and off time. Cycles occurrences are measured in Hertz (Hz). Ciclo  una incidencia completa de encendido apagado. Incluido el tiempo total de encendido y el de apagado. Los ciclos se miden en Hertz (Hz). Cycling clutch  A clutch that is turned on/off to control temperature. Embrague con funcionamiento cíclico  Embrague que se pone en marcha y se apaga para regular la temperatura. Cylinder  A circular tube-like opening in a compressor block or casting in which the piston moves up and down or back and forth; a circular drum used to store refrigerant. Cilindro  Apertura circular parecida a un tubo en un bloque del compresor o una pieza en los que el pistón se mueve de arriba abajo o de un lado a otro; un tambor circular utilizado para el almacenaje de refrigerante. DC  See Direct current (DC). CC  Ver Direct current [Corriente continua (cc)]. Deep-tissue temperature  The sub-surface temperature, such as the internal temperature of the human body of 98.68F . Temperatura interna  La temperatura bajo la superficie, tal como la temperatura interna del cuerpo humano que es el 98.68F . Defrost  To remove frost. Decongelar Deshelar. Deice  To remove ice or heavy frost. Deshelar  Derretir hielo o una gran cantidad de escarcha. Delta P  A term used when referring to a difference in pressure. P delta  Término utilizado al referirse a una diferencia en presión. Delta T  A term used when referring to a difference in temperature. T delta  Término utilizado al referirse a una diferencia en temperatura. Desiccant  A drying agent used in refrigeration systems to remove excess moisture. The deciccant is located in the receiver-drier or accumulator. Desecante  Agente secador utilizado en sistemas de refrigeración para eliminar un exceso de humedad. El desecante está ubicado en el receptor/secador o en el acumulador. Diode  An electrical check valve. Current flows only in one direction through a diode.

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Diodo  Válvula eléctrica de retención. La corriente fluye en

una sola dirección a través de un diodo. Direct current (DC)  A type of electrical power used in mobile applications. A unidirectional current of substantially constant value. Corriente continua (cc)  Tipo de potencia eléctrica utilizada en circunstancias cuando el objeto va a ser móvil. Una corriente de un solo sentido de un valor substancialmente constante. Discharge  Bleeding some or all of the refrigerant from a system by opening a valve or connection and permitting the refrigerant to escape slowly. Descarga  Desangramiento de una porción o de todo el refrigerante de un sistema al abrir una válvula o conexión y permitir su escape gradual. Discharge line  Connects the compressor outlet to the condenser inlet. Línea de descarga  Conecta la salida del compresor a la entrada del condensador. Discharge stroke  See Compression stroke. Carrera de descarga  Ver Compression stroke [Carrera de compresión]. Discharge valve  The outlet valve. Válvula de descarga  La válvula de salida. Disposal  Get rid of something. Eliminación  Eliminar algo. Distilled water  One hundred percent pure H 2 O. Agua destilada El H 2 O cien por ciento puro. DIY Do-it-yourself. “DIY”  Expresión en jerga que significa que una persona hace algo por su propia cuenta. Dobson unit (DU)  A measure of ozone density level, named after Gordon Dobson, a British meteorologist who was the inventor of the measuring device (called a spectrophotometer). Unedad Dobson (DU)  Una medida al nivel de densidad del ozono, nombrado por Gordon Dobson, un meteorologista inglés que fue el inventor de un dispositivo de medida (llamado el espectrofotómetro). DOT  U.S. Department of Transportation. DOT  Departamento de Transportes de los Estados Unidos deAmerica. Drier  A device containing desiccant; a drier is placed in the liquid line to absorb moisture in the system. Secador  Dispositivo que contiene un desecante; se ubica un secador en la línea de líquido para absorber la humedad presente en el sistema. Dual systems  Two systems. Sistemas dobles  Dos sistemas.

Duty cycle  The length of time that an output actuator

is energized during one complete on-off cycle, it is a measurement of pulse-width modulation.

Ciclo de servicio  el período de tiempo en que un impulsor

de salida está energizado durante un ciclo de encendidoapagado completo. Es una medición de la modulación de ancho de pulso.

Electrolysis  The decomposition of a compound caused by the

action of an electric current passing through it.

Electrólisis  La decomposición de un compuesto causada por

la acción de un corriente eléctrica que pasa por en medio.

Electromagnet  A soft iron core surrounded by a coil of wire

that will temporarily become a magnet when an electrical current is passed through it.

Electroimán  Un núcleo de hierro blando rodeado por una

bobina de alambre que se convierte brevemente en un imán cuando es atrave-sado por un corriente eléctrico.

Electromagnetic clutch  An electrically controlled device used

to start and stop compressor action.

Embrague electromagnético  Dispositivo controlado

electrónicamentey utilizado para arrancar y detener la acción del compresor.

Ethylene glycol  A colorless liquid used in the production of

antifreeze HOCH 2 CH 2 OH .

Glicol etileno  Un líquido sín color que se usa en la producción

del anticongelante HOCH 2 CH 2 OH .

Evacuate  To create a vacuum within a system to remove all air

and moisture.

Evacuar  Dejar un vacío dentro de un sistema para eliminar

todo aire y humedad.

Evaporation  The changing of a liquid to a vapor while picking

up heat.

Evaporación  La conversión de un líquido en vapor al acumular

el calor.

Evaporator  The component of an air-conditioning system

that conditions the air.

Evaporador  Componente en un sistema de

acondicionamiento de aire que acondiciona el aire.

Exhaust  A pipe through which used gases or vapors pass. See

also Discharge.

Escape  Tubo por el cual pasan los gases or vapores gastados.

Ver tambien Discharge [Descarga].

Expansion tank  An auxiliary tank that is usually connected

to the inlet tank or a radiator to provide additional storage space for heated coolant; often called a coolant recovery tank.

Tanque de expansión  Tanque auxiliar que normalmente se

conecta al tanque de entrada o a un radiador para proveer almacenaje adicional del enfriante calentado. Llamado con frecuencia tanque para la recuperación de enfriante.

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Expansion tube  A metering device used at the inlet of some

evaporators to control the flow of liquid refrigerant into the evaporator core. Also see Fixed orifice tube (FOT).

Tubo de expansión  Dispositivo para la dosificación y utilizado

a la entrada de algunos evaporadores para regular el flujo de refrigerante líquido dentro del núcleo del evaporador. Ver tambien Fixed orifice tube (FOT) [Tubo de orificio fijo].

Expansion valve  A term often used when referring to a

thermostatic expansion valve.

Válvula de expansión  Un término que se usa comunmente

para referirse a una válvula de expansión termoestática.

Fan  A device that has two or more blades attached to the

shaft of a motor. The fan is mounted in the evaporator and causes air to pass over the evaporator. A fan is also a device that is mounted on the water pump and has four or more blades that cause air to pass through the radiator and condenser.

Ventilador  Dispositivo provisto de dos aletas o más fijadas

al arbol de un motor. El ventilador está montado en el evaporador y hace que el aire pase sobre el evaporador. Un ventilador también puede ser un dispositivo montado en la bomba de agua y que tiene cuatro aletas o más que hacen que el aire pase por el radiador y el condensador.

Fan clutch  A device used on engine-driven fans to limit their

terminal speed, reduce power requirements, and lower noise levels.

Embrague de ventilador  Dispositivo utilizado en ventiladores

acciona-dos por motores para limitar su velocidad terminal, disminuir requisitos de potencia, y bajar los niveles de ruino.

Field coil  See Clutch Field and Electromagnet. Bobina del campo  Ver Clutch field [Campo del embrague] y

Electromagnetic [Electroimán].

Fixed orifice tube (FOT)  A refrigerant metering device used

at the inlet of evaporators to control the flow of liquid refrigerant allowed to enter the evaporator.

Tubo de orificio fijo  Dispositivo para la dosificación de

refrigerante utilizado a la entrada de los evaporadores para regular el flujo de refrigerante líquido permitido entrar en el evaporador.

Flooded  See Flooding. Inundado  Ver Flooding [Inundación]. Flooding  A condition caused by too much liquid refrigerant

being metered into the evaporator.

Inundación  Condición ocasionada por una cantidad excesiva

de refrigerante líquido dosificado al evaporador.

Flush  To remove solid particles such as metal flakes or dirt.

Refrigerant passages are purged with a clean dry gas such as nitrogen (N).

Limpiar por inundación  Remover las partículas sólidas, como

por ejemplo escamas metálicas o polvo. Se purgan los

pasajes de refrigerante con un gas limpio y seco, como por ejemplo el nitrógeno (N). FOTCC  Fixed orifice tube cycling clutch. FOTCC  Tubo de orificio fijo del embrague con

funcionamiento cíclico.

FPI  Feet per inch or fins per inch. FPI  Pies por pulgada o aletas por pulgada. Fuse  An electrical device used to protect a circuit against

accidental overload or unit malfunction.

Fusible  Dispositivo eléctrico utilizado para proteger

un circuito contra una sobrecarga imprevista o una disfunción de la unidad.

Gas  A state of matter. A vapor that has no particles or

droplets of liquid.

Gas  Estado de materia. Vapor desprovisto de partículas o

gotitas de líquido.

Gauge  A device used to measure pressure or force scaled in

English or metric values.

Calibrador  Dispositivo utilizado para medir la presión o

fuerza; provisto de una escala en valores ingleses y/o métricos.

Global warming  The gradual warming of the earth’s

atmosphere due to the greenhouse effect. See Greenhouse effect.

Calentamiento mundial  Calentamiento gradual de la

atmósfera de la Tierra debido al efecto de invernadero. Ver Greenhouse effect [Efecto de invernadero].

Global warming potential (GWP)  Global warming potential is

an index number that is an estimate of how much a given mass of a gas will contribute to global warming compared to the same mass of carbon dioxide, where carbon dioxide is given the number 1.

Potencial de calentamiento global (GWP)  el potencial de

calentamiento global es un índice numérico que es un cálculo estimativo de cuánto contribuirá una masa dada de gas al calentamiento global comparada con la misma masa de dióxido de carbono, donde el dióxido de carbono recibe el número 1.

Greenhouse effect  A greenhouse is warmed because glass

allows the sun’s radiant heat to enter but prevents radiant heat from leaving. Global warming is caused by some gases in the atmosphere that act like greenhouse glass; hence, the term greenhouse effect.

Efecto de invernadero  Se calienta un invernadero porque

el vidrio permite la entrada del calor radiante del sol pero impide la salida del calor radiante de la Tierra. El calentamiento mundial es ocasionado por algunos gases en la atmósfera que actuan como el vidrio de un invernadero; por eso, se utiliza el término efecto de invernadero.

Halide  Any compound of a halogen with another element

such as refrigerant.

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Halogenuro  Cualquier compuesto de un halogenuro y otro

elemento, como por ejemplo el refrigerante.

Halogen  Refers to any of the five chemical elements—astatine

(At), bromine (Br), chlorine (Cl) fluorine (F), and iodine (I)—that may be found in some refrigerants.

Halógeno  Se refiere a cualquier de los cinco elementos

químicos—astatinio (At), bromo (Br), cloro (Cl), fluoro (F), y yodo (I)—que pueden estar presentes en algunos refrigerantes.

Head pressure  Pressure of the refrigerant from the discharge

reed valve through the lines and condenser to the expansion valve orifice.

Altura piezométrica  Presión del refrigerante de la válvula de la

lámina de descarga a través de las líneas y el condensador al orificio de la válvula de expansión.

Heat  Energy; any temperature above absolute zero. Calor  Energía; cualquier temperatura superior al cero

absoluto.

Heater core  A heat exchanger that extracts the heat from

coolant warmed by the engine to heat the passenger compartment.

Núcleo de calor  Un cambiador de calor que extrae el calor

del refrigerante calentado por el motor para calentar el compartimento del pasajero.

Heat load  The load imposed on an air conditioner due to

ambient temperature, humidity, and other factors that may produce unwanted heat.

Carga de calor  Carga impuesta sobre un acondicionador de

aire debido a la temperatura ambiente, humedad, y otros factores que pueden producir calor no deseado.

HFC  See Hydrofluorocarbon. HFC  Ver Hidrofluorocarbono. High pressure  A relative term to describe excessive

refrigerant pressure in the high side of an air-conditioning system.

Alta presión  Un término relativo que describe una presión

excesiva del refrigerante en el lado alto de un sistema de aire acondicionado.

High-pressure cutoff switch  An electrical switch that is

activated by a predetermined high pressure. The switch opens a circuit during high-pressure periods.

Interruptor de cierre de alta presión  Interruptor eléctrico

que es accionado por una alta presión predeterminada. El interruptor abre un circuito durante períodos de alta presión.

High-pressure switch  See High-pressure cutoff switch. Autómata manométrico de alta presión  Ver High-pressure

cutoff switch [Interruptor de cierre de alta presión].

High side  That part of an air-conditioning system extending

from the compressor outlet to the metering device inlet.

Lado alto  Esa parte de un sistema de aire acondicionado que se

extiende de la salida del compresor a la entrada del dispositivo medidor.

HL/LO  A term often used to refer to bi-level. HI/LO (alto/bajo)  Término utilizado con frecuencia para

referirse a binivel.

Hot gas line  A line that carries hot gas such as the discharge

line from the compressor to the condenser.

Línea de gas caliente  Línea que conduce el gas caliente, como

por ejemplo la línea de descarga, desde el compresor hasta el condensador.

Humid Damp. Húmedo  Que contiene humedad. Humidity  See Moisture. See also Relative humidity. Humedad  Ver Moisture [Humedad]. Ver también Relative

humidity [Humedad relativa].

HVAC  The abbreviation used for heating ventilation and air

conditioning.

HVAC  La abreviación que se usa para la ventilación del calor

y el aire acondicionado.

H-valve  An expansion valve with all parts contained within

that is used on some Chrysler and Ford lines.

Válvula H  Válvula de expansión que contiene todas las partes

dentro de sí misma; se utiliza dicha válvula en algunos modelos de vehículos de las compañias automotrices Chrysler y Ford.

Hybrid organic acid technology (HOAT)  G-05 extended-

life coolants are ethylene-glycol Glysantin-based formula refrigerants that are low in silicate, have low pH, and are phosphate-free. HOAT coolants use both organic and inorganic carbon-based additives for long life protection.

Tecnología de ácido orgánico híbrido (HOAT) Los

refrigerantes de vida extendida G-05 son refrigerantes cuyo base es una fórmula de etilenglicol Glysantin con bajo silicato, bajo pH y sin fosfato. Los refrigerantes HOAT utilizan aditivos de carbono orgánicos e inorgánicos para protección de larga duración.

Hydrocarbon  An organic compound containing only

hydrogen (H) and carbon (C).

Hidrocarbono  Compuesto orgánico que contiene solo el

hidrógeno (H) y el carbono (C).

Hydrochloric acid  A corrosive acid produced when water and

R-12 are mixed, as within an automotive air-conditioning system.

Ácido hidroclórico  Ácido corrosivo producido cuando se

mezcla el agua con el R-12, como por ejemplo dentro de un sistema automotriz para el acondicionamiento de aire.

Hydrogen  The lightest of all known substances; it is colorless,

odorless, and flammable (H).

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Hidrógeno  La más ligera de todas las substancias conocidas

que es sin color, sin olor y es inflamable. Hydrolysis  The chemical reaction with water whereby a substance is changed into one or more other substances. Hidrólisis  La reacción química con el agua en el cual una sustancia se cambia a una o más substancias. Hydrofluorocarbon (HFC)  A compound consisting of hydrogen, fluorine, and carbon. HFCs are a class of replacement refrigerants for CFC refrigerants and are not ozone depleting. Hidrofluorocarbono (HFC)  Un compuesto de hidrogeno, fluór y carbono. Los HFC pertenecen a una clase de refrigerantes que reem-plazan los refrigerantes CFC y no reducen el ozono. Hydrostatic pressure  The pressure exerted by a fluid. Presión hidrostática  Presión ejercida por un fluído. Hygroscopic  Readily absorbing and retaining moisture. Higroscópico  Que absorbe y conserve facilmente la humedad. Idiot light  Slang term often used for engine coolant and oil pressure warning lights; also called telltale light. Luz para idiotas  Término en jerga utilizado con frecuencia para las luces de advertencia de enfriante de motor y/o de presión de aceite. Impeller  A rotating member with fins or blades used to move liquid, for example, the rotating part of a water pump. Impulsor  El elemento rotativo provisto de aletas utilizadas para mover líquido, p.e., la parte giratoria de una bomba de agua. Infrared  It is the invisible light rays just beyond the red end of the visible spectrum and have a penetrating heating effect. Infrarrojo  son los rayos de luz invisible que se encuentran justo después del extremo rojo del espectro visible y tienen un efecto de calor penetrante. Inject  To insert, usually by force or pressure. Inyectar  Insertar, normalmente por medio de la fuerza o presión. Insulator  A nonconductor such as the covering of a wire (electrical) or a tube (thermal). Aislador  Elemento no conductor, como por ejemplo la cubierta de un alambre (eléctrico) o un tubo (térmico). Intake  See Suction. Toma  Ver Suction [Succión]. kiloPascal absolute  See kPa absolute. KiloPascal absoluto  Ver kPa absolute [kPa absoluto]. kPa  An abbreviation for the metric pressure measure “kilopascal,” sometimes written “kiloPascal,” equivalent to 0.145 psi on the English scale. kPa  Una abreviación de la medida métrica de presión

“kilopascal” que a veces se escribe “kilopascal”, equivalente a 0.145 libra por pulgada cuadrada en la gama inglesa.

kPa absolute  A metric unit of measure for pressure measured

from absolute zero.

kPa absoluto  Unidad métrica de medida para presión medida

del cero absoluto.

Latent heat  The amount of heat required to cause a change of

state of a substance without changing its temperature.

Calor latente  La cantidad de calor requerida para ocasionar

un cambio de estado de una sustancia sin cambiar su temperatura. Liquid line  The line connecting the drier outlet with the expansion valve inlet. The line from the condenser outlet to the drier inlet is sometimes called a liquid line. Línea de líquido  Línea que conecta la salida del secador con la entrada de la válvula de expansión. La línea de la salida del condensador a la entrada del secador a veces se llama una línea de líquido. Low pressure  A relative term to describe below-normal pressure in the low side of an air-conditioning system. Baja presión  Un término relativo para describir una presión bajo lo normal en el lado bajo de un sistema del aire acondicionado. Low-pressure cutoff switch  An electrical switch that is activated by a predetermined low pressure. This switch opens a circuit during certain low-pressure periods. Interruptor de cierre de baja presión  Interruptor eléctrico que es accionado por una baja presión predeterminada. Dicho interruptor abre un circuito durante ciertos períodos de baja presión. Low-pressure switch  See Low-pressure cutoff switch. Autómata manométrico de baja presión  Ver Low-pressure cutoff switch [Interruptor de cierre de baja presión]. Low side  That part of the air-conditioning system extending from the inlet of the evaporator metering device to the inlet of the compressor. Lado bajo  Esa parte del sistema del aire acondicionado que se extiende de la entrada del dispositivo medidora del evaporador a la entrada del compresor. Low-side service valve  A device located on the suction side of the compressor that allows the service technician to check low-side pressures or perform other necessary service operations. Válvula de servicio del lado de baja presión Dispositivo

ubicado en el lado de succión del compresor; dicha válvula permite que el mecánico verifique las presiones en el lado de baja presion o que lleve a cabo otras funciones de servicio necesarias. Lubricant  A substance, more commonly referred to as “oil,” thought of as a petroleum-based product that is used to coat moving parts to reduce friction between them. The term generally refers to the new synthetic lubricants, such as polyalkaline glycol (PAG) and polyol ester (POE) that are used with HFC refrigerants.

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Lubricante  Una substancia, comunmente referido como

“aceite” que se suele definir como un producto a base de petroleo que se usa para cubrir las partes en movimiento para reducir la fricción entre ellas. El término generalmente se refiere a los lubricantes nuevos sintéticos, tal como el glicol polialcalino (PAG) y el poliol ester (POE) que se usan con los refrigerantes HFC.

Malfunction  Failure to work or perform. Disfunción  Dejar de funcionar correctamente. Master control  A primary or main control. Regulador maestro  Control primario o principal. Matter  Anything that occupies space and possesses mass. All

things in nature are composed of matter.

Materia  Todo lo que ocupe espacio o tenga masa. Todas las

cosas en la naturaleza se componen de materia.

Metering device  A device for metering the proper amount of

refrigerant into an evaporator. The two types for automotive air-conditioning system service are thermostatic expansion valve (TXV) and orifice tube (OT).

Dispositivo medidora  Un dispositivo para medir la cantidad

adecuada del refrigerante entrando al evaporador. Los dos tipos en el servicio del sistema aire acondicionador automotivo son la válvula de expansión termostático (TXV) y el tubo del orificio (OT).

Miscible  Another word for mixable. Miscible  Otra palabra que significa que se puede mezclar. MIX  A term often used when referring to HI/LO. MEZCIA.  Término utilizado con frecuencia al referirse a HI/

LO (alto/bajo).

Mode  Manner or state of existence of a thing; for example,

hot or cool.

Nitrogen (N)  An odorless, tasteless, and colorless element that

composes over 80 percent of the atmosphere and is essential for all animal and plant life.

Nitrógeno (N)  Elemento inodoro, insípido e incoloro que

compone mas de un 80 por ciento de la atmósfera y es esencial para toda vida vegetal y animal.

Normally closed (nc)  A switch or device that is closed in its

relaxed (normal) position.

Normalmente cerrado  Conmutador o dispositivo que está

cerrado en su posición relajada (normal).

Normally open (no)  A switch or device that is open in its

relaxed (normal) position.

Normalmente cerrado  Conmutador o dispositivo que está

cerrado en su posición relajada (normal).

Ohm (Ω)  The unit used to measure the amount of electrical

resistance in a circuit or an electrical device. One ohm is the amount of resistance present when one volt pushed one ampere through a circuit or device.

Ohmio (Ω)  la unidad utilizada para medir la cantidad de

resistencia eléctrica de un circuito o dispositivo eléctrico. Un ohmio es la cantidad de resistencia presente cuando un voltio empuja un amperio a través de un circuito o dispositivo.

Ohm’s law  Defines the relationship between voltage,

resistance, and current.

Ley de Ohmio  define la relación entre la tensión (o voltaje), la

resistencia y la corriente.

Organic acid technology  The term used to describe the

chemical additive package in extended life coolant.

Tecnología de ácidos orgánicos  El término que se usa para

describir el paquete de aditivos de químicas del refrigerante de larga vida.

Modo  Manera o estado de existencia de una cosa; p.e., calor o

Orifice  A small hole of calibrated dimensions for metering

Mode door  A diverter door within the duct system for

Orificio  Un hoyo pequeño de dimensiones calibradas para

Puerta de modo  Puerta desviadora dentro del sistema de

Orifice tube  See Expansion tube and Fixed orifice tube (FOT).

fresco.

directing air through the heater and evaporator core. conductos para conducir el aire a través del núcleo del calentador y/o del evaporador.

Moisture  Droplets of water in the air; humidity, dampness, or

wetness.

Humedad  Gotitas de agua en el aire. Molecule  Two or more atoms chemically bound together. Molécula  Dos o más átomos quimicamente ligados. Negative  Minus, less than zero. The ground (−) side of

a battery or DC electrical circuit. A pressure below atmospheric; a vacuum.

Negativo  Menos de cero. El lado puesto a tierra (−) de un

acumulador o corriente eléctrica de corriente continua. Una presión inferior a la de la atmósfera; un vacío.

fluid or gas in exact proportions.

medir los flúidos o los gases en proporciones exactas.

Tubo de orificio  Ver Expansion tube [Tubo de expansion] y

Fixed orifice tube [Tubo de orificio fojo (FOT)].

Overcooling  A general term used if the engine does not reach

design operating temperature in a predetermined time period, such as would be the case if the thermostat were removed.

Sobreenfriamiento  Término general utilizado si el motor

no alcanza la temperatura de functionamiento de diseño dentro de un período pre-determinado de tiempo, como por ejemplo si se removara el ter-mostato.

Overflow tank  Another term used when referring to

the coolant recovery tank that allows for both coolant expansion and contraction from the cooling system of the engine.

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Tanque de derrame  Otro término que se usa cuando se

refiere al tanque de rescate del refrigerante que permite la expansión y contracción del refrigerante debido al sistema refrigerante del motor.

Overheating  A general term used if the engine exceeds design

operating temperature.

Sobrecalentamiento  Término general utilizado si el motor

excede la temperatura de funcionamiento de diseño.

Oxygen (O)  An odorless, tasteless, colorless element that

forms about one-fifth of our atmosphere. An essential element for animal and plant life.

Oxígeno (O)  Elemento inodoro, insipido e incoloro que forma

más o menos la quinta parte de nuestra atmósfera. Es un elemento esencial para toda vida vegetal y animal.

Ozone (O3)  An unstable pale-blue gas with a penetrating odor;

it is an allotropic form of oxygen (O) that is usually formed by a silent electrical discharge in the air.

Ozono (O 3 )  Gas inestable de color azul palido que tiene

un olor pene-trante; es una forma alotrópica de oxígeno (O) normalmente pro-ducido por una descarga eléctrica silenciosa en el aire.

Ozone depletion  The reduction of the ozone layer due to

contamination, such as the release of CFC refrigerants into the atmosphere.

Agotamiento del ozono  La reducción de la capa de ozono

debido a la contaminación, tal como los refrigerantes CFC a la atmósfera.

Performance  The way in which something functions. Ejecución  La manera en la cual algo funciona. Perspiration  The salty fluid secreted by sweat glands through

the pores of the skin.

Sudor  Fluído salado secretado por las glándulas sudoríparas a

través de los poros de la piel.

Pitch  Set at a particular degree or angle. Inclinación  Puesto a un grado o ángulo específico. Plenum  See Plenum chamber. Pleno  Ver Plenum chamber [Cámara impelente]. Plenum chamber  An area filled with air at a pressure that is

slightly higher than the surrounding air pressure, such as the chamber just before the blower motor.

Cámara impelente  Área en la cual existe una condición de

sobrepresión, como por ejemplo la cámara justo enfrente del motor del soplador.

PM  Preventive maintenance. PM  Mantenimiento preventativo. POE  An abbreviation for the synthetic lubricant polyol ester. POE  Abreviatura del lubrificante sintético poliolester. Positive  The hot (1) side of a battery or electrical circuit.

Also, a pressure above atmospheric.

Positivo  El lado cargado (1) de un acumulador o circuito

eléctrico. También una presión superior a la de la atmósfera. Power train control module  Generally abbreviated PCM, it is the computer system for the engine management and emission systems. Módulo de control del trén motriz  Generalmente abreviado de PCM y es el sistema de computador de los sistemas de regulación del motor y emisiones. Predetermined  The preset parameters used. Predeterminado  Los parámetros prescritos que se usan. Pressure cap  A radiator cap that increases the pressure of the cooling system and allows higher operating temperatures. Tapa de presión  Tapa de radiador que eleva la presión del sistema de enfriamiento y permite un funcionamiento a temperaturas mas altas. Pressure switch  An electrical switch that is actuated by a predetermined low or high pressure. A pressure switch is generally used for system protection. Autómata manométrico  Interruptor eléctrico accionado por una alta o baja presión predeterminada. Generalmente se utiliza un autómata manométrico para la protección del sistema. Price leader  An item that a merchant may sell at cost or near cost to attract customers. Artículo en venta  Un artículo que un negociante puede vender en costo o casi en costo para atraer a la clientela. Programmer  The part of an automatic temperature control system that controls the blower speed, air mix doors, and vacuum diaphragms. Programador  Parte de un sistema de regulación automática de temperatura que regula la velocidad del soplador, puertas de mezcla de aire, y diafragmas al vacío. Propylene glycol  A colorless liquid used in the production of antifreeze, C 3 H 8 O 2 ; it is considered a low toxicity antifreeze. Propileno glicol  Un líquido sin color que se usa en la producción del anticongelante, C 3 H 8 O 2 , y que se considera un anticongelante de baja toxicidad. Pulse width modulation (PWM)  On-off duty cycling of a component. The period of time for each cycle does not change; only the amount of on time in each cycle changes. The length of time in milliseconds that an actuator is energized. Modulación por ancho de pulsos (PWM)  El ciclo útil de un componente de conexión. El período de tiempo de cada ciclo no cambia; Sólo la cantidad de tiempo en cada ciclo cambia. La longitud de tiempo en milisegundos que se energiza un actuador. Pump  The compressor. Also refers to the vacuum pump. Bomba  El compresor. Se refiere tambien a la bomba de vacío. Pump down  See Evacuate. Vaciar  Ver Evacuate [Evacuar].

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Pure  Not mixed with anything else. Puro  Quo no se ha mezclado con ninguna otra cosa. R-12  An abbreviation to identify the chlorofluorocarbon

family of ozone-depleting refrigerants. R-12, or CFC-12, was a popular refrigerant for automotive air-conditioning systems service until it was phased out of production.

R-12  Una abreviación para identificar la familia de los

refrigerantes clo-rofluorocarburo que agotan la capa de ozono. El R-12, o CFC-12, fue un refrigerante de sistemas de aire acondicionado automotivos muy popular hasta que su producción fue restringida.

R-1234yf  is a low GWP refrigerant developed by Honeywell

and Dupont.

R-1234yf  es un refrigerante con bajo potencial de

calentamiento global (GWP) desarrollado por Honeywell y DuPont.

R-134a  An abbreviation to identify the ozone-friendly

hydrofluorocarbon family of refrigerants. R-134a, or HFC134a, is the refrigerant of choice for replacing R-12 in automotive air-conditioning systems.

R-134a  Una abreviación para identificar la familia de los

refrigerantes clorofluorocarburo que no agotan la capa de ozono. El R-134a, o HFC-134a, es el refrigerante que más se usa para reemplazar el R-12 en los sistemas de aire acondicionado automotivo.

R-744  The trade name for carbon dioxide (CO 2 ) gas, it is

considered to be one of the alternative refrigerant gases that will be used for refrigerant systems.

R-744  El nombre registrado del gas carbónico (CO 2 ), que se

considera ser uno de los gases refrigerantes alternativos que serán usados para los sistemas refrigerantes.

Radiation  The transfer of heat without heating the medium

through which it is transmitted.

Radiación  La transferencia del calor sin calentar el medio por

el cual se está transmitiendo.

Radiator  A coolant-to-air heat exchanger. The device that

removes heat from coolant passing through it.

Radiador  Intercambiador de calor del enfriante al aire. El

dipositivo que remueve calor del enfriante que pasa por él.

Ram air  The term used to describe the flow of air striking the

front of a vehicle as it travels in a forward direction.

Aire admitido en marcha  El término que se usa para describir

el flujo del aire que golpea la parte delantera del vehículo mientras que éste viaja en un movimiento delantera.

RCD  Refrigerant containment device. RCD  Dipositivo para contener refrigerante. Receiver  A container for the storage of liquid refrigerant. Receptor  Recipiente para el almacenaje de refrigerante líquido. Receiver-dehydrator  A combination container for the storage

of liquid refrigerant and a desiccant.

Receptor-deshidratador  Recipiente de combinación para el

almacenaje del refrigerante líquido y un desecante.

Receiver-drier  See Receiver-dehydrator. Receptor-secador  Ver Receiver-dehydrator [Receptor/

deshidratador].

Reciprocating  To move to and fro, fore and aft, or up and

down.

Movimiento alternativo  Moverse de un lado para otro, de

atrás para adelante, o de arriba para abajo.

Reciprocating piston(s)  A compressor assembly that uses

the back and forth movement of a piston to cause a rotary motion of the compressor crankshaft.

Pistones recíprocos  Una asamblea de compresor que usa

el movimiento oscilante de un pistón para causar un movimiento rotario del cigueñal del compresor.

Recirculate  To reuse. To circulate a fluid or vapor over and

over again.

Recircular  Utilizar de nuevo. Hacer circular un fluído o vapor

repetida-mente.

Reclaim  To process used refrigerant to new product

specifications by means that may include distillation. This process requires that a chemical analysis of the refrigerant be performed to determine that appropriate product specifications are met. This term implies the use of equipment for processes and procedures usually available only at a reprocessing facility.

Recuperar  Procesar refrigerante gastado a nuevas

especificaciones para productos por un medio que puede incluir la distilación. Este proceso require que se realice un análisis químico del refrigerante para determinar si se pueden cumplir con las especificaciones apropiadas para dicho producto. Este término implica la utilización de equipo para procesos y procedimientos normalmente disponibles solo en una instalación de reprocesamiento.

Recover  To remove refrigerant in any condition from a system

and to store it in an external container without necessarily testing or processing it in any way.

Recobrar  Remover refrigerante en cualquier condición de

un sistema y almacenarlo en un recipiente externo sin necesariamente probarlo o procesarlo.

Recovery cylinder  A recovery cylinder for R-12 and R-134a

must meet DOT specifications 4BA-300. These cylinders are characterized by a combined liquid/vapor valve located at the top. A dip tube is used to feed liquid refrigerant from the bottom so it can be dispensed without inverting the cylinder. A recovery cylinder should be painted gray with a yellow shoulder.

Cilindro de recuperación  Un cilindro de recuperación para

R-12 y/o R-134a tiene que cumplir con las especificaciones 4BA-300 del DOT. Se caracterizan estos cilindros por una válvula combinada de líquido y vapor ubicada en la parte superior. Se utiliza un tubo probador para alimentar el

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refrigerante líquido desde la parte inferior para que pueda dispensarse sin invertir el cilindro. Un cilindro de recuperación debe ser pintado el color gris con un resalto amarillo. Recovery tank  See Recovery cylinder and Expansion tank. Tanque de recuperación  Ver Recovery cylinder [Cilindro de recuperación] y Expansion tank [Tanque de expansión]. Recycle  To clean refrigerant for reuse by oil separation and to pass through other devices such as filter-driers to reduce moisture, acidity, and particulate matter. Recycling applies to procedures usually accomplished in the repair shop or at a local service facility. Reciclar  Limpiar el refrigerante para ser utilizado de nuevo por medio de la separación de aceite y del pasaje a través de otros dispositivos, como por ejemplo filtro-secadores, para disminuir la humedad, acidez, y materia partícula. El reciclamiento se aplica a los procedimientos normalmente realizados en el taller de reparación o en la instalación de servicio local. Reed valve  The leaves of steel located on the valve plate of a compressor. The suction reed valve opens to admit refrigerant on the intake stroke of the compressor and closes to block refrigerant flow on the exhaust stroke. The discharge reed valve, on the other hand, is closed to block refrigerant flow on the intake stroke and opens to expel refrigerant on the exhaust stroke. Válvula de lámina vibrante  Las láminas del acero ubicados en la placa de la válvula del compresor. La válvula succión de lámina abre para admitir al refrigerante en la carrera de entrada del compresor y cierra para bloquear el flujo del refrigerante en la carrera de escape. La válvula de descarga de lámina, en cambio, es cerrada para bloquear el flujo del refrigerante en la carrera de entrada y abre para expeler el refrigerante en la carrera de escape. Refrigerant  The chemical compound used in a refrigeration system to produce the desired cooling. Refrigerante  Compuesto químico utilizado en un sistema de refrigeración para producir el enfriamiento deseado. Refrigeration  To use an apparatus to cool, keep cool, chill, and keep chilled under controlled conditions by natural or mechanical means as an aid to ensuring personal safety and comfort. To cool the air by removing some of its heat content. The removal of heat by mechanical means. Refrigeración  Utilizar un aparato para enfriar y mantener el frío bajo condiciones controladas por medios naturales o mecánicos para ayudar a asegurar la seguridad y comodidad personales. Enfríe el aire removiendo una porción de su contenido de calor. La remoción del calor por medios mecánicos. Relative humidity  The actual moisture content of the air in relation to the total moisture that the air can hold at a given temperature. Humedad relativa  Contenido verdadero de humedad del aire en relación a la humedad total que el aire puede mantener a una temperatura dada.

Remote bulb  A sensing device connected to the expansion

valve by a capillary tube. This device senses the tailpipe temperature and transmits pressure to the expansion valve for its proper operation. Bombilla a distancia  Dispositivo sensor conectado a la válvula de expansión por un tubo capilar. Este dispositivo siente la temperatura del tubo de escape y transmite presión a la válvula de expansión para su funcionamiento correcto. Reserve tank  See Overflow tank. Tanque de derrame  Ver Overflow tank (Tanque de derrame). Restriction  A blockage in the air-conditioning system caused

by a pinched or crimped line, foreign matter, or moisture freeze-up.

Limitación  Bloqueo en el sistema de acondicionamiento de

aire ocasionado por una línea pellizcada o arrugada, una materia extraña, o la congelación de humedad.

Restrictor  Decreases the flow of a liquid or gas. Limitador  Disminuye el flujo de un líquido o un gas. Retrofit  To modify equipment that is already in service using

parts and materials made available after the time of original manufacture.

Retromodificación  Modificar el equipo que ya está en servicio

usando las partes y/o los materiales disponibles después del tiempo de la fabricación original.

Reverse flow  Direction opposite that of which is considered

the standard direction. In engine cooling systems, reverse flow systems circulate coolant first through the cylinder head(s) and then through the engine blow.

Flujo en reverso  La dirección opuesta de la que se considera

la dirección normal. En los sistemas de refrigeración automotivos los sistemas de flujo en reversa circulan el refrigerante primero por la(s) culata(s) de cilindro y luego por el bloque motor.

Rheostat  A wire-wound variable resistor used to control

blower motor speed.

Reostato  Resistor variable devanado con alambre utilizado

para regular la velocidad del motor del soplador.

Rotary  The turning motion around an axis. Rotario  El movimiento de girar alrededor de un eje. Saddle valve  A two-part accessory valve that may be clamped

around the metal part of a system hose to provide access to the air-conditioning system for service.

Válvula de silleta  Válvula de accesorio de dos partes que

puede fijarse con una abrazadera a la parte metálica de una manguera del sistema para proveer acceso al sistema de acondicionamiento de aire para llevar a cabo el servicio.

SAE  Society of Automotive Engineers. SAE  Sociedad de Ingenieros Automotrices. SATC  Semiautomatic temperature control.

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SATC  Regulador semi automático de temperatura. Screen  A metal mesh located in the receiver, expansion

valve, and compressor inlet to prevent particles of dirt from circulating through the system.

Cribadora  Malla metálica ubicada en el receptor, la válvula

de expansión, y la entrada del compresor para evitar que las partículas de polvo se circulen a través del sistema.

Scroll  A spiral, rolled, or convoluted form. Arollado  Una forma de espiral, de enrollado o convoluto. Sensible heat  Heat that causes a change in the temperature of

a substance but does not change the state of the substance.

Calor sensible  Calor que ocasiona un cambio de temperatura

de una sustancia pero que no cambia el estado de dicha sustancia.

Sensor  A temperature-sensitive unit such as a remote bulb or

thermistor. See Remote bulb and Thermistor.

Sensor  Unidad sensible a la temperatura, como por ejemplo

una bombilla a distancia o termistor. Ver Remote bulb [Bombilla a distancia] y Thermistor [Termistor].

Serpentine  Refers to the circuitous and twisted or winding

path taken by one drive belt used to turn numerous pulleys.

Serpentina  Refiere a la senda indirecto y girando or

torciéndose que toma una correa de impulso para girar poleas numerosas.

Serpentine belt  A flat or V-groove belt that winds through all

of the engine accessories to drive them off the crankshaft pulley.

Correa serpentina  Correa plana o con ranuras en V que

atraviesa todos los accesorios del motor para forzarlos fuera de la polea del cigueñal.

Service port  A fitting found on some control devices and in

the low-and high-sides of an air-conditioning system, used to gain access into the system for diagnostics and service procedures.

Puerta de servicio  Un montaje que se encuentra en algunos

dispositivos de control y en los lados de baja y alta presión de un sistema de aire acondicionado que sirve para dar acceso al sistema para efectuar los procedimientos de diagnóstico y/o el servicio.

Service valve  See Service port. Valvula de servicio  Ver Service Port [Orificio de servicio]. Shroud  A duct-like cover to ensure that maximum airflow is

directed over the engine by the engine-driven fan assembly.

Gualdera  Cubierta parecida a un conducto para asegurar que

un flujo máximo de aire es conducido sobre el moto por el conjunto del ventilador accionado por el motor.

SNAP  Acronym used for the EPA’s Significant New

Alternatives Policy program, which reviews alternatives to CFC-12 (R-12) refrigerant.

SNAP  Una sigla del programa Poliza de Alternativas Nuevas

Significantes de la EPA (Agencia de Protección del Medio

Ambiente) que revisa las alternativas del refrigerante para el CFC-12 (R-12). Snapshot  A feature of OBD II that shows, on various scanners,

the conditions that the vehicle was operating under when a particular trouble code was set. For example, the vehicle was at 2258F, ambient temperature was 558F, throttle position was part throttle at 1.45 volts, rpm was 1,450, brake was off, transmission was in third gear with torque converter unlocked, air-conditioning system was off, and so on.

Instantáneo  Una característica del OBD II que muestra, en

varios detectores, las condiciones bajo las cuales operaba el vehículo cuando se registró un código de fallo. Por ejemplo, el vehículo regis-traba 2258F, la temperatura del ambiente era el 558F, la posición del regulador estaba en una posición parcial de 1.45 voltios, el rpm era 1,450, el freno estaba desenganchada, la transmisión estaba en la ter-cera velocidad con el convertidor del par desenclavado, el sistema de acondicionador de aire estaba apagado, y etcétera.

Specific heat  The quantity of heat required to change one

pound of a substance by 18F .

Calor específico  Cantidad de calor requerida para cambiar

una libra de una sustancia en un grado Fahrenheit.

Stabilize  To keep from fluctuating. Estabilizar  Prevenir las fluctuaciones. Starved  Refers to a condition whereby too little refrigerant is

metered into the evaporator.

Falta de refrigerante  Se refiere a una condición en la cual

no se dosifica la cantidad suficiente de refrigerante al evaporador.

Strainer  See Screen. Colador  Ver Screen [Cribadora]. Stroke  The distance a piston travels from its lowest point to

its highest point.

Carrera  Distancia que un pistón viaja desde el punto más bajo

hasta el mas alto.

Suction  A negative force or pressure. Succión  Fuerza o presión negativa. Suction line  The line connecting the evaporator outlet to the

compressor inlet.

Conducto de succión  Línea que conecta la salida del

evaporador a la entrada del compresor.

Suction pressure  Compressor inlet pressure. Reflects the

pressure of the system on the low side.

Presión de succión  La presión de la entrada del compresor.

Refleja la presión del sistema del lado de baja presión.

Suction service valve  See Low-side service valve. Válvula de succión de servicio  Ver Low-side service valve

[Válvula de servicio del lado de baja presión].

Suction valve  The low-side service valve is often referred to as

the suction valve.

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Válvula de succión  La válvula de servicio del lado bajo de

presión suele referirse como la válvula de succión.

Superheat  Adding heat intensity to a gas after the complete

evaporation of a liquid.

Sobrecalentar  El agregar intensidad calorífica a un gas

después de la evaporación completa de un líquido.

Surface temperature  The inner temperature of a body, such as

water.

Temperatura de la superficie  La temperatura interior de un

cuerpo, tal como el agua.

Swash plate  A type of concentric plate found on some

compressor crankshafts used to move the pistons to and fro or back and forth.

Placa oscilante  Tipo de placa concéntrica ubicada en algunos

cigueñales de compresor y utilizada para mover los pistones de un lado para otro o de un lado a otro.

Telltale light  A dash lamp to indicate a malfunction such as

low oil pressure or overheating; also called an “idiot light.”

Luz indicadora  Una lámpara en el tablero de instrumentos

para indicar una disfunción, como por ejemplo la baja presión del aceite o el sobrecalentamiento; tambien ilamada “luz para idiotas”.

Temperature  Heat intensity measured on a thermometer. Temperatura  Intensidad calorífica medida con un

termómetro.

Temperature–pressure relationship  The relationship that

exists, in the English system of measure, of the similarities between temperature and pressure readings of refrigerants R-12 and R-134a in a refrigeration system.

Relación temperatura-presión  La relación que existe en el

sistema de medida inglés de las similaridades entre las lecturas de temperatura y presión de los refrigerantes R-12 y R-134a en el sistema de refrigeración.

Temperature switch  A switch actuated by a change in

temperature at a predetermined point.

Interruptor de temperatura  Interruptor accionado por un

cambio de temperatura a un punto predeterminado.

Thermistor  A temperature-sensing resistor that has the ability

to change values with a change in temperature.

Termistor  Resistor sensible a temperatura que tiene la

capacidad de cambiar valores al ocurrir un cambio de temperatura.

Thermostat  A device used to cycle the clutch to control the

rate of refrigerant flow as a means of temperature control. The driver has control over the temperature desired.

Termostato  Dispositivo utilizado para ciclar el embrague para

regular la proporción del flujo de refrigerante como medio de regulación de temperatura. El conductor puede regular la temperatura deseada.

Thermostatic expansion valve  The component of a

refrigeration system that regulates the rate of flow of

refrigerant into the evaporator as governed by the action of the remote bulb-sensing tailpipe temperatures. Válvula de expansión termostática  Componente de un sistema

de refrigeración que regula la proporción del flujo de refrigerante en el evaporador, lo cual es controlado por la acción de la bombilla a distancia que siente las temperaturas del tubo de escape.

Toxicity  Toxic or poisonous quality. Toxicidad  Calidad tóxica o venenosa. Ultraviolet (UV) radiation  The invisible rays from the sun that

have damaging effects on the earth. Ultraviolet radiation causes sunburns.

Radiación ultravioleta  Rayos invisibles del sol que tienen

efectos dañosos en la tierra. La radiación ultravioleta es la causa de la insolacion.

Vacuum  Any pressure below atmospheric pressure. Vacío  Cualquier presión inferior a la de la atmósfera. Vacuum motor  A device designed to provide mechanical

action by the use of a vacuum signal.

Motor de vacío  Dispositivo diseñado para proveer acción

mecánica por medio del uso de una señal de vacío.

Vacuum pot  See Vacuum motor. Olla de vacio  Ver Vacuum motor [Motor de vacío]. Vacuum signal  Level of vacuum received. Señal de vacío  El nivel del vacío que se ha recibido. Vapor  See Gas. Vapor  Ver Gas. Variable displacement  To change the displacement of a

compressor by changing the stroke of the piston(s).

Desplazamiento variable  Cambiar el desplazamiento de

un compressor al cambiar la carrera del pistón o de los pistones.

Vent  A condition whereby fresh outside air may be

introduced into the vehicle.

Ventilación  Condición por medio de la cual el aire fresco

exterior puede introducirse al vehículo.

Virgin  Newly manufactured or produced, not previously used. Virgen  Fabricado o producido últimamente; no utilizado

previamente.

Visual inspection  An inspection by sight as opposed to smell,

hearing, or touch.

Inspección visual  Una inspección usando el sentido de vista

en vez del olfato, el oído o el tacto.

Voltage (V)  The difference or potential that indicates an

excess of electrons at the end of the circuit farthest from the electromotive force. It is the electrical pressure that causes electrons to move through a circuit. One volt is the amount of electrical pressure required to move one amp through one ohm of resistance.

430 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Tensión o voltaje (V)  la diferencia o potencial que indica

un exceso de electrones en el extremo del circuito más alejado de la fuerza electromotriz. Es la presión eléctrica que provoca que los electrones se muevan a través de un circuito. Un voltio es la cantidad de presión eléctrica necesaria para mover un amperio a través de un ohmio de resistencia.

Wobble plate  An offset plate that is secured to the main shaft

and moves the piston(s) to and fro.

Placa oscilante  Placa de desviación que se fija al árbol

principal y mueve el pistón o los pistones de un lado para otro. Zener clamping diode  A one-way electrical gate with a threshold voltage used to suppress damaging voltage spikes to integrated circuits. Diodo estabilizador zener  Una entrada eléctrica de una vía con un umbral de voltaje que se usa para suprimir los picos dañosos de voltaje en los circuítos integrados.

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INDEX A Absolute cold, 52 Absolute zero, 37 Absorb, 209 Access valves, 407 Accumulator, 20, 198–199, 407 Additives, 124–125, 211 Adiabatic expansion, 394 Air baffles, 100–101 Air-conditioner/heater system schematic, 339 Air conditioning, 118 cleaning, 262 defined, 2 EPA technician certification, 22–21 industry, 27 operation, cost of, 31 Air-conditioning system advanced diagnostic tools, 268–270 charging, 226–227 connections, 273 contamination, 274–275 cross contamination, 396 leaks, 270–272 performance testing, 203–204 preventive maintenance (PM), 267–268 receiver-drier, 180–182 restrictions, 273–274 Air delivery, 312–317 Air door control system, 329–333 Airflow, 229 Air humidity sensor, 371 Air intake, 310 Air movement, 50–51 Allotrope, 4 Alternating current (AC), 58 Alternative refrigerants, 392. See also HFC-134a (R-134a) health and the environment, 405 standards, 406 use conditions, 406 use of, 405–406 Aluminum (Al), 34 Aluminum core/plastic header radiator, 86 Ammeter, 66

Amperage, 58, 66 Amperes (A), 58 Anode, 70 Antifreeze, 23–24, 125–129 disposal, 24 mixing types of, 24 vehicle engine protection, 24 Arid, 50 Artificial ice, 2 ASE certification, 28–30 Aspirator, 369 Astatine (At), 26 Atmosphere, 4–6 Atmospheric pressure, 352 Atmospheric valve, 91 Atom, 34 Autofrost, 401 Automatic temperature controls (ATC), 316, 317, 356–358 Auxiliary components, 278 Auxiliary evaporator, 278 Average, 247 Axial plate, 280

B Barrier, 175 Bellows, 346 Bellows-type thermostat, 106, 109 Belt tension, 227 Bi-level, 315 Bimetallic thermostat, 106, 113 Blend door, 310 Blend refrigerants, 20–21 Block valve, 188–190 Blower motor credit card resistor, 75–77 HVAC housing, 73 power transistor module, 77 resistor block, 74–75 speed, 74 Blower operation, 229 Blow-off valve, 90–91 Body control module (BCM), 77–78 Boiling, 40

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Boiling-point of coolant, 89, 126 ethylene glycol/water concentrations, 89, 126 of water by increasing pressure, 210, 213 of water in vacuum, 210, 213 Bowden cable, 310 Boyle’s law, 52–53 Brake booster vacuum switch, 372 British thermal unit (Btu), 37, 41 Broken discharge valve, 298 Bromine (Br), 26 Bypass, 96

C Cabin air filters, 325–328 Calorie, 41, 46 Calsonic V-5 compressor, 288 Capillary tube, 184, 261 Carbon (C), 33 Carbon cycle, 11–12 Carbon dioxide (CO2), 5–6, 393–395 emissions, 11–151 Carbonic acid, 275 Case/duct systems air delivery, 312–317 air intake, 310 cabin air filters, 325–328 combined case, 311 core section, 311–312 distribution section, 312 dual-zone duct system, 319–320 evaporator drain, 323 mode door adjustment, 334 odor control, 323–325 rear heat/cool system, 320–23 split case, 307–309 visual inspection, 334 Cathode, 70 Cellular core, 86, 88 Centrifugal impeller-type pump, 95 Certificating agency, 20 Certification ASE, 28–30 EPA, 16–17, 30–31 CFC-12 (R-12), 36 EPA technician certification, 16 protection regulations, 16

recovery equipment for, 223–225 temperature-pressure relationships, 244–246 CFCs (chlorofluorocarbon), 8–10, 33. See also CFC-12 (R-12) Charging the system, 226–227 Charles’ Law, 53–54 Check valve, vacuum, 355 Chil-It, 401 Chlorine (Cl), 8, 26, 33 Circuit breaker, 338 Circuit breakers, 67–68 Circuit faults, 65 Circuit resistance, 60–61 resistors, 68 Clean Air Act (CAA), 15, 30 Climate control module. See Body control module (BCM) Climate control network, 383–386 Closed cooling system, 84 Clutch, 227–228, 281–288 cycling clutch, 199 fixed orifice tube/cycling clutch (FOTCC) system, 192 noncycling clutch, 199 Clutch-cycling low-pressure switch, 347 Clutch cycling pressure switch (CCPS), 410 Clutch diode, 79 Cold, defined, 51–52 Cold leak, 216 Color code, 191, 409 Combined case, 311 Compatibility, 235–236 Compression, 171 Compression stroke, 171, 289 Compressor discharge pressure switch, 349, 350 Compressors, 398, 407 action of, 288–290 clutch, 281–288 compression stroke, 171 design of, 279–280 diagnosing and repairing, 300 electric motor–driven, 301–303 electronic variable displacement, 297–300 failure, 301 function, 278 intake stroke, 171 operation, 171–172, 290

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reciprocating, 170, 286–288 refrigerant, compress, 279 rotary vane, 290 scotch yoke, 293 scroll compressor, 291–293 servicing tips, 237–238 variable displacement, 294–296 Concentration, 89–91 Condensers, 176–180, 398, 408 Conduction, 45 Connections, 273 Contaminated refrigerant, 205, 403–404 disposal of, 405 Contaminated vacuum pump oil, 213 Contamination, 274–275 Continuous action, 290 Controller area network (CAN), 379–386 Control system air door, 329–333 automatic temperature controls, 356–360 control devices, 352–355 controller area network (CAN), 379–386 coolant temperature warning system, 350–352 electronic temperature control, 360 factory-installed wiring, 349–350 faults, 333–334 fuse and circuit breaker, 338 heated and climate controlled seating, 386–388 master control, 340–343 pressure cutoff switch, 347 scan tools for, 376–378 thermostat, 344–348 vacuum-operated devices, 353 vacuum source, 354 vacuum system diagram, 355–356 Control thermostat, 251 Control valve, 121 Convection, 46–47 Coolant. See also Antifreeze percentage/protection chart, 127 recovery system tank, 93 Coolant pump, 95–97 hybrid electric engine, 97–100 Coolant recovery system, 91–94 Coolant temperature gauge, 351–352 Coolant temperature sensor, 371–372 Coolant temperature warning system, 350–352

Cooling, 311 humidification, 3 Cooling system, 82–84 additives, 124–125 coolant pump, 95–97 coolant recovery system, 91–94 hoses and clamps, 120–121 overflow tank, 91 pressure cap, 89–91 preventive maintenance, 129–130 pulley and belt, 109–112 radiator, 85–89 Core section, 311–312 CO2 (R-744) systems, 393–395 Crankshaft, 280 Credit card resistor, 75–77 Cross-contaminated refrigerant, 205 Cross contamination, 396 Current, 58 Current flow, 60–61 Cycling clutch orifice tube (CCOT) system, 192 Cylinder head water jackets, 95

D Dalton’s Law, 54–55 Dams, 408 Declutching fan, 113–114 Deep-tissue temperature, 46 Defrost, 306–307, 318 Delta P (Δp), 352 Desiccant, 182 Desiccants, 398 Diagnosis, 227–232 Diagnostic tools, advanced, 268–270 Diamond, 33 Digital multimeter (DMM) circuit types, 60 series circuit, 60 Digital volt ohmmeter (DVOM), 85, 286 Diode forward/reverse biased, 70 semiconductor devices, 70 Direct current (DC), 58 Discharge, 285 Discharge line, 175–176 Discharge stroke, 288 Discharge valve, 288

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Disposal antifreeze, 23 of contaminated refrigerant, 405 Distilled water, 125–127 Distribution section, 311 Dobson Unit (DU), 6 Domestic refrigeration, 2–3 Double shaft (DBL) end, 74 Drier (receiver-drier), 181 Drop-in refrigerant, 221 Dual fan systems, 117 Dual systems, 359 Dual-zone duct system, 319–320 Duracool, 402 Duty cycle, 77 DVOM. See Digital volt ohmmeter (DVOM)

E Earth’s atmosphere, 4–6 Electric actuator motors, 330–333 Electrical principles basics, 58–59 blower motor, 71–78 circuit resistance, 68–69 circuit types, 60–67 clutch diode, 79 diode, 70–71 electromagnetic clutch, 78–79 fuses/circuit breakers, 67–68 relays, 71–73 Electrical resistance, 58 Electrical symbols, 339 Electric fans, 116–119 Electricity, 57 Electric motor-driven compressors, 301–303 Electrolysis, 88 Electromagnetic clutch, 78–79, 170 Electromotive force (EMF), 58 Electronically controlled viscous cooling fan, 114–116 Electronic HVAC control module self-diagnosis, 378–379 Electronic (Halogen) leak detectors, 218–220 Electronics, 57, 60 Electronic temperature control systems, 360–375 Electronic thermostat, 104–106 Electronic variable displacement compressor, 294–296 Elf Atochem, study, 413 Engine block water jackets, 95 Engine-mounted fan, 112–115

Ethylene glycol (EG), 23, 125–126 Evaporation, 39–40, 48 Evaporator, 3, 193–197, 398, 409 coil temperature, 244 drain, 323 temperature sensor, 370–371 thermistor, 370 Exhaust stroke, 289 Expansion core plugs, 95 Expansion tank, 87, 94

F Factory-installed wiring, 349–350 Fans, 112–119 declutching, 113–114 electric, 116–119 electronically controlled viscous cooling, 114–116 engine-mounted, 112–114 flexible, 116 Fan shrouds, 100–101 Faults, control system, 333–334 Fittings, 231–232 Fixed orifice tube (FOT), 191–193 Fixed orifice tube/cycling clutch (FOTCC) system, 192 Fixed resistors, 68–69 Flammability, 405 Flexible fans, 116 Flooded evaporator, 194 Fluorescent leak detectors, 217–218 Fluorine (F), 26 Flush, 413 Flushing system, 398, 413 Freeze, 399–400 Freeze plugs, 95 Free Zone/RB-276, 400 Freon (R-12), 27. See also CFC-12 (R-12) FRIGC FR-12, 400 Fully charged automotive battery, 267 Fuses, 67–68, 338 Fuses/circuit breakers bimetallic strip, 67 in-line holders, 68 maxi-fuse, 67 Fusible link, 343

G Gas laws, 52 Gauges, 351–352

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GHG-HP, 400 GHG-X4, 401 GHG-X5, 401 Global warming, 11–15 Global Warming Potential (GWP), 14, 393 Gooseneck, 96 Gravity, 44 Greenhouse effect, 6, 11–15

H Halogens, 26, 216 Hazardous materials, 24–26 Hazardous refrigerant, 216 Headers, 85 Head pressure, 263 Heat, 37–38 definition of, 37 energy, 41–42 flow, 44 human body, produced by, 46–47 law of, 37 measurement, 84–85 specific, 37–42 Heat/cool, 317–318 Heated and climate controlled seating, 385–388 Heater core, 91, 122–123 Heater system, 121–124 control valve, 123 heater core, 122–123 hoses and clamps, 121–121 Heater turn-on switch, 375 Heating, 310 Heating core, 83 Heating/ventilation/air-conditioning (HVAC) system, 323 Heat load, 193 HFC-134a (R-134a), 36 characteristics of, 16–17 EPA technician certification, 20 lubricants for, 233–235 recovery equipment for, 221–225 replacement choice, 397–399 temperature-pressure relationships, 244–248 HFO-1234yf (R-1234yf ), 393 High pressure, 272–273, 279 High pressure injuries, 20–21 High-pressure switch, 349, 411 High side restrictions, 265 High-side temperature switch, 360–361, 363

Honda Air Device Systems (HADS) compressors, 288–289 Honeycomb, 86 Hoses, 409 diagnosis, 231 lubricants, 397 Hot Shot, 400 Humid, 50 Humidity, 2–3, 50 H-valve, 188–190 Hybrid electric engine, 97–100 Hybrid organic acid technology (HOAT), 128 Hydrocarbons, 400 Hydrochloric acid (HCl), 210 Hydrofluorocarbons (HFCs), 16 Hydrogen (H), 34 Hydrolysis, 235 Hydrostatic pressure, 21 Hygroscopic, 237

I Idiot light, 350 Idler pulley, 281–283 Ikon-12, 402 Impeller, 96 In-car temperature sensor, 369–370 Inexpensive retrofit, 395–396 Infrared radiation (heat), 11 Infrared temperature sensor (ITS), 371 Inject, 217 Input sensors, 364–366 Insulator, 45, 345 Intake stroke, 288–289 International Standards Organization (ISO), 71 Iodine (I), 26

K Kar Kool, 400 Kilometer, 278 KPa absolute, 213–215, 352 Krypton (Kr), 5 Kyoto Protocol, 393

L Lamps, 350–351 Latent heat, 37, 39, 44 of fusion, 43 of vaporization, 40, 43

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Law of Heat, 37–38 Lead (Pb), 34 Leak detectors, 216 electronic (halogen), 218–220 fluorescent, 217–218 soap solution, 216 visible dye, 217 Leaks, 270–272 Leak testing soap solution, 216 visible dye, 217 Liquid line, 183, 231 Liquid, sensible heat of, 39 Low-pressure condition, 278 Low-pressure switch, 348–349, 364 Low-side restrictions, 265–267 Low-side temperature switch, 361, 363 Lubricants, 233–235, 397–399

M Malfunction, 244, 257 Master control, 340–343 Material Safety Data Sheets (MSDS), 24–26 Matter, 33 MAX, 312–313 Melting, 38–39 Metering devices, 252, 398–399, 409–410 Microprocessor, 70, 72 Mineral-free distilled water, 127, 129 Miscible, 233 MIX, 315, 318–319 Mobile air conditioning, 3–4 Mobile Air Conditioning Society (MACS), 399 Mode, 306 Mode doors, 311 adjustment, 334 Moisture, 209–212, 251 contamination, 265 definition of, 203 at high altitudes, 214–215 prevention, 212 removal, 209–212 at high altitudes, 214–215 Molecule, 35 Motion of molecules, 36–37 MT-31, 402 Multimeter, 66 Multiwound motor, 340

N Nitrogen (N), 5, 34 Noncondensable gas, 207–209 Noncycling clutch, 199

O OBD-II, generic codes body, 376–377 network, 378 Odor control, 323–325 Ohms (Ω), 80 Ohm’s law current flow, 59 resistance, 58–63, 67 Oil, 397–398 Organic acid technology (OAT), 128 Orifice, 183 Orifice tube, 410 Orifice tube failure, 193 O-rings, 398, 409 Outside temperature sensor (OTC), 367–369 Overflow tank, 91 Overheating, 112, 125, 262–263, 398 Oxygen (O), 34 Oxygen molecule (O2), 35 OZ-12®, 402 Ozone (O3) legislation protecting, 393 Ozone-depleting potential (ODP), 405

P Panel (Norm), 313–315 Panel/floor (bi-level), 312, 315 Personal digital assistant (PDA) diagnostics, 225–226 Perspiration, 48 Photodiode, 71 Pitch, belts, 111 Plenum, 309 PN junction, 70 Polyalkylene glycol (PAG), 234 Polyol ester (POE), 234–235, 397, 414 Positive pressure, 352 Positive temperature coefficient (PTC) heaters, 124 Potentiometers, 68–69 Pour point, 236 Power module, 77 Power steering cutoff switch, 373

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Power train control module (PCM), 114, 118–119 Power transistor module. See Power module Predetermined temperature level, 199 Pressure cap, 87, 89–91 Pressure cutoff switch, 347–349 Pressure cutout switch, 398 Pressure cycling switch, 347, 364 Pressure switch, 347 clutch cycling, 410 high-pressure, 411 retrofit, 410 Pressure valve, 90–91 Preventive maintenance (PM), 129–130, 267–268 Programmer, 359 Propylene glycol (PG), 126 Pulse width–modulated (PWM), 77 Pump down, 212 Purity test, 405

Q QuickDetectTM sealant detector, 206

R R-176, 402 R-405A, 402 Radiation, 44–48 Radiator, 83, 85–89 Radiator-condenser fan, 228 R-406A/GHG, 401 Ram air, 83 Rear heat/cool system, 320–23 Receiver (receiver-drier), 182 Receiver-drier, 180–182, 411 Recharging systems, 221 Reciprocating compressor, 171 Reciprocating (piston-type) compressors, 286–290 Reciprocating pistons, 170 Recirculate, 310 Reclaim, refrigerant, 221–222 Record keeping requirements, 225 Recover, refrigerant, 221–222 Recovery systems, 221 equipment, 223–225 Recovery tank, 92–93 Recycle, refrigerant, 221–222 Recycling systems, 221 Reed valves, 171

Refrigerant. See also Alternative refrigerants; HFC-134a (R-134a); Recovery systems; Refrigerant cylinders; Retrofit charging, 226–227 contaminated, 402–403 CO2 (R-744) systems, 393–395 hazardous, 216 HFO-1234yf (R-1234yf ), 393–395 mixed types, 215–216 moisture in, 209–212 reclaim, 221–222 recover, 221–222 recycle, 221–222 replacement of, 397–399 sealant contamination, 206–207 substitute, 399–402 virgin, 209 Refrigerant-12 (CFC-12), 37 Refrigerant analyzer, 205–206 Refrigerant containment device, 410–411 Refrigerant cylinders, 18–20 Refrigerant pressure sensors, 361–364 Refrigerant reclaimers, 206 Refrigeration, cycle, 167–169 Refrigeration oil, 213, 232–238 classification of, 235–237 compatibility, 235 handling rules, 238 pour point, 236 servicing tips, 237–238 viscosity, 235 Refrigeration system condition five: insufficient cooling/no cooling, 257–260 condition four: insufficient cooling or no cooling, 254–256 condition one: normal operation, 247–251 condition seven: insufficient/no cooling, 262–265 condition six: insufficient cooling, 260–261 condition three: insufficient cooling or no cooling, 253–254 condition two: insufficient cooling, 251–253 evacuating, moisture removal, 212–214 moisture contamination, 265 noncondensable gas, 207–209 restriction diagnosis, 265–267 Relative humidity (RH), 50 Relays diagnostic process, 71 electromagnetic switch, 71

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Remote bulb, 261 Reserve tank, vacuum, 354 Resistance, 58 Resistor block, 74–75 Restriction diagnosis, 265–267 Restrictions, 251–252, 273–274 Restrictor, vacuum, 355 Retrofit components, 407–411 compressors, 398 contaminated refrigerant, 403–404 disposal of contaminated refrigerant, 405 do-it-yourselfer, 402 evaporator, 409 hoses, 409 industry study, 413–414 inexpensive, 395–396 labeling, 411–412 problems, 396 purity test, 405 system charge, 397 Reverse flow, 95 Rheostats, 68–69 Rotary compressor, 280 Rotary vacuum valve system, 329 Rotary vane compressors, 287, 290–291 Rotary water valve, 98–100

S Saddle clamp access valves, 407 Safety lubricants, 235 Scan tools, 375–377 Scotch yoke compressors, 287, 293 Screen/Strainer (receiver-drier), 183 Scroll compressor, 280, 287, 291–293 Sealant contamination, 206–207 Seals, 100–101, 409 Seats, heated and climate controlled, 385–388 Semiautomatic temperature control (SATC) system, 317 Sensible heat, 37, 39–40, 44 Sensor input information, analyzing, 373–375 Series–parallel circuit, 62–63 Serpentine belt, 281 Service valve ports, 231 Servicing tips, 237–238 Sight glass, 230–231 Significant New Alternative Policy (SNAP) program, 206 Society of Automotive Engineers (SAE), 206

Solenoid/relay, 70 Solid expansion thermostat, 103–104 Solid, sensible heat of, 38 Solid-state coil control components, 72 Source voltage, 64 Specific gravity, 52 Specific heat, 37–38 Starved system, 194 Stroke, 171 Subcooling, 270 Subsurface temperature, 46 Suction, 286–287 Suction line, 231 Suction stroke, 171, 288 Suction valve, 288 Sudsing liquid detergent, 216 Sun load sensor, 368–369 Superheat, 40–41, 409 Swash plate, 280 Sweep evacuation, moisture, 215 Synthetic lubricants, 234 System components accumulator, 198–199 condenser, 176–180 discharge line, 175–176 evaporator, 193–197 hoses and lines, 172–176 H-valve, 188–190 liquid line, 183 receiver-drier, 180–182 thermostatic expansion valve, 183–187 System diagnosis, 241–244 System leaks, 231

T Tapped/stepped resistors, 68–69 Telltale lamp, 350 Temperature, 48–50, 69 Temperature-pressure relationships R-12 (CFC-12), 244–246 R-134A (HFC-134A), 246 Thermistor, 69, 351, 366, 367, 370–372 Thermostat, 83, 101–103, 344–345 bellows-type, 106, 109 bimetallic, 106, 109 construction, 345 electronic, 104–106 installation and handling, 346

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operation, 345 service, 106–109 solid expansion, 103–104 Thermostat capillary tubes, 344, 345 Thermostatic expansion valve, 183–187, 409–410 Thermostat outlet hosing, 96 Thermostat service, 106–109 Threaded shaft (THD) end, 74 Throttle position sensor, 372 Triple evacuation, moisture, 215

U Undercharge, 242

V Vacuum, 212 circuits, 352–53 definition of, 352 pots, single-and dual-chamber, 353 source, 54–55 system diagram, 355–356 terms, 353 Vacuum control system, 329 Vacuum-operated devices, 353–354 Vacuum signal legend, 355–356 Vacuum solenoids, 330 Vacuum valve, 90–91 Vaporization, 40 Vapor, sensible heat of, 40–41

Variable displacement (VD) compressor, 192, 294–296 Variable displacement orifice tube (VDOT) system, 192 Variable resistors, 68–69 Vehicle speed sensor, 372 Vent, 315–317 Virgin refrigerant, 209 Viscosity, 235 Visual inspection, 334 Viton®, 398 Voltage (V), 58, 61 Voltage drop, 63–64 Voltmeter, 63, 69

W Water (H2O), 34–35, 402 Windchill factor, 51 Wiring diagram bidirectional mode door actuators, 332 electronic thermostat, 108 of multi-relay fan control, 119 multispaced blower motor, 343 resister element heated seat, 387 symbols used in, 340 typical thermistor, 366 Wobble plate, 280 Worm-gear clamp, 120

Z Zener clamping diode, 288

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6th Edition

Shop Manual

for Automotive Heating & Air Conditioning

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Shop Manual

for Automotive Heating & Air Conditioning Mark Schnubel Naugatuck Valley Community College Waterbury, Connecticut

Sixth Edition

Australia • Canada • Mexico • Singapore • Spain • United Kingdom • United States

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Today’s Technician™: Shop Manual for Automotive Heating & Air Conditioning, Sixth Edition Mark Schnubel SVP, GM Skills & Global Product Management: Dawn Gerrain Product Director: Matthew Seeley Product Team Manager: Erin Brennan Senior Director, Development: Marah Bellegarde Senior Product Development Manager: Larry Main Senior Content Developer: Meaghan Tomaso Product Assistant: Maria Garguilo Vice President, Marketing Services: Jennifer Ann Baker Production Service/Compositor: SPi Global Marketing Manager: Jonathon Sheehan Senior Production Director: Wendy Troeger Production Director: Andrew Crouth Senior Content Project Manager: Cheri Plasse Senior Art Director: Benjamin Gleeksman Cover image(s): © cla78/Shutterstock

© 2017, 2013 Cengage Learning WCN: 02-200-201

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Library of Congress Control Number: 2015956683 Book Only ISBN: 978-1-305-49761-0 Package ISBN: 978-1-305-49762-7 Cengage Learning 20 Channel Center Street Boston, MA 02210 USA Cengage Learning is a leading provider of customized learning solutions with office locations around the globe, including Singapore, the United Kingdom, Australia, Mexico, Brazil, and Japan. Locate your local office at: www.cengage.com/global Cengage Learning products are represented in Canada by Nelson Education, Ltd. To learn more about Cengage Learning, visit www.cengage.com Purchase any of our products at your local college store or at our preferred online store www.cengagebrain.com

Notice to Reader Publisher does not warrant or guarantee any of the products described herein or perform any independent analysis in connection with any of the product information contained herein. Publisher does not assume, and expressly disclaims, any obligation to obtain and include information other than that provided to it by the manufacturer. The reader is expressly warned to consider and adopt all safety precautions that might be indicated by the activities described herein and to avoid all potential hazards. By following the instructions contained herein, the reader willingly assumes all risks in connection with such instructions. The publisher makes no representations or warranties of any kind, including but not limited to, the warranties of fitness for particular purpose or merchantability, nor are any such representations implied with respect to the material set forth herein, and the publisher takes no responsibility with respect to such material. The publisher shall not be liable for any special, consequential, or exemplary damages resulting, in whole or part, from the readers’ use of, or reliance upon, this material.

Printed in the United States of America Print Number: 01 Print Year: 2016

Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Contents Photo Sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii Job Sheets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xii Chapter 1  Shop Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

• General Shop Safety 1 • Personal Safety 4 • General Hybrid Electric Vehicle Safety 10 • Safety in the Shop 13 • OSHA 15 • Safety Rules for Operating Power Tools 20 • The Value and Techniques of Safety Sense 22 • Safe Use of Tools 23 • Terms to Know 34 • ASE-Style Review Questions 35

Chapter 2  Typical Shop Procedures and Tools . . . . . . . . . . . . . . . . . . . . . . 45 • Shop Rules and Regulations 45 • Service Tools 48 • Hand Tools 52 • Special Tools 52 • Refrigerant Identifier 55 • Other Special Tools 56 • Sources of Service Information 60 • Content of Service Information 61 • Service Manual Procedures and Specifications Service Procedures 61 • Repair Order 63 • The Metric System 64 • Terms to Know 65 • ASE-Style Review Questions 66

Chapter 3  Basic Electrical Troubleshooting and Service . . . . . . . . . . . . . . 73 • Introduction 73 • Electrical Diagnosis and Testing 74 • Using a Digital Multimeter 74 • Voltmeter Function 75 • Ohmmeter Function 77 • Ammeter Function 78 • Testing Circuit Protection Device 79 • Testing for Opens 83 • Troubleshooting the Blower Motor Circuit 84 • Terms to Know 91 • ASE-Style Review Questions 92 • ASE Challenge Questions 94

Chapter 4  Diagnosis and Service of Engine Cooling and Comfort ­Heating Systems����������������������������������������������������������������������������������������������� 101 • The Cooling System 101 • Radiators 103 • Electrochemical Activity 105 • Coolant Pump 105 • Pressure Cap 106 • Thermostats 108 • Pulleys 110 • Belts and Tensioner 110 • Fans 119 • Hoses and Clamps 123 • Recovery Tank 126 • Heater System 126 • Antifreeze 129 • Flush the Cooling System 130 • Hybrid Electric Cooling System Service 134 • Troubleshooting the Heater and Cooling System 135 • Terms to Know 137 • ASE-Style Review Questions 137 • Ase Challenge Questions 138

Chapter 5  The Manifold and Gauge Set . . . . . . . . . . . . . . . . . . . . . . . . . . 157

• The Manifold and Gauge Set 157 • Manifold 160 • Connecting the Manifold and Gauge Set 163 • Basic Performance Testing the Air-Conditioning System 168 • Test the Thermostats and Control Devices 170 • Terms to Know 171 • ASE-Style Review Questions 171 • Ase Challenge Questions 172

Chapter 6  Servicing System Components . . . . . . . . . . . . . . . . . . . . . . . . 181 • English and Metric Fasteners 181 • Safety 182 • Diagnostic Techniques 184 • Proper Tools, Equipment, and Parts 185 • Service Procedures 186 • Preparation 186 • Refrigerant Recovery 187 • Refrigerant Recovery For R-1234yf 188 • Servicing Refrigerant Hoses and Fittings 188 • Replacing Air-Conditioning Components 196 • Removing and Replacing the Thermostatic Expansion Valve (TXV) 196 • Removing and Replacing the Fixed Orifice Tube (FOT) 198 • Removing and Replacing the Accumulator 202 • Removing and Replacing the Condenser 203 • Removing and Replacing the Receiver-Drier 203 • Superheat or Pressure Switch 204 • In Conclusion 205 • Terms to Know 206 • ASE-Style Review Questions 206 • Ase Challenge Questions 207 v Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Contents Chapter 7  Air-Conditioning System Servicing and Testing . . . . . . . . . . 235 • Refrigeration Contamination 236 • Unloaded System Performance Testing 238 • Sealant Contamination Detection 241 • Leak Testing the System 243 • Compressor 243 • Soap Solution 245 • Tracer Dye Leak Detection 246 • Halogen (Electronic) Leak Detection 247 • Evacuating the System 250 • Triple Evacuation Method 250 • Charging the System 254 • Charging the R-1234yf System 259 • Install the Can Tap Valve on a “Pound” Container 261 • Using Pound Cans (System Off ) 261 • Charging from a Bulk Source with a Manifold and Gauge Set 263 • Testing Refrigerant for Noncondensable Gas 265 • Terms to Know 267 • ASE-Style Review Questions 268 • Ase Challenge Questions 269

Chapter 8  Diagnosis of the Refrigeration System . . . . . . . . . . . . . . . . . 293 • Air-Conditioning Diagnosis 293 • System Inspection 293 • Air-Conditioning Pressure Diagnostics 295 • Defective Components 299 • Causes of Failure 302 • Functional Testing 302 • Diagnosing H-Block Thermostatic Expansion Valve System 303 • Diagnosing Thermostatic Expansion Valve Systems 304 • Refrigerant System Charge Level Determination Temperature Method 305 • Insufficient Cooling: Cycling Clutch Orifice Tube (CCOT) 306 • Diagnosing Orifice Tube Systems 307 • System Charge Test 309 • Diagnosing Variable Displacement Compressor Orifice Tube Systems 312 • Diagnosing Ford’s fot System 314 • Poor Compressor Performance 317 • Terms to Know 318 • ASE-Style Review Questions 318 • Ase Challenge Questions 319

Chapter 9  Compressors and Clutches . . . . . . . . . . . . . . . . . . . . . . . . . . 335 • Compressor 335 • Compressor Clutch 335 • Testing Compressor Clutch Electrical Circuit 335 • Compressor Identification 340 • Refrigerant Lubricant 345 • Refrigerant Lubricant Diagnosis 347 • Removing and Replacing the Compressor 347 • Stretch to Fit Belts 349 • Installing Inline Filter 353 • Nippondenso 354 • Servicing the Nippondenso Compressor 354 • Replacing the Shaft Seal 354 • Checking and Adding Oil to the Nippondenso Compressor 354 • Refilling the Compressor 357 • Servicing the Nippondenso Compressor Clutch 357 • Panasonic (Matsushita) 361 • Servicing the Panasonic Vane-Type Compressors 361 • Checking and Adjusting Compressor Oil Level 361 • Procedure 361 • Servicing the Clutch Assembly 361 • Servicing the Compressor Shaft Seal 362 • Servicing the Compressor 363 • Sanden 364 • Servicing the Sanden (Sankyo) Compressor 364 • Replacing the Compressor Shaft Oil Seal 364 • Checking Compressor Oil Level 367 • Servicing the Clutch 368 • Electrically-Driven Air-Conditioning Compressor 371 • Terms to Know 376 • ASE-Style Review Questions 376 • Ase Challenge Questions 377

Chapter 10  Case and Duct Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397 • Fresh Air Inlet 398 • Component Replacement 398 • Blower Motor 400 • Replacing the Power Module or Resistor 400 • Replacing the Heater Core 402 • Replacing the Evaporator Core 403 • Removing and Replacing the Evaporator 404 • Odor Problems 407 • Testing the Vacuum System 408 • Temperature Door Cable Adjustment 412 • Mode Selector Switch 412 • Cabin Air Filter 414 • Electric Mode Door Actuator 415 • Problems Encountered 416 • Terms to Know 418 • ASE-Style Review Questions 418 • Ase Challenge Questions 419

vi Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Contents Chapter 11  Diagnosis and Service of System Controls . . . . . . . . . . . . . 445

• Fuses and Circuit Breakers 446 • Thermostat 448 • Electromagnetic Clutch 450 • Pressure Switches and Controls 455 • Coolant Temperature Warning Switches 456 • Vacuum Switches and Controls 456 • Breakout State 457 • Automatic (Electronic) Temperature Controls 458 • Climate Control System Sensors 461 • Temperature and Mode Door Control 470 • Diagnosing SATC and EATC Systems 472 • EATC System Diagnosis 475 • Trouble Codes 486 • Entering BCM Diagnostics 489 • Retrieving Cadillac BCM Trouble Codes 491 • Terms to Know 493 • ASE-Style Review Questions 493 • Ase Challenge Questions 494

Chapter 12  Retrofit (R-12) [CFC-12] to R-134a [HFC-134a] . . . . . . . . . 515 • Introduction 515 • Purity Test 515 • Access Valves 518 • Recover Only—An Alternate Method 520 • Retrofit 521 • Procedure 521 • Refrigerant Recovery 523 • Flush the System? 526 • Evacuating the System 528 • Charging an R-134a Air-Conditioning System 533 • Conclusion 536 • Terms to Know 538 • ASE-Style Review Questions 538 • Ase Challenge Questions 540

Appendix A  ASE Practice Examination . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549 Appendix B  Metric Conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555 Appendix C  Air-Conditions Special Tool Suppliers . . . . . . . . . . . . . . . . . . . 556 Appendix D  Where to Send Contaminated Refrigerant . . . . . . . . . . . . . . . 557 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 559 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 575

vii Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Photo Sequences 1 Typical Procedure for Servicing the Serpentine Drive Belt�������������������������������������������������� 112 2  Draining and Refilling the Cooling System������������������������������������������������������������������������������ 131 3  Typical Procedure for Connecting a Manifold and Gauge Set to an ­R-134a or R1234yf Air-Conditioning System���������������������������������������������������������������������������������������� 165 4  Typical Procedure for Recovering (Purging) Refrigerant from the ­System������������������������ 191 5  Assemble Beadlock Hose Assembly������������������������������������������������������������������������������������������ 193 6  Typical Procedure for Replacing a Fixed Orifice Tube���������������������������������������������������������� 200 7  Typical Procedure for Checking for Leaks ������������������������������������������������������������������������������ 249 8  Typical Procedure for Evacuating the System�������������������������������������������������������������������������� 251 9  Typical Procedure for Completing the System Charge���������������������������������������������������������� 257 10 Typical Procedure for Inspecting an Air-Conditioning System ������������������������������������������ 294 11 Bench Testing the Compressor Clutch Coil and Diode �������������������������������������������������������� 339 12 Typical Procedure for Removing and Replacing the Nippondenso ­Compressor Shaft Seal Assembly���������������������������������������������������������������������������������������������� 355 13 Typical Procedure for Removing a Blower Motor������������������������������������������������������������������ 401 14 Typical Procedure for Testing a Check Valve�������������������������������������������������������������������������� 411 15 Removing and Replacing the Mode Selector Switch�������������������������������������������������������������� 413 16 Procedure for Testing PCM-Controlled Air Conditioners���������������������������������������������������� 453 17 Typical Procedure for Replacing a Heater Flow Control Valve�������������������������������������������� 471 18 Removing and Replacing a Schrader Valve Core in a Service Valve���������������������������������������� 529

viii Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Job Sheets 1 Personnel and Shop Safety Assessment�������������������������������������������������������������������������������������� 37 2 Compare and Identify Safe and Unsafe Tools���������������������������������������������������������������������������� 39 3 The Need for Health and Safety �������������������������������������������������������������������������������������������������� 41 4 Identify and Correct Hazardous Conditions ���������������������������������������������������������������������������� 43 5 Identify the Responsibilities of the Employee���������������������������������������������������������������������������� 67 6 Use a Manufacturer’s Service Manual���������������������������������������������������������������������������������������� 69 7 Compare the English and Metric Systems of Measure������������������������������������������������������������ 71 8 Test a Blower Motor���������������������������������������������������������������������������������������������������������������������� 97 9 Testing and Replacing Fuses and Circuit Breakers ������������������������������������������������������������������ 99 10 Drain and Fill Coolant������������������������������������������������������������������������������������������������������������������ 139 11 Leak Test a Cooling System�������������������������������������������������������������������������������������������������������� 141 12 Replace Thermostat���������������������������������������������������������������������������������������������������������������������� 143 13 Troubleshoot an Electric Engine Cooling Fan������������������������������������������������������������������������ 145 14 Inspect Engine Cooling System Hoses�������������������������������������������������������������������������������������� 147 15 Inspect Heater Control Valve ���������������������������������������������������������������������������������������������������� 149 16 Inspect and Test Fan and Fan Clutch���������������������������������������������������������������������������������������� 151 17 Diagnostic Check List������������������������������������������������������������������������������������������������������������������ 153 18 Bench Test Thermostat���������������������������������������������������������������������������������������������������������������� 155 19 Interpreting Gauge Pressure ������������������������������������������������������������������������������������������������������ 175 20 Interpreting System Conditions ������������������������������������������������������������������������������������������������ 177 21 Identifying Refrigeration System Type�������������������������������������������������������������������������������������� 179 22 Determining the Type of Air-Conditioning System �������������������������������������������������������������� 209 23 Determining the Refrigerant Type�������������������������������������������������������������������������������������������� 211 24 Component Temperature Testing���������������������������������������������������������������������������������������������� 213 25 Identifying Hose Fittings ������������������������������������������������������������������������������������������������������������ 215 26 Recover and Recycle Refrigerant������������������������������������������������������������������������������������������������ 217 27 Replacing the Receiver-Drier/Accumulator���������������������������������������������������������������������������� 219 28 Replacing the Superheat or Pressure Switch���������������������������������������������������������������������������� 221 29 Air-Conditioning System Performance Test���������������������������������������������������������������������������� 223 30 Replace AC Expansion Valve������������������������������������������������������������������������������������������������������ 225 ix Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Job Sheets 31 Replace A/C Orifice (Expansion) Tube������������������������������������������������������������������������������������ 229 32 Replace Air-Conditioning Condenser�������������������������������������������������������������������������������������� 231 33 Replace the A/C Refrigerant Line���������������������������������������������������������������������������������������������� 233 34 Analyzing Refrigerant Gas Sample Purity�������������������������������������������������������������������������������� 271 35 Refrigerant Leak Detecting with Electronic Leak Detector�������������������������������������������������� 273 36 Air-Conditioning System Unloaded Performance Test �������������������������������������������������������� 275 37 Maximum Heat Load System Diagnostic Work Sheet���������������������������������������������������������� 279 38 System Evacuation������������������������������������������������������������������������������������������������������������������������ 281 39 Charge Air-Conditioning System with Refrigerant���������������������������������������������������������������� 283 40 Air-Conditioning System Diagnosis������������������������������������������������������������������������������������������ 285 41  Operation and Maintenance of Refrigerant Recovery/Recycling Equipment�������������������� 287 42  Check Stored Refrigerant for Noncondensable Gases and Label Container��������������������� 289 43 Inspect the V-Belt Drive�������������������������������������������������������������������������������������������������������������� 321 44 Inspect the Serpentine Drive Belt���������������������������������������������������������������������������������������������� 323 45  Refrigerant System Charge Level Temperature Method (Delta-T)�������������������������������������� 325 46 Inspect the Condenser ���������������������������������������������������������������������������������������������������������������� 329 47 Heat Transfer through the Condenser�������������������������������������������������������������������������������������� 331 48 Remove and Replace Condenser Assembly ���������������������������������������������������������������������������� 333 49 Compressor Identification���������������������������������������������������������������������������������������������������������� 379 50  Refrigerant Oil Return Operation and Compressor Oil Selection/Replacement���������������������������������������������������������������������������������������������������������������� 381 51 Check and Correct Compressor Oil Level ������������������������������������������������������������������������������ 383 52 Replace A/C Compressor Assembly������������������������������������������������������������������������������������������ 385 53 Compressor Clutch Amperage Draw and Resistance Test���������������������������������������������������� 387 54 Inspect and Test the Clutch Coil and Diode���������������������������������������������������������������������������� 391 55 Removing and Replacing a Compressor Clutch���������������������������������������������������������������������� 393 56 Installation of Auxiliary Liquid Line Filter ������������������������������������������������������������������������������ 395 57 Case/Duct System Diagnosis������������������������������������������������������������������������������������������������������ 421 58 Air Delivery Selection������������������������������������������������������������������������������������������������������������������ 423

x Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Job Sheets 59 Replace Case and Duct System Components�������������������������������������������������������������������������� 427 60 Adjust a Door Cable �������������������������������������������������������������������������������������������������������������������� 429 61 HVAC Odor Control Treatment������������������������������������������������������������������������������������������������ 431 62 Temperature Control Diagnosis������������������������������������������������������������������������������������������������ 433 63 Electronic Actuator Control Diagnosis������������������������������������������������������������������������������������ 435 64 Remove and Replace the Heater Core�������������������������������������������������������������������������������������� 437 65 Remove and Replace the Evaporator ���������������������������������������������������������������������������������������� 439 66 Remove and Replace a Blower Motor �������������������������������������������������������������������������������������� 441 67 Inspect and Replace Cabin Air Filter���������������������������������������������������������������������������������������� 443 68  Diagnose Temperature Control Problems in the Heater/Ventilation System�������������������� 495 69 Using a Scan Tool to Access HVAC System���������������������������������������������������������������������������� 501 70 Testing an Ambient Air Temperature Sensor�������������������������������������������������������������������������� 503 71 Automatic Temperature Control Diagnostics ������������������������������������������������������������������������ 505 72 Testing an In-Car Temperature Sensor������������������������������������������������������������������������������������ 507 73 Testing an Evaporator Temperature Sensor���������������������������������������������������������������������������� 509 74 Testing a Sun Load Sensor���������������������������������������������������������������������������������������������������������� 511 75 Testing an Infrared Temperature Sensor���������������������������������������������������������������������������������� 513 76  Determining Refrigerant Purity in a Mobile Air-Conditioning System by Verbal Communication���������������������������������������������������������������������������������������������������������� 541 77  Determining Refrigerant Purity in a Mobile Air-Conditioning System by Testing �������������������������������������������������������������������������������������������������������������������������������������� 543 78 Identifying Retrofit Components���������������������������������������������������������������������������������������������� 545 79 R-12 to R-134a Retrofit���������������������������������������������������������������������������������������������������������������� 547

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Preface Thanks to the support that the Today’s Technician™ series has received from those who teach automotive technology. Cengage Learning, the leader in automotive-related textbooks, is able to live up to its promise to provide new editions regularly. We have listened and responded to our critics and our fans and present this new updated and revised sixth edition. By revising our series regularly, we can and will respond to changes in the industry, changes in technology, changes in the certification process, and to the ever-changing needs of those who teach automotive technology. The Today’s Technician™ series features textbooks that cover all mechanical and electrical systems of automobiles and light trucks (while the “Heavy-Duty Trucks” portion of the series does the same for heavy-duty vehicles). Principally, the individual titles correspond to the main areas of ASE (National Institute for Automotive Service Excellence) certification. Additional titles include remedial skills and theories common to all of the certification areas and advanced or specific subject areas that reflect the latest technological trends. Each text is divided into two volumes: a Classroom Manual and a Shop Manual. Unlike yesterday’s mechanic, the technician of today and for the future must know the underlying theory of all automotive systems and be able to service and maintain those systems. Dividing the material into two volumes provides the reader with the information needed to begin a successful career as an automotive technician without interrupting the learning process by mixing cognitive and performance learning objectives into one volume. The design of Cengage’s Today’s Technician™ series was based on features that are known to promote improved student learning. The design was further enhanced by a careful study of survey results, in which the respondents were asked to value particular features. Some of these features can be found in other textbooks, whereas others are unique to this series. Each Classroom Manual contains the principles of operation for each system and subsystem. The Classroom Manual also contains discussions on design variations of key components used by the different vehicle manufacturers. This volume is organized to build on basic facts and theories. The primary objective of this volume is to allow the reader to gain an understanding of how each system and subsystem operates. This understanding is necessary to diagnose the complex automobiles of today and tomorrow. Although the basics contained in the Classroom Manual provide the knowledge needed for diagnostics, diagnostic procedures appear only in the Shop Manual. An understanding of the basics is also a requirement for competence in the skill areas covered in the Shop Manual. A spiral-bound Shop Manual covers the “how-to’s.” This volume includes step-by-step instructions for diagnostic and repair procedures. Photo Sequences are used to illustrate some of the common service procedures. Other common procedures are listed and are accompanied with fine-line drawings and photos that allow the reader to visualize and conceptualize the finest details of the procedure. This volume also contains the reasons for performing the procedures, as well as when that particular service is appropriate. The two volumes are designed to be used together and are arranged in corresponding chapters. Not only are the chapters in the volumes linked together, the contents of the chapters are also linked. This linking of content is evidenced by marginal callouts that refer the reader to the chapter and page on which that same topic is addressed in the other volume. This feature is valuable to instructors. Without this feature, users of other two-volume textbooks must search the index or table of contents to locate supporting information in the other volume. This is not only cumbersome, but it also creates additional work for an xii Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Preface instructor when planning the presentation of material and when making reading assignments. It is also valuable to the students; with the page references they also know exactly where to look for supportive information. Both volumes contain clear and thoughtfully selected illustrations, many of which are original drawings or photos especially prepared for inclusion in this series. This means that the art is a vital part of each textbook and not merely inserted to increase the number of illustrations. The page layout used in the series is designed to include information that would otherwise break up the flow of information presented to the reader. The main body of the text includes all of the “need-to-know” information and illustrations. In the wide side margins of each page are many of the special features of the series: items that are truly “nice-to-know” information such as simple examples of concepts just introduced in the text, explanations or definitions of terms that will not be defined in the glossary, examples of common trade jargon used to describe a part or operation, and exceptions to the norm explained in the text. This type of information is placed in the margin out of the normal flow of information. Many textbooks attempt to include this type of information and insert it in the main body of text; this tends to interrupt the thought process and cannot be pedagogically justified. By placing this information off to the side of the main text, the reader can select when to refer to it. Jack Erjavec Series Advisor

Highlights of this Edition—Classroom Manual The Classroom Manual of this edition has been updated to include new technology used in the automotive heating and air-conditioning systems of today’s vehicles while still retaining information on systems used in older vehicles that are still in use. In addition, an emphasis has been placed on updating images throughout the text with full-color photos. Charts, graphs, and line drawings are now also in full color to be more visually appealing and improve the content comprehension by the reader. Coverage of R-1234yf has been added throughout the text. Chapter 2 covers the basic theories required to fully understand the operation and diagnosis of the complete HVAC system. A chapter on electricity and electronic fundamentals has been added covering the application and use of digital multimeters for those readers that have a limited background in electrical applications. This is intended to improve their understanding of electrical applications material covered in later chapters and prepare them with the electrical knowledge needed to complete future job sheets. Chapter 4 covers the automotive heating system and engine cooling system, including systems used on today’s hybrid electric vehicles. The electronic thermostat used on some of today’s vehicles is thoroughly explained along with the rationale behind its use. The rest of the text is laid out in a logical order, beginning with basic air-conditioning system operating principles and progressing to diagnosis of the refrigerant system. The end-of-chapter questions in all chapters have been revised and updated. Updated coverage on advanced electronics has been included, from the operation of electronic variable compressors and electric motor–driven compressors to advanced sensors such as the airborne pollutants sensor. Chapter 11 on HVAC system controls has been updated to include more information on advanced climate control systems while still including a thorough description of CAN system operation. xiii Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Preface Highlights of this Edition—Shop Manual Safety information remains the first chapter of the Shop Manual and covers general safety issues as well as topics specific to automotive HVAC service. This chapter includes an indepth discussion on high-voltage safety on today’s hybrid and electric vehicles and the equipment necessary to service these vehicles. As with the Classroom Manual, an emphasis has been placed on updating Shop Manual images and photo sequences throughout the text, with full-color photos and line art. Chapter 3, “Basic Electrical Troubleshooting and Service,” has been added. This chapter contains detailed information on digital multimeter usage for electrical system diagnosis and troubleshooting. Chapter 4 and later chapters cover service information related to the system information covered in the corresponding Classroom Manual chapters. Many new job sheets have been added and existing job sheets have been updated, with 100 percent of the NATEF tasks covered. The latest use of tools and technology has been integrated into the text, including hybrid electric compressors and the operation and use of SAE standard J2788 refrigerant recovery/recycling/recharging equipment needed to service today’s small-capacity refrigerant systems. Added coverage of today’s automatic climate control system service and diagnosis has been updated and includes specific examples. This edition of the Shop Manual will guide the student/technician through all the basic tasks related to automotive heating and airconditioning service and repair.

xiv Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Classroom Manual

Chapter 4

Engine Co o and Comf ling ort Heating S ystems

Features of this manual include:

Upon Comp letion an d Review of this Ch apter, yo Explain the eng u should ine cooling sys be able to tem and its com ■■ Recogn ponents. : ize the various

COGNITIVE OBJECTIVES

■■

components of cooling system the automotive . Identify the diff erent types of radiators. ■■ Explain the operation and function of (water) pump. the coolant

These objectives outline the contents of the chapter and define what the student should have learned upon completion of the chapter.

Introduc

Each topic is divided into small units to promote easier understanding and learning.

tion

Normal ope ration of the automobile excessive eng engine produc ine heat, wh es heat that ich is a produc then dissipate must be car t of d ried away. Th as conduction in the radiator. This is acc combustion, is transf is erred to the omplished by and convention coolant and operational two heat tra . The cooling design temper sys tem , when operati nsfer principles known ature for the The cooling ng eng pro ine system functio perly, mainta and automatic radiator. Eng ins ns tra by an nsm circ ine heat is pic ula ission. ked up by the ting a liquid coolant thr hot outside air passing thr ough the eng coolant by con ine and the ough the rad the heater cor duction and iator by convec Shop Manua e, l tion. Coolant is given up to the less compartment which also uses the con vection proces is also circula Chapter 4, pag . e 101 ted through s to supply hea ted air to the passenger The Coolin g System The purpos e of engine during the automotive cooling system is to the combustion carry the hea constant eng process away t that is ine operatingBypass from the eng temperatureHousing tions. Due to ine (Figure 4-1 generated by the during var yin inefficiencie ) to maintain A defective cool s of the inte g engine spe Serpentine energy fro a near ing rna m eds and ope gasoline is con l combustion system may imp rating condipulley hub internal com engine, as mu verted into air bustion tem heat. The coo ch as 70 per air conditioning peratures, wh cent of the the engine’s ling system has ich may exc heat is sent out a performance. diff icu eed lt task with the exhaust walls, heads, 4,5008F (2, 482 system elleris and pistons 8C). Actually, Impand absorbed and into remove abo most of ut 35 percen Seal the ambient air. The dis cooling system sipated by the cylinder t of the total Another imp heat produc is designed, ortant functio ed by the the temperatures refore, to n eng of the cooling ine. as quickly as sys tem is pos emissions are to allow the ft engine to rea increased, inte sible. When engSha ines are bel ch operating rnal compon ents wear fast ow operating temperatu re, exhaust er, and operati 82 on is less effi cient.

MARGINAL NOTES These notes add “nice-toknow” information to the discussion. They may include examples or exceptions, or may give the common trade jargon for a component.

Discuss the req uirements for a closed cooling Explain the pur system. pose, advanta ge, and operati thermostat. on of a ■■ Recogn ize the safety hazards associa system service. ted with a coo ling ■■ Explain the operation of various type s of cooling fans . ■■

■■

■■

97603_ch04_h

r_082-132. indd 82

Bearings Drain 11/18/15 4:48 PM

Inlet from radiator Parts of a wat FIGURE 4-18

er pump.

eable de, nonservic an impeller bla p that moves t and outlet, part of the pum ies of flat or g with an inle rnal rotating s of a housin a ser inte h sist wit the con is te p r pla The pum sists of a flat ls. The impelle casting. This g(s), and sea impeller con h the pump system. The sealed bearin more sealed t passes throug h the cooling to a shaft tha is equipped with one or impeller coolant throug vanes and is mounted shaft. As the or prevent rust, to the des t el g bla ste por ss ved cur passage enterin al seal to sup erally stainle ern the gen to ext is rd ich and shaft, wh forced outwa opposite the an internal is end and s ft and sha blie ter are bearing assem is drawn in from the cen pulley is mounted on the fan is also attached. Coolant pumps to , the belt lant generally referred rotates, coo ugal force. A ted cooling fan uired and is ck by centrif ps. engine-moun e of the special tools req as water pum the engine blo icles equipped with an aus veh lly rebuilt bec 9). impeller. On p is not genera t (Figure 4-1 pum bel t lan ing coo tim the tive A defective t is driven by bly. as preven-ta es d as an assem have a coolant pump tha timing belt is ser viced l mil lace nua rep 000 Ma 90, p y at Sho en the s ma viced Some vehicle is generally replaced wh belts are ser e 105 Chapter 4, pag most timing t pump a air because (Figure 4-20). This coolan radiator with id a future rep the of rotations s of avo to lion tom ce mil lly e for intenan to the bot maBattery , and it genera been in ser vic t is connected model engine lant the pump has Battery and coo r lant pump inle and yea the coo of lar the s, ion ine fit a particu tionFuelact The bypass pump es On most eng preformed to collapsing due to the suc letrelay ough passag This hose is redirects coolant p out is thr coolant has vent it from rubber hose. coolant pum the away from the Ign. ral wire to pre ved up. The block. After back contains a spi at housing engine isIgn.rev h the engine ost the oug rm en thr the thermostat and t wh the r lan h p hes the coo Restrictiator throug pump impelle to the water pum ment pump. eller, which pus it is returned to the rad ant iable-displace tricting behind the imp Potentio ine block, to enable cool is closed, res pump is a var h the engmeter trifugal waterIgn. p. When the thermostat ow the thermostat passed throug circulation in the r hose. A cen bel pum e iato Flap ng sag the rad duri m er pas k and upp engine bloc switch via a bypass n, coolant flow t does not har ine lan ope is eng coo at e. of the ost cycl h flow Power the therm the warm-up ing the ulates throug supply pump. When , coolant circ t flowThermos to the water result of coolan relay tat ine block are often the the eng . leading from is leaks, which failures to improper The thermostat cooling system coolant pump failure the h bearing oug andDiagnos is thr t cause of tic these leaks uen outlet hosing is ed freq st link e mo connection rred The dies hav sometimes refe Air mass . Industry stu ABS gooseneck. meter bearing failure

CROSS-REFERENCES TO THE SHOP MANUAL Reference to the appropriate page in the Shop Manual is given whenever necessary. Although the chapters of the two manuals are synchronized, material covered in other chapters of the Shop Manual may be fundamental to the topic discussed in the Classroom Manual.

TERMS TO KNOW DEFINITIONS Many of the new terms are pulled out into the margins and defined.

to as the

PM 11/18/15 4:48

96 Electronic control module

97603_ch04_h

indd 96

r_082-132.

Control unit for radiator fan

Radiator fan M

Radiator fan 2 M

Engine speed sender

Positive

Output signal

Ground

FIGURE 4-36 An exampl e of a typical

Coolant temperature sender

Input signal

electronic thermostat

AUTHOR’S NOTES

Radiator outlet sender

wiring diagram.

Bidirectional

Author’s Note: If a vehicle comes into your shop overheatin coolant or water to the g, do not add system until it has comp letely cooled down. The process is necessary to cool-down avoid thermal shock to the engine and coolin components. Thermal g system shock could cause comp onents to crack and gaske making a bad situation ts to fail, worse. 108

97603_ch04_hr_082-132.indd

This feature includes simple explanations, stories, or examples of complex topics. These are included to help students understand difficult concepts.

108

11/18/15 4:49 PM

xv Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

ol Ethylene glyc FIGURE 4-66

A BIT OF HISTORY This feature gives the student a sense of the evolution of the automobile. It not only contains nice-to-know information, but should also spark some interest in the subject matter.

antifreeze.

glycol antifree

ze.

FIGURE 4-68

Distilled wat

indd 126

r_082-132.

97603_ch04_h

REVIEW QUESTIONS

er.

Short-answer essay, fill-inthe-blank, and multiple-choice questions are found at the end of each chapter. These questions are designed to accurately assess the student’s competence in the stated objectives at the beginning of the chapter.

temperature increase the ___ perature and of the coolan boiling point ____________ ______ the freezing t in an autom temperature system? ___ the boiling of the coolan otive cooling t. 10. A typical 4. Describe cooling syst the operation em 4:49 PM of /15 con a ___ thermostat. typical cooling 11/18 tain ____________ s a mix system ant ifre eze and ______ ture of water which 5. What are _________ offe the adv ____________ rs an excellent balance of both being adjusted antages of engine tem ___ freeze poi per boiling point nt and ______ protection. electronically to current operating dem ature _________ ands on the controlled coo ling system? 6. Describe Multiple Ch an advantage oice of a declutchin cooling fan. g engine-driven 1. All of the follow are tru 7. Describe e about engine except: an advantage thermostats of an electric cooling fan. A. A stuck -motor-driv open thermo en stat will cause overcooling. 8. Briefly, wh engine at is the pur pos B. A stuck e of the coolan recovery tank closed thermo ? t stat will cause overheating. 9. What is a engine PTC C. A faulty can it be foun heater and on what veh thermostat will icles d? effect vehicle D. A thermo emissions. stat may be rem 10. What are ove the advantage running hot d from a syst . s of a 50/50 em if it is and water? mix of antifre 2. Engine coo eze lant is design ed to provid ing except: Fill in the Bl e all of the foll anks owA. Provide water pump 1. Radiators lubrication. B. Inhibit rus are constructed t and corros of _________ ____________ ion. ______, C. Lower the ___, and/or plastic. boiling point 2. A frequen of the solution D. Lower the t coo . freezing tem by worn ___ lant pump failure is due perature of the ____________ to often cau 3. If a thermo solution. sed . stat 3. If the gasket lowing will occ fails in the open positio or sealing sur n, all of the folur, except: faces of a pre cap are dam A. A vehicle aged, the coo ssure may fail emissi ling system Swollen ____________ ons test. cannot be B. A loss of ___. engine coolant 4. A thermo . C. Poor hea stat failing in ter performanc the ___ will result in e. D. A longer engine ______ ____________ positio than normal n _________. warm-up per 5. Engine-dr 4. All of the iod. iven fans are following stat balanced to ____________ ements about systems are preven ___ engine cooling true EXCEPT ____________ , _______________, coo t : A. Extended lant pump ___ failure, and life coolant and /or seal dam Chafed 6. Many elec age stan bot . dard life coo h ethylene glyc tric cooling lant are ol based. fans are trolled by the B. It is ok for ____________ ultimately cona tech ____________ ___, _________ with a low tem nician to install a thermo ___. ______, stat perature rati ng than the orig thermostat. 7. Electric coo inal ling fans ma C. Extended y ___ warning, eve life coolant is n with the ign ____________ without rated to last 100k miles. the position. ition ______ in excess of _________ in D. Electric cooling fans Soft may turn on even engine is not when an running.

12 6

A list of new terms appears after the Summary.

Propylene

re, heric pressu -level atmosp psi cap will at ambient sea 15 iator with a as a coolant, ine because ature of water 8F (1008C). Water in a rad eng per an tem in g t lan The freezin point is 212 ight as a coo itives that are and the boiling er be used stra or other necessary add is 328F (08C) ter should nev properties, (1208C). Wa a), , lubricating boil at 2508F be red (Toyot ion protection also ros can cor but no in color it offers and water en or yellow ylene glycol antifreezes. 8C) in is generally gre of 50/50 percent eth 9.4 available in col (12 F 8 gly ne 265 OF yle ture point of A BIT Standard eth mende d mix and a boiling ter is increased k. The recom nt of 2348F (236.78C) to distilled wa ling point is HISTORY blue, or pin poi ylene glycol boi has a freeze methyl centage of eth 48C) and the 70 (Figure 4-69) Prior to 1930, cap. If the per 2848F (264. sed beyond to psi rea t 15 inc sed a mos be h rea e the centalcohol was a radiator wit t, the freeze point is dec mended that the mixtur ses as the per engine n ay heat decrea dow commonly used ired is not recom 70/30 percen aw It to ry tion C). 8 car tec 5.6 to requ coolant 2768F (13 es freeze pro ne antifreeze and increased to e ability of the ylene glycol only provid ance ture of ethyle ne glycol. Th constant mainten ze A straight mix than water at . Straight eth percent ethyle 8F (135.68C). er free cient col increases 276 of gly effi e nt less to ensure prop t ylen poi age of eth a boiling is 15 percen lene glydamage. 98C) but has ylene glycol protection. Ethy severe engine In warmer duced to 228F (218. d because eth resulting in ed col was first intro never be use ts to develop, ature expect uired for 1927, but glycol should cause hot spo be to the lowest temper by Prestone in tection is req t and could pro uld hea a, ng sho stan rni a d ovi lifo cte rem any climate level sele it did not become ory Southern Ca protection. In tion. The fact The protection as southern Florida and anti-boiling rica for as dard year-round lub ll h p we suc as pum , t es, y 1960s. ll as coolan climate zon sion inhibitors protection to fill until the earl tection, as we and anticorro will provide the antirust ial for this pro cent antifreeze, which eze is essent ene than 30 per zone, antifre d with propyl l contain no less late uld mu for sho t eze ifre coolan r for anima coolant is ant toxic and safe ol ognized 258F (2158C). rnative to ethylene glycol entially non Rec Propylene glyc ess ally is ner col gly “Ge A safer alte is safe col, propylene pylene glycol is classified (C 3H8O2 ) is the mean that it ethylene gly for pro icity does not base stock used glycol. Unlike the environment. Also, ation. Low tox REVIEW QU ive and ill g Administr most automot life, children, d as factor y-f uced. TI . Food and DruES red use ON U.S tly and atly ren zes the gre S a by free anti glycol as Safe” soning is and not cur rra®. Propylene and aftermarket the risk of poi is a colorless, e Brands Sie col Saf ilable on the to drink, butShorcol gly ava and ene is ® in pyl t-A d Tox pro nswer Pre viscous liqui Essay stone Propylene gly s Lowe glycol. A 50/50 mixture Fof(124.48C) in a radiator nds are has its pure form, 1. ula Whratbra is the teripos stices as ethylen a boiling point of 2568 8. Hea antifreeze. Pop 78C) and a and 256. cor of the C) and 708F (ter rmal characpur a low toxicity, otive cooaling ze point of 2 _________ e leaks are detected by a loss 2. What are 268F (232.28automtur has similar the freesyst an of 2 has nt e poi the ______ and em is considered ze of two ? mix t free typper es cen a wet ______ of radiator cor a 15 psi cap. ____________ llywater has a in the a 100 aut as _________ om ere h e otiv environmenta wh tha ___. wit , t are found e cooling cap a radiator ive to with a 15 psi 9. An antifre 3. Wh (187.88C) in system? friendly alternat 8Ftho at me eze solution nt of 370 d(s poi ) ol. is ling use glyc boi ___ d lene to ___ tem ethy

TERMS TO KNOW LIST

FIGURE 4-67

Hardened

97603_ch04_h

r_082-132.

Terms to Know

13 1

indd 131

al hose defec FIGURE 4-70 Typic

Antifreeze Bypass Centrifugal impeller Control valve Distilled water Electrolysis Ethylene glycol Expansion tank Heater core Hybrid organic acid technology (HOAT) Organic acid technology (OAT) Overcooling Overflow tank

ts.

road a minimum sustained ther m is to provide for 1258F (528C). Ano tion of a cooling syste ient temperature of The design considera ient temperature .8 km/h) at an amb amb (144 an in c mph 90 traffi of ested stop-and-go speed operation iderations cong cons n in ng desig e drivi of . Thes tes criteria is for 30 minu experiencing any overheating problems ng. out lar day-to-day drivi engine of 1158F (468C) with to encounter in regu cted. The life of an s that one is likely it be found and corre exceed the condition ced. The high-lim the problem should redu s, tly heat grea over is ne If the engi formulated allowed to overheat erve y pres tuall to habi val is that proper heat remo and or a transmission uate adeq ire cating oil requ properties of lubri istics. lubricating character

11/18/15 4:49 PM

SUMMARIES Each chapter concludes with a summary of key points from the chapter. These are designed to help the reader review the contents.

SUMMARY

Pitch Power train control module (PCM) Pressure cap Propylene glycol Radiator Ram air Recovery tank Reverse flow Thermostat

es: following procedur should include the tenance program The preventive main thermostat. Test or replace the pressure cap. Test or replace the the radiator hose(s). Inspect or replace heater hoses. the ce repla or ■■ Inspect the cooling system. ■■ Pressure test antifreeze solution. the ce repla , and belt(s). or ■■ Test p, heater, control valve ect the coolant pum ■■ Visually insp

■■

■■

■■

130 11/18/15 4:49 PM

32.indd 130

97603_ch04_hr_082-1

xvi Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Shop Manual To stress the importance of safe work habits, the Shop Manual also dedicates one full chapter to safety. Other important features of this manual include: Chapter 4

PERFORMANCE OBJECTIVES

Diagnosis and Service of Engine Cooling and Comfor t Heating Systems

These objectives outline the contents of the chapter and identify what the student should have learned upon completion of the chapter. These objectives also correspond to the list of required tasks for NATEF certification.

Each chapter begins with a list of the Basic Tools needed to perform the tasks included in the chapter. Whenever a Special Tool is required to complete a task, it is listed in the margin next to the procedure.

Upon Completion and Review of this Chapter, you shou ld be able to: Identify

the major components of the automotive engine cooling and comfort heating system. Compare the different types of radiators. ■■ Discuss the function of the coolant pump. ■■ Explain the need for a pressurized cooling system. ■■ Describe the advantage of a thermostat in the cooling system. ■■

■■

■■

Although this textbook is not designed to simply prepare someone for the certification exams, it is organized around the NATEF task list. These tasks are defined generically when the procedure is commonly followed and specifically when the procedure is unique for specific vehicle models. Imported and domestic model automobiles and light trucks are included in the procedures.

■■

■■

Understand the procedures used for testing the various cooling system components. Recognize the hazards associ ated with cooling system service. Understand troubleshooting procedures for determining the malfunction of cooling system components.

A typical gasoline engine is only about 15 percent efficient; is used to move the vehicl e. That means that 85 percen only about 15 percent of the energy t of all energy developed is wasted in friction and by the engine heat—heat that must be removed. While the heat of combu stion may reach as high as 4,0008F (2,2008C), most when the exhaust valve of it is expelled opens. This results in an actual about 7508F (4108C) to net engine temperature about 1,5008F (8158C). range from This is still a great deal be removed. The coolan of heat, tempe t, a mixture of water (H and rature must O) and ethylene glycol, Checkthermit transfer this heat from the ostat iswhen the liquid used engine to the radiator.2 to opens

The Cooling System

Classroom Manual Chapter 4, page 82

The cooling system (Figur A common leak point e 4-1) is made up of severa l components, all of which to its proper operation. is due to loose hose They are the radiator, pump are essential , pressure cap, thermostat, heater core, hoses and clamp clamps. cooling fan, s, and coolant. oomcomm Classr The most on cooling system proble ms are a result of a leakin Manualpresents a tem seldom g system. A sound sysproblem. Leaks are genera Ambien t 101 lly page easy 4, types are to find using Chapter available. The following temperature is the is a typical procedure for Heat a pressure tester. Several pressure testing operation. 1. Allow the engine and stat coolin temperature of the thermo ng a g system : coolant to cool to ambie FIGURE 4-17 Checki nt temp 2. Remove the pressure eratu surroun re. ding air. cap. Note the pressure range pulley is acoolan indicated on the cap (Figur r and turn on the burner. 3. Adjus An idler t the t e 4-2). ts on a stove burne below the bottom or level to a point just and conten tension 4. Attach used tothe to open at its rated temof the fill neck valve Place the container pressure tester 6. the should radiator.begin The fillvalue, (Figur neck isreplace e 4-3). r. The thermostat of the direction reroute rated 5. While its F 8 3 6 obser Obser ve the thermomete than ving the gauge7., pump more the part of the begins to open the tester until ea 4-17). of a belt. pressuIfreitequal achiev ed. If the pressure can be perature value (Figur to the cap rating is radiator on which If yes, achieved, proceed with step 6. If the rated value? achieved, make a visual thermostat. 8C) abovetheitspressur pressure canno 258F (11 e cap is inspecthe t be tion for leaks. opened at approximately 8. Is the thermostat fully ostat. A drive pulley attached. therm the e replac If not, the thermostat is all right. transmits or inputs power into a component.

97610_ch04_hr_101-156.indd

Replace any belt that appears to be worn, frayed, or damaged.

CUSTOMER CARE

replacement interval stated for the ostat is generally no service maintenance item, therm Customer Care: There ostat. But, as a preventive nt is changed. 101 of the cooling system therm coola e engin the suggested when replacement should be

This feature highlights those little things a technician can do or say to enhance customer relations.

101

A serpentine belt is a flat or multi V-grooved belt that winds through all of the engine accessories to drive them off the crankshaft pulley with both sides of the belt being drive surfaces.

TERMS TO KNOW DEFINITIONS

11/16/15 7:04 PM

Pulleys

e due to colms that may occur are damag tforward; inspection. Pulley proble Pulleys require periodic . In all cases, repair is straigh gs in an idler or drive pulley tine belt systems will wear serpen on lision or defective bearin used s pulley g or pulley. Plastic necessary. replace the faulty bearin t and replace them when cracks over time; inspec and develop grooves and

r Belts and Tensione

air-conditioning otive engine cooling and belts used in the autom Photo Sequence 1 There are two types of the V-belt (Figure 4-19). belt (Figure 4-18) and drive belt. system: the serpentine tine serpen the ing Replacing l procedure for servic typicaione m similar to the one shown a Belt ates aTens illustr r belt locate the routing diagra on the A V-belt is a belt removal of the serpentine The following proced in the engine bay, often Prior to ure is typical for m located under the hood in is often replac designed to runthe ing an e service information. automatic 4-18. This diagra particular the vehicl Figurefactur belt tensio d in ner. in manu be locate Alway also er’s cover. may s follow recom m mend a single V-shaped diagra ed The procedures for each vehicl or support g prior to removal. radiat routin e. 1. belt Attach the of drive a a of socket sketch a groove s with wrenc to draw h to the emoun choos icians ting bolt of the autom tensioning for those system r belt propeatic 4-20). techn tensio or idler pulley with (Figure Some ner pulley be used to ensure bolt ner, a springatic belt tensio A belt tension gauge may 2. Rotate the tensio only the tapered be odel vehicles have an autom ner assemblyMany clockwlate-m ise (cw) sted that a new belt again al adjustment. until the 3. Remove manu it isn sugge belted, tensio surface being the adjust the belt has ally been frompulley ing. manu is relieve the stretch belt idler d. the and pulley g . If first, then remove theallow MostDisconnect for initial seatin loaded time the drive surface. 4. and idler remove about other pulley of operation to belt from set15 minut aside anyescompo eters) or so.s. ned after and nents kilom 5. Remove the tensio hinder systems require (8,000 ing miles tensio tensio ner removal. ner assembly from every 5,000 check theedmoun ting bracket. several V belts The belt should then be

Many of the new terms are pulled out into the margin and defined.

to drive all of the engine accessories.WARNAuto matic ING: Becau

Belt Tensioner -loaded automatic se of high spring pressu are equipped with a spring engin late-model re, does not disassemble ns, such as with tensioner. uratio theconfig autom The drive belts on most with all belt atic belt tensioner may be used atic autom An ner. tensio 6. Remove the g and air conditioning. pulley ut power steerin and remov e the or withobolt pulley from the tensioner. 7. Install the pulley and pulley bolt in the tensio ner. Tighten the bolt to An indexing 8. Install the tensioner 45 ft.-lb (61 N ⋅ m). assembly to the mounting tab is a mark or 110 bracket. An indexing tab is generally located on the (Figure 4-21) back of the tensioner to protrusion on mating align with the slot in the bracket. Tighten the nut mounting to 50 ft.-lb (67 N ⋅ m). components to 9. Replace any components removed in step 4. ensure that they will 10. Position the drive belt over all pulleys, except the be assembled in 110 1-156.indd idler 11. pulley 04_hr_10 Using . a socket wrench on the pulley their proper97610_ch position. mounting bolt of the autom tensioner cw. atic tensioner, rotate the 12. Place the belt over the idler pulley and allow the tensioner to rotate back should spring back smoot into position. It hly and with adequate tensio n pressure on the belt.

CAUTIONS AND WARNINGS Throughout the text, cautions are given to alert the reader to potentially hazardous materials or unsafe conditions. Warnings are also given to advise the student of what can go wrong if instructions are not followed or if a nonacceptable part or tool is used.

TOOLS LISTS

BASIC TOOLS Basic mechanic’s tool set

CAUTION:

When installing the serpentine accessory drive belt, the belt must be routed correctly. If not, the water pump may rotate in the wrong direction (Figure 4-22), causing the engine to overheat.

11/16/15 7:05 PM

Belt Failure Troublesh

ooting

A variety of critical engine components stop worki ng when a serpentine belt components may includ e the water pump, altern fails. These ator, air conditioning compr steering pump to name essor, and power some of the more comm on belt-driven accessories. It is important Turn clockwise to remove belt

Tensioner

Socket wrench Idler pulley

Fan blade

FIGURE 4-20 Rotate the tensioner clockw ise (cw) to loosen the belt.

114

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114

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xvii

Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

PHOTO SEQUENCES

PHOTO PHO SEQTO UEN SEQ CEUEN 1

Many procedures are illustrated in detailed Photo Sequences. These detailed photographs show the students what to expect when they perform particular procedures. They can also provide a student a familiarity with a system or type of equipment that the school may not have.

P2-1 Ensure that the engine is cold, and slowly remove the radiato r cap. CAUTION: If the radiato r cap is removed from a hot cooling system , serious personal injury may result.

CE 2

(continued)

Draining and Refi lling the Cooling System

P2-2 Place a drain pan of adequate size under the radiator drain cock.

CROSS-REFERENCES TO THE CLASSROOM MANUAL

P2-3 Install one end of a tube or hose on the draincock and position the other end in the drain pan.

Reference to the appropriate page in the Classroom Manual is given whenever necessary. Although the chapters of the two manuals are synchronized, material covered in other chapters of the Classroom Manual may be fundamental to the topic discussed in the Shop Manual.

Fuse

t*

P2-4 Open the radiato r draincock and allow the radiator to t drain until 12-V theBat flow stops.

Thermosta

F/L

P2-5 Place a drain pan of adequate size under the engine.

P2-6 Remove the drain plug from the engine block and allow torengine block mothe to drain until theFan flow stops. NOTE: There may be more drainag e from the radiator at this time.

12-V Ign Fuse

Fan relay Selector switch

Norm Max Off

t) engine *(Thermosta perature coolant tem switch fuse Connect a FIGURE 4-37

d jumper wire

from the batt

Bi-level Vent Heat Def

ery positive

to the cooling

fan connec

eck for poo P2-8 Remove the pans right. Ch alldispose isand of the st coolant in yes, the fanconsist h step 9. d wit entcee rted and mu with local t and run? If a manner pro . If no, motor is sho regulat ions. Did the fan star m if necessary wn? If yes, the

Chapter 4, pag

air the Is it blo motor and rep fuse in the jumper wire. replaced. ck the and must be 9. Again che If no, the motor is open be replaced.

97610_ch04_hr_101-156.indd

CASE STUDIES

131

d Hoses an

131 uld rs. This sho every few yea more Clamps be replaced ic schedule, clamps should e on a period ur. don and occ If es to m. ly hos gra like pro tem as

s if Replace all hose to be any are found defective.

A customer brin gs temperature gaug his car into the shop because e does not oper the ate. It remains all of the time , regardless of on engine heat cond cold The lead wire itions. to the sending nected, and a unit is discon123 -156.indd test r_101 light 04_h is 0_ch used to probe 9761 The test light comes on for voltage. when the igni placed in the ON tion switch position. When the lead is conn is ected

to ground (−) through a 10 0 resistor, the needle moves dash unit to the full hot position. This operation acco is a normal rding to the serv ice manual. The diagnosis is that the sending unit is tive. It is replaced defecafter approval the temperature by the custome r and gauge system is returned to operation. normal

Terms to Know

Ambient tempera ture Constant tens ion hose clamp Dissipate Drive pulley Fan relay Fill neck Heat exchang er Idler Indexing tab Serpentine belt

ASE-STYL

V-belt

E REVIEW QUESTION

S 1. Engine ove rcooling is bei ng discussed: Technician A says that a the be the cause rmostat stuc 5. Technician of this conditi k open could A says that as on. a neoprene Technician B ages and wea serpentine belt says that a mis rs cracks will the cause of that if there form on the this condition. sing thermostat could be are belt ribs and span, the belt more than three cracks Who is correc in a 4-inch should be rep t? lace Tec d. hnician B say A. A only resist crackin s that serpentine belts C. Both A B. B only made of EPD g and instead and B M similar to tire exhibit wear D. Neither to wea the belt ribs r, 2. Technician and A nor B tha used to asse A say ss belt wear. t a depth gauge should system, it sho s that when pressure test be Who is correc uld hold pre t? ssure for 5 min ing a cooling Technician B utes. A. A only says that a wet heater core carpet may leak . C. Both A indicate a B. B only and B Who is correc D. Neither t? 6. Technician A nor B A. A only A say every 2 years. s that antifreeze should C. Both A B. B only be changed and B Technician B D. Neither say s tha 3. All of the t extended-life A nor B up to 5 years. follow coolant may serpentine belt ing may cause the back last Who is correc side of a to separate exc t? ept : A. Contact A. A only ing stationary object B. Excessive C. Both A B. B only heat and B C. Fractured D. Neither splice 7. An overhe A nor B ating conditi D. Pulley mis on is being disc alignment Technician A ussed: says that rep 4. Coolant loss lacing the the one of a low is being disc er rmo tem stat wit per uss ature rating ed: Technician A coolant tem will reduce the h perature. says that a mis the problem sing thermo Technician B . stat could be says that rep Technician B lacing the pre with one of a lower rating say ssu may be the pro s a heater control valv will reduce the re cap temperature. e stuck open blem. coolant Who is correc Who is correc t? t? A. A only A. A only C. Both A B. B only C. Both A B. B only and B and B D. Neither D. Neither A nor B A nor B

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r_101-156.

indd 137

SERVICE TIPS

sys nance , are not Engine cooling good preventive mainte ating engine of a by an overhe 11/16/15 7:05 PM become part : those caused airs, such as SERVICE TIP is a expensive rep have Some engines The following ng ser viced. s such bei is icle additional hose a veh ss Hoses bypa hoses when ll sma tem a sys as the leak . ck all cooling the the point of hose between Carefully che for this ser vice: rust color at re. and ist ite, green, or coolant pump rating pressu simple checkl noted by a wh ine is at ope k, leaks, usually the engine bloc s when the eng nearby component. iou obv 1. Check for y ally er carr swelling, usu caused by a belt or oth erioration. hoses used to p. chemical det 2. Check for the fing, usually coolant pum coolant to heat uld indicate cha the wo r t for nea tha eck e ally hos 3. Ch heating, usu ttle body on fuel e. t or spongy ed thro sof hos a eat the rep for and y, replace 4. Check or corroe indicating injected engines, ts or flakes awa e is missing (due to rust a brittle hos to 5. Check for hose. If its outer layer spli ing wir short hoses used the the reinforc ant 6. Squeeze iator hose. If interconnect cool the lower rad es if any nts hos pone ter com hea 7. Squeeze carrying iator and the hose. this rad t lace nes the tha rep engi of er ), ain all tom sion on cert e to replace vince the cus Do not good practic possible to con (Figure 4-38). Hose. It is a is not always hoses Replacing a defective. It overlook these found to be the of them are when checking ure 4-40). p and (Fig pum e t hos lan e. cooling system. from the coo h ends of the should be don se bot loo l. at it k ova ak bac hose to bre ilitate its rem hose clamp the fac the n p e tur hel l Slid and wil 1. e st carefully twi ough the hos ter to slice thr 2. Firmly but ng a box cut 12 3 radiator. Usi ure 4-41). the hose (Fig 3. Remove

case stud y

Case Studies concentrate on the ability to properly diagnose the systems. Beginning with Chapter 3, each chapter ends with a case study in which a vehicle has a problem, and the logic used by a technician to solve the problem is explained.

tor.

Classroom Manual e 120

s at the fan r connection

P2-7 Close the radiato r draincock and replace the engine block drain plug.

8.

(1) terminal

Whenever a shortcut or special procedure is appropriate, it is described in the text. These tips are generally those things commonly done by experienced technicians.

PM 11/16/15 7:05

TERMS TO KNOW LIST A list of new terms appears after the case study.

ASE-STYLE REVIEW QUESTIONS Each chapter contains ASE-style review questions that reflect the performance objectives listed at the beginning of the chapter. These questions can be used to review the chapter as well as to prepare for the ASE certification exam.

13 7

11/16/15 7:05 PM

xviii Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

JOB SHEETS

JOB SHEE T

(Located at the end of each chapter, the Job Sheets provide a format for students to perform procedures covered in the chapter. A reference to the NATEF Task addressed by the procedure is referenced on the Job Sheet.

be able to rem ove and replace NATEF Corre cooling system lation NATEF AST and MAST Correlations Diagnosis and : ENGINE RE Repair; PAIR: Lubrica Task #4. Ins tion and Co pect oling System with recomme and test coolant; drain s and recover nded coolan coolant; flus t; bleed air as h and refill coo req uir ed. (P-1) Tools and Ma ling system terials Late-model vehicle Shop manua l Two pans Safety glasse s or goggles Hazardous wa ste container Funnel

Rubber hose Hand tools, as

An ASE practice exam, located in the Appendix, is included to test students on the content of the complete Shop Manual.

t

Upon comple tion of this job coolant. sheet, you sho uld

Describe the

ASE PRACTICE EXAMINATION

10

Name ______ ____________ ____________ ________ Da te _________ ____________ ___ Coolan

Drain and Fill

required

Vehicle being Worked on. Year ______ ____________ __ Make ___ VIN ______ ____________ ____________ ______ Model ___________ ____________ Engine type __________ Procedure and size ___ ____________ ____________ Follow the pro _ cedure outline a guide where d in the ser vic ver applicable e manual. Pho . to Sequence 2 ma y also be used 1. Ensure tha Nas t the engine AMINATIO is cold, and slowly remove ACTICE EX E PR ASthe radiator cap . WARNING: A If the radiat or cap is rem personal inj APPENDIX ury may res oved from below is 0. The ult. a hot stragtion illulin thecoo sys t the, : serious ter reading in thatem 2. Place a dra 7. The voltme cause of this problem is A7 le in ng pan oni ditiof ade most probab Con qua Air rted te of and size sho a tub ting under the e or hose on gs are diniato Win rad omotive Hearad A. the Aut em m r dra syst dra Exa inc ng incnock and ins ock . Position dings are ope iator draditi Final inconi ock and tall one end or? the other end of the air-con vapw B. Win to a allo the radiato ponent part in ed the drain from a liquid not energiz r dra 3.toPla 1. What com cha ayinis unt cenge a drain pan C. toRel igerant il the flow sto pan. Open the of adequate causes the refr ps. engine block size underD.theMotor is seized r ato por and Eva eng allo A. ine. Remove w the engine the block to dra ssor in until the flow drain plug from the B. Compre stops. ser C. Conden Voltmeter device ess D. Metering ove exc rem oning system compartment? the air-conditi the passenger 2. How does the air entering duct walls. humidity from collects on the re istu ser. Mo den con A. denses on the r. Moisture con B.97610_ch the evaporato 04_hr_101 condenses on C. Moisture -156.indd 139ted by the blower motor. is separa re istu Mo ditioning D. of the air-con test e anc system perform high-side and low-side r 3. During a on both the the compresso rati and e ope sam em syst ut the most dings are abo owing is the pressure rea ich of the foll Wh d. age clutch is eng pressure line likely cause? ion in the low A. A restrict valve plate compressor B. A faulty the system tamination of con re istu C. Mo valve ed expansion ch of D. A restrict ant tank, whi osable refriger formed? arding a disp 4. Before disc procedures should be per prevent closed to is e the following valv k e the tan A. Make sur atmosphere. g agent. venting to the igerant flushin tank. tank with refr ant left in the B. Flush the aining refriger rem any the pressure. C. Recover te ina elim valve to the tify D. Open the l must iden retrofit labe A says that a ant oil. 5. Technician the ount of refriger l must identify labe type and am ofit says that a retr alled. Technician B refrigerant inst new of t amoun t? and B Who is correc C. Both A A nor B A. A only D. Neither y onl B B. ssor clutch to se a compre owing may cau foll the of 6. All slip, except : ant ge of refriger A. Overchar e belt B. Loose driv air gap C. Improper age D. Low volt

13 9 Blower motor relay

11/16/15 7:05 PM

Blower motor Blower motor relay

Ammeter

Blower motor 20 A fuse

54 9

PM 11/20/15 1:09

97610_em_app

indd 549 A_hr_549-554.

xix Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Supplements Instructor Resources The Instructor Resources, now available both online and on DVD, are a robust ancillary product that contains all preparation tools to meet any instructor’s classroom needs. It includes chapter outlines in PowerPoint with images, video clips, and animations that coincide with each chapter’s content coverage, chapter tests powered by Cognero with hundreds of test questions, an Image Gallery with all photos and illustrations from the text, theory-based Worksheets in Word that provide homework or in-class assignments, the Job Sheets from the Shop Manual in Word, a NATEF correlation chart, and an Instructor’s Guide in electronic format. To access these Instructor Resources online, go to login.cengagebrain.com, and create an account or log into your existing account.

MindTap MindTap for Today’s Technician: Automotive Heating & Air Conditioning, 6th edition, is a personalized teaching experience with relevant assignments that guide students to analyze, apply, and improve thinking, allowing you to measure skills and outcomes with ease. ■■

Relevant readings, multimedia, and activities are designed to guide students through progressive levels of learning, from basic knowledge to analysis and application.

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Personalized teaching becomes yours through a Learning Path built with key student objectives and your syllabus in mind. Control what students see and when they see it.

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Analytics and reports provide a snapshot of class progress, time in course, engagement, and completion rates.

MindTap for Today’s Technician: Automotive Heating & Air Conditioning, 6th edition, meets the needs of today’s automotive classroom, shop, and student. Within the MindTap, faculty and students will find editable and submittable job sheets based on NATEF tasks. MindTap also offers students engaging activities that include videos, matching exercises, and ­assessments.

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Reviewers The author and publisher wish to thank the instructors who reviewed this text and offered their invaluable feedback: Dan Cifalia Mesa Community College Mesa, AZ

William McGrath Moraine Valley Community College Palos Hills, IL

Lance David College of Lake County Grayslake, IL

Rouzbeh “Ross” Oskui Monroe County Community College ­Monroe, MI

Randy Howarth Hudson Valley Community College Troy, NY

Christopher Parrot Vatterott College Wichita, KS

Shannon Kies University of Northwestern Ohio Lima, OH

Mike Shoebroek Austin Community College Austin, TX

John Koehn Pueblo Community College Pueblo, CO

Ira Siegel Moraine Valley Community College Palos Hills, IL

Christopher J. Marker University of Northwestern Ohio Lima, OH

Stephen Skroch Mesa Community College Mesa, AZ

Gary McDaniel Metropolitan Community College–Longview Longview, MO

Christopher C. Woods University of Northwestern Ohio Lima, OH

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Chapter 1

Shop Safety

Upon Completion and Review of this Chapter, you should be able to: ■■

■■

■■

Recognize the hazards associated with the automotive repair industry. Identify hazardous conditions that may be found in the automotive repair facility.

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Discuss the philosophy regarding health and safety.

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Compare and identify unsafe and safe tools.

■■

Understand the limitations, by design, of hand tools.

Explain the need for a health and safety program.

General Shop Safety Many studies have been made to determine which of the school shops are the more hazardous. The automobile mechanics shop, it has been found, ranks third in frequency of accidents. It is exceeded only by the wood shop and the machine shop. Principal hazards and injuries in the automotive shop are: ■■ Flammable materials ■■ Bruised and cut fingers ■■ Acid burns ■■ Strains and hernia ■■ Falls ■■ Eye injuries There is little manual lifting required in the modern automotive repair shop. Most lifting, when required, is accomplished with hoists, jacks, and other lifting devices. When using such equipment, understand and follow all applicable safety procedures. When manual lifting is required, lift with the legs—not with the back (Figure 1-1). Get help for heavy or bulky objects. Many schools have designated their shops “total eye protection areas.” This means that everyone who enters the shop must wear eye protective equipment. It is essential to wear safety goggles on any job where the eyes may be endangered, such as when grinding, using compressed air, working underneath cars, or servicing an air-conditioning system. Chemical or splash-proof goggles as well as a face shield (Figure 1-2) should be worn when servicing batteries or when boiling out or testing radiators for leaks. Sparks near an automobile battery may create a hazard and can cause an explosion. The accumulation of hydrogen vapor at the top of the cell being charged is very explosive. Do not test a battery by “flashing” or “sparking” the terminals with a piece of wire to see if it has a charge.

There are many airborne hazards in the automotive shop.

Always use proper tools. Use a battery tester for testing batteries.

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Straight back Position body over load. Keep back as erect as possible.

Weight close to body

Use leg muscles.

Legs bent FIGURE 1-1  Use legs, not back, for lifting.

Always wear eye protection.

FIGURE 1-2  A face shield may be worn over goggles for more protection.

Use only extension lights, cords, and sockets that are in good condition. Portable lights should be protected by a rubber- or neoprene-covered steel guard. All portable lights should have a third-wire ground. Do not place cords or wires across the floor where they may become a tripping hazard. Do not use portable electric tools unless they are electrically grounded with a third wire or are designated “double insulated.” Be sure that the extension cables used with portable electric tools are in good condition and are of the proper size. Do not attempt to use any power tools or equipment in the automotive shop until the proper and safe use has been fully explained by the instructor. Hammers with broken handles, defective screwdrivers, and greasy tools can all be the cause of serious accidents. Keep all tools clean and free from grease. Never engage in horseplay of any kind in the auto shop. This includes running, scuffling, and throwing tools or materials. Never use compressed air except for the purpose for which it is intended. Horseplay with compressed air equipment or dusting off clothing or work benches 2 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 1-3  Always use safety stands.

with compressed air is extremely dangerous. Flying particles of metal or glass may be blown into the eyes or the skin. Also, compressed air blown into the skin or body openings can cause serious injury and even death. An approved hoist should be used for work underneath a car. The proper instruction, use, and operation of a hoist should be a work assignment for each learner in any automotive technician training program. Vehicles raised by jack, chain hoist, or end lift should always be supported with safety stands (Figure 1-3) or with other approved safety devices. Before use, these devices should be carefully inspected for damage. Never crawl or work under a vehicle that is not supported by safety stands. This precaution should even be followed for inspection purposes. When working under a vehicle: ■■ Use a creeper. ■■ Keep legs and arms clear of passageways. ■■ Keep vehicle doors closed. ■■ Do not place tools above the technician. ■■ Other technicians should not work on top of the vehicle. ■■ Wear safety glasses, goggles, or face shield. ■■ Do not leave creepers, tools, or other equipment where anyone can step on or trip over them. Burns may result from working on a car that has not cooled off, most frequently by coming in contact with the manifold, exhaust pipe, or engine coolant. Gasoline and diesel engines should only be operated in a shop or other area where there is adequate ventilation or there are provisions to connect the exhaust to an approved system that is designed to remove harmful exhaust fumes from the work area. Before starting the engine, make sure that the car is out of gear. On cars with automatic transmissions, make sure that the gear select lever is in the neutral or park position when the motor is running. Set the parking brake. Ensure that there is no one working under the hood of the vehicle. Be especially cautious around moving parts such as the flywheel, fan blades, belt, gears, and alternator pulley. Keep long sleeves rolled up when working on any moving machinery. Do not lubricate an engine while it is running, and do not attempt to wipe moving parts of the engine. Keep hands out of the area of moving parts. Handle fluids carefully so that they do not splash in the eyes. Use a syringe when transferring fluids. It is important that brake fluid and some synthetic lubricants not be allowed to come into contact with a painted surface. Many such fluids contain ingredients that can soften, blister, and remove paint. 3 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 1-4  Always wear safety glasses.

Disconnect the battery ground cable before servicing the vehicle. See the manufacturer’s precautions.

Refrigerant pressure can exceed 300 psig (2,068 kPa). A technician is a person who has been technically trained to understand and repair the technicalities of the system on which they are working on. Hazards are possible sources of danger that may cause damage to a structure or equipment or that may cause personal injury.

To avoid burns from accidental short circuits and to prevent accidental engagement of the starting motor, be sure to disconnect the battery ground cable and insulate the connection before working on the electrical system of the car. Never consider a job complete until a check has been made to ensure that all parts that were removed have been replaced. Also, observe the following rules: ■■ Always refer to manufacturer’s specifications. ■■ Keep tools clean and in good condition. Screwdriver blades should be kept sharp and square; handles should be of a nonconducting material. ■■ Use the proper type and size of tool. Use box wrenches in preference to open-end wrenches; use adjustable wrenches as little as possible. Do not use files as punches or chisels; they are brittle and may shatter. ■■ Use handles on files. ■■ Do not put sharp-edged tools—such as chisels, punches, and open knives—in your ­pockets, even temporarily; keep guards on sharp edges or points of tools in tool kits. ■■ Push sharp tools away from you instead of drawing them toward you. ■■ Whenever possible, do not hold the screw or work piece with one hand and the ­screwdriver or tool with the other hand. ■■ Keep your face away from tools. ■■ Wear goggles when grinding or when working on any job that may involve flying debris (Figure 1-4). ■■ When working around moving machinery, do not wear gloves, ties, or loose clothing that may become caught in the machine and cause you severe injury. ■■ Do not wear rings when working. ■■ Remove all loose jewelry, such as chains and watches. ■■ Use the proper fuel. Some vehicles use fuels other than gasoline and diesel fuel, such as liquified petroleum gas (LPG) and compressed natural gas (CNG) as well as alcohol and alcohol blends. Hydrogen gas may be used in the future.

Personal Safety Technicians working in the automobile repair industry may be exposed to a wide variety of hazards in the form of gases, dusts, vapors, mists, fumes, and noise, as well as ionizing or nonionizing radiation. In the course of their work, automotive air conditioning

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technicians may not be directly exposed to all such hazards, but they must be aware of all the potential dangers that may exist in the facility. Some of the most common hazards include: ■■ Asbestos ■■ Carbon monoxide ■■ Caustics ■■ Solvents ■■ Paints ■■ Glues ■■ Heat and cold ■■ Oxygen deficiency ■■ Radiation ■■ Refrigerants

Fibrous Material (Asbestos)

Perhaps one of the most serious of the hazards found in an automotive repair facility is the exposure to asbestos fibers. Asbestos has been used in brake linings and clutch friction plates for many years. Exposure to asbestos may result in asbestosis or lung cancer. The problem is so serious that work with asbestos must now be done in accordance with Standard 1910.93a of the Occupational Safety and Health Administration (OSHA). Materials that are less hazardous have now replaced most asbestos applications, but asbestos must still be considered a hazard. Always follow all applicable procedures associated with good industrial hygiene any time there is a possibility of airborne fibers. Technicians must not be exposed to unsafe levels of airborne asbestos. It is required that: ■■ Asbestos waste and debris must be collected in impermeable bags or containers. ■■ All asbestos and materials bearing asbestos must be appropriately labeled. ■■ Special clothing and approved respirators are to be worn when handling asbestos. ■■ Technicians handling asbestos must be given regular periodic physical checkups. ■■ Methods to limit technician exposure to asbestos include isolation and ventilation of dust-producing operations and wetting the material before handling.

WARNING: The risk of cancer for people who smoke while working with ­asbestos is almost 90 times greater than for people who do not smoke.

Carbon Monoxide

Alternate fuels such as propane and CNG, diesel and gasoline-powered vehicles, and some hot work operations, such as welding, all produce carbon monoxide (CO). The technician’s exposure to carbon monoxide may be excessive if such operations are conducted in low-ceilinged or confined areas. Corrective action must be taken if the levels exceed safe standards. The technician must always work in a well-ventilated area to avoid exposure to excessive vapors and fumes.

Caustics, Solvents, Paints, Glues, and Adhesives

Many caustics, acids, and solvents are used in the automotive industry for cleaning operations (Figure 1-5). Epoxy paints, resins, and adhesives are used regularly in body repair and refinishing shops. Always read the cautions printed on the container label before using the contents.

Asbestos is a silicate of calcium (Ca) and magnesium (Mg) mineral that does not burn or conduct heat. It has been determined that asbestos exposure is hazardous to health and must be avoided. Occupational Safety and Health Administration (OSHA) is a federal agency in charge of workplace safety. Respirators are masks designed to protect the wearer from airborne contaminants and to provide clean air. Ventilation is the act of supplying fresh air to an enclosed space, such as the inside of an automobile. Smokers are at greater risk than nonsmokers by almost 10:1. Carbon monoxide (CO) is a major air pollutant that is potentially lethal if inhaled, even in small amounts. It is an odorless, tasteless, colorless gas composed of carbon (C) and oxygen (O) formed by incomplete combustion of any fuel containing carbon.

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FIGURE 1-5  Many hazardous solvents may be used in the automotive shop.

Lack of oxygen is evidenced by dizziness and drunkenness.

Some of the more common organic chemicals may cause dizziness, headaches, and sensations of drunkenness; they can also affect the eyes and respiratory tract. The use of many chemicals in this special trade industry can cause various types of skin irritations and, in extreme cases, dermatitis. Proper use and availability of appropriate protective equipment is essential. Such equipment includes: ■■ Gloves ■■ Goggles or face shields ■■ Aprons ■■ Respirators Any hazardous materials that come in contact with skin should be washed off immediately. In addition, an eye wash fountain or safety shower (Figure 1-6) should be provided. For example, an exploding battery may saturate the entire body and clothing with sulfuric acid. The fastest way to reduce the effects of this type of contamination is to step into a shower while disrobing.

FIGURE 1-6  Showers should be available for personal safety.

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Adequate ventilation is necessary to avoid excessive exposure to fumes and vapors during operations in confined spaces. Spray booths with a personal respiratory system are required in many areas for production spray operations involving adhesives and paints.

Heat and Cold

Consideration should be given to ensure that the temperature of the work area assigned to the technician be maintained within acceptable narrow limits. When exposed to extremes of heat and cold, it has been found that the technician’s work performance can suffer because of: ■■ Fatigue ■■ Sunburn ■■ Discomfort ■■ Collapse ■■ Other health-related problems

Oxygen Deficiency

If proper precautions are not observed, many operations carried out in a confined space, such as the repair of an automotive air-conditioning system, can be very dangerous. Not only may the technician be exposed to various toxic gases, but the atmosphere may also be deficient in oxygen, which would immediately pose a danger to life. Other vapors, which may not be harmful in themselves, displace the oxygen essential to life. Such potential hazards should be approached only when absolutely necessary and when there are adequate procedures outlining the proper precautions and safeguards, such as: ■■ Air line ■■ Respirator ■■ Lifeline ■■ Buddy system

Radiation

Lasers, which are used for some alignment procedures, may produce intense, nonionizing radiation. While it should be avoided, this minor radiation is not generally considered harmful. Welding, however, produces ultraviolet (UV) light that is hazardous to the eyes and skin. If proper safeguards are not observed, both ionizing and nonionizing radiation can be very hazardous. Only qualified and trained technicians should use such equipment. It is often a requirement that such technicians be licensed by a federal, state, or local authority. Welders, for example, may be certified by the American Welding Society (AWS). WARNING: Refrigerants may be flammable. R-1234yf is considered a mildly flammable refrigerant and should not be exposed to an open flame, hot surface, or any ignition source such as a spark. Do not smoke while working with refrigerant gases.

Refrigerants

The primary problem that may occur during the installation, modification, and repair of an automotive air-conditioning system is the leakage of refrigerant. Refrigerants may be considered in the following classes: ■■ Nonflammable substances where the toxicity is slight, such as some hydrofluorocarbons—Refrigerant-134a (R-134a), for example. Although considered fairly safe, this refrigerant may decompose into highly toxic gases, such as hydrochloric acid or chlorine, upon exposure to hot surfaces or open flames.

Radiation is the transfer of heat without heating the medium through which it is transferred. Ultraviolet (UV) is the part of the electromagnetic spectrum emitted by the sun (or other light source) that lies between visible violet light and x-rays. Refrigerant is a chemical compound, such as R-134a, used in an air-conditioning system to achieve the desired chilling effect. Good refrigerants are those that boil at atmospheric pressure and temperatures and are condensable when pressurized.

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FIGURE 1-7  Material safety data sheets (MSDS) are supplied by hazardous chemical manufacturers on request.

Toxic and corrosive refrigerants such as ammonia, often used in recreational vehicle (RV) absorption refrigerators, may be flammable in concentrations exceeding 3.5 percent by volume. Ammonia is the most common refrigerant in this category and is very irritating to the eyes, skin, and respiratory system. In large releases of ammonia, the area must be evacuated. Reentry to evaluate the situation may only be made wearing appropriate respiratory protective devices and protective clothing. As ammonia is readily soluble in water (H 2O), it may be necessary to spray water in the room via a mist-type nozzle to lower concentrations of ammonia. ■■ Highly flammable or explosive substances, such as propane, must be used with strict ­controls and safety equipment. While propane is not used as a refrigerant in mobile refrigeration, it is a fuel often found in mobile applications. If a refrigerant escapes, action should be taken to remove the contaminant from the premises. If ventilation is used, exhaust from the floor area must be provided for gases heavier than air and, similarly, from the ceiling for gases lighter than air. For an analytical analysis of the product, consult the material safety data sheet (MSDS) (Figure 1-7) provided by the manufacturer. ■■

Ozone-friendly HFC-134a is the refrigerant preferred by the automotive industry to replace CFC-12.

Material safety data sheets (MSDS) contain specific information about a product covering health hazards, medical treatment, reactivity, cleanup, environmental impact, and all safety-related issues associated with the use and storage of the product. MSDS are required for all chemicals used or stored on the premises and are obtainable from the supplier.

Antifreeze

There are two basic types of antifreeze available: those with ethylene glycol (EG), and those with propylene glycol (PG). EG-Based Antifreeze.  EG-based antifreeze is a danger to animal life. Properly handled and installed, however, EG antifreeze presents little problem. If it is carelessly installed, improperly disposed of, or leaks from a vehicle’s cooling system, it can be very dangerous. EG-based antifreeze causes thousands of accidental pet deaths in the United States each year. Animals are attracted to EG antifreeze because of its sweet taste. As little as 2 ounces can kill a dog, and only 1 teaspoon is enough to poison a cat. This antifreeze can also be a hazard to small children in an undiluted quantity of as little as 2 tablespoons. Toxicologists report that EG antifreeze inside the body is changed into a crystalline acid that attacks the kidneys. The effects are fast acting, and one must act immediately if it is suspected that an animal or child may have ingested EG antifreeze.

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A

B

FIGURE 1-8  Ethylene glycol-based (A) and propylene glycolbased antifreeze (B).

The signs of EG poisoning in pets include excessive thirst and urination, lack of coordination, weakness, nausea, tremors, vomiting, rapid breathing and heart rate, convulsions, crystals in urine, diarrhea, and paralysis. Pets do not often survive EG poisoning because owners do not usually recognize the symptoms until it is too late for treatment. PG-Based Antifreeze.  A safer alternative is an antifreeze and coolant formulated with propylene glycol. Unlike EG antifreeze, PG-based antifreeze is essentially nontoxic and hence safer for animal life, children, and the environment. PG antifreeze is classified as “Generally Recognized as Safe” (GRAS) by the United States Food and Drug Administration (U.S. FDA). Actually, propylene glycol is used in small quantities in the formula of many consumer products such as cosmetics, medications, snack food, and as a moisturizing agent in some pet food. PG-based antifreeze coolant protects against freezing, overheating, and corrosion the same as conventional EG-based antifreeze coolants. PG-based antifreeze coolants should not be mixed with toxic EG-based antifreeze coolants (Figure 1-8) because the safety advantage will be lost.

Welding, Burning, and Soldering

Fumes from welding and other hot-work operations actually contain the metals being welded together, such as cadmium (Cd), zinc (Zn), lead (Pb), iron (Fe), or copper (Cu), as well as the filler material, flux, and the coating on the welding rods. Such operations may also generate other gases such as CO and ozone (O 3 ) at concentrations that may be hazardous to health. When extensive hot-work operations, such as welding, are performed in confined areas, there can be an excessive fume exposure to these materials. Ventilation or respiratory protection may be needed for certain operations. Eye protection for the welder and for other technicians working in or near the vicinity of welding operations should be provided because of the UV light produced during such operations. Engineering controls such as local exhaust ventilation are required before use of personal protective equipment as a control measure. When effective engineering controls are not feasible or while they are being instituted, personal protective equipment is required.

Flux is used to promote “wetting” during soldering.

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General Hybrid Electric Vehicle Safety Since the hybrid electric vehicle (HEV) system can use voltages in excess of 300 volts (both DC and AC), it is vital the service technician be familiar with, and follow, all safety precautions. Many high-voltage electric vehicles today use a high-voltage electric air conditioning compressor as part of the refrigerant system. Failure to perform the correct procedures can result in electrical shock, battery leakage, an explosion, or even death. The following are some general service precautions to be aware of: ■■ Test the integrity of the rubber insulating gloves (electrical lineman gloves) prior to use. ■■ Wear high-voltage (HV) insulating gloves when disconnecting the service plug and use the leather top glove during heavy or abrasive service procedures. WARNING: Do not attempt to test or service the system for 5 minutes after the high-voltage service plug is removed. At least 5 minutes is required to discharge the high-voltage capacitors inside the inverter module. ■■

■■ ■■ ■■

Never cut the orange high-voltage power cables. The wire harness, terminals, and connectors of the high-voltage system are colored orange. In addition, high-voltage components may have a “High Voltage” caution label attached to them. Use insulating tools. Do not wear metallic objects that may cause electrical shorts. Wear protective safety goggles when inspecting the high-voltage battery. WARNING: Be sure to use the proper safety equipment when working on any high-voltage system. Failure to do so may result in a serious or fatal injury

■■ ■■ ■■

■■ ■■

■■

SPECIAL TOOLS DMM capable of reading 400 volts AC/DC Insulating gloves Insulating tape

■■

Follow the service information diagnostic procedures. Never open high-voltage components. Before touching any of the high-voltage system wires or components, wear insulating gloves, make sure that the high-voltage service plug is removed, and disconnect the auxiliary battery. Remove the service disconnect prior to performing a resistance check. Remove the service plug prior to disconnecting or reconnecting any HV connections or components. Isolate any high-voltage wires that have been removed with insulation tape. Properly torque the high-voltage terminals. WARNING: When the vehicle has been left unattended, recheck that the service disconnect has not been reinstalled by a well-meaning associate.

When working on an HEV, always assume the HV system is live until you have proven otherwise; you can never be too safe. Your first mistake may be your last! If the vehicle has been driven into the service department, you know that the HV system was energized since most HEVs do not move without the HV system operating. It is critical that the proper tools be used when working on the HV system. These include protective hand tools and a digital multimeter (DMM) with an insulation test function. The meter must be capable of checking for insulation up to 1000 volts and measuring resistance at over 1.1 mega ohms. In addition, the DMM insulation test function is used to confirm proper insulation of the HV system components after a repair is performed. 10 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 1-9  It is recommended to follow the one-hand rule when testing any high-voltage system.

Whenever possible use the one-hand rule when servicing the HV system (Figure 1-9). The one-hand rule means working with only one hand while servicing the HV systems so that in the event of an electric shock the high voltage will not pass through your body. It is important to follow this rule when performing the HV check out procedure since confirmation of HV system power down has not been proven yet.

Insulated Glove Integrity Test

The rubber isolating gloves (lineman gloves) that the technician must wear for protection while serving the HV system are your first line of defense when it comes to preventing contact with energized electrical components and must be tested for integrity before they are used. Also, pay attention to the date code on the gloves, gloves have an expiration date, they do not last forever. In addition for heavy services, use the leather protective glove on top of the isolating gloves. Not just any gloves will do, lineman gloves must meet current ASTM D120 specifications and NFPA 70E standards. These requirements are enforced by OSHA as part of their CFR 1910.137 regulation. These standards dictate testing, retesting, and manufacturing criteria for lineman gloves. For HV vehicles the lineman gloves must meet Class “0” requirements of a rating of 1000 volts AC (Figure 1-10). Electrical protective gloves are categorized by the amount of voltage—both AC and DC—they have been proof-tested to. In addition, the technician should wear rubber-soled shoes, cotton clothing, and safety glasses with side shields as part of their personnel protective equipment. Remove all jewelry and make sure that metal zippers are not exposed. Always have a second set of isolating gloves available and let someone in the shop know their location. When preparing to work on any high-voltage vehicle, let associates know in the event they must come to your aid. OSHA regulations require that all insulating gloves must be electrically tested before first issue and retested every 6 months thereafter by a test laboratory. For this reason most shops will discard and replace gloves after 6 months. Any unused gloves after 12 months must be retested or discarded. The manufacturers and suppliers of insulating gloves can assist in providing test laboratory locations for retest certification of the glove if you prefer over replacement. It is recommended that gloves be stored out of direct sunlight and away 11 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 1-10  Insulated rubber isolation gloves rated Class “0” must be worn when working on high-voltage system.

from sources of ozone (i.e., electric motors). They should be stored in a glove bag flat, never folded, and hung up rather than laid down on a flat surface. WARNING: Do not use insulating gloves that have been used for over 6 month or are new in the package but older than 12 months unless they have been recertified by a licensed test laboratory. Perform a daily or prior to use safety inspection of insulating gloves before working on any HV vehicle. ■■

■■ ■■ ■■

Daily or prior to use safety inspection of rubber insulating gloves procedure includes: Visually inspect rubber gloves prior to use for cracks, tears, holes, signs of ozone damage, possible chemical contact, and signs of abrasion or after any situation that may have caused damage to the gloves. OSHA requires a glove air inflator test. Blow air into glove to inflate them and seal the opening by folding the base of the glove. Slowly role the base of the glove toward the fingers to increase the pressure (Figure 1-11).

FIGURE 1-11  Insulated rubber isolation must be tested for leaks before working on high-voltage system.

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FIGURE 1-12  The high-voltage service plug is generally located near the HV battery.

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Look and feel for pin holes on all surface sides. If a leak or damage is detected discard the glove. For extra precaution the glove should be rendered unusable (i.e., cut in half ).

High-Voltage Service Plug

The HEV is equipped with a high-voltage service plug that disconnects the HV battery from the system. Usually this plug is located near the battery (Figure 1-12). Prior to disconnecting the high-voltage service plug, the vehicle must be turned off. Some manufactures also require that the negative terminal of the auxiliary battery be disconnected. Once the high-voltage service plug is removed, the high-voltage circuit is shut off at the intermediate position of the HV battery. The high-voltage service plug assembly contains a safety interlock reed switch. The reed switch is opened when the clip on the high-voltage service plug is lifted. The open reed switch turns off power to the service main relay (SMR). The main fuse for the high-voltage circuit is inside the high-voltage service plug assembly. However, never assume that the high-voltage circuit is off. The removal of the highvoltage service plug does not disable the individual high-voltage batteries. Use a DMM to verify that 0 volts are in the system before beginning service. When testing the circuit for voltage, set the voltmeter to the 400 VDC scale. After the high-voltage service plug is removed, a minimum of five minutes must pass before beginning service on the system. This is required to discharge the high-voltage from the condenser in the inverter circuit. To install the high-voltage service plug, make sure that the lever is locked in the DOWN position (Figure 1-13 ). Slide the plug into the receptacle, and lock it in place by lifting the lever upward. Once it is locked in place, it closes the reed switch returning power to the system.

Safety in the Shop In general, the automotive air conditioning technician may be involved in all phases of automotive service, including electrical and mechanical repairs, relating to air conditioning malfunctions. Some of the common occupational safety and health problems found during walk-around surveys of typical service repair facilities include: ■■ Poor housekeeping: refuse and nonsalvageable materials not being removed at regular intervals; electrical cords and compressed-gas lines scattered on floors (Figure 1-14); and oily, greasy spots or water pools on floor areas.

Housekeeping is the systematic practice of maintaining an area in clean, safe working order and includes the proper storage of materials and chemicals.

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Battery case Lock Lever

FIGURE 1-13  The high-voltage service plug lever must be placed in the down and locked position after installation.

FIGURE 1-14  Keep electrical cords, gas lines, and air hoses off the floor of the work area.

All machine pulleys and belts should be guarded.

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Ineffective and, in many cases, nonexistent guard rails and toe-boards around open pit areas. Use of unsafe equipment, such as damaged creepers with missing crosspieces and broken wheels. The unsafe stacking of stock and other material. Failure to identify “safety” zones. Pulleys, gears, and the “point of operation” of equipment without effective barrier guards or other guarding devices or methods. Inadequate ventilation or unacceptable respirator programs for operations in confined spaces. Handling of resins, cements, oils, and solvents without protection, causing skin problems or dermatitis. Electrical hazards such as “U” ground prong missing from power tools (Figure 1-15); ungrounded extension cords and electrical equipment; and frayed, damaged, or misused power and extension cords.

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FIGURE 1-15  An unsafe male electrical plug.

Unsecured and improper storage of compressed-gas cylinders. Fire hazards caused by improper storage and use of flammable and combustible materials and the presence of various ignition sources. ■■ Improper lifting and material handling techniques. ■■ Unsafe work practices that could result in burns from hot-work operations such as ­welding, burning, and soldering. Although the above deficiencies cover some of the most significant problem areas, this list should not be considered exhaustive. ■■ ■■

OSHA OSHA was established in 1970 to ensure safe and healthful conditions for every American worker. The agency’s enforcement, educational, and partnership efforts are intended to reduce the number of occupational injuries, illnesses, and deaths in America’s workplaces. Since its inception, the workplace death rate has been cut in half. Still, about 17 Americans die on the job every day. OSHA is committed to a commonsense strategy of forming partnerships with employers and their employees. They conduct firm but fair inspections, develop easy-to-understand regulations, and eliminate unnecessary rules to assist employers in developing quality health and safety programs for their employees. State consultants, authorized and funded largely by OSHA, conduct consultation visits with employers who request assistance in establishing safety and health programs or in identifying and dealing with specific hazards at their workplaces. OSHA will also conduct unannounced inspections at work sites under its jurisdiction. An inspection is made when three or more workers are hospitalized because of injury or if a job-related death occurs. An inspection will also occur based on an employee complaint. Only half of their staff of about 2,200 are safety and health officers, so many inspections are handled by telephone and fax, often without the requirement for an on-site inspection. In 1996 and 1997, OSHA simplified the written text outlining its regulations by eliminating almost 1,000 pages and by putting over 600 other pages into plain English. Employers must post a full-sized 10 3 16 in. (254 3 406 mm) OSHA or state-approved poster, such as that shown in Figure 1-16, where required. This is generally in a “common” area where it will be seen by all employees. 15 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 1-16  OSHA poster in employees’ “common” area.

Health and Safety Program

Hazardous conditions or practices not covered in the standards promulgated by OSHA in 1970 are covered under the general duty clause of the act: “Each employer shall furnish to each employee a place of employment which is free from recognized hazards that are causing or are likely to cause death or serious physical harm.” A health and safety program is an effective method to help ensure a safe working environment. The purpose of such a program is to recognize, evaluate, and control hazards and potential hazards in the workplace. Hazards may be identified by: ■■ Performing self-inspections ■■ Soliciting employee input ■■ Interviews ■■ Suggestions ■■ Complaints ■■ Promptly investigating accidents ■■ Reviewing injury and illness records ■■ Other information sources Typical examples of hazards are: ■■ Unsafe walking surfaces ■■ Unguarded machinery ■■ Electrical hazards ■■ Improper lifting ■■ Air contaminants In the classroom, the instructor may assign students safety and health management responsibilities in the areas of both program development and implementation. Regular

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meetings and informal discussions should be held to discuss safety promotions and actual or potential hazards. To ensure program success, the participation and cooperation of all class members is essential. Leadership is also necessary. The students assigned the responsibility for carrying out the program must be delegated the proper authority and have the instructor’s support. All participants must be aware of the program activities through a systematic interchange of information. Students cannot take an interest in the program if they are unaware of what is occurring. Conversely, well-informed students will likely show interest and a desire to participate. In the learning as well as the work environment, persons may be exposed to excessive levels of a variety of harmful materials. These include: ■■ Gases ■■ Dusts ■■ Mists ■■ Vapors ■■ Fumes ■■ Certain liquids and solids ■■ Noise ■■ Heat or cold Of the illnesses reported, respiratory problems caused by dusts, fumes, and other toxic agents are the most prevalent. Often, health hazards are not recognized because materials used are identified only by trade names. A further complication arises from the fact that materials tend to contain mixtures of substances, making identification still more difficult. To begin identifying occupational health hazards, a materials analysis or product inventory should be made of which all hazardous substances are listed and evaluated. If the composition of a material cannot be determined, the information should be requested from the manufacturer or supplier who must provide an MSDS for its product. These sheets contain safety information about materials, such as toxicity levels, physical characteristics, protective equipment requirements, emergency procedures, and incompatibilities with other substances. A process analysis should be performed, noting all chemicals used and all products and byproducts formed. When doing such an analysis, allied activities such as maintenance and service operations should be included: ■■ Welding performed around chlorinated materials, such as R-12, may cause the formation of toxic gases in addition to welding fumes. ■■ Exhaust gases from cars and trucks with internal combustion engines contain CO. ■■ When certain cleaning agents are mixed, poisonous gases such as chlorine are sometimes formed. It should be noted that skin conditions such as chemical burns, skin rashes, and dermatitis constitute over half of all occupational health problems. The use of protective creams or lotions, proper personal protective clothing (Figure 1-17) and other protective equipment, and good personal hygiene practices can often prevent these problems. There are various control methods that can be used to prevent or reduce the technician’s exposure to air contaminants. They are as follows: ■■ Substituting less-toxic materials. ■■ Isolating or placing the potentially hazardous process in a separate room or in a corner of the building to reduce the number of technicians exposed. ■■ Ventilating, including local exhaust ventilation, where contamination is removed at the point of generation, and general mechanical ventilation. ■■ Limiting the total amount of time a technician may be exposed to a health hazard via administrative controls.

The law requires suppliers to furnish MSDS on request.

Toxic gases may be found around welding operations.

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FIGURE 1-17  Protective creams and lotions may be used when necessary.

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Training and educating technicians about the hazards to which they are to be exposed and how to reduce or limit that exposure (Right-to-know Laws training). See www.ccargreenlink.org for information on online training for schools. Practicing personal hygiene cannot be overemphasized. Technicians should wash their hands before eating. If chemicals such as caustic epoxies or resins come in contact with the skin, they should be washed off immediately. Avoiding eating around toxic chemicals or in contaminated areas. Changing clothing and washing them daily if they become contaminated with toxic chemicals, dusts, fumes, or liquids. Using personal protective equipment such as respirators, hearing protection devices ­(Figure 1-18), protective clothing, and latex gloves when appropriate.

General Philosophy.  A health and safety program helps identify unsafe acts or conditions in the workplace. For many of these, there may not be specific standards for rectifying the dangers they pose. Nevertheless, it is important to find a solution for these recognized problems.

FIGURE 1-18  Use personal hearing protection.

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During the analysis of the workplace for health and safety problems, it may also become apparent that “the letter of the law” is not being met. If it is apparent that the “intent” of the law is being met, instead of making changes, a variance may be requested from OSHA. The application for a variance must show it is “as effective as” the OSHA standards in ensuring a safe work environment. The decision not to make changes must be made only with the concurrence of OSHA. Even when a citation is issued, it is desirable that the employer have demonstrated the willingness to comply with the intent of the law by operating effective, ongoing safety and health programs, by correcting imminent dangers in the workplace, and by maintaining records of purchases, installations, and other compliance-promoting activities. Therefore, after an OSHA compliance visit and a citation, the employer can substantiate the intent to provide a safe and healthy workplace for employees by producing records that document that purpose and may be given the benefit of having shown “good faith,” which can serve to reduce penalties.

Technician Training

The following are suggestions that can help reduce unsafe acts and practices in the shop: ■■ Be constantly aware of all aspects of safety, particularly good housekeeping, and the ­elimination of slipping, tripping, and other such hazards. ■■ Be knowledgeable in the maintenance and operation of any special equipment. Do not attempt to use such equipment without first having been instructed in its proper use. ■■ Use appropriate personal protective and safety equipment, such as safety glasses ­(Figure 1-19) and, whenever necessary, respiratory apparatus. ■■ Develop and maintain check points to be observed as part of the standard and emergency procedures. ■■ Be knowledgeable in the proper use of portable fire extinguishers. Know where fire extinguishers are located. ■■ Know who is trained and responsible for emergency first aid treatment and the procedures for reporting an emergency. At least one technician should be trained in first aid on each shift at each site. ■■ The Coordinating Committee for Automotive Repair (CCAR) offers safety and pollution prevention training at www.SP2.org.

Safety glasses must be worn at all times.

FIGURE 1-19  Use personal eye protection.

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FIGURE 1-20  Remove the chuck key before turning on power to the drill press.

Safety Rules for Operating Power Tools The following rules apply to those who use and operate power tools. To ensure safe operation the technicians must: ■■ Know the application, limitations, and potential hazards of the tool used. ■■ Select the proper tool for the job. ■■ Remove chuck keys (Figure 1-20) and wrenches before turning the power on. ■■ Not use tools with frayed cords or loose or broken switches. ■■ Keep guards in place and in working order. ■■ Have electrical ground prongs in place (see Figure 1-10). ■■ Maintain working areas free of clutter. ■■ Keep alert to potential hazards in the working environment, such as damp locations or the presence of highly combustible materials. ■■ Dress properly to prevent loose clothing from becoming caught in moving parts. ■■ Tie back long hair or otherwise protect it from becoming caught in moving parts. ■■ Use safety glasses, dust or face masks, or other protective clothing and equipment when necessary. ■■ Do not surprise or distract anyone using a power tool.

Machine Guarding

It is generally recognized that machine guarding (Figure 1-21) is of the utmost importance in protecting the technician. In fact, it could be said that the degree to which machines are guarded in an establishment is a reflection of management’s interest in providing a safe workplace. A technician cannot always be relied on to act safely enough around machinery to avoid accidents. One’s physical, mental, or emotional state can affect the attention paid to safety while working. It follows that even a well-coordinated and highly trained technician may at times perform unsafe acts that can lead to injury and death. Therefore, machine guarding is important. Combustible material must be stored in special metal cabinets.

Good Housekeeping Helps Prevent Fires

Maintaining a clean and orderly workplace reduces the danger of fires. Rubbish should be disposed of regularly. If it is necessary to store combustible waste materials, a covered metal receptacle is required.

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FIGURE 1-21  Machine guarding is essential for safety.

Cleaning materials can create hazards. Combustible sweeping compounds such as oiltreated sawdust can be a fire hazard. Floor coatings containing low-flash-point solvents can be dangerous, especially near sources of ignition. All oily mops and rags must be stored in closed metal containers (Figure 1-22). The contents should be removed and disposed of at the end of each day. Some of the common causes of fires are: ■■ Electrical malfunctions ■■ Friction ■■ Open flames ■■ Sparks ■■ Hot surfaces ■■ Smoking

FIGURE 1-22  Oily rags are stored in metal containers approved for that purpose.

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FIGURE 1-23  Aisles should be identified for safety.

The proper housekeeping and safety policies can help reduce these fire hazards. It can also help to eliminate many tripping hazards.

Walking and Working Surfaces

All areas, passageways, storerooms, and maintenance shops must be maintained in a clean and orderly fashion and be kept as dry as possible. Spills should be cleaned up promptly. Floor areas must be kept clear of parts, tools, and other debris. Areas that are constantly wet should have nonslip surfaces where personnel normally walk or work. Every floor, working place, and passageway must be maintained free from protrusions such as nails, splinters, and loose boards. Where mechanical handling equipment is used, such as lift trucks, sufficient safe clearances must be provided for aisles at loading docks, through doorways, and wherever turns or passage must be made. Low obstructions that could create a hazard are not permitted in the aisle. All permanent aisles must be easily recognizable. Usually aisles are identified by painting or taping lines on the floors (Figure 1-23).

The Value and Techniques of Safety Sense Safety sense with tools pays off. The technician should think safety whenever applying a tool to the task. Some of the tips presented in this chapter may seem to be nothing more than common safety sense; they are included because technicians who overlook them are apt to be injured. Safety sense reminds the technician to protect against the possibility of something going wrong. Whenever tools are used, there is a risk of tools breaking or slipping. And there is also a risk that the part on which tools are used may break loose, too.

Bracing against a Backward Fall

Always pull on a wrench handle; never push on it. It is far easier to brace against a backward fall than against a sudden lunge forward should the tool slip or break. To brace against a backward fall when pulling on a wrench, place one foot well behind the other. WARNING: Never push a wrench. Have you ever pulled an open-end wrench right off the nut or bolt? This danger can be minimized by using a wrench of the proper size and by making sure that it is positioned so that the jaw opening faces in the direction of pull. 22 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Haste Makes Waste

A technician attempted to make a speedy adjustment to the shift linkage while the engine was running. When the technician lost control of his wrench, he was lucky to receive nothing more serious than a few bruises. Engines should be turned off when making adjustments whenever possible. There are, of course, adjustments that must be made with the engine running. The secret, then, is safety: Be safe. Take care. Take time. Haste makes waste.

Safety Accessories

Safety glasses are essential eye protection when metal strikes metal, such as in using punches and chisels, or when grinding metal tools or parts on a power grinder. Safety glasses are recommended for everyone working in a shop. In many situations, safety glasses and hard hats are required for anyone entering the premises.

Putting Safety Sense into Action ■■

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Make a thorough check of the toolbox. Discard all tools that do not meet minimum safety standards. Where necessary, replace them with quality tools. Investigate procurement standards to make certain that only professional-quality tools are purchased by your company. Instruct one technician or the tool room attendant in the repair of ratchets, screwdrivers, and other tools. Instruct technicians in the care of hand tools at a regular departmental safety meeting. Use bad-example tools picked from toolboxes to illustrate the hazards. Advise those using ratchets to bring them into the tool room at regular periods for service. Set up a small stock of repair parts for ratchets, screwdrivers, pliers, and other small tools with replaceable parts. Make spot checks for correct tool application. Review shop tooling to ensure that an adequate selection of tools is readily available for all jobs. This step is important to the elimination of makeshift tool procedures. Investigate tool applications involving moving machinery, and correct or minimize any hazards noted. Incorporate safety sense tips into tool safety education programs in departmental meetings.

Start a health and safety program in your shop.

Safe Use of Tools The proper use of tools is an important consideration for today’s technician. This notion may be divided into two major categories: 1. The use of safe tools. 2. The safe use of tools. The two go hand in hand, for without one, there cannot be the other. The formula for tool safety comprises the following three general rules: 1. Use safe tools. 2. Maintain tools in a safe condition. 3. Use the right tool for the task.

Use the proper tool. Do not use, for example, a metric tool on an English fastener.

Rule #1: Use Safe Tools

The safe use of tools and equipment is fundamental to any automotive technician safety program. The first step in any tool safety program is to upgrade tools to maintain minimum 23 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 1-24  Tools should fit intended applications.

safety standards. This requires inspecting all current tools on hand and replacing any that are defective or do not meet minimum quality standards. Quality Standards for Tools.  Tools that serve the automotive industry are put to rugged use. If they are to stand up, the tools must be designed and manufactured according to rigid quality standards. Some of the more important points for consideration when selecting tools include: ■■

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Tools should be made of alloy steel. Finer-grade alloys impart toughness to the metal used in the manufacture of tools. If a tool made of an alloy steel is inadvertently overloaded, it will deform before it will break, thus providing a warning to the user. Tools should be tempered by heat. Tool strength and lasting quality is enhanced by precision heat treatment of the metal. Tools should be machined accurately. If a tool is to fit the intended application accurately (Figure 1-24), without slip or binding, machining must be held to close tolerances. Tools should be designed for safety. Firm, safe tool control with a minimum of effort should be provided by a lightweight, balanced design. Design features should include those that prevent slipping or accidental separation of tool parts.

Unsafe Tools.  Identifying and discarding unsafe tools is an important part of developing the habit of tool safety. In addition to those tools that are easily recognized as below standard, broken, or otherwise damaged, you should avoid using homemade and reworked tools. Few repair facilities are equipped to work steel into tools suitable for high-leverage automotive repair applications. Homemade tools are therefore often heavy and awkward to handle. Lighter and stronger tools, for virtually any purpose, are commercially available and should replace all homemade relics. Grinding or otherwise reworking a tool to fit a particular application usually results in a tool that no longer measures up to safety requirements. Grinding a tool robs it of metal needed for strength. Heat created by grinding, bending, and brazing impairs the temper of the metal, which also weakens the tool. These tools, too, should be replaced. Light-Duty Tools.  There are many inexpensive tools (Figure 1-25) in the marketplace. Most are intended for amateur or do-it-yourself (DIY) mechanics or other light-duty applications. Examples include stamped or die-cast tools made of nonalloy carbon steel. These tools are not designed for professional use and are not suitable for general use in the automobile repair trade. 24 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 1-25  Light-duty tools are not intended for use in professional automotive shops.

Rule #2: Maintain Tools in a Safe Condition

When safe tools are used in the workplace, the next step is to keep them in safe condition. A routine inspection on a regular basis leads to repairing or replacing those tools that are worn or otherwise considered no longer safe. The following tips on specific tool care will help minimize the risk of personal injury due to tool failure. Ratchets.  Ratchets are mechanical devices and, as such, are subject to mechanical failure. Frequent causes of failure are worn parts and dirt. The results of failure are slippage, which in turn can lead to possible injury. To reduce the risk of ratchet failure, a program of preventive maintenance—cleaning and lubricating the ratchet mechanism—should be performed at least once every 6 months. Screwdrivers.  Screwdrivers with worn, chipped, or broken tips (Figure 1-26) are a potential menace to the technician who works with them. Such tools have little grip on the screw head and frequently jump the slot, leaving the technician open to injury.

Keep tools in good repair.

Use the proper screwdriver for the screw.

FIGURE 1-26  Damaged screwdrivers should be repaired or replaced.

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FIGURE 1-27  Grind down the flat surfaces.

CAUTION:

If excessive ­grinding is required, it is best to replace the screwdriver. Only the tip of the screwdriver is ­tempered, and excess grinding will remove the ­tempered area.

Regular inspection and replacement of screwdrivers is a must because of the performance expected of these tools. The following procedure can be used to repair screwdrivers with slightly worn or nicked tips: 1. Very lightly grind down the flat surfaces using the grinder. Avoid overheating and ­destroying the temper of the metal (Figure 1-27). The amount of material removed should be minor. “Quench” the tip in H2O every few seconds to keep it cool. 2. Square off the edges and the tip (Figure 1-28). 3. Test the tip for correct fit (Figure 1-29). 4. Use a file or an oil stone to remove burrs. Wrenches and Sockets.  Tools that show signs of “old age” are prime candidates for ­replacement. Because worn-out wrenches and sockets take only a partial “bite” on the corners of a nut, they are often likely to slip on a heavy pull.

FIGURE 1-28  Square off the edges and the tip.

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FIGURE 1-29  Test the tip for correct fit.

A regular inspection of the tool box for worn tools will prevent many mishaps. Look for: ■■ Open-end wrenches with battered, spread-out jaw openings. ■■ Sockets or “box-sockets” whose walls have been battered and rounded by use. ■■ Tools that have been abused, such as standard thin-wall (hand-use) sockets with lappedover metal around square drive opening (revealing their use on impact wrenches) and wrenches or handles bearing hammer marks. These tools should also be scrapped because hammer or impact shock leads to metal fatigue, which substantially weakens tools of this type. It is important, too, that dirt and grit are not caked inside sockets. Such debris may prevent the socket from seating fully on the nut or bolt head. This would concentrate the twisting force at the very end of the socket, possibly causing the socket to break even with a moderate pull.

Keep tools clean.

Other Tools.  Routine inspection of toolboxes will also uncover other unsafe tool conditions that could result in accidents: ■■ Hammers with cracked heads or handles ■■ Pliers with smoothly worn gripping sections ■■ Pliers with rivets or nut-and-bolt assemblies that have become sloppy Many hand tool accidents can be traced to poor housekeeping. Safety, as well as good workmanship, dictates that tools be properly stored and cleaned. A misplaced tool frequently is the cause of a technician’s tripping or being hit by a falling object. Tools should always be kept in tote trays, boxes, or chests when not being used. Tools with oily handles can be slippery and dangerous. Technicians should establish a habit of wiping off tools with a dry shop rag before starting each job or, better yet, before putting them away after use. With tools, as with everything else, good housekeeping makes good safety sense.

Rule #3: Use the Right Tool for the Task

Safe tools, in safe condition, are only half of the tool safety story. The other half rests with the technicians who use the tools. Every technician in the shop who works with tools should understand the type, size, and capacity of the tools they use. 27 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Hand tools are available in an endless assortment of types, styles, shapes, and sizes—­ perhaps over 5,000 in all. Each tool is designed to do a certain job quickly, safely, and easily. Here are three important considerations in selecting tools for a task: Type of Tool.  The safest tool is the tool that is specifically designed for the particular task. The use of makeshift tools just to “get by” is one of the major causes of hand tool accidents. Size and Shape of Tool.  The safest tool is one that fits the job squarely and snugly. Misuse can lead to the tool’s slipping or breaking. This can lead to injury. Capacity of Tool.  Every tool has a design safety limit. Exceeding the design limit can result in tool failure. The following sections look more carefully at specific tools commonly used in the workshop.

Wrenches and Socket Wrenches A combination wrench has a box on one end and is open on the other.

These are the safest tools for turning bolts. Some bolt-turning tools have definite safety advantages over others. Here is a list of tools suitable for bolt turning in order of preference: 1. Box-sockets and socket wrenches (Figure 1-30). These tools are preferred for bolt-turning jobs where a heavy pull is required and safety is a critical consideration. A socket or boxsocket completely encircles the hex nut or bolt and grips it securely at all six corners. It cannot slip off laterally, and there is no danger of springing jaws. 2. Open-end and flare-nut wrenches (Figure 1-31). Firm, strong jaws make open-end wrenches a very satisfactory tool for medium-duty bolt-turning work. Many technicians work with combination wrenches, using the open end to speed the nut on or off and the box end for breaking loose or final tightening. Flare-nut wrenches are recommended for those jobs where sockets or box-sockets cannot be used. Flare-nut wrenches are a “must” for use in servicing automotive air conditioning hoses. 3. Adjustable wrenches. The adjustable wrench, commonly referred to by its trade name, Crescent, is recommended only for light-duty applications where time is an important factor and the proper tool is not readily available. Adjustable wrenches (Figure 1-32) are prone to slip because of the difficulty encountered in setting the correct wrench size. They also have a tendency for the jaws to “work” as the wrench is being used. For these reasons, an adjustable wrench should not be considered

FIGURE 1-30  An assortment of sockets and drivers.

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A

B FIGURE 1-31  Flare-end (A) and open-end (B) wrenches.

A

B

C FIGURE 1-32  Adjustable wrenches: 10 in. (A), 8 in. (B), and 6 in. (C).

an all-purpose tool. Though often used for that purpose, pliers are not on the list of tools ­recommended for bolt turning. Overloading Wrenches and Socket Wrenches.  The “safety limit” of a wrench or socket wrench is determined by the length of its handle. Use of a pipe extension or other “cheater” to move a tightly rusted nut can overload the tool past its safety limit. When the tool being used cannot turn the nut, a heavier-duty tool is required. Both openend and box-socket wrenches are available in a heavy-duty series that can be safely used with tubular handles from 15 in. to 36 in. in length and can be substituted for a wrench that is too light for the job. Table 1-1 presents a breakdown of government minimum proof loads for ratchets and other socket wrench handles. These figures can be used as a guide for the safe use of socket wrenches. 29 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

TABLE 1-1:  MAXIMUM TORQUE LOAD FOR SOCKET WRENCHES Drive

Minimum Torque (in.-lb)

Proof Load (ft.lb)

Load Approximate Equivalent

¼ in.

450

37

Pulling 100 pounds at the end of a 4.5 in. handle

3

⁄8 in.

1,500

125

Pulling 200 pounds at the end of a 7.5 in. handle

½ in.

4,500

375

Pulling 200 pounds at the end of a 22.5 in. handle

¾ in.

9,500

792

Pulling 200 pounds at the end of a 47.5 in. handle

1 in.

17,000

1,417

Pulling 200 pounds at the end of a 85 in. handle

Use of Hammer with Wrenches.  Wrenches and socket wrench handles should never be used as hammers, nor should a hammer be used on these tools to break loose a tightly seized nut or bolt. Hammer abuse weakens the metal and can cause the tool to fail under a heavy load. Sometimes, however, hammer shock is the only cure for an extra stubborn nut or bolt. In such cases, here are the suggested tools to use: ■■ Sledge-type box-sockets. They have plenty of “beef and are especially tempered for use with a sledge hammer. ■■ Cupped-anvil box-sockets. These air-driven tools were developed to meet the requirements of heavy processing industries. ■■ Impact driver. This tool transmits a hammer blow into rotary shock. It is especially useful for smaller nuts and bolts and can also be used on screws. Use thick-wall ­sockets with an impact driver.

Sockets for Impact Use.  Sockets used with impact wrenches or impact drivers should be the thick-wall power type (Figure 1-33). Thin-wall chrome standard sockets designed for hand use will weaken under impact shock and are likely to fail on a high-leverage application. Impact abuse is one of the most frequent causes of socket failure. Selecting the Correct Size.  Selection of the correct wrench size is a necessary part of safe bolt-turning work. A wrench or socket one size too large will not grip the corners of the nut securely. The result can be a bad slip during a heavy pull. There is a correct wrench size available for virtually every nut or bolt made in the United States, Canada, Great Britain, and Europe. Wrench size is determined by measuring the nut or bolt head across the flats.

Use a six-point hex socket on worn nuts and bolts.

Danger of “Cocking.”  Sockets and box-sockets should also fit squarely. When these tools are “cocked,” they are likely to break even under a moderate load. This is due to “binding” that concentrates the entire strain at one point, rather than spreading it evenly over the tool. The point at which the strain is concentrated becomes vulnerable to failure.

A

B

FIGURE 1-33  Thin-wall chrome standard sockets (A) are not intended for impact use. A thick-wall socket (B) is used with an impact wrench.

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FIGURE 1-34  An open-end wrench should contact the entire flat surface.

Cocking is a frequent cause of tool failure. It can usually be avoided by using different arrangements of sockets, flex-sockets, and extensions, or by substituting box-sockets of different lengths and offsets. Selecting Open-End Wrenches.  For the most secure grip, open-end wrench jaws should contact the entire length of two flat surfaces of the nut or bolt head (Figure 1-34). When it is necessary to reach the fastening at extreme angles, there is a danger that the wrench will slide off. This can usually be avoided by the use of crowfoot, offset-head, or taper-head open-end wrenches. Correct Style of Socket or Box-Socket.  Here are some rules that govern the selection of the safest tool for the job: ■■ When turning a fitting where corners are rounded by wear or corrosion, single-hex sockets or box-sockets offer more protection because they grip a larger amount of the surface of the fitting. ■■ On square fittings, use a single-or double-square, not a double-hex. ■■ Where bolt clearance is a problem, avoid tool breakage by using deep, extra-length sockets. Special-Purpose Tools.  Many special-purpose tools are designed for jobs where a critical clearance problem exists and tool jaws or walls are extra thin. Examples are wrenches and sockets for removing and replacing air conditioning compressor clutch retaining nuts and bolts. These tools are plenty safe for the job intended but should not be used for general boltturning work. The usual result is overload and failure.

Pliers

Pliers (Figure 1-35) are often misused as general-purpose tools. Their use should be limited to gripping and cutting operations for which they were designed. Pliers are not recommended for bolt-turning work for two reasons: (1) because their jaws are flexible, they slip frequently when used for this purpose; and (2) they leave tool marks on the nut or bolt head, often rounding the corners so badly that it becomes extremely difficult to service the fittings in the future. Keep Pliers Jaws Parallel.  For a firm, safe grip with a minimum of effort, pliers jaws should be as nearly parallel as possible. Use of the right size pliers and proper positioning make this possible. 31 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 1-35  Typical pliers.

Avoid Overloading Cutting Pliers.  To avoid overloading the tool, the user should select the pliers that will cut a wire using the strength of only one hand. Another tip: The inside of the cutting jaws should point away from the user’s face to prevent injury from flying cuttings.

Screwdrivers Torx bit drivers are also referred to as star bits.

The screwdriver is not an all-purpose tool, although some attempt to use them as such in place of lining-up punches, chisels, and prybars. The usual result is a damaged tool and a possible injury. The use of screwdrivers should be limited to screw turning only. Correct Tool for Phillips Screws.  It is very common for those not familiar with tools to try to turn a Phillips screw with a standard tip screwdriver designed for use on slotted screw heads. They usually end up with the tool slipping off the job, a nicked screwdriver tip, and a hopelessly chewed-up fastener. Only a Phillips tip screwdriver (Figure 1-36) should be used on a Phillips screw. Phillips versus Reed and Prince.  The tools to turn these “look-alike” screws are not interchangeable (Figure 1-37). A screwdriver of one type will not seat properly in the other screw head.

FIGURE 1-36  A Phillips screwdriver is used with a Phillips screw.

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Keystone

Cabinet

Phillips

Torx ®

Clutch head

Hex head

Reed & Prince (Frearson)

Square recess

FIGURE 1-37  Typical screw head types.

TABLE 1-2:  PHILLIPS SCREWDRIVER SELECTION GUIDE Phillips

Machine Screw Diameter

Sheet-Metal Screw Diameter

1

#4 and smaller

#4

2

#5 to #10

#5 to #10

3

#12 to 5/6 in.

#12 to #14

4

3/8 in. and larger

Selecting the Right Size.  Selection of screwdriver tip size is an important factor in the safe use of these tools. An oversized tip will tend to jump from the slot. A screwdriver with an undersized tip is also likely to twist out. In either case, a slip of the tip can result in a trip to the first aid kit. Here is an easy rule to remember: Use the largest screwdriver that will fit snugly in the slot. The length of the tip should be the same as that of the slot. Table 1-2 may be used as a guide in determining which size Phillips should be used for a particular fastener. Lining Up with the Screw.  Screwdrivers should line up with the screw on which they are being used to provide sufficient contact between the tip and the screw head. To avoid an outof-line application, substitute a different length or an offset-type screwdriver.

Punches

There are several types of punches (Figure 1-38), each designed to do certain jobs properly and safely. Misuse often ends up in tool breakage. The jobs for which each punch tool was designed are: ■■ Starter or drift punch: For starting tightly jammed pins and bolts and for driving pins clear through a hole after they have been started. ■■ Pin punch: A speedy combination punch for starting and driving pins through holes, to be used only on light-duty jobs.

Use the correct size punch and chisel.

Correct Punch or Chisel Size.  The greatest tool life and safety will result from the selection of the chisel whose cutting edge is the same width or wider than the area to be cut. This avoids unnecessary strain on a small chisel trying to do a big job. When punches are used, the largest punch that will fit the job without binding should be used. Use of an undersized punch is apt to result in wedging the part being driven as well as tool failure.

Pullers

The puller is the only quick, easy, and safe tool for forcing a gear, wheel, pulley, or bearing off a shaft (Figure 1-39). Use of prybars or chisels often causes the part to cock on the shaft, making it even more difficult to remove. Also, with the wrong tools for the job, the 33 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

60°–70°

Center punch (showing included angle)

Starting punch

Pin punch

Aligning punch

Straight shank brass punch FIGURE 1-38  Typical punches.

Terms to Know Asbestos Carbon monoxide (CO) Hazards Housekeeping Material safety data sheet (MSDS) Occupational Safety and Health Administration (OSHA) Radiation Refrigerant Respirators Technician Ultraviolet (UV) Ventilation

FIGURE 1-39  A typical puller.

operator must exert a great deal of force that is difficult to control, thereby creating an unnecessary hazard. When a puller is used, the technician enjoys a mechanical advantage that reduces the amount of force required. Furthermore, the puller is so designed that the force that is used is always under control. Selecting the Correct Size.  Selection of the correct size puller can prevent serious accidents. Some important considerations are: ■■ The jaw capacity of the puller should be such that when the tool is applied to the job, the jaws press tightly against the part being pulled.

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■■

■■

■■

In pulling gears, the jaws should be wide enough to cover as many gear teeth as possible to minimize the danger of breakage. Use a puller with as large a pressure screw as possible, but avoid using one that is larger than the hole in the part that is to be pulled. Power capacity of pullers is stated in tons. To avoid the danger of overloading, it is best to use the largest capacity puller that will fit the job.

ASE-STYLE REVIEW QUESTIONS 1. Technician A says to lift heavy objects using the legs, not the back. Technician B says that one should get help when lifting heavy objects. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 2. Technician A says that ethylene glycol is essentially a nontoxic anti-freeze and hence is safer for children and animals. Technician B states that toxicologists report that propylene glycol inside the body is changed into a crystalline acid that attacks the kidneys. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 3. All of the following statements are true concerning high-voltage system safety, EXCEPT: A. Turn the power switch to the OFF position prior to performing a resistance check. B. Do not attempt to test or service the system for 5 minutes after the high-voltage service plug is removed. C. Test lineman gloves for damage and leaks prior to use. D. Disconnect the motor generators prior to turning the ignition off. 4. Technician A says that exhaust gases from internal combustion engines contain carbon monoxide gas. Technician B says that exhaust gases from internal combustion engines contain phosgene gas. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

5. The shop’s safety program is being discussed. Technician A says that the program will be ineffective if the technician does not work with care. Technician B says that the program will be ineffective if the rules are not observed. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 6. Tool quality is being discussed. Technician A says that mechanics’ tools should be made of alloy steel. Technician B says that mechanics’ tools should be tempered. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 7. Technician A says that an OSHA is a state agency responsible for Occupational Standards for Heating and Air Conditioning. Technician B says that an OSHA poster must be displayed in the employees’ common area, such as the break room. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 8. Technician A says the wire harness, terminals, and connectors of the high-voltage system are identified by red. Technician B says to remove the service plug prior to disconnecting or reconnecting any HV connections or components. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

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9. Technician A says that a flare nut wrench may be used on a flare nut. Technician B says that an open-end wrench may be used on a flare nut. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

10. Technician A says that placing one foot behind the other braces oneself against a fall if the wrench slips while pulling. Technician B says that placing one foot in front of the other braces oneself if the wrench slips while pushing. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

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JOB SHEET

1

Name ______________________________________ Date _________________________

Personnel and Shop Safety Assessment As a service professional, one of your first concerns should be safety. Upon completion of this job sheet you should have an increased awareness of personnel and shop safety. As you take this personnel assessment and survey your shop answering the following questions, you will learn to evaluate your workplace and personnel safety. Procedure Always wear eye protection when working or walking around a service facility. 1. Before you evaluate your work place you must first evaluate yourself. Are you dressed for work?   ∙ YES   ∙ NO a. If yes, why do you believe your attire is appropriate?  b.  If no, what must you correct to be properly attired?  2. Are your safety glasses OSHA approved?   ∙ YES   ∙ NO a.  Do you have side shields?   ∙ YES   ∙ NO 3. Are you wearing leather boots or shoes with oil resistant soles?   ∙ YES   ∙ NO a.  Does your footwear have steel toes?   ∙ YES   ∙ NO 4. Is your shirt tucked into your pants?   ∙ YES   ∙ NO 5. If you have long hair is it tied back or under a hat?   ∙ YES   ∙ NO Next carefully inspect your shop, noting any potential hazards. Note: A hazard is not necessarily a safety violation but in an area of which you must be aware (i.e., pothole in parking lot). 6. Are there safety areas marked around grinders and other machinery? ∙ YES   ∙ NO 7. What is the air pressure in the shop set at?  8. Where are the tools stored in the shop?  9. What recommendations would you make to improve the tool storage? 

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10. Have you been instructed on proper use of the shop vehicle hoist (lift)?   ∙ YES   ∙ NO a.  If not ask your instructor to demonstrate vehicle lift use. 11. Where is the first aid kit located?  12. Where is the eye wash station located?  13. List the location of the exits.  14. What is the emergency evacuation plan and where are you to assemble once you ­evacuate the building? 

15. Where are the MSDSs located?  16. Does the shop have a hazardous spill response kit?   ∙ YES   ∙ NO

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2

JOB SHEET Name ______________________________________ Date _________________________

Compare and Identify Safe and Unsafe Tools Upon completion of this job sheet, you should be able to identify unsafe tools. Tools and Materials Miscellaneous and assorted hand tools Procedure Lay out the tools and separate them into two groups—safe and unsafe. Briefly describe and inventory the tools as follows: 1. Screwdrivers

SAFE

UNSAFE

WHY (UNSAFE)

_________

_________

_________

2. Pliers

_________

_________

_________

3. Open-end wrench

_________

_________

_________

4. Box-end wrench

_________

_________

_________

5. Punch/chisel

_________

_________

_________

6. Hammer

_________

_________

_________

7. Socket wrench

_________

_________

_________

8. Snapring tools

_________

_________

_________

9. * _________

_________

_________

_________

10. * _________

_________

_________

_________



TOOL

* Other (describe) _______________ What can the results be of using an unsafe tool such as a: 11. Hammer?  12. Screwdriver?  13. Pliers?  14. Wrench:  Open-end?  Box-end?  Socket?  15. Punch or chisel?  39 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Instructor’s Response _____________________________________________________________

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JOB SHEET

3

Name ______________________________________ Date _________________________

The Need for Health and Safety Upon completion of this job sheet, you should be capable of participating in a health and safety program. Tools and Materials None required Procedure Briefly describe your plan to eliminate or avoid the following health and safety hazards: 1. Engine exhaust fumes.  2. Caustic chemicals.  3. Liquid refrigerant.  4. Hot engine parts.  5. Cooling fan start without notice.  6. Coolant boilover.  7. Oil spill on floor.  8. A discharged fire extinguisher.  9. Spontaneous combustion.  10. Electrical shock. 

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Instructor’s Response 

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JOB SHEET

4

Name ______________________________________ Date _________________________

Identify and Correct Hazardous Conditions Upon completion of this job sheet, you should be able to identify hazardous conditions and to make recommendations for correction. Tools and Materials None required Procedure Inspect your work area, identify five hazardous or potentially hazardous conditions, and briefly describe your plan to prevent or eliminate them. 1.  2.  3.  4.  5.  Inspect adjoining areas, identify five hazardous or potentially hazardous conditions, and briefly describe your plan to prevent or eliminate them. 6.  7.  8.  9.  10. 

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Instructor’s Response 

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Chapter 2

Typical Shop Procedures and Tools Upon Completion and Review of this Chapter, you should be able to: ■■

■■

Identify the responsibilities of the employer and employee.

■■

Identify required and alternative services and the special tools required.

■■

Discuss how to use and interpret service information procedures and specifications. Compare the English and metric system of measurement as related to automotive technologies.

Shop Rules and Regulations There are many rules and regulations that are imposed in an automotive repair facility. Some have to do with the Occupational and Safety Health Administration (OSHA), safety of the customer or technician, and fire and local ordinances; others are at the discretion of management. In any event, it is expected that everyone associated with the facility will help ensure that all rules and regulations are followed. For example, it is generally posted that customers are not permitted in the service area (Figure 2-1). Reasons given include insurance requirements, fire codes, or local ordinances. The real reason, some feel, is that customers simply get in the way, ask foolish questions, and slow down production. Understandably, the average customer does not have a knowledge of the operation of an automobile and, much less, the routine procedures associated with an automotive repair facility. The actual reason, then, is for customer safety.

CAUTION AUTHORIZED PERSONNEL ONLY Service Bays Are A Safety Area. Eye Protection Is Required At All Times. Insurance regulations prohibit customers in the service bay area during work hours. We suggest you check out our everyday low prices until your technician has completed the work on your car. Thank you for your cooperation. FIGURE 2-1  Rules and regulations are posted to provide for safety.

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Employee–Employer Relationship Facilities are environments created and equipped to service a particular function, such as a specialty garage used to service motor vehicles. Hygiene refers to a system of rules and principles intended to promote and preserve health.

OSHA-required “Right-To-Know” Law should be posted. Available positions should be posted.

It is very important that a good rapport exists between the technician and those for whom he or she works. This is known as employer–employee (facility owner or representativestechnician) relationship. Note that the word representatives is plural. That means that the beginning technician may have to be accountable to and answer to several supervisors. Many look at this as a great advantage, for after finishing formal training, the real learning experiences begin—on the job. Employer–employee relationships are a two-way street. There are certain assumed obligations of both parties. Having a good understanding of these obligations eliminates any problems that may arise relating to what you may expect or what your employer may expect of you.

Work Area

First, and perhaps foremost, you are entitled to a clean, safe place to work (Figure 2-2). There should be facilities for your personal hygiene and accommodations for any handicap that you may have.

Opportunity

The work environment should provide you an opportunity to successfully advance. This could be in the form of in-house training or an incentive to further your studies in vocational education programs. Today, it is desirable for a technician to obtain a 2-year Associate of Science degree in automotive technology. This can be a general (generic) program or it could be manufacturer-specific such as the General Motors Automotive Service Education Program (ASEP). Others, such as Chrysler, Honda, Ford, and Toyota, have similar programs. Opportunity includes fair treatment. This means that all technicians must be considered and treated equally without prejudice or favoritism.

Supervision

There should be a competent and qualified supervising technician who can lead you in the right direction if you have problems, suggest alternative methods, and tell you when you are correct.

Wages and Benefits

There are other aspects of your employment, other than how much you will be paid, that should be known. For example, how often and on what day are you paid? Is it company policy to hold back pay? If you are being paid a commission, do you have a guarantee? What are the

FIGURE 2-2  The service bay area should be well organized.

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fringe benefits? If there is a health plan, what is the employee’s contribution, if any? Is there a waiting period before being eligible? Does the company have a tool purchase plan? If there is a paid vacation plan, find out the details; generally, 1 week is given after 1 year and 2 weeks after 3 years or more. And, finally, while it does not seem important now, is there a retirement plan? If so, get the details; if not, it is time to consider a personal plan for the future.

Employee Obligations

There are also employee obligations. They are really more simple than employer obligations, for all you have to do is be a caring, loyal employee. This probably begins with your ability to follow directions (Figure 2-3). Remember, you are being paid to follow instructions. Doing it your way may not be in the best interest of the employer. If you have any questions or any doubts, ask. “I didn’t know what you meant” is not a good response after something is botched.

Fringe benefits are the extra benefits aside from salary that an employee may expect, such as vacation, sick leave, insurance, or employee discounts.

Attitude.  Proceed with a positive attitude. Your attitude can have an effect on your fellow technicians as well as your supervisors. Saying, “That’s not the way we did it in school” does not portray a positive attitude. Responsibility.  Be responsible and take pride in your work. Regardless of the task assignment, remember that someone has to sweep the floor—it may be you. Never forget that your primary responsibility is to make your employer a profit. Always be busy and productive. Be willing to learn and take advice from the senior technicians. You may be surprised how little time it takes to become one of their peers. Dependability.  Be dependable. Repair orders for the following day are often scheduled in advance. Habitual lateness or absenteeism cannot be tolerated. Pride.  Remember, the most important technician in that facility is you, and you work for the most important and best company in town—perhaps anywhere. Failure to adhere to these four basic ideals will affect your long-term success and could result in termination of employment.

Take pride in everything you do and be dependable.

FIGURE 2-3  Listen to and follow the directions of your supervising master technician.

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Service Tools Manifold and gauge set is a manifold block complete with gauges and charging hoses. A can tap is a device used to pierce, dispense, and seal small cans of refrigerant.

Special tools are needed to perform service, testing, and many repair procedures on most automotive air-conditioning systems. In addition to common mechanics’ hand tools, such as pliers, screwdrivers, wrenches, and socket sets, you will need a manifold and gauge set with hoses, a refrigerant can tap, a thermometer, and safety glasses or other suitable eye protection. In addition to the technicians’ tools, the shop must have the required refrigerant recovery, recycle, and recharge systems for all refrigerant types serviced at their service facility in order to perform refrigerant service. The Society of Automotive Engineers (SAE) has set standards for recovering and recycling refrigerant, and the Environmental Protection Agency (EPA) has acknowledged these standards in Section 609 of the Clean Air Act. Other equipment the shop may supply includes antifreeze recovery, recycle, and recharge systems; electronic scales; electronic leak detectors; and electronic thermometer. With the proliferation of alternative blends of refrigerants, a refrigerant gas electronic purity identifier should also be considered a necessary piece of equipment to avoid contamination of service equipment.

Manifold and Gauge Set SERVICE TIP:

You will encounter many new tools while learning to service today’s airconditioning systems. It is important that you first familiarize yourself with how to use these new tools before you attempt a service procedure. The first step is to always read thoroughly the directions that accompany any service tool; in the long run, this will save you time, money, and aggravation.

The manifold and gauge set (Figure 2-4) generally consists of a manifold with two hand valves and two gauges, a compound gauge and a pressure gauge, and three hoses. There are several types of manifold and gauge sets. Regardless of the type, they all serve the same purpose. Note that the manifold has fittings for the connection of three hoses. The hose on the left, below the compound gauge, is the low-side hose. On the right, below the pressure gauge, is the high-side hose. The center hose is used for system service, such as for evacuating and charging (see Chapter 5). Some manifolds may be equipped with two center hoses: a small hose, generally 1 4 in. or 6 mm, for refrigerant recovery and charging; and a large hose, generally 5 16 in. or 8 mm, for evacuation. Regardless of the type selected, a separate and complete manifold and gauge set with appropriate service hoses having unique fittings are required for each type of refrigerant that

Dedicated manifold and gauge sets with hoses must be provided for each of the two types of refrigerant currently used for automotive air conditioning service.

FIGURE 2-4  The manifold and gauge set.

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is to be handled in the service facility. This means that a shop may need four sets: one set for R-12(CFC-12) refrigerant, one set for R-134a(HFC-134a) refrigerant, one set for R-1234yf (HFO-1234yf ) refrigerant, and a set for contaminated refrigerant. Low-Side Gauge.  The low-side gauge, also referred to as the compound gauge, will indicate either a vacuum or pressure (Figure 2-5). Generally, this gauge will be calibrated from 30 in. Hg (0 kPa absolute) vacuum to 250 psig (1,724 kPa) pressure. Actually, the pressure calibration is to 150 psig (1,035 kPa) with respect to 250 psig (1,724 kPa) maximum. That means that pressures to 150 psig (1,035 kPa) may be read with reasonable accuracy, while pressures to 250 psig (1,724 kPa) may be applied without damage to the gauge movement. The low-side gauge is found at the left of the manifold. Pressure Gauge.  The high-side gauge (Figure 2-6) is usually calibrated from 0 psig (0 kPa) to 500 psig (3,448 kPa). Insomuch as the high side of the system will never go into a vacuum, pressures below 0 psig (0 kPa) are not indicated on the high-side gauge. The high-side gauge is also often referred to as the pressure gauge. The high-side gauge is found at the right of the manifold and is identifiable by a red housing. The Manifold.  Note the “circuits” in the manifold. When both hand valves are closed (Figure 2-7), both the low- and high-side hose ports are connected only to the low- and highside gauges. If, in this case, the hoses are connected from the manifold to an air-conditioning system, the low-side gauge will indicate the pressure on the low side of the system. The highside gauge will indicate the pressure on the high side of the system. The gauges will always show respective system pressures when the manifold hand valves are closed. If either the low- or high-side manifold hand valve is cracked open and the center hose is not connected to anything, refrigerant will escape from the system. This is a procedure known as purging. If the center utility hose is connected to a recovery station or other closed system and the low-side or high-side manifold hand valve is opened, both gauges will still indicate system pressure. If, however, both manifold hand valves are cracked, the pressures will equalize in the manifold and neither of the gauges will accurately indicate system pressure. The center hose is used to evacuate, recover, or charge the air-conditioning system. Procedures for this service and system problems relating to gauge pressure indications are given in Chapter 6 of this manual as well as the classroom text.

The low-side gauge is the left-side gauge on the manifold used to read refrigerant pressure in the low side of the system and is identifiable by a blue housing. The high-side gauge is the right-side gauge on the manifold used to read refrigerant pressure in the high side of the system.

SERVICE TIP:

The hand valves should be closed finger tight; excessive force will damage the valve seat. The hand valves should only be open to either add or remove something from the system. Never open the highside valve while the vehicle is running.

FIGURE 2-5  The low-side (compound) gauge.

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FIGURE 2-6  The high-side (pressure) gauge.

Low-side (blue)

High-side (red)

FIGURE 2-7  Manifold circuit with both hand valves closed.

Can Tap

The can tap is used to dispense refrigerant from a “pound” can. The true 1-pound can of refrigerant has not been produced since the late 1960s. “Pound” disposable cans actually contain 12 oz. (340 g) or 14 oz. (397 g) of refrigerant today. Disposable can taps can be flat top or the more popular HFC-134a screw top (Figure 2-8). Small refrigerant cans are also available with a dye charge to aid leak detection. The screw-top tap may also be used for single-charge cans of refrigerant oil. Some can taps are designed to fit either type. To install the can tap on either flattop or screw-top cans using a universal-type can tap, proceed as follows: 1. Wear suitable eye protection. 2. Hold the can at arm’s length, in an upright position. 3. Affix the clamp-type fixture on the can top. 50 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 2-8  Typical can taps with “pound” cans of refrigerant.

4. Turn the can tap handle fully counterclockwise (ccw). 5. Screw the handle assembly into the clamp fixture. When ready to dispense refrigerant as outlined in Chapter 6, turn the can tap handle fully clockwise (cw). This pierces the can. The can tap should not be removed until the contents of the can have been dispensed. It should be noted that small “pound” cans of refrigerant are not legally sold in some states. Other state requirements limit sales of small containers of refrigerant to certified and properly licensed shops and technicians only.

Safety Glasses

There are several types of safety glasses available (Figure 2-9). A safety shield-type goggle may be used with or without eyeglasses. It is important to note that the glasses or goggles selected be a type that is approved for working with liquids or gases, meeting the ANSI Z87.1-1989 standard.

Manufacturers’ specifications must be used. A service procedure for a 2006 Silverado, for example, may be different from a 2012 Silverado.

A

C

B

FIGURE 2-9  Typical safety glasses and goggles: face shield (A), goggle (B) and safety glasses with side shield (C).

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While removing an air-conditioning system compressor not long ago, a technician accidentally allowed an open-end wrench to come into contact with the battery terminals. The resulting short caused a spark, which, in turn, caused the battery to explode. The technician was wearing safety goggles to keep his prescription glasses in place; he never thought that they might serve an even more important purpose. Although he suffered facial burns, his eyes were protected by the safety goggles. Wearing prescription glasses alone would have offered very little protection since they generally have no peripheral shielding.

Hand Tools Common hand tools, such as wrenches, pliers, screwdrivers, punches, and hammers, are necessary. Other tools, such as a 3 8 -inch drive socket set, are helpful but not a necessity. Many of the hand tools referred to throughout this text may be found around the house. If not, it is suggested that they only be purchased as needed. It is not necessary, for example, to purchase a complete set if only a few sizes are needed.

Special Tools A vacuum pump is a mechanical device used to evacuate the refrigeration system to rid it of excess moisture and air.

Basically, three special tools will expand your service and repair capabilities considerably. It is helpful to have a thermometer, a leak detector, and a vacuum pump.

Thermometer

A glass-type or a dial-type thermometer may be used. The glass type is usually less expensive, but it is more easily broken. Regardless of the type, it is suggested that the temperature range be from 08F to 2208F (217.88C to 104.48C) (Figure 2-10). Inexpensive thermometers purchased in housewares or automotive departments in large department stores may not be as accurate as a refrigeration thermometer. For this reason, they are not recommended. For more accurate and reliable service, an electronic digital thermometer is recommended.

Leak Detector

In most cases, leaks can be detected by the use of a soap solution. A good dishwashing liquid mixed with an equal amount of clean water and applied with a small brush will indicate a leak by bubbling. A commercially available product, such as “Leak Finder,” can also be used.

C

A

B

FIGURE 2-10  Typical thermometers: digital pocket thermometer (A), dial pocket thermometer (B), and infrared electronic thermometer (C).

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Electronic.  Though considerably more expensive, electronic leak detectors, called halogen leak detectors, are desirable because they offer great sensitivity and can pinpoint a leak as slight as 0.15 (4 g) per year. It should be noted that halogen leak detectors are available that can be used to test either R-12 (CFC-12) R-134a (HFC-134a), or R-1234yf (HFO-1234yf ) refrigerants (Figure 2-11). When refrigerant vapor enters a halogen leak detector’s search probe, the device emits an audible or visual signal. Fluorescent.  Fluorescent leak detectors (Figure 2-12) are becoming increasingly more popular. A fluorescent dye is injected into the system where it remains without affecting cooling performance. When a leak is suspected, an ultraviolet lamp will quickly and efficiently pinpoint the problem area. Many manufacturers now use refrigerant containing a fluorescent dye for the initial charge of the air-conditioning system. Nitrogen.  If time permits, many technicians prefer to hold a standing pressure test using nitrogen to determine the integrity of an air-conditioning system after extensive leak repairs have been made. This test is especially helpful if the leak was difficult to locate. It provides added assurance that the leak was located and repaired.

FIGURE 2-11  A typical electronic leak detector.

FIGURE 2-12  A typical fluorescent leak detector.

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WARNING: Nitrogen is under very high pressure. Make no attempt to disperse nitrogen without having proper pressure regulators in place. Take care of the special tools and equipment provided by the service facility. Treat them like they were your own.

To perform this test, the air-conditioning system is evacuated and then pressurized to 100 psig (689.5 kPa) and allowed to “rest” overnight. Since the nitrogen is dry and stable, the pressure should be within a few pounds (kiloPascals) of 100 psig (689.5 kPa) the following morning. Nitrogen poses no threat to the environment and may be purged from the air-conditioning system to the atmosphere. The air-conditioning system is then evacuated to remove any residual nitrogen and air from the system.

WARNING: A halogen leak detector must not be used in a space where explosives, such as gases, dust, or vapor, are present. Use halogen leak detectors in a well-ventilated area only. By-products of decomposing CFC and HCFC refrigerants, hydrochloric and hydrofluoric acid, are a health hazard.

WARNING: Take care not to inhale these fumes. To minimize the danger, work in a well-ventilated area when leak checking an air-conditioning system.

Vacuum Pump

It is necessary to remove as much moisture and air from the system as possible before charging it with refrigerant. This is best accomplished with the use of a vacuum pump (Figure 2-13). The vacuum pump is one of the most expensive pieces of service equipment required. It is usually provided by the service facility. Some refrigerant recovery equipment has a vacuum pump incorporated into the equipment. High-volume service facilities, however, cannot generally tie up an expensive piece of equipment for the time required to adequately evacuate an automotive air-conditioning system. So, many service technicians will purchase a stand-alone electric or compressed-airoperated vacuum pump. The shop air-powered vacuum pump is a low-cost option that many

FIGURE 2-13  A typical high-vacuum pump.

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technicians choose to increase their productivity and free the recovery/recycle machine for another vehicle in the shop.

Refrigerant Identifier To determine what type refrigerant is in a system, a refrigerant identifier (Figure 2-14), should be used prior to servicing the refrigeration system of any vehicle. The refrigerant identifier is used to identify the purity and quality of a gas sample taken directly from a refrigeration system or a refrigerant storage container. The identifier, such as Rotunda’s Refrigerant Analyzer, will display: ■■ R-12: If the refrigerant is CFC-12 and its purity is better than 98 percent by weight. ■■ R-134a: If the refrigerant is HFC-134a and its purity is 98 percent or better by weight. ■■ FAIL: If neither CFC-12 nor HFC-134a have been identified or if it is not at least 98 percent pure. ■■ HC: If the gas sample contains hydrocarbon, a flammable material. A horn will also sound. R-1234yf refrigerant identification equipment must meet SAE standard J2912. Equipment that meets this standard can be used to identify both R-134a and R-1234yf. An R-1234yf refrigerant recover/recycle/recharge machine may also have a built-in identifier that must meet J2927. After the analysis is completed, the identifier will automatically purge the sampled gas and be ready for the next sample for analysis. If the correct refrigerant—R-12, R-134a, or R-1234yf—that should be in the system has not been identified or is not at least 98 percent pure, consider the refrigeration system to be contaminated and perform all service accordingly. It is important to always refer to the equipment manufacturers’ instructions for specific and proper tool usage and to specific local regulations relating to refrigerant handling. WARNING: If the sample reveals that the refrigeration system contains a flammable hydrocarbon, do not service the system unless extreme care is taken to avoid personal injury.

FIGURE 2-14  A typical refrigerant identifier.

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The high cost of the equipment required for removal and storage, as well as the proper disposal of contaminated refrigerant, often discourages the customer from having repairs made. There are not many sites in the United States that dispose of contaminated refrigerants. Disposal is usually accomplished by burning at a very high temperature and it requires expensive equipment. For more information about contaminated refrigerant disposal on a local level, check with the local automotive refrigerant supplier. If they can offer no assistance, and often they cannot, consult a major commercial refrigeration supply house.

Other Special Tools Other special tools available to the service technician are generally supplied by the service facility. These tools include a refrigerant recovery and recycling system, an antifreeze recovery and recycling system, an electronic thermometer, and an electronic scale. Also, special testers are available for automatic temperature control (ATC) testing, and special tools are available for servicing and repairing compressors. The following is a brief description of these tools. They are covered in more detail in the appropriate chapters of both the classroom text and shop manual.

Refrigerant Recovery and Recycle System

The service center must have a recovery, recycle, and recharge machine for each type refrigerant to be serviced. To address the issue of small capacity refrigerant systems, the EPA adopted SAE standard J2788, effective December 2007, covering the accuracy level of refrigerant recovery, recycling, and recharging equipment produced after that date. Standard J2788 supersedes the previous standard J2210. Refrigerant recovery, recycling, and recharging equipment must now be certified J2788 compliant. A modification to the SAE standard is J2788H, which is acceptable for use on high-voltage electric air conditioning compressors and is designed to avoid refrigerant oil cross contamination. This equipment must be capable of measuring and displaying the amount of refrigerant recovered to an accuracy level of 1/2 1 oz. When recharging a refrigerant system with an SAE J2788 compliant machine, it must charge a system with 1/2 0.5 oz of accuracy. It should be noted that refrigerant service equipment built prior to the SAE J2788 standard taking effect may have displays down to a tenth of a pound but this does not mean that they are accurate to a tenth of a pound. Always consult the specific specifications information for the model and manufacturer of the equipment you are using, especially if it was manufactured prior to 2008. With the addition of R-1234yf refrigerant, the SAE developed standard J2843 for recovery/recycling/recharge equipment. The refrigerant equipment for R-1234yf not only meets the same stringent charging and recover requirements as the R-134a J2788 systems but also includes the mandatory use of a refrigerant identifier prior to recovery of refrigerant. Even a minor error in refrigerant charge level (weight) can affect air conditioning system performance. This is particularly true of small capacity systems, those under 1.5 lbs of refrigerant. Air conditioning systems today are smaller than ever before, more efficient and still offer outstanding performance. In addition, systems manufactured today are much less susceptible to leaks and can go five years or longer on the original factory charge. Some refrigerant recovery, recycle, and recharge machines, however, may be used for both CFC-12 and HFC-134a. A system, similar to the one shown in Figure 2-15, is a single-pass system with an onboard microprocessor that controls the evacuation time as well as the amount of refrigerant charged into the system. The mixing of CFC-12 and HFC-134a refrigerants is prevented by the use of a sliding lock-out panel allowing only one set of manifold hoses to be connected at any time. Also, the fittings on the hoses prevent them from being connected to the wrong port. Each type of refrigerant has a separate dedicated set of hoses and recovery tank. A self-clearing loop removes residual refrigerant from the machine before connecting the other set of hoses and recovery tank. 56 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 2-15  A typical refrigerant recovery/recycle machine.

Having made an initial pass through the filter-drier on its way to the recovery tank, the recovered refrigerant in the tank is always clean and ready to reuse. The refrigerant is then recirculated through the filter-drier during evacuation to provide the cleanest possible refrigerant with no extra time or procedures involved. Other desirable features of a recovery, recycle, and recharge system include an automatic air purge, a high-performance vacuum pump, and an automatic shut-off when the tank is full.

Antifreeze Recovery and Recycle System

An antifreeze recovery and recycle machine, such as Prestone’s ProClean Plus™ Recycler (Figure 2-16), is a self-contained system that drains, fills, flushes, and pressure tests the cooling system. It can also be used to recycle coolant. A typical cooling system drain, recycle, and refill takes about 20 minutes. This particular system adds additives during the recycle phase to bond heavy metals, such as lead (Pb) and other contaminants. This renders them into nonleachable solids that are not hazardous as defined by the EPA. Additives separate the contaminants so they can easily be removed. Also, inhibitors are added to protect against corrosion and acid formation. The recycled coolant exceeds ASTM and SAE performance standards for new antifreeze. This eliminates the problems of waste disposal such as costs and the necessity of storing and hauling used coolant. Other onboard functions of the illustrated machine include standard coolant exchange, flushing procedures, pressure testing for leaks, and vacuum fill for adding coolant to an empty system. Its tank-within-a-tank design holds 40 gallons of used coolant for recycling in the inner section, and up to 60 gallons of recycled coolant in the outer section.

Electronic Thermometer

A single- or two-probe, handheld electronic thermometer, such as shown in Figure 2-17, is commonly used in automotive air-conditioning system diagnosis and service. The two-probe model is used to quickly and accurately measure superheat as required for critically charging some HFC-134a air-conditioning systems. The range for most battery-powered digital electronic thermometers is generally on the order of 2508F to 2,0008F (2468C to 1,0938C), and they have an accuracy greater than 60.3 percent with a switchable resolution of 1.0 to 0.1 degree in either the 8C or 8F scale. 57 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 2-16  A typical antifreeze recovery/recycle machine.

FIGURE 2-17  A typical electronic thermometer.

The desirable effective operating range for a thermometer for automotive air-conditioning system use is 328F (08C) to 1208F (48.98C). The digital readout for a handheld electronic thermometer should be no less than 1 2 in. (12.7 mm) for easy reading.

Electronic Scale

An electronic scale (Figure 2-18) may be used for CFC-12 or HFC-134a refrigerants to deliver an accurate charge by weight, manually or automatically. Automatic charging is generally accomplished by programming the amount of refrigerant to be charged into the onboard 58 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 2-18  A typical electronic scale.

solid-state microprocessor. The charge is stopped, and an audible tone signals that the programmed weight has been dispersed. A liquid crystal display is used to keep track of refrigerant dispersed. Some models have a switchable pounds/kilograms readout with a resolution of 0.05 lb. (0.02 kg). The 10 in. (2.5 cm) scale platform will handle up to a 50 lb. (23 kg) bulk tank of refrigerant and is equipped with control panel fittings and two hoses to accommodate both CFC-12 and HFC-134a refrigerants.

Automatic Temperature Control (ATC) Testers (Scan Tool)

There are many different types of testers available. The scan tool (Figure 2-19) is very popular and is used to enhance troubleshooting efforts to quickly locate the root of a problem. They are available in a wide variety of brands, prices, and capabilities. One good feature is that not only can a scan tool be used to retrieve trouble codes, some allow the technician to monitor and view sensor and computer information. This feature, known as serial data or the data stream, helps to pinpoint a heating, ventilation, or air conditioning (HVAC) problem. A scan tool can sometimes even take the role of a manifold and gauge set by obtaining system pressure readings through transducers in refrigerant lines. Depending on the vehicle, the scan tool, and the software, the serial data that is obtained from an ATC system can include information such as blend door position and blower motor voltage. Some scan tools have a feature known as bidirectional function that enables the technician to activate various air-conditioning system components, such as the cooling fan and compressor clutch relay. Some scan tools have a recorder mode that is very useful in diagnosing

FIGURE 2-19  A typical scanner for automatic temperature control (ATC) testing.

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FIGURE 2-20  Special tools required for compressor service.

intermittent problems. To use the recorder mode, the technician hooks up the scan tool and drives the vehicle. When the intermittent problem is experienced, the technician pushes the appropriate button and the malfunction will generally be captured and stored in short-term memory. Back at the shop, the stored information can be retrieved for evaluation.

Compressor Tools

There are several special tools required for compressor clutch and shaft seal service (Figure 2-20). Clutch plate tools are used to remove the clutch plate to gain access to the shaft seal. They are also used for reinstalling the clutch plate after service. These tools should be compact in design for working in close quarters so that it may often be possible to service the compressor clutch and shaft seal without having to remove the compressor from the vehicle. Basically, a shaft seal service kit includes an adjustable spanner wrench, clutch plate remover/installer, snapring pliers, ceramic seal remover/installer, seal seat remover/installer, shaft seal protector, seal assembly remover/installer, thin wall socket, O-ring remover, and O-ring installer. For clutch pulley and bearing service, service tools will include a pulley puller, pulley installer, bearing remover/installer, and rotor and bearing installer. Special compressor service tools are designed to fit a particular application. Though some are interchangeable, most are not. For example, the seal seat remover/installer used on GM’s models R4 and A6 compressors may also be used on Diesel Kiki models DKS-12 and DKS-15 compressors, as well as on Sanden/Sankyo model 507, 508, and 510 compressors. If there is any doubt about the application of any particular tool, do not use force. If it does not fit freely, it may not be the correct tool for the task. Often, good service tools are found at a very low cost at flea markets and garage sales. Nevertheless, the cost of having the required tool is often more than offset by the savings in the time required to accomplish a task.

Sources of Service Information There are many sources for information available to the automotive technician today. These include service manuals produced by, but not limited to, manufacturers, Mitchell, Haynes, and Chilton. Service information comes in model-specific print form, CD, or DVD format. Today, the print form of service information is costly, is not as readily available, and is space prohibitive. These reasons and more have given way to computer-based systems. Mitchellon-Demand and ALLDATA are two of the largest suppliers of CD/DVD-based and online information systems used by service facilities, offering systems and subscriptions for coverage 60 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

of all the major automotive manufacturers, both domestic and import. These systems may also include estimating and shop management software. With the complexity of today’s vehicles, these full-coverage information systems have become a required tool, and many large service centers subscribe to both. The Internet has also become a major source of service information with both Mitchellon-Demand and ALLDATA offering access to the most current updated information via an Internet connection. There are also Internet organizations for technicians such as International Automotive Technician’s Network (iATN), Identifix (www.identifix.com) as well as numerous web pages. One note of caution regarding the wealth of information available on the Internet is to rely on original equipment and aftermarket manufacturers’ “in-house” publications and other reliable sources of information. The Internet contains both accurate and inaccurate information, so find sources that other technicians use and recommend. Also, the local library generally has an automotive book section. One should not forget the valuable information that appears in the monthly publications by the Mobile Air Conditioning Society (MACS) as well as other automotive trade magazines made available to their members. Finally, if you are taking any secondary or postsecondary automotive classes, be sure to take notes and to save all of the handouts provided by your instructor, which often contain valuable information not available from other sources. Be sure to index your class notes and the handouts in a notebook for future reference. Although it may not seem so at first, this information can become more relevant and important for your ongoing study and practice and can serve as valuable reference material.

Content of Service Information It is not possible to provide information on all the various specifications or service procedures that may be performed on the many different makes and models of automobiles in service today. Both experienced and inexperienced technicians rely on service information to outline procedures and specifications for repairs and diagnostics. Service information is generally written in a straightforward, easy-to-follow format. They generally provide information in a step-by-step sequence based on manufacturer recommendations.

Service procedures are suggested routines for the step-by-step act of troubleshooting, diagnosis, and repairs.

Service Manual Procedures and Specifications Service Procedures To find a particular service procedure in any service source, it is first necessary to know the exact vehicle year, make, and model. The following sequence is based on the use of a computer-based information system; the steps, though not exactly the same, are similar in a print-based service manual. It may be necessary to refer to the VIN (vehicle identification number) (Figure 2-21). The VIN identifies specific information about the vehicle. Part of

VIN is an acronym for “vehicle identification number.”

FIGURE 2-21  Vehicle identification number (VIN) is observed through the windshield.

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the VIN is the WMI (world manufacturer identifier) code. The first three positions in the VIN uniquely identify the maker of the vehicle. The vehicle descriptor section is positions 4 through 8 of the VIN and identifies specific characteristics of the vehicle. The eighth position identifies the engine size, while the tenth position identifies the year the vehicle was built. The vehicle identifier section is the last eight positions of the VIN and is used for the identification of a specific vehicle. In addition, the last five characters are always numeric and contain no letters. It is a good practice to fill in the vehicle year, make, and model as well as the VIN on the back of the repair order and to confirm that the information on the front of the repair ticket is correct. First select the vehicle year, make, and model (Figure 2-22). Next, locate the general group from the systems list (Figure 2-23) for the procedure you are looking for. Since we are concerned with automotive air conditioning, select heating and air conditioning and locate the procedure for replacing the heater blower motor. Most service application software also includes a “Help” section if you are unsure how to proceed, or you may choose to go to the Table of Contents section. The proper removal and installation procedures are outlined. If these step-by-step procedures are followed, there should be no problem with the removal and installation of the blower motor assembly; the key to any service is to follow the steps as listed.

Specifications Specifications provide information on system capacities. This information is also generally given in the owner’s manual.

Specifications are found in the same manner as service procedures. Suppose, for example, that the cooling system capacity must be known in order to properly add 50 percent antifreeze solution for maximum winter protection. This information is generally located in the section entitled “Maintenance and Lubrication” and the “Powertrain” section. Locate the engine size for the vehicle you are servicing, and reference the cooling system capacity listed in the specification chart. After the system has been thoroughly flushed and drained, the cooling system capacity must be divided by two in order to determine the correct amount of coolant to add to obtain a 50/50 mixture. WARNING: Neither the manufacturer’s service manuals nor any school text, such as this one, can anticipate all conceivable ways or conditions under which a particular service procedure may be performed. It is therefore impossible to provide precautions for every possible hazard that may exist. The technician must always exercise extreme caution and pay heed to every established safety practice when performing automotive air conditioning service procedures.

SERVICE INFORMATION To view service information, First select the Year, Make, and Model of the vehicle and click on "NEXT" Or click here to enter a Vehicle Identification Number (VIN) YEAR: Select year

MAKE: Select make

MODEL: Select model

Next >

Reset Vehicle Selection FIGURE 2-22  Typical vehicle selection screen on computer-based information systems.

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FLUID CAPACITIES APPLICATION

SPECIFICATION METRIC

ENGLISH

Automatic transmission Pan removal Complete overhaul Dry

7.0 liters 9.5 liters 12.7 liters

7.4 quarts 10.0 quarts 13.4 quarts

10.7 liters 11.0 liters

11.3 quarts 11.7 quarts

4.3 liters 3.75 liters

4.5 quarts 4.0 quarts

4.3 liters 3.75 liters

4.5 quarts 4.0 quarts

Fuel tank

64.0 liters

17.0 gallons

Power steering system

0.70 liters

1.5 pints

Engine cooling system 3.4 L engine 3.8 L engine Engine oil 3.4 L engine With filter change Without filter change 3.8 L engine With filter change Without filter change

< Back

Forward >

Print

FIGURE 2-23  Typical example of a fluid capacities chart found in service information.

Repair Order The vehicle repair order (Figure 2-24) is a legal document that must filled out for every vehicle worked on, no matter how insignificant the repair may seem. This applies to vehicles being worked on at the premises or on the road as part of roadside assistance offered by some repair facilities under the auspices of the business license. In addition, a repair order must be completed whether the repair is at no charge (free) or is a repeat repair (come-back) in the same manner as a routine repair. It must be remembered that even when a repair is performed for free, the repair facility is still legally obligated, just as it would be for any fee-based repair. In addition, a repair order should also be completed if an employee vehicle is going to be serviced, even if the employee is going to perform the service on his or her own vehicle. And last but not least, the repair order should be signed, authorizing the work and agreeing to the original cost estimate. Being a legal document, every notation a technician makes on the repair order must be accurate and complete. The technician should also verify that the VIN, make, model, and mileage, as well as other specific information, are correct. Any existing physical vehicle damage (e.g., dent, cracked glass) should be noted at the time the repair order is filled out so as to avoid controversy when the customer returns to pick up the vehicle. While a vehicle is in for service, additional maintenance or repairs may be suggested to the owner to address concerns noted by the technician or as part of routine maintenance suggested by a manufacturer. Sometimes customers decide not to approve this additional work. The recommendations should be noted on the repair order and the customer should sign, acknowledging his or her refusal to address the shop recommendations. This is especially important

Trade Jargon: When a vehicle must return to the repair facility for a repeat repair due to a part failure or improperly performed repair, this repeat repair is referred to as a “come-back.” If the come-back was due to technician error or negligence, the technician is generally not compensated for the repeat repair.

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JACK’S SHOP

Customer Information Company ______________________________ MAKE SURE YOU HAVE Name _________________________________ ALL OF THE Address CUSTOMER’S CONTACT _______________________________ INFORMATION! ______________________________________ City __________________________________ State _________ Zip code ________________ Home: (_____) _________________ Work: (_____) _________________ Cell: (_____) _________________ Other: ( ) Description of Service

REPAIR ORDER

1234TODAY’S Some Street DATE Sometown, AA 98765 (555)123-7890

DATE __ /__/___

Vehicle Information Year: _____________ Make: __________________________________ YOU MUST HAVE COMPLETE Model: __________________________________ AND ACCURATE INFORMATION Color: __________________________________ IN ORDER TO PROPERLY VIN: __________________________________ REPAIR THE VEHICLE! Engine: _________________________________ License Number: _____________ ST ________ Odometer reading: Repair Estimate

_______________________________________________Total Parts:

THIS IS ONE OF THE MOST IMPORTANT SPACES YOU NEED TO FILL IN! EXPLAIN WHAT THE CUSTOMER WANTS AND WHY THE VEHICLE HAS BEEN BROUGHT INTO THE SHOP.

Time

Price

R&R Right Front Strut R&R Air Filter

2.3 0.1

138.00 6.00

STANDARD TIME FOR EACH SERVICE

______________

Total Labor: ______________ IN MOST______________ STATES, YOUR Other charges: ESTIMATE MUST BE Initial estimate: ______________ Estimate given by: WITHIN 10% OF THE FINAL YOUR Date BILL. TAKE Time TIME AND GIVE AS Phone: __________ __________ ACCURATE AN ESTIMATE In person __________ __________ AS YOU CAN! Additional authorized amount: __________ Revised estimate: ______________ Authorization given by: Date Time Phone: __________ __________

Services

EACH SERVICE PERFORMED

12345

HOURLY LABOR RATE MULTIPLIED BY TIME

Totals Date completed ___/___/___ Tech _______________

144.00

Services

Part #

Description

Qty.

Price Ext.Price

Parts

80.42

JE8538 RE4949 XX3344z

Strut assembly Air filter Shop supplies

1 1 1

73.47 73.47 6.95 6.95 10.00 10.00

Shop supplies

10.00

Sub total

234.42

WHAT THETax CUSTOMER PAYS 6%

14.07

THIS INFORMATION NEEDS TO BE COMPLETE FOR ACCURATE BILLING AND FOR INVENTORY MAINTENANCE.

Total

$

248.49

FIGURE 2-24  This repair shows a recent history (top) and the customer’s complaint (center).

KiloPascals is a unit of measure in the metric system. One kiloPascal (kPa) is equal to 0.145 pound per square inch (psi) in the English system.

if the repair is required for vehicle safety or system failure. Some service facilities will even tow the vehicle back to the owner’s home at no cost to the owner to limit the shop’s liability.

The Metric System The United States is slowly but surely joining the rest of the world in a uniform system of physical measurement known as the metric system. In the metric system, speed is measured in kilometers per hour (km/h), pressure is measured in kiloPascals absolute (kPa absolute) or kiloPascals (kPa), liquid is measured in liters (L), temperature in degrees Celsius (8C), length in millimeters (mm) or meters (m), and weight

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in grams (g) or kilograms (kg). Whenever practical, measures in this text are given in both English and metric units. The metric equivalent is given in parentheses following the English measure. For example: The freezing point of water at atmospheric pressure is 328F (08C) and its boiling point is 2128F (1008C). There are several terms commonly used in the English system of measure that are the same as those used in the metric system of measure. Those most familiar to the automotive technician include ohm, volt, and ampere. Some English standard measures cannot be converted into the standard metric measure. For example, there is no standard metric measure for 3 8 in. An English 3 8 in. measure is actually equal to 9.53 mm in the metric measure. Therefore, if you need to remove 3 8 in. cap-screws from a plate, a 9 mm wrench would be too small, while a 10 mm wrench would be too large. For the purpose of conversion, the metric equivalents in this text are held to one or two decimal places. For example, a temperature of 698F converts into 20.55555555558C. Little is gained by carrying the conversion to three or even two decimal places. The difference between one and ten decimal places in this example amounts to only 8 /1008F (0.088F) or 44 /1,0008C (0.0448C), hardly worth consideration for the purpose of practical application. As in the example given, the conversion of 698F to 8C will then be given as 20.68C, rounded off to the nearest decimal place. Pressure in the metric system is measured in terms of the Pascal (Pa). One pound per square inch (1 psi) is equal to 6.895 3 10 3 Pascals. For a more practical application, the kiloPascal (kPa) is used. One pound per square inch (1 psi) is equal to 6.895 kiloPascals (6.895 kPa). This equation applies to both the absolute (psia) and atmospheric (psig) pressure conversions. A conversion chart for English-to-metric and metric-to-English values is given in Figure 2-25.

The metric system is known as “Systéme International d’Unites,” a French term that literally translates to “International System of Units.”

METRIC TO ENGLISH Multiply

By

To Get

Celsius (°C) gram (g) kilogram (kg) kilometer (km) kilopascal (kPa) liter (L) meter (m) milliliter (mL) millimeter (mm)

1.8 (+32) 0.035 3 2.205 0.621 4 0.145 0.264 2 3.281 0.033 8 0.039 4

Fahrenheit (°F) ounce (oz.) pound (lb.) mile (mi.) lb/in.2 (psi) gallon (gal.) foot (ft.) ounce (oz.) inch (in.)

ENGLISH TO METRIC Fahrenheit (°F) foot (ft.) fluidounce (fl. oz.) gallon (gal.) inch (in.) mile (mi.) ounce (oz.) pound (lb.) lb/in.2 (psi)

(–32) 0.556 0.304 8 29.57 3.785 25.4 1.609 28.349 5 0.453 6 6.895

Celsius (°C) meter (m) milliliter (mL) liter (L) millimeter (mm) kilometer (km) gram (g) kilogram (kg) kilopascal (kPa)

FIGURE 2-25  English/metric conversion chart.

Terms to Know Can tap Facilities Fringe benefits The high-side gauge Hygiene KiloPascals Manifold and gauge set Service procedures Specifications The low-side gauge Vacuum pump VIN 65

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ASE-STYLE REVIEW QUESTIONS 1. Technician A says that rules are made to protect the customer. Technician B says that rules are made to protect the technician. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

6. Technician A says that safety glasses should be approved for gases. Technician B says that safety glasses should be approved for liquids. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

2. Technician A says that the repair order is a legal document that must be filled out for every vehicle worked on. Technician B says that a repair order does not need to be filled out for a no charge (free) repair. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

7. Technician A says to determine the type of refrigerant used in a system, a refrigerant identifier should be used prior to servicing the vehicle’s refrigerant system. Technician B says that when working on a refrigerant system you should work in a well ventilated area. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

3. Technician A says the low-side gauge on the manifold gauge set is on the left and has a green housing. Technician B says the high-side gauge on the manifold gauge set is on the left and has a red housing. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

8. Technician A says that the English/metric measurement unit for pressure is psig/kPa. Technician B says that the English/metric measurement unit for temperature is Fahrenheit/Centigrade. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

4. Technician A says that you only need one manifold gauge set and it may be used for any type of refrigerant you need to service. Technician B says a vacuum pump is an essential piece of equipment for servicing a refrigerant system. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

9. Technician A says that a vacuum pump is used to remove moisture from a system. Technician B says that an air pump is used to remove air from a system. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

5. Technician A says a service information system may include estimating and shop management software. Technician B says service information you find on the Internet contains both accurate and inaccurate information. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

10. Technician A says that you are entitled to a clean, safe place to work. Technician B says as an employee your obligation is to be a loyal, caring individual, and have the ability to follow directions. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

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JOB SHEET

5

Name ________________________________________ Date _______________________

Identify the Responsibilities of the Employee Upon completion of this job sheet, you should understand the obligations of an employee. Tools and Materials Pad and pencil Procedure

1. There are four primary employee obligations: attitude, responsibility, dependability, and pride. Can you think of any other obligations that may be an asset to the employee? If so, list them in the space provided.

_______________________________________________________________________________

2. Give several examples of employee attitude in the workplace.

_______________________________________________________________________________



_______________________________________________________________________________

3. Give several examples of employee responsibility in the workplace.

_______________________________________________________________________________



_______________________________________________________________________________

4. Give several examples of employee dependability in the workplace.

_______________________________________________________________________________



_______________________________________________________________________________

5. Give several examples of employee pride in the workplace.

_______________________________________________________________________________



_______________________________________________________________________________

6. Give examples of the other obligations you thought of in step 1.

_______________________________________________________________________________



_______________________________________________________________________________

Instructor’s Response   

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JOB SHEET

6

Name ________________________________________ Date _______________________

Use a Manufacturer’s Service Manual Upon completion of this job sheet, you should understand how to use a service manual. Tools and Materials A late-model vehicle A service manual for the vehicle or computer-based information system NATEF Correlation NATEF AST and MAST Correlations: HEATING AND AIR CONDITIONING: General: A/C System Diagnosis and Repair. Task #2. Research applicable vehicle and service information, vehicle service history, service precautions, and technical service bulletins. (P-1) Procedure Assume that you are to replace a circuit breaker in the vehicle you selected. 1. What vehicle did you select? Make _____________ Model _____________ Year ______________ VIN ______________ 2. Which service manual do you have? Title _________________________________ Year __________________________________ 3. Does the service manual cover the vehicle that you selected? _______________________ If not, explain:  4. Locate the Group Index and determine which group includes the circuit breaker. What group did you select?  5. Is the circuit breaker in the group that you selected?  If not, what group did you find it in? 

_____________________________________________________________________________

6. Using information found in the manual, were you able to find the circuit breaker?

_____________________________________________________________________________

If not, what problems were encountered? 

______________________________________________________________________________

7. Were you able to determine the difference between the circuit breaker and the hazard signal flasher unit? _____________________ Were they similar? _____________________ 8. How were they different? 

______________________________________________________________________________ 69

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Instructor’s Response _____________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________

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JOB SHEET

7

Name ________________________________________ Date _______________________

Compare the English and Metric Systems of Measure Upon completion of this job sheet, you should understand the English and metric systems of measure. Tools and Materials Miscellaneous and assorted nuts and bolts Set of English (fractional inch) open-end wrenches Set of metric (millimeter) open-end wrenches Procedure Ask your instructor to identify for you a 1 4 -28 bolt and a 5 16 -24 bolt. 1. What size wrench fits the head of the 1 4 -28 bolt? 2. What size wrench fits the head of the 5 16 -24 bolt? 3. Using the formula given in the shop manual, convert 1 4 in. into metric millimeters. a. First, convert 1 4 in. into a decimal value. What is the decimal value? b. Next, multiply the decimal value by the formula. 4. Is there a metric wrench the size determined in step 3b? _________ Explain: _________

______________________________________________________________________________

5. Is there a metric fastener the size as determined in step 3b? _______ Explain: ________

______________________________________________________________________________

6. Is there a metric fastener close to the size determined in step 3b? _____ Explain: ______

______________________________________________________________________________

7. Will the English wrench fit the fastener selected in step 6? _______ Explain: __________

_______________________________________________________________________________

8. Are the two fasteners, determined in steps 1 and 6, interchangeable? Explain:

_______________________________________________________________________________

9. Is the metric fastener identified in step 6 interchangeable with the 5 16 -24 English fastener? ______________________________ Explain: ______________________________ 10. Is the metric fastener identified in step 6 closer in size to the 1 4 -28 fastener or the 5 -24 fastener? ______________________________________________________________ 16

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Instructor’s Response  ���������������������������������������������������������������������������������� ����������������������������������������������������������������������������������

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Chapter 3

Basic Electrical Troubleshooting and Service Upon Completion and Review of this Chapter, you should be able to: ■■

Demonstrate a basic understanding of Ohm’s law.

■■

Describe how to troubleshoot a blower motor circuit.

■■

Discuss the use of a digital multimeter.

■■

Test and diagnose the fuses and blower motor relay.

■■

Describe how to test circuit protection devices.

■■

Discuss how to test the blower motor.

■■

Discuss how to test for opens in an electrical circuit.

■■

Describe how to test the blower motor speed resistor.

Introduction Today’s heating and air conditioning technicians need detailed knowledge about automotive electrical and electronics. This chapter is intended as a review of basic electrical and electronic concepts that must be mastered and is not intended as a substitute for a complete course on electrical and electronics. Troubleshooting heating and air-conditioning electrical problems involves the same methods and equipment as any other automotive circuit problem. In order for electrical circuits to function correctly, they must have the correct voltage, amperage, and resistance. Obtaining proper circuit readings through measurement, and then comparing these measurements to system specifications, is the key to effective fault diagnosis. In order to do this, the technician must have a slid understanding of basic electrical principles and testing procedures. Many different types of faults can occur in an electrical circuit. Some common problems that can occur are opens, shorts, or excessive or unwanted resistance in a circuit. An open circuit is a circuit that has a break in the normal current flow path or, stated differently, a circuit that lacks continuity. A circuit may develop an open on either the insulated (positive) side or the ground (negative) side. A short occurs when two or more circuits are crossed (connected), which decreases the resistance in the circuit. Shorts may occur between power and ground, which generally will cause protection devices such as fuses to fail and sometimes wires to burn. Shorts may also occur between power wires, often referred to as a circuit-to-circuit short, which can cause a circuit to be powered on when an unrelated circuit is energized. In effect, the two circuits become parallel circuits and are turned on and off when one circuit is controlled. This can have very strange effects on the circuits involved, leaving technicians to scratch their heads. Shorts could also occur between ground wires, although this type of failure often goes undetected unless the circuit is ground switched. High or unwanted resistance can occur anywhere in a circuit. However, the effect of high resistance is the same and regardless of where it is, voltage is used. If a circuit has higher than normal resistance current flow, the circuit will be reduced. Unwanted resistance in areas other than the designed load in the circuit will reduce current flow in the circuit and reduce the amount of voltage drop by the component load in the circuit.

Voltage: It is the electrical pressure that causes electrons to move through the circuit. Amperage: A term used to describe the number of electrons moving past a fixed point in a conductor in one second. Current is measured in units called amperes or amps. Resistance: Opposition to current flow. Opens: An electrical term used to indicate that a circuit is not complete or is broken.

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Short: An unwanted electrical path; sometimes this path goes directly to ground. Open circuit: A term used to indicate that current flow is stopped. By opening the circuit, the path for electron flow is broken. Voltage drop: A resistance in the circuit that reduces the electrical pressure available after the resistance. The designed resistance in the circuit is the load component, such as a blower motor, and would drop or use all the available voltage. Unwanted voltage drops in a circuit could be unwanted resistance in circuit conductors, connections.

Electrical Diagnosis and Testing The following is a typical systematic approach for applying the diagnostic procedures used to determine air-conditioning system electrical problems. Those who lack a general knowledge of automotive electricity and electronics may review this information in the Today’s Technician series, Automotive Electricity and Electronics. A basic understanding of Ohm’s law is needed to understand how and why a circuit operates. Review Ohm’s law and the theory of series, parallel, and series–parallel circuits. E I

E

or R

I

R

E 5 voltage; measured in volts; most automotive circuits are measured in DC volts (direct current) I 5 current; measured in amperes R 5 resistance; measured in ohms E 5I 3R I 5 E /R R 5 E /I There are eight basic conditions that one may encounter relating to the electrical system of the automotive air conditioner. These conditions are:

1. Everything works electrically, but there is poor or no cooling 2. Nothing works 3. Only the clutch works 4. Only the evaporator blower works 5. Only the cooling fan works 6. The clutch does not work 7. The evaporator blower does not work 8. The cooling fan does not work Because of the complex electrical wiring of most factory-installed air-conditioning systems (Figure 3-1 and Figure 3-2), it is generally necessary to consult electrical schematics of appropriate manufacturer’s shop manuals for proper troubleshooting and testing procedures. The following, however, may be considered typical for basic testing of most systems. If everything works but there is poor or no cooling, the problem is likely to be in the vacuum, refrigeration, or duct system. One might also suspect an engine cooling system problem. If nothing works, the complaint is obvious. The system is not cooling, and there is no air moving over the evaporator. A visual inspection will reveal that neither the compressor nor the evaporator fan motor is working, although the cooling fan may or may not be working. It will also be obvious that the blower motor is not running. The logical conclusion, then, is that the main fuse, circuit breaker, or fusible link is defective. The problem could also be in the master control or wiring.

Using a Digital Multimeter It is imperative that a technician is able to use a digital multimeter (DMM) (Figure 3-3) on today’s computer-controlled circuits. Digital multimeters use a liquid crystal display and are computers that determine the measures values using an averaging method to determine values to be displayed to the user. The DMM have a high impedance or input resistance, typically 74 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Hot all the time

Hot all the time

Hot all the time

Hot in run

25A Blower motor ICA 4 relay 2

ON

2

3 Junction box

Cooling fan motor

4

3 Blower motor

M

Blower speed resistor

2

M

ON OFF

85

DGER

ON OFF

1

3 6 2 7 LO

ML

MH

Cooling fan motor relay

HI

OFF

ON

5

OFF

3

4 M

4

ON

3 Clutch relay

1 Clutch coil

1 1

OFF

1

HI MH ML

OFF LO

Blower switch

OFF

8

2

2 21

83

~

~

OFF

10A

~

25A

~

Engine control module

A/C 200

A/C switch

5

3

1

~ GMD 2

~ GMD 7

~

~ 4

Air inlet sensor

~

~

~

A/C control unit

9

~ 8

10

Air thermo sensor

FIGURE 3-1  A typical import automotive air-conditioning system schematic.

at least 10 megaohms, which prevents the meter from drawing current when connected to a circuit. This high-impedance level reduces the risk of damage to circuits and computer components. A DMM may have manual ranges or it may be auto ranging. If the meter you are using is an auto-ranging meter, it will automatically switch between ranges for the selected setting. When using an auto-ranging meter, it is important to pay attention to the display screen to see what range the meter is in and what the multiplier to use is.

Voltmeter Function The voltmeter setting of a DMM allows the user to measure the voltage available at the terminals of any component or connector. A voltmeter has two leads, one positive red lead and one negative black lead. To display correctly the red lead should be connected to the most positive 75 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Hot at all times

Hot in run

UBEC

IP Fuse Panel

HVAC 30A

HVAC 20A

HVAC controller Off Hot in run

Off

A/C fuse 10A

Hot at all times

UBEC

Ign fuse 10A

Compressor clutch relay

A/C clutch

Blower motor

Blower motor relay

5v A/C pressure transducer

FIGURE 3-2  A typical domestic automatic air-conditioning system schematic.

FIGURE 3-3  Typical digital multimeter (DMM) used in the automotive field.

76 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

B

V DIGITAL MULTIMETER

V

MAX MIN

RECORD

%

0 1 2 3 4 5 6 7 8

9 0

HZ

MIN MAX

HZ

DIGITAL MULTIMETER

mV

RECORD

mA A

V

MAX MIN

%

A

V

0 1 2 3 4 5 6 7 8

9 0

HZ

MIN MAX

HZ

A

mA A

COM

V

mV mA A

V

A

V

A

mA A

COM

V

1Ω

+

M

1Ω

A

– Battery

+

FIGURE 3-4  A voltmeter is connected in parallel to the circuit being tested.

C

– Battery

FIGURE 3-5  Checking voltage in a closed circuit. 10.92 V 0.54 Voltage drop

DIGITAL MULTIMETER RECORD

MAX MIN

%

0 1 2 3 4 5 6 7 8

9 0

HZ

MIN MAX

0.05 Ω

HZ

mV mA A

V

A

V

−

A

mA A

COM

V

12 V

+

2Ω

2Ω

0.05 Ω 10.9 A

0.54 Voltage drop

FIGURE 3-6  A voltage drop test across two bulbs wired in parallel. Notice that each wire also uses a small amount of voltage due to unwanted resistance, causing bulb voltage to be lower than desired.

side of the circuit and the black lead to the most negative side of the circuit. On a DMM, the black lead is connected to the port on the DMM labeled “COM” and the red lead to the DMM terminal labeled “V.” When testing a circuit or component, the voltmeter is connected in parallel with the circuit (Figure 3-4). When checking voltage in a closed circuit as in Figure 3-5, the voltage at point “A” would be 12 volts. The voltage at point “B” would be 6 volts due to a 6-volt drop across the 1-ohm resister. And there would be 0 volts at point “C” because all the voltage was used by the two loads in the circuit. A voltage drop is the loss of voltage through wires, connectors, and loads in a circuit. A voltage drop is the amount of electrical energy that is converted into another form of energy. A voltage drop test is the preferred method of testing for unwanted resistance in a circuit when the circuit is under a load (turned on). To measure the voltage drop across a load or suspected unwanted load (resistance), it must first be determined what point is the most positive and what point is the most negative. If a wire or wiring has higher than designed resistance, the wire will drop some of the available voltage and less than source voltage will be available for the load(s) (bulbs) in the circuit (Figure 3-6). This unwanted resistance will cause current flow to go down and the bulbs in Figure 3-6 will be dimmer than they should be if the unwanted resistance was not present.

Ohmmeter Function An ohmmeter in a digital multimeter uses voltage from an internal battery to send a very small current through the meter leads and determines the amount of resistance based on the amount of voltage dropped across whatever the leads are connected to. An ohmmeter reads from zero (0) to infinity (` ). A zero reading means there is no resistance in the component or circuit, which may indicate a short in a component that should have some resistance; an infinity (` ) 77 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

reading indicates an open circuit. On a DMM, the black lead is connected to the port on the DMM labeled “COM” and the red lead to the DMM terminal labeled “ V.” With the DMM turned on and set to the ohm setting, hold the leads apart and see how the meter displays infinite resistance; some meters display this with “OL” displayed on the screen for out of limits. In order to test the resistance of a component, the circuit or component must be open and isolated so that voltage cannot flow; otherwise, the DMM may be damaged and the reading displayed will not be accurate. When testing a component, the ohmmeter leads are connected in parallel with the isolated component (Figure 3-7). The red lead should be connected to the positive side of the component and the black lead to the most negative side of the component. Many ohmmeters have an audible signal when there is continuity to aid in testing. Continuity only means that current can flow and that the circuit is not open. Do not mistake continuity for resistance. Resistance is the measured number displayed on the DMM screen.

Ammeter Function Amperage flow in a circuit can be measured using an ammeter. The test leads from the ammeter must be placed in series with the circuit being tested (Figure 3-8). To measure amperage flow in a circuit using a digital multimeter, the meter must be set to the ampere scale (A) and the black lead must be placed in the black COM port and the red lead must be placed in the red A (ampere) port. Next, a wire or connector from a component in the circuit being tested must be disconnected. The meter leads must then be placed in series with the circuit. The red lead should be connected to the positive side of the circuit and the black lead should be connected to the least positive side, or in other words in the direction of current flow based on the conventional theory that current flows from positive to negative. Most multimeters have a 10-ampere internal fuse as protection and as such this is the maximum amount of current flow the meter is capable of measuring without damage. If you are not using an auto-ranging meter, start with the highest scale and work down to obtain the most accurate reading. WARNING: Failure to connect the digital multimeter correctly when testing amperage invasively will result in digital multimeter damage, circuit damage, or both. Many computers have been destroyed as a result of improper digital multimeter use. Always ask if you are not sure how to test a circuit or if your equipment is adequate for the task at hand. DIGITAL MULTIMETER RECORD

MAX MIN

%

0 1 2 3 4 5 6 7 8

9 0

HZ

MIN MAX

HZ

mV mA A

V

A

V

A

mA A

COM

V

+ − + −

A DIGITAL MULTIMETER RECORD

MAX MIN

%

0 1 2 3 4 5 6 7 8

9 0

HZ

MIN MAX

HZ

mV mA A

V

Fuse removed to de-energize circuit

FIGURE 3-7  When measuring resistance with an ohmmeter, the leads are connected in parallel with the component being tested after power has been removed from the circuit or the component has been isolated.

A

V

A

mA A

COM

V

FIGURE 3-8  To measure amperage flow in a circuit using a digital multimeter, the meter must be set to the ampere scale (A) and the black lead must be placed in the black COM port and the read lead must be placed in the red A (ampere) port. The meter leads must then be placed in series with the circuit.

78 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

SERVICE TIP:

Using an inductive pickup is a non invasive way of testing circuit amperage and is generally the preferred method of monitoring circuit amperage.

Overload: Excessive current flow in a circuit.

B+

12.6V

Inductive pickup

B–

FIGURE 3-9  A digital multimeter with an inductive pickup attached for measuring current flow in a circuit. This is a noninvasive method that is quick and easy.

The safest and easiest way to test for amperage flow in a circuit is to use an inductive pickup that can be placed around a wire (Figure 3-9). This is a noninvasive method that virtually eliminates the possibility of unwanted damage to a circuit through technician error. You must make sure you choose an inductive probe that is capable of measuring the amount of current you are testing as they are available in a range of sensitivities. There is generally an arrow on the inductive pickups clamp housing indicating the direction of current flow (conventional theory) for proper connection to the circuit being tested. An inductive pickup senses the magnetic field created as current flows through a conductor and converts this signal into a small millivolt signal. Connecting the inductive pickup to the multimeter is not as straightforward. The black lead from the inductive probe is connected to the black COM port, the red lead must be placed in the red V (voltage) port, and the meter must be set to the voltage scale since it is actually reading the voltage signal sent out of the inductive pickup. To read the meter you must convert the millivolt signal displayed. Most inductive probes will generate 100 millivolts for every ampere that flows through the circuit. If the meter displays 540 mV, then you would have 5.4 amps flowing through the circuit. Many auto-ranging meters will display this as 0.540 V so you will need to move the decimal point one place to the right to correctly interpret the reading.

Testing Circuit Protection Device Circuit protection devices are designed to turn off the system whenever excessive current load is detected or a circuit overload occurs. The most common circuit protection devices used are fuses and circuit breakers and on older platforms fusible link wire. A fuse is a replaceable component with an element that will melt should the current passing through it exceeds its rated value. Fuses are most commonly located in a box or panel (Figure 3-10) located under the

Fuses: A replaceable circuit protection device that will melt if the current passing through it exceeds the rating number of the fuse creating an open in the circuit. Circuit breaker: A circuit protection device that will create an open in the circuit if the current passing through it exceeds the amperage rating number. But will automatically reset and close once the current overload drops below the rated value. Fusible link: A wire made of meltable material with special heat resistant insulation. When there is a current overload in the circuit, the link melts and opens the circuit.

79 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 3-10  A typical fuse panel located in the engine compartment containing several styles of fuses along with relays.

hood in the engine compartment or under the dash assembly in the passenger compartment. The fuse location is generally numbered and the main component abbreviated next to the fuse or on the diagram of fuse location on the fuse panel cover. Plastic blade fuses (Figure 3-11) are by far the most common style and come in several sizes. The fuse current rating is printed Blade type fuses Micro2 fuse 30

Micro3 fuse 15

15

Maxi fuse

40 Low-profile mini fuse 4 ATO (regular) fuse 10

Mini fuse 3

FIGURE 3-11  Plastic blade-type fuses are the most common and come in six physical sizes: micro2, micro3, low-profile mini, mini, regular, and maxi.

80 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

on the top in amperes and the fusible element can be viewed through the translucent colored body when removed from the fuse panel. To aid in identifying the ampere rating of a bladestyle fuse, a common color scheme is used (Figure 3-12). Another common fuse style on Japanese and some domestic car lines is the PAL fuse or fusible link (Figure 3-13). PAL fuses have a color-coded plastic housing with a clear plastic window on the top to view the physical integrity of the fusible link element without removing the fuse from the fuse panel. Fuses may be visually inspected for breaks in the element and discoloration caused by a circuit overload (Figure 3-14). Fuses may be tested with a test light on an energized circuit by connecting the test light clip to a good body ground and then touching the test light probe to the top of the fuse on each side of the conductor element or terminal. A good fuse will illuminate the test light on both sides (Figure 3-15). If in doubt as to the physical integrity of a fuse it can be removed and checked with an ohmmeter. A good fuse will have continuity and extremely low resistance. Blade-style fuses may also be easily checked using a test light when the circuit is powered on. All fuses are rated at the current at which they are designed to fail or blow. Circuit breakers are commonly used on a component that may experience a temporary high current surge such as electric motors and air-conditioning compressor electromagnetic clutches. Like fuses, circuit breakers are rated in amperes at the current at which they are designed to open. Unlike fuses they do not fail once an overload occurs but instead open the circuit and then automatically reset after a short period of time. Most circuit breakers have a bimetallic cycling design with a bimetal arm made of two different metals bonded together, often wrapped with a very fine coil wire, although some circuit breakers are of a solid-state design (Figure 3-16). In a bimetallic circuit breaker, the metal arm heats from excessive current Color

Current LowMicro2 Micro3 Mini Reg rating profile

Dark blue

0.5 A

Black

1A

Gray

2A

Violet

3A

Pink

4A

Tan

5A

Brown

7.5 A

Red

10 A

Blue

15 A

Yellow

20 A

Clear

25 A

Green

30 A

Blue-green

35 A

Orange

40 A

Red

50 A

Blue

60 A

Amber/tan

70 A

Clear

80 A

Violet

100 A

Purple

120 A

Maxi

Gray

Brown

FIGURE 3-12  Plastic blade-type fuses use a common color chart to aid identification.

81 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

TM

A. Auto Link PAL Color Code Lt. Blue – 20A Pink – 30A Green – 40A Red – 50A Yellow – 60A

TM

B. Auto Link PAL Color Code Pink – 30A Yellow – 60A Black – 80A Blue – 100A Gray – 120A

A

B

C

TM

US Carded No. PAL 020 BP PAL 030 BP PAL 040 BP PAL 050 BP PAL 060 BP

Canadian Carded No. PAL 020 CABP PAL 030 CABP PAL 040 CABP PAL 050 CABP PAL 060 CABP

Straight Male Terminal

US & Canadian Boxed No. PAL 130 PAL 160 PAL 180 PAL 1100 PAL 1120

C. Auto Link PAL Color Code Pink – 30A Green – 40A Red – 50A Yellow – 60A Brown – 70A Black – 80A Blue – 100A Gray – 120A

Female Terminal

US & Canadian Boxed No. PAL 020 PAL 030 PAL 040 PAL 050 PAL 060

US Carded No. PAL 130 BP PAL 160 BP PAL 180 BP PAL 1100 BP PAL 1200 BP

Canadian Carded No. PAL 130 CABP PAL 160 CABP PAL 180 CABP PAL 1100 CABP PAL 1120 CABP

13/16" Bent Male Terminal

US & Canadian Boxed No. PAL 230 PAL 240 PAL 250 PAL 260 PAL 270 PAL 280 PAL 2100 PAL 2120

US Carded No. PAL 230 BP PAL 240 BP PAL 250 BP PAL 260 BP PAL 270 BP PAL 280 BP PAL 2100 BP PAL 2120 BP

Canadian Carded No. PAL 230 CABP PAL 240 CABP PAL 250 CABP PAL 260 CABP PAL 270 CABP PAL 280 CABP PAL 2100 CABP PAL 2120 CABP

D. Auto Link PALTM Mini Female Terminal Color Code Pink – 30A Green – 40A

US & Canadian Boxed No. PAL 330 PAL 340 TM

E. Auto Link PAL

D

E

F

Color Code Pink – 30A Green – 40A Red – 50A Black – 80A Blue – 100A

US Carded No. PAL 330 BP PAL 340 BP

Canadian Carded No. PAL 330 CABP PAL 340 CABP

9/16" Bent Male Terminal

US & Canadian Boxed No. PAL 430 PAL 440 PAL 450 PAL 480 PAL 4100

US Carded No. PAL 430 BP PAL 440 BP PAL 450 BP PAL 480 BP PAL 4100 BP

Canadian Carded No. PAL 430 CABP PAL 440 CABP PAL 450 CABP PAL 480 CABP PAL 4100 CABP

F. Auto Link PALTM Locking Female Terminal Color Code Brown – 25A Green – 30A

US & Canadian Boxed No. PAL 525 PAL 530

US Carded No. PAL 525 BP PAL 530 BP

Canadian Carded No. PAL 525 CABP PAL 530 CABP

FIGURE 3-13  PAL fuses are commonly found on Japanese and some domestic vehicles.

GOOD

BLOWN

FIGURE 3-14  A fuse element may be visually inspected for failure.

at its rated value, which causes the two metals to expand at differing rates and the arm to flex open when the rated current level is reached, opening the circuit contacts in the breaker. With no current flowing, the bimetal strip cools closing the contacts, allowing current to flow again. Automatically resetting circuit breakers are sometimes referred to as cycling circuit breakers because they cycle open and closed until current flow returns to normal levels. Circuit breakers may be located in the fuse panel or may be built into a component like wiper motors. Circuit breakers are tested in the same manner that fuses are tested. WARNING: Circuit breakers and fuses should only be replaced with the same ampere rating as the original designed for the circuit. A lower-rated protection device will fail and a higher-rated protection device could cause an electrical fire or catastrophic circuit failure. 82 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Test light bulb Test light prob Fuse

CAUTION:

Avoid using a test light on a microprocessor circuit. A common test could draw more current than a circuit can provide or handle.

FIGURE 3-15  Fuses may be tested with a test light by connecting the test light clip to a good body ground and then touching the test light probe to the top of the fuse on each side of the conductor element. A good fuse will illuminate the test light on both sides.

Low-expansion metal

High-expansion metal Contacts

Terminals

Current flow FIGURE 3-16  In a bimetallic circuit the metal arm heats up and flexes open when the rated current level is reached, opening the circuit being protected.

Testing for Opens A circuit has an open when there is not a complete path for current to flow. Open circuits may be caused by cut wire, a faulty component, or broken or loose connections. It is possible to test for open circuits using a voltmeter, ohmmeter, test light, self-powered test light, or fused jumper wire. The test equipment chosen will depend on the circuit being tested and accessibility. The first step is to determine the normal operation of the circuit (Figure 3-17) before determining what is wrong. Most technicians will begin diagnosing a circuit from the most accessible, place first. If the load in the circuit, such as a bulb, is easily accessible, turn the circuit on and test for voltage at the input to the load (Figure 3-18). The steps below outline the basic procedures for locating an open circuit: 1. Turn the circuit ON and measure voltage at the fuse. 2. If the fuse has power, next test for power at the circuit load (Figure 3-18). If there is source voltage at point A, check for voltage at point B. If source voltage is present at point B, then there is an open on the ground side of the component (load). 83 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

12 V DIGITAL MULTIMETER MAX MIN

RECORD

%

0 1 2 3 4 5 6 7 8

HZ

9 0

MIN MAX

HZ

mV mA A

V

SERVICE TIP:

A

V

A

mA A

+

V

COM

Attaching an alligator clip adapter to the meters (COM) black lead and connecting it to the vehicles chassis ground will free up your hands to focus on connecting the red positive lead to test points.

– Battery

1

2

DIGITAL MULTIMETER MAX MIN

%

0 1 2 3 4 5 6 7 8

9 0

4

Current flows through lamps 1 & 2, which shine brightly.

0V RECORD

3

HZ

MIN MAX

HZ

mV mA A

V

A

V

A

mA A

COM

V

FIGURE 3-17  In a normally operating parallel circuit, there should be source voltage before the load and zero volts after the load.

Fuse

Light switch

Lamp

A Ignition switch

B

12 V DIGITAL MULTIMETER RECORD

MAX MIN

%

0 1 2 3 4 5 6 7 8

9 0

HZ

MIN MAX

HZ

mV mA A

V

A

V

–

+

A

mA A

COM

V

Battery FIGURE 3-18  In a normally operating circuit, there should be source voltage available to the load at point A and there should be 0 volts available at point B.

3. If voltage was not present at point A, then the open is before the component (load). 4. Working toward the battery, test all connections for voltage. If voltage is present at a connection, then the open is between that connection and the previous connection without voltage present (Figure 3-19).

Troubleshooting the Blower Motor Circuit Before troubleshooting, check the battery charge (Figure 3-20). The voltage should be 12.4 volts or more. If not, recharge or replace the battery before proceeding. If the engine starts and runs, however, this test is not necessary. Proceed as follows for systematic testing of the blower motor electrical circuit. Select DC volts on the digital multimeter for the following steps. 84 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

12 V DIGITAL MULTIMETER RECORD

MAX MIN

%

0 1 2 3 4 5 6 7 8

9 0

HZ

MIN MAX

HZ

mV mA A

V

A

V

A

mA A

COM

V

Open

Fuse

Light switch

Lamp

A Ignition switch

B

0.00 V DIGITAL MULTIMETER RECORD

MAX MIN

%

0 1 2 3 4 5 6 7 8

9 0

HZ

MIN MAX

HZ

mV mA A

V

A

V

–

+

A

mA A

COM

V

Battery FIGURE 3-19  An open in a circuit is located between the points where voltage was measured and where it was not.

FIGURE 3-20  Testing battery voltage.

Testing the Fuses and Blower Motor Relay (Figure 3-21) 1. Connect black test lead of a digital multimeter (DMM) to ground and the other test lead to the hot side of the fuse or circuit breaker, point A. Turn the ignition switch to the ON position, the air-conditioning switch to A/C, and the blower motor switch to high speed. Note the DMM reading. Next, disconnect the test lead from point A and connect it to point B. Note the reading and disconnect the DMM. a. If there are 0 volts at either point A or B, a broken, disconnected, or defective wire or a defective fuse is indicated. b. If there are less than 12 volts at either point, look for a loose or corroded ­(high-resistance) connection before the fuse that is causing the low voltage. c. If there are 12 volts or more at both points, proceed with step 2. 85 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Fuse

Fuse

A

B C

E

25A

1

D

Blower motor 10CA 4 relay

F OFF ON 3

H

2

G

To blower motor

FIGURE 3-21  Test points for fuses and blower motor relay.

2. Connect the DMM from ground to the other side of the fuse, point C, and note the reading. a. The reading should be the same as at point A. If there are 0 volts, the fuse is ­defective and must be replaced. WARNING: Before replacing the fuse, turn off the air conditioner and ignition switch. b. Disconnect the DMM lead from point C and attach it to point D. Note the reading, then disconnect the DMM positive (red) lead. c. The reading should be the same as at point B. If there are 0 volts, the fuse is defective and must be replaced. (See Warning above.) d. If 12 volts or more are noted at points C and D, proceed with step 3. 3. Connect the DMM lead to point E. The voltage reading should be the same as at point A. Disconnect the DMM. a. If there are 0 volts, look for a broken or disconnected wire. b. If less than 12 volts, look for a loose or corroded terminal. c. If 12 volts or more are noted, proceed with step 4. 4. Connect the DMM to point F and note the voltage. Disconnect the DMM. a. If 0 volts are noted, the switch is open. Skip to step 5. NOTE: It should be closed. b. If 12 volts or more are noted, the relay has power to the coil. Proceed with further testing. 5. Connect one DMM lead to point F and the other lead to point G. This is a voltage drop test of the relay coil assembly; your reading should be close to source voltage (12 volts). a. If there are 0 volts, the relay coil is internally open or the ground circuit is open. Inspect the ground circuit. If it is okay, the blower relay needs to be replaced. b. If 12 volts or more are noted, proceed to step 6. c. If less than 12 volts are noted, there is excessive resistance in the relay coil circuit. Perform voltage drops on the wiring, switches, and connections (each should drop less than 0.2 volt). 6. Connect the DMM red lead to point H and black lead to ground. a. If 12 volts or more are noted, the blower motor should operate. If the blower motor does not operate, proceed to the diagnostic steps under “Testing the Blower Motor” in the next section. 86 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

b. If there are 0 volts, replace the relay. c. If less than 12 volts are detected, check for loose or corroded connections. If connections are okay, replace the relay.

Testing the Blower Motor (Figure 3-22)

Turn the ignition switch to the ON position, the air conditioning switch to A/C, and the blower motor switch to high speed. Set the DMM to a DC volt scale. 1. Connect the DMM to point A of the blower motor. a. The voltage should be the same as measured at point H of the previous test, 12 volts or more. b. If 0 volts are noted, look for a disconnected wire or connection. c. If less than 12 volts, look for a loose or corroded wire or connector. d. If there are 12 volts or more, proceed with step 2. Wiring and switches in a circuit should have a voltage drop of less than 0.2 volt, and the entire circuit’s total voltage drop (aside from the load device in the circuit, which should drop close to source voltage) should not add up to more than 0.5 volt in general. Remember, the sum of all voltage drops must add up to source voltage. 2. Connect the DMM in parallel as depicted in Figure 3-23. a. If the meter reads 12 volts or more and the blower motor will not operate, replace the blower motor. If the blower motor operates but turns slowly, proceed to step 3. b. If the voltage is 0 volts, check for an opening in the ground circuit wire. If the ground wire is okay, replace the blower motor. c. If the voltage is less than 12 volts, check for unwanted resistance in the connectors, wiring of the blower motor circuit, and repair fault. Use a voltage drop test of the suspect area to confirm the diagnosis (wiring should drop less than 0.1 volt). Blower motor relay

Blower motor

A

Voltmeter DIGITAL MULTIMETER %

FIGURE 3-22  Testing the blower motor circuit.

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DIGITAL MULTIMETER %

Voltmeter

Blower motor relay

Blower motor FIGURE 3-23  Blower motor voltage drop test.

CAUTION:

If an ammeter is accidentally connected to a circuit in parallel instead of in series serious damage to circuit, ammeter or both will result.

CAUTION:

Never connect an ammeter in series to a circuit that is protected by a fuse with a higher rated amperage value than the rated value of the meters internal fuse.

3. If the blower motor operates slowly, check the amperage draw of the blower motor and compare the results to the manufacturer’s specifications. Connect the DMM as outlined in Figure 3-24, and set the meter to the ampere (A) scale. a. Disconnect the blower motor harness connection from the motor, and connect a jumper lead from the ground (negative) terminal of the harness connector to the blower motor ground (negative) terminal. Blower motor relay

Ammeter DIGITAL MULTIMETER %

Blower motor

20 A fuse

FIGURE 3-24  Blower motor current test with meter in series.

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b. Connect a fused jumper lead (the fuse rating should be lower than the rating on the internal fuse of the meter and that of the circuit being tested) from the blower motor harness positive connector terminal to the meter positive (red) lead and connect the meter negative (black) lead to the positive terminal on the blower motor. The meter should now be wired in series with the blower motor. c. Compare the amperage draw to the manufacturer’s specifications; if they are higher than specifications, replace the blower motor.

Testing the Blower Motor Speed Resistor (Figure 3-25).

Though blower motor speed resistor resistance values differ between vehicle makes, they are typically as suggested in this procedure. Before conducting this test, disconnect all wires from the resistor. NOTE: DO NOT connect the DMM to the disconnected wires. 1. Select the ohm scale of the DMM (on manual DMM select the 200 V scale). Connect one lead of the DMM to terminal 2 of the blower motor resistor. a. Touch the other DMM test lead to terminal 4 of the blower motor resistor. The resistance should be within manufacturer specifications (i.e., 0.3120.35 V). b. Touch the other DMM test lead to terminal 1 of the blower motor resistor. The resistance should be within manufacturer specifications (i.e., 0.8821.0 V). c. Touch the other DMM test lead to terminal 3 of the blower motor resistor. The resistance should be within manufacturer specifications (i.e., 1.822.1 V). 2. If the resistance is not as specified by the manufacturer, the blower motor resistor should be replaced.

Testing the Blower Motor Switch (Figure 3-26).

Methods of testing the blower motor switch, depending on vehicle make and model, are outlined in the manufacturer’s service manual. Procedures given here assume reasonable access to the control. Remove the connectors from the switch. Test 1: 1. Select the ohm scale of the DMM (on manual DMM select the 200 V scale). Connect one test lead to terminal 5 of the blower motor switch. a. Connect the other test lead to terminal 3 of the blower motor switch and, while observing the meter, turn the switch to LO. NOTE: The meter should have gone from infinity (` ) to a very low resistance, such as 0 V.

To blower motor

Blower speed resistor 3

2 1

4 L ML MH H

To blower speed switch FIGURE 3-25  Test points for blower motor speed resistor.

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3 6 2 7 LO

ML

8

MH

HI

Off Off LO

Blower switch 5

HI MH ML

1

FIGURE 3-26  Test points for blower motor switch.

b. Disconnect the test lead and connect it to terminal 6 of the blower motor switch and, while observing the meter, turn the switch to ML. NOTE: The meter should have gone from infinity (` ) to a very low resistance, such as 0 V. c. Disconnect the test lead and connect it to terminal 2 of the blower motor switch and, while observing the meter, turn the switch to MH. NOTE: The meter should have gone from infinity (` ) to a very low resistance, such as 0 V. d. Disconnect the test lead and connect it to terminal 7 of the blower motor switch and, while observing the meter, turn the switch to HI. NOTE: The meter should have gone from infinity (` ) to a very low resistance, such as 0 V. Test 2: 1. Connect one test lead to terminal 1 of the blower motor switch. a. Connect the other test lead to terminal 8 of the blower motor switch. b. While observing the meter, turn the switch to LO. NOTE: The meter should go from infinity (` ) to a very low resistance, such as 0 V.

c. While observing the meter, turn the switch to ML, MH, then to H. NOTE: The meter should remain on a very low resistance, such as 0 V.

If the blower motor speed control switch failed either of the above tests, it must be replaced.

Testing the A/C Switch (Figure 3-27).

Methods of testing the A/C switch, depending on vehicle make and model, are outlined in the manufacturer’s service manual. Procedures given here are typical and assume reasonable access to the switch. 1. Gain access to the A/C switch and disconnect all wires. 2. Select the ohm scale of the DMM (on manual DMM select the 200 V scale). 3. Connect one test lead of the DMM to terminal 1 of the A/C switch. a. Connect the other test lead to terminal 5 of the A/C switch. b. While observing the meter, turn the switch to ECO. NOTE: The meter should go from infinity (` ) to a very low resistance, such as 0 V. 4. Disconnect the test lead from terminal 5 and connect it to terminal 3. While observing the meter, turn the switch to A/C. NOTE: The meter should go from infinity (` ) to a very low resistance, such as 0 V. 5. If the A/C switch failed either of the above tests, it must be replaced. 90 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

25A

Blower motor ICA 4 relay

OFF

ON

2

3 Junction box

4

3 Blower motor

85

M

Blower speed resistor

DGER

3 6 2 7 LO

ML

MH

8

HI

OFF OFF LO

Blower switch

3

5

ML

HI MH

1 1 DVOM OFF

A/C 200

ECON

5

3

A/C Switch Test 1 Test 2 FIGURE 3-27  Testing the A/C switch.

Terms To Know

case study A customer complains that the blower motor will only operate on high speed. The technician confirms the customer complaint. The technician checks the fuses and all are good. Next, the technician checks for power at the resistor block and finds that all voltage readings to the resistor block are within specifications. But when the technician checks for power at the blower motor, 12.4 volts is available in high speed but only 0.4 volts is available at all other speeds. Upon further

inspection, the technician performs a voltage drop test at the resistor block output terminal and finds that 12.0 volts is being dropped at the output connector of the resistor block and the terminal is partially melted. The technician receives approval for the repair and replaced the resistor block output connector and terminal. Next, the technician confirms the repair by testing for all blower motor speeds and returns the repaired vehicle to the customer.

Voltage Amperage Resistance Opens Shorts Open circuit Voltage drop Overload Fuses Circuit breakers Fusible link

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ASE-STYLE REVIEW QUESTIONS 1. Refer to Figure 3-28 below. Technician A says that the compressor clutch diode in the clutch electrical circuit is in series with the compressor clutch coil. Technician B says that a blown HVAC 20 A fuse in the IP fuse block will prevent blower motor operation in all speeds except high. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 2. A test lamp has been connected from the blower motor ground to the “hot” side of the fuse or circuit breaker: Technician A says that if the lamp does not light, a defective ground wire is indicated. Technician B says that if the lamp lights, a defective blower motor is indicated. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 3. Technician A says when testing a circuit or component the voltmeter is connected in parallel with the circuit. Technician B says a DMM has a low impedance or input resistance, which allows the meter to draw current when connected to a circuit. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 4. Technician A says a voltage drop is the amount of electrical energy that is converted to another form of energy. Technician B says a voltage drop test is the preferred method of testing for unwanted resistance in a circuit when the circuit is under a load (turned on) Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 5. Technician A says if a wire or wiring in a circuit has higher than designed resistance, the wire will drop some of the available voltage. Technician B says unwanted resistance will cause current flow to go up in a circuit and the circuit protective fuse will fail. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

6. Technician A says in order to test the resistance of a component with a DMM, the circuit or component must be open and isolated so that voltage cannot flow. Technician B says that the term “continuity” means that current can flow in the circuit and that there was no problem found. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 7. Technician A says when testing for amperage flow in a circuit the DMM leads must then be placed in parallel with the circuit. Technician B says that the easiest way to test for amperage flow in a circuit is to use an inductive pickup. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 8. Technician A says a fuse is a replaceable component with an element that will melt should the current passing through it exceed its rated value. Technician B says a fuse is commonly used on a component that may experience a temporary high current surge such as an air-conditioning compressor electromagnetic clutch. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 9. Technician A says a circuit has an open when there is a complete path for current to flow. Technician B says that an open circuit will not cause a circuit protection device such as a fuse to fail. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 10. Technician A says a fuse should only be replaced with the same ampere rating as the original designed for the circuit. Technician B says circuit breakers can be replaced with one of a slightly lower ampere rating if the original size designed for the circuit is not available. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

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Hot at all times

UBEC HVAC 30A

Hot in run

IP Fuse Panel HVAC 20A

HVAC controller Off Hot in run

Off

A/C fuse 10A

Hot at all times

UBEC

Ign fuse 10A

Compressor clutch relay

A/C clutch

Blower motor

Blower motor relay

5v A/C pressure transducer

FIGURE 3-28  For ASE-Style Review Question #1.

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ASE CHALLENGE QUESTIONS Blower motor relay

Fusible link A

Fusible link B

C E

25A

1

D

Blower motor 10CA 4 relay

F Blower motor

A

OFF ON 3

2

G

To blower motor

V DIGITAL MULTIMETER %

1. The blower motor does not operate, although there are 12 volts available at motor terminal “A” in the illustration above. The most likely problem is: A. “Blown” fuse or open circuit breaker B. Defective relay ground C. Defective blower motor relay D. Loose or defective motor ground wire

2. The blower motor does not operate. The voltage at point F on the illustration above is 0 volts. The most likely cause of this problem is a defective: A. 10-ampere fuse B. 25-ampere fuse C. Blower motor relay coil D. Blower motor relay contacts 3. All of the following could reduce electrical circuit current flow except: A. Too small a diameter wire B. Internal wire corrosion C. A power wire that is shorted to a ground path D. A loose electrical terminal connection 4. If a poor electrical connection is suspected, which is the most effective test to perform? A. Resistance measurement at the connector B. Amperage draw test of the circuit C. A voltage drop test at the connector D. Check source voltage at the connector

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5. Refer to the figure below. The blower motor operates at high speed only. The most likely cause of this problem would be: A. An open at the blower speed resistor B. A faulty blower motor relay C. A short to ground at blower switch terminal 7 D. A faulty ground at the blower switch Hot all the time

Hot all the time

Hot all the time

Hot in run

25A Blower motor ICA 4 relay 2

ON

2

3 Junction box

Cooling fan motor

4

3 Blower motor

M

Blower speed resistor

2

M

ON OFF

85

DGER

ON OFF

1

3 6 2 7 LO

ML

MH

OFF

Cooling fan motor relay

HI

ON

5

OFF

3

4 M

Clutch coil

4

ON

3 Clutch relay

1

1 1

OFF

1

HI MH ML

OFF LO

Blower switch

OFF

8

2

2 21

83

~

~

OFF

10A

~

25A

~

Engine control module

A/C 200

A/C Switch

5

3

1

~ GMD 2

~ GMD 7

~

~ 4

Air inlet sensor

~

~

~

A/C control unit

9

~ 8

10

Air thermo sensor

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JOB SHEET

8

Name ________________________________________ Date _______________________

Test a Blower Motor Upon completion of this job sheet, you should be able to test a blower motor circuit and determine proper operation of the blower resistor or power module. NATEF Correlation NATEF AST and MAST Correlations: HEATING AND AIR CONDITIONING: Operating Systems and Related Controls Diagnosis and Repair. Task #1. Inspect and test A/C-heater blower, motors, resistors, switches, relays, wiring, and protection devices; perform necessary action. (P-1) Tools and Materials Late-model vehicle Shop manual Voltmeter Fused jumper wire Safety glasses or goggles Hand tools, as required Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN _____________________________ Engine type and size ____________________________ Procedure After each of the following steps, write a brief description of your procedure, followed by your findings.

Test the blower motor: 1. With the ignition switch is in the ON position, turn the blower control to: a. HIGH ___________________________________________________________________ b. MED-HI _________________________________________________________________ c. MED-LO _________________________________________________________________ d. LOW ____________________________________________________________________ Did the blower run in any speed? Explain: _______________________________________ 2. Turn the blower control and ignition switch OFF. Disconnect the blower motor and connect the voltmeter: one lead to ground and the other lead to the disconnected wire. Is there a voltage? ___________________________ Why? ___________________________

_______________________________________________________________________________

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3. Reconnect the blower motor connector. Using T-pins back probe the blower motor power and ground wires. Connect the DMM red lead to the power feed wire and connect the DMM black lead to the ground wire (or blower motor housing, in some applications). 4. Turn the ignition switch ON. While observing the voltmeter, turn the blower control to: a. HIGH ___________________________________________________________________ b. MED-HI _________________________________________________________________ c. MED-LO _________________________________________________________________ d. LOW ____________________________________________________________________ Was there voltage noted in any speed position? Explain: ___________________________ _________________________________________________________________________ e. Turn the blower control and ignition switch OFF. 5. Connect one end of a fused jumper wire to the battery’s positive terminal. While wearing OSHA-approved safety glasses or goggles, carefully connect the other end of the jumper wire to the blower motor terminal. Was there a “spark”? ____________________ Did the fuse “blow”? ___________________ Did the motor “run”? ___________________ Describe what happened. _____________________________________________________

_______________________________________________________________________________

6. Conclusion. Write a brief summary of your findings.

_______________________________________________________________________________



_______________________________________________________________________________



_______________________________________________________________________________



_______________________________________________________________________________

Instructor’s Response _____________________________________________________________ ________________________________________________________________________________ _____________________________________________________________________________

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JOB SHEET

9

Name ________________________________________ Date _______________________

Testing and Replacing Fuses and Circuit Breakers Upon completion of this job sheet, you should be able to test and replace fuses and circuit breakers. NATEF Correlation NATEF AST and MAST Correlations: HEATING AND AIR CONDITIONING: Operating Systems and Related Controls Diagnosis and Repair. Task #3. Diagnose malfunctions in the vacuum, mechanical, and electrical components and controls of the heating, ventilation, and A/C (HVAC) system; determine necessary action. (P-2) Tools and Materials Vehicle with accessible fuse/circuit breaker panel Test light (fused, nonpowered) Test light (fused, powered) Ohmmeter Tools, as needed Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN _____________________________ Engine type and size ____________________________ Procedure Using a nonpowered test light, perform the following tasks. Write a brief description of your procedure and of your findings. 1. Connect one probe of the test light to ground. a. Touch the other probe to the positive side of the fuse panel bus bar.

_______________________________________________________________________________

_______________________________________________________________________________ b. Touch the other probe to the other side of selected fuses and circuit breakers.

Fuses: _________________________________________________________________________



_______________________________________________________________________________



Circuit breakers: ________________________________________________________________



_______________________________________________________________________________

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2. Remove a selected fuse and a circuit breaker. Make note of their location and amperage.

_______________________________________________________________________________



_______________________________________________________________________________

3. Touch the probes of the self-powered test light to the two ends of the fuse.

_______________________________________________________________________________



_______________________________________________________________________________

4. Touch the probes of the self-powered test lamp to the two terminals of the circuit breaker.

_______________________________________________________________________________



_______________________________________________________________________________ NOTE: For steps 5 and 6, DO NOT connect the ohmmeter to the self-powered test lamp.

5. Hold the same test as step 3 using an ohmmeter.

_______________________________________________________________________________



_______________________________________________________________________________

6. Hold the same test as step 4 using an ohmmeter.

_______________________________________________________________________________



_______________________________________________________________________________

7. Perform any other tests as outlined by your instructor.

Test ___________________________________________________________________________



Results ________________________________________________________________________



_______________________________________________________________________________



_______________________________________________________________________________

Instructor’s Response _____________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________

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Chapter 4

BASIC TOOLS Basic mechanic’s tool set

Diagnosis and Service of Engine Cooling and Comfort Heating Systems

Upon Completion and Review of this Chapter, you should be able to: Identify the major components of the automotive engine cooling and comfort heating system.

■■

■■

Compare the different types of radiators.

■■

■■

Discuss the function of the coolant pump.

■■

Explain the need for a pressurized cooling system.

■■

Describe the advantage of a thermostat in the cooling system.

■■

■■

Understand the procedures used for testing the various cooling system components. Recognize the hazards associated with cooling system service. Understand troubleshooting procedures for determining the malfunction of cooling system components.

A typical gasoline engine is only about 15 percent efficient; only about 15 percent of the energy is used to move the vehicle. That means that 85 percent of all energy developed by the engine is wasted in friction and heat—heat that must be removed. While the heat of combustion may reach as high as 4,0008F (2,2008C), most of it is expelled when the exhaust valve opens. This results in an actual net engine temperature range from about 7508F (4108C) to about 1,5008F (8158C). This is still a great deal of heat, and it must be removed. The coolant, a mixture of water (H2O) and ethylene glycol, is the liquid used to transfer this heat from the engine to the radiator.

The Cooling System The cooling system (Figure 4-1) is made up of several components, all of which are essential to its proper operation. They are the radiator, pump, pressure cap, thermostat, cooling fan, heater core, hoses and clamps, and coolant. The most common cooling system problems are a result of a leaking system. A sound system seldom presents a problem. Leaks are generally easy to find using a pressure tester. Several types are available. The following is a typical procedure for pressure testing a cooling system: 1. Allow the engine and coolant to cool to ambient temperature. 2. Remove the pressure cap. Note the pressure range indicated on the cap (Figure 4-2). 3. Adjust the coolant level to a point just below the bottom of the fill neck of the radiator. 4. Attach the pressure tester (Figure 4-3). 5. While observing the gauge, pump the tester until a pressure equal to the cap rating is achieved. If the pressure can be achieved, proceed with step 6. If the pressure cannot be achieved, make a visual inspection for leaks.

Classroom Manual Chapter 4, page 82

A common leak point is due to loose hose clamps. Ambient temperature is the temperature of the surrounding air. The fill neck is the part of the radiator on which the pressure cap is attached.

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Overflow recovery tank

Radiator cap

Radiator hose Thermostat

Heater control

Heater core

AIR FLOW Heater hoses

Radiator Water pump

Combustion chamber

Water jacket

FIGURE 4-1  A typical automotive cooling system.

FIGURE 4-2  A pressure cap showing the pressure rating.

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FIGURE 4-3  Attach a pressure tester to the radiator neck.

FIGURE 4-4  Pump the tester until a pressure equal to the cap rating is noted on the gauge.

6. Let the system stand for 5 minutes. Recheck the gauge. If pressure drops rapidly, proceed to step 7. If the pressure is the same as in step 5, the system is all right, and it is safe to proceed to step 8. If the pressure has dropped slightly, repressurize the system to the top end of the pressure rating and proceed to step 7. If no leak is detected, proceed to step 8. Prior to removing the pressure tester form the system; de-pressuring the tester according to tool manufacturers recommendation. 7. Locate the source of the leak by visibly inspecting all connections. Also inspect the passenger compartment for signs of coolant on the floor. Repair the source of the leak, then repeat steps 4–6 to verify the repair. 8. Check the radiator pressure cap. The cap should be able to hold the pressure noted on the cap (Figure 4-4). If the cap fails the test, replace the cap.

Radiators The purpose of the radiator is to dissipate heat that is picked up by the coolant in the engine into the air passing through its fins and tubes. This is accomplished by natural or forced means. Natural means are created by ram air as the vehicle is in motion. Forced means are created by an engine- or electric motor–driven fan.

Classroom Manual Chapter 4, page 89

A heat exchanger is a device that causes heat to move from one medium to another (e.g., fluid to air, air to air, air to fluid, or fluid to fluid). Dissipate is to disperse, scatter, reduce, weaken, or use up.

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FIGURE 4-5  A typical automotive radiator.

The shroud is a design consideration of the engine cooling system and, as such, should not be removed.

Although radiators (Figure 4-5) are often neglected by the vehicle owner, they generally have a long service life. The service life is greatly increased if periodic and scheduled routine maintenance, outlined in the owner’s manual, is performed. Eventually, however, most radiators will develop a leak or become clogged with rust or corrosion due to lack of attention. For most radiator repairs, the radiator must be removed from the vehicle and “shopped out” to a specialty shop that is equipped with the proper specialized tools, equipment, and knowledgeable service technicians to perform this type of repair. If a radiator is badly damaged, such as would result from a collision, it is often less expensive to replace it with a new unit. The following is a typical procedure for removing a radiator from the vehicle. The actual procedure for any particular make or model vehicle is provided in the manufacturer’s specifications. If there is an engine-mounted cooling fan (Figure 4-6), start with step 1. If there is an electric cooling fan (Figure 4-7), start with step 2. 1. If the fan is equipped with a shroud, remove the attachments and slide the shroud toward the engine. Proceed to step 3. 2. Remove the electrical connector from the fan motor. Remove the fasteners from the fan assembly brackets and lift the fan assembly out. Care must be taken not to damage the radiator cooling fins. Water pump pulley

Fan Clutch FIGURE 4-6  A typical engine-mounted belt-driven cooling fan.

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Radiator

Cooling fan motor

Condenser fan motor

FIGURE 4-7  A typical electric motor–driven cooling fan.

3. Carefully remove the upper and lower coolant hoses from the radiator. 4. Remove the transmission cooler lines (if the vehicle has an automatic transmission) from the radiator. Plug the lines to prevent transmission fluid loss. 5. Remove the radiator attaching bolts and brackets. 6. Carefully lift out the radiator.

Electrochemical Activity

CAUTION:

Take care not to damage the delicate fins of the radiator when removing it.

As noted in the Classroom Manual, electrochemical activity and electrolysis can take place in the cooling system with devastating results. Many components can be damaged, resulting in their eventual failure, such as radiator and heater cores, the water pump, hoses, and even head gaskets. The following test will check for stay voltage in the cooling system. 1. First set the digital volt-ohmmeter (DVOM) to the direct current (DC) millivolt scale. 2. Connect the negative probe to the negative post of the battery and submerge the positive lead into the coolant at the radiator filler neck, making sure the probe does not touch any metal. 3. Note the meter reading. The voltage reading should be below 0.10 volt. If higher voltage readings are obtained, proceed to step 4. If the voltage is at or below 0.10 volt, the system is okay. Electrolysis can also be caused by stray voltage from electrical components. 4. Start the vehicle, turn on the accessories, and retest. If the voltage is above 0.10 volt, methodically shut off all systems to isolate the circuit-causing voltage.

Coolant Pump The coolant pump (Figure 4-8) may be thought of as the heart of the cooling system. Its purpose is to move the coolant through the system as long as the engine is running. To replace a coolant pump, it is often necessary to remove accessories, such as the power steering pump, air conditioning compressor, alternator, or the air pump, to gain access. It is advisable to refer to the specific manufacturer’s service manuals when replacing the coolant pump. The following, however, is a typical procedural outline. 1. Remove the radiator as previously outlined, if necessary, to gain access to the coolant pump. 2. Loosen and remove all belts. If there is an engine-mounted fan, proceed with step 3. If there is an electric fan, proceed with step 4. 3. Remove the fan and fan/clutch assembly.

A centrifugal pump is a variabledisplacement pump. Restricting the flow of coolant does not harm the pump.

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Water pump

Gasket Water pump pulley FIGURE 4-8  A typical coolant pump.

CAUTION:

For reassembly, note the size and length of the bolts removed. The bolts may be both English and metric and all may not be the same length.

4. Remove the coolant pump pulley. 5. Remove accessories as necessary to gain access to the water pump bolts. 6. Remove the lower radiator hose from the water pump. 7. Remove the bypass hose, if equipped. 8. Remove the bolts securing the water pump to the engine. 9. Tap the water pump lightly, if necessary, to remove it from the engine. 10. Clean the old gasket material from all surfaces. Take care not to scratch the mating surfaces. 11. Install new gaskets and seals and coat bolts with thread sealant (liquid Teflon), if specified by the manufacturer. Reverse the removal steps to install a new water pump assembly and torque the fasteners to the manufacturer’s specifications.

Pressure Cap Classroom Manual Chapter 4, page 90

If a pressure cap fails to hold pressure or if it fails to release high pressure, it must be replaced.

A radiator pressure cap (Figure 4-9) is necessary to maintain the desired engine temperature without coolant loss. A pressure cap is usually designed to operate in the 14–17 psi (97–117 kPa) pressure range. Pressure caps may be tested using a cooling system pressure tester and an adapter. The requirement is that a pressure cap not leak at a pressure below what it is rated and that it must open at a pressure above what it is rated.

FIGURE 4-9  Typical radiator pressure caps.

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To pressure test a radiator cap, proceed as follows: 1. Attach the adapter to the pressure tester (Figure 4-10). 2. Install the pressure cap to be tested (Figure 4-11). 3. Pump the pressure tester to the value marked on the pressure cap (Figure 4-12). 4. Did the cap hold pressure? If yes, proceed with step 5. If no, replace the cap. 5. Pump to exceed the pressure rating of the cap. 6. Did the cap release pressure? If yes, the cap is good. If no, replace the cap.

FIGURE 4-10  Attach the adapter to the pressure tester.

FIGURE 4-11  Install the pressure cap.

FIGURE 4-12  Pump the tester to a pressure equal to the cap rating.

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Classroom Manual Chapter 4, page 83

The thermostat operating temperature is a part of the design consideration of the engine and should not be altered.

Thermostats The purpose of the thermostat (Figure 4-13) is to trap the coolant in the engine until it reaches its operating temperature. It then restricts the flow of coolant leaving the engine until overall coolant temperature is at or near operating temperature. Even when fully open, the thermostat provides a restriction to coolant flow in order to create a pressure difference. This pressure difference prevents water pump cavitations and forces coolant circulation through the cylinder block and head(s). A typical procedure for removing a thermostat follows.

Thermostat Removal 1. Reduce the engine coolant to a level below the thermostat. 2. Remove the bolts holding the thermostat housing onto the engine (Figure 4-14). It is not necessary to remove the radiator hose from the housing. 3. Lift off the thermostat housing (Figure 4-15). Observe the pellet-side down position of the thermostat to ensure proper replacement. Do not install the thermostat backward. 4. Lift out the thermostat (Figure 4-16). 5. Clean all the old gasket material from the thermostat housing and engine-mating surface. Many thermostats today use O-ring seals, while other thermostats have centers that are offset. Be sure the replacement thermostat physically matches the one being removed. Install the new thermostat in the same position as the one that was removed, and torque it to the manufacturer’s specifications.

FIGURE 4-13  A typical cooling system thermostat.

FIGURE 4-14  Remove the bolts holding the thermostat housing.

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FIGURE 4-15  Lift off the thermostat housing.

FIGURE 4-16  Lift out the thermostat.

There are several ways to test a thermostat. Many, however, believe that if a thermostat is suspect, it should be replaced. The labor cost for the time required to test a thermostat often outweighs the cost of a thermostat. Following is a procedure for testing a thermostat that has been removed from the engine.

Thermostat Testing WARNING: The water (H2 O) temperature may reach 2128F (1008C). Wear suitable protection. 1. Note the condition of the thermostat. 2. Is the thermostat corroded or open? If no, proceed with step 3. If yes, replace the thermostat. 3. Note the temperature range of the thermostat. 4. Suspend the thermostat in a heatproof glass container filled with water. 5. Suspend a thermometer in the container. Neither the thermostat nor the thermometer should touch the container or touch each other. 109 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Check temperature when thermostat opens

Classroom Manual Chapter 4, page 101 Heat An idler is a pulley used to tension or reroute the direction of a belt. A drive pulley transmits or inputs power into a component. Replace any belt that appears to be worn, frayed, or damaged. A serpentine belt is a flat or multi V-grooved belt that winds through all of the engine accessories to drive them off the crankshaft pulley with both sides of the belt being drive surfaces. A V-belt is a belt designed to run in a single V-shaped groove of a drive or idler pulley with only the tapered surface being the drive surface. Most systems require several V belts to drive all of the engine accessories.

FIGURE 4-17  Checking thermostat operation.

6. Place the container and contents on a stove burner and turn on the burner. 7. Observe the thermometer. The thermostat valve should begin to open at its rated temperature value (Figure 4-17). If it begins to open more than 638F its rated value, replace the thermostat. 8. Is the thermostat fully opened at approximately 258F (118C) above its rated value? If yes, the thermostat is all right. If not, replace the thermostat.

Customer Care: There is generally no service interval stated for the replacement of the cooling system thermostat. But, as a preventive maintenance item, thermostat replacement should be suggested when the engine coolant is changed.

Pulleys Pulleys require periodic inspection. Pulley problems that may occur are damage due to collision or defective bearings in an idler or drive pulley. In all cases, repair is straightforward; replace the faulty bearing or pulley. Plastic pulleys used on serpentine belt systems will wear and develop grooves and cracks over time; inspect and replace them when necessary.

Belts and Tensioner There are two types of belts used in the automotive engine cooling and air-conditioning system: the serpentine belt (Figure 4-18) and the V-belt (Figure 4-19). Photo Sequence 1 illustrates a typical procedure for servicing the serpentine drive belt. Prior to removal of the serpentine belt locate the routing diagram similar to the one shown in Figure 4-18. This diagram is often located under the hood in the engine bay, often on the radiator support cover. The diagram may also be located in the vehicle service information. Some technicians choose to draw a sketch of the belt routing prior to removal. A belt tension gauge may be used to ensure proper belt tensioning for those systems with manual adjustment. Many late-model vehicles have an automatic belt tensioner, a springloaded idler pulley. If the belt is manually adjusted, it is suggested that a new belt again be tensioned after about 15 minutes of operation to allow time for initial seating and stretching. The belt should then be checked every 5,000 miles (8,000 kilometers) or so.

Automatic Belt Tensioner

The drive belts on most late-model engines are equipped with a spring-loaded automatic tensioner. An automatic belt tensioner may be used with all belt configurations, such as with or without power steering and air conditioning. 110 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 4-18  A typical serpentine belt routing.

Alternator pulley

Belt cross section

Power steering pump pulley

AC compressor pulley Water pump pulley

Air pump pulley Crankshaft pulley

FIGURE 4-19  A typical V-belt routing.

Belt-driven engine accessories are often replaced due to noise or other problems only to learn that the automatic tensioner was at fault. Table 4.1 is an aid in diagnosing drive belt problems. If an automatic spring tensioner shows any sign of binding during belt replacement, the tensioner needs to be replaced. 111 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

PHOTO SEQUENCE 1 Typical Procedure for Servicing the Serpentine Drive Belt

P1-1  Release the belt tension, following specific instructions provided in the manufacturer’s shop manual.

P1-2  Remove the belt.

P1-3  Inspect the pulleys for nicks, cracks, bent sidewalls, corrosion, or other damage.

P1-4  Place a straightedge across pulleys to check for alignment.

P1-5  Turn each pulley one-half revolution and repeat step 4.

P1-6  Inspect the drive belt. Check for wear.

P1-8  Replace the belt by reversing steps 1 and 2.

P1-9  Do not use belt dressing on a serpentine belt. Belt dressing may soften the belt and cause deterioration.

P1-7  If rib sections are missing, the belt should be replaced, and pulley’s should be inspected.

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TABLE 4-1:  TROUBLESHOOTING DRIVE AND ACCESSORY BELT PROBLEMS Problem

Possible Cause

Possible Remedy

Belt slipping

Belt too loose Coolant or oil on belt or pulley Accessory bearing failure (seized) Belt hardened and glazed

Replace of tighten belt Clean pulleys and replace belt Replace faulty bearing Replace belt

Belt squeal when accelerating

Belt glazed or worn

Replace and tension belt

Belt squeak at idle

Belt too loose Dirt or paint embedded in belt Misaligned accessory pulleys Improper pulley

Replace or tighten belt Replace and tension belt Align pulleys Replace pulley

Noise (rumble heard or felt)

Belt slipping Defective bearing Belt misalignment Improper belt Accessory-included vibration Resonant frequency vibration

Tighten belt Replace bearing Align belts Install proper belt Locate cause and correct Vary belt tension or replace belt

Belt rolls over (V-belt)

Broken cord in belt Belt too loose Belt too tight

Replace and tension belt Replace or tighten belt Replace or loosen belt

Belt jumps off

Broken cord in belt Belt too loose Belt too tight Pulleys misaligned Improper pulley

Replace and tension belt Replace or tighten belt Replace or loosen belt Align pulleys Replace pulley

Belt jumps grooves

Belt too loose Belt too tight Improper pulley Foreign objects in pulley grooves Pulley misaligned Broken belt cordine

Replace or tighten belt Replace or loosen belt Replace pulley Clean grooves or replace pulley Align pulley Replace belt

Broken belt

Excessive tension Belt damaged during installation Severe misalignment Bent or damaged bracket or brace Pulley or bearing failure

Replace belt and adjust tension Replace belt Replace and align belt Repair as required and replace belt Repair as required and replace belt

Rib chunking (rib separation)

Foreign objects embedded in pulley Installation damage

Remove objects and replace belt Replace belt

Rib or belt wear

Pulley misalignment Abrasive environment Rusted pulleys Sharp or jagged pulley groove tips Rubber deteriorated

Align pulleys Clean and replace belt Clean rust or replace pulleys Replace pulley Replace belt

Belt cracking between ribs

Belt mistracked from pulley groove Pulley groove tip has worn away rubber

Replace belt Replace belt

Backside of belt separated

Contacting stationary object Excessive heat Fractured splice

Correct problem and replace belt Replace belt Replace belt

Cord edge failure

Excessive tension Contacting stationary object Incorrect pulley Incorrect belt

Replace belt and adjust tension Correct problem and replace belt Replace pulley and belt Replace belt

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Replacing a Belt Tensioner

The following procedure is typical for replacing an automatic belt tensioner. Always follow the particular manufacturer’s recommended procedures for each vehicle. 1. Attach a socket wrench to the mounting bolt of the automatic tensioner pulley bolt (Figure 4-20). 2. Rotate the tensioner assembly clockwise (cw) until the belt tension has been relieved. 3. Remove the belt from the idler pulley first, then remove the belt from the other pulleys. 4. Disconnect and remove and set aside any components hindering tensioner removal. 5. Remove the tensioner assembly from the mounting bracket. WARNING: Because of high spring pressure, do not disassemble the automatic tensioner.

An indexing tab is a mark or protrusion on mating components to ensure that they will be assembled in their proper position.

6. Remove the pulley bolt and remove the pulley from the tensioner. 7. Install the pulley and pulley bolt in the tensioner. Tighten the bolt to 45 ft.-lb (61 N ⋅ m). 8. Install the tensioner assembly to the mounting bracket. An indexing tab (Figure 4-21) is generally located on the back of the tensioner to align with the slot in the mounting bracket. Tighten the nut to 50 ft.-lb (67 N ⋅ m). 9. Replace any components removed in step 4. 10. Position the drive belt over all pulleys, except the idler pulley. 11. Using a socket wrench on the pulley mounting bolt of the automatic tensioner, rotate the tensioner cw. 12. Place the belt over the idler pulley and allow the tensioner to rotate back into position. It should spring back smoothly and with adequate tension pressure on the belt.

CAUTION:

Belt Failure Troubleshooting

When installing the serpentine accessory drive belt, the belt must be routed correctly. If not, the water pump may rotate in the wrong direction (Figure 4-22), causing the engine to overheat.

A variety of critical engine components stop working when a serpentine belt fails. These components may include the water pump, alternator, air conditioning compressor, and power steering pump to name some of the more common belt-driven accessories. It is important Turn clockwise to remove belt

Tensioner

Socket wrench Idler pulley

Fan blade FIGURE 4-20  Rotate the tensioner clockwise (cw) to loosen the belt.

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Idler pulley Tensioner assembly Indexing mark Indexing arrow

FIGURE 4-21  Tensioner indexing tab.

PS TI

PS TI

WP

AP

AC

AP

AC

CP A

WP

CP B

LEGEND: AC - A/C Compressor Pulley AP - Alternator Pulley CP - Crankshaft Pulley

PS - Power Steering Pulley TI - Tensioner/Idler Pulley WP - Water Pump Pulley

FIGURE 4-22  If the belt is not installed correctly, the water pump will be turned in the opposite directions: clockwise (A) and counterclockwise (B).

to be able to identify the reason for a belt failure to ensure that the replacement belt will last and avoid premature failure. Often by observing the belts appearance we can determine the potential causes for the failure or damage. Serpentine belts may be constructed of either neoprene or ethylene propylene diene M-class rubber, which is more commonly called EPDM. The majority of belts manufactured today are made of EPDM. Below is a list and photos of some common belt failures, which outline their cause and the solutions recommended by belt manufacturers. Cracking.  Cracks that are small and perpendicular to the ribs of the belt that occur frequently around its circumference (Figure 4-23) is probably one of the most common reasons for belt 115 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 4-23  Cracks are caused by continuous flexing and bending in high heat conditions and is the most common reason for belt replacement.

replacement. These cracks are caused by continuous flexing and bending in high heat conditions found under the hood as the belt bends around pulleys during normal operation. On neoprene belts eighty percent of the belt life is gone if three or more cracks are found in a three-inch segment of the belt and the belt should be replaced. As a common practice with all belt failures check belt tensioner and idlers pulleys for bearing wear and operation. Belts made of EPDM should not show cracking for 100,000 miles. But EPDM belts may show rib height material wear. EPDM Belt Wear.  Belts made of EPDM wear with age and often require replacement between 80,000–100,000 miles under normal operating conditions. The EPDM belt is more elastic than a standard neoprene belt and resists cracking even at higher mileage, so looking for visible cracks is not an effective method for deterring belt wear and aging. A better indicator of when to replace EPDM belts is rib wear (Figure 4-24). To aid in determining belt wear a belt wear depth gauge is available (Figure 4-25). One free source for this belt wear depth gauge is Gates Belts (www.gatesprograms.com/beltwear). As little as 5–10 percent wear can effect operation; if belt wear is indicated, replacement is required. Abrasion.  Abrasion may cause a shiny or glazed appearance on one or both sides of the belt. In severe cases cord fibers may be visible (Figure 4-26). It is caused by a belt making contact with an object such as a flange bolt or foreign object. It may also be caused by improper belt tension, pulley surface wear, or a binding pulley bearing. Inspect belt tensioner for proper operation, replace if necessary. Improper Installation.  A belt rib on either edge begins separating from main body plies (Figure 4-27). If left unnoticed the outer covering may separate causing the belt to unravel. It is caused by improper replacement procedure when one of the belt ribs is placed outside of one of the pulley grooves during installation. Verify that the belt has the same number of ribs as its companion pulley grooves. Once damage has occurred the belt must be replaced. Ensure that all belt ribs fit properly in all pulley groves when replacing. Pilling.  Pilling occurs as belt material is sheared off from the ribs building up in the grooves (Figure 4-28). It is generally caused by insufficient belt tension, pulley misalignment or wear. It is more common on diesel engines, but can happen on any power train. Pilling can lead to belt noise and vibration. The pulley grooves should be inspected for buildup, the alignment should be checked, and the belt will need to be replaced. It is wise to replace the drive belt as well as the automatic belt tensioner when any pulleydriven component is replaced. By only replacing one system component vibration is increased 116 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

New Belt

Worn Belt

Pulley Fit

Rib Wear Rounded rib tip—Material loss results in belt riding directly on top of pointed pulley tips. Belt can be sheared or slip off the drive.

Material loss reduces clearance between belt and pulley. Water and debris have difficulty passing between the two. Hydroplaning of belt can result. Belt Seating

Material loss results in belt seating further down in pulley. This reduces wedging force necessary to transmit power. FIGURE 4-24  EPDM belts are designed to last 100K miles, but over time the material will wear on the sides and valleys. A 10 percent loss of material is enough to cause performance issues.

FIGURE 4-25  A simple belt wear gauge can be used to detect EPDM belts for groove wear.

dramatically (Figure 4-29). This vibration may be both felt and heard leading to customer complaints and the performance and longevity of the new component may be compromised. The green line on the graph indicates vibration minimization with a new belt, tensioner, and component. The red graph line indicates vibration caused by an ageing drive belt, tensioner, and belt-driven components at 150,000 miles. The blue line indicates the vibration results of just replacing one belt-driven component and reusing the old belt and tensioner. The old belt and tensioner do not dampen new component vibration effectively. Excessive vibration leads to excessive noise and component bearing wear. Today all belt drive components are closely 117 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 4-26  Abrasion is due to belt making contact with an object such as a flange bolt or foreign object.

FIGURE 4-27  A belt rib on either edge begins separating from main body plies caused by improper replacement procedure.

FIGURE 4-28  Pilling occurs as belt material is sheared off from the ribs building up in the grooves.

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Arm Vibration to Represent System Dynamics 200 150 100 50 0 250 2100 2150 2200

Close-up section of tensioner movement engine idle 150K mile components

New alt. without changing belt/tensioner

OE or New aftermarket alt., belt, and tensioner

FIGURE 4-29  When a belt driven component is replaced it is advisable to also replace the belt drive and automatic tensioner to limit system vibration.

integrated and each depends on the belt and tensioner to keep the entire system at optimum operating performance. It is critical that you as a technician check every component in the system; this includes idler pulleys if used.

Fans Coolant pump-mounted fans (Figure 4-30) occasionally require service. They are damaged due to metal fatigue, collision, road hazards, and abuse. Any condition that causes an out-ofbalance pump-mounted fan will result in early pump failure. A check for fan problems is a rather simple task. 1. Remove the belt(s). 2. Visually inspect the fan for cracks, breaks, loose blades, or other damage. Is the fan sound? If yes, proceed with step 3. If no, replace the fan. 3. Hold a straightedge across the front of the fan. Are all blades in equal alignment? If yes, proceed with step 4. If no, replace the fan. 4. Slowly turn the fan while looking for any out-of-true conditions or any other damage.

Classroom Manual Chapter 4, page 112

If there is any doubt as to the physical condition of the fan, replace it.

FIGURE 4-30  A damaged coolant pump-mounted fan.

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Classroom Manual Chapter 4, page 113

If in doubt, replace the fan clutch.

Classroom Manual Chapter 4, page 116

Classroom Manual Chapter 4, page 117

5. Turn the fan fast and look for out-of-true conditions. 6. If the fan fails either test (step 4 or 5), it must be replaced. Due to high operating speeds, it is not recommended that repairs be attempted to an engine cooling fan blade.

Fan Clutch

Most air conditioned vehicles with a coolant pump-mounted fan have a fan clutch (Figure 4-31). This device adds about 6 lb (2.7 kg) to the coolant pump shaft, further increasing the need for a balanced fan. There are several basic tests for troubleshooting a fan clutch. First, make certain that the engine is cold and that it cannot be accidentally started while inspecting the fan clutch. 1. Visually inspect the clutch for signs of fluid loss. 2. Check the condition of the fan blades. 3. Check for a slight resistance when turning the fan blades. Spin the fan; if it rotates more than twice on its own power, the clutch is bad. 4. Check for looseness in the shaft bearing. 5. Install a timing light and tachometer to the engine and place the thermometer between the radiator fins and fan clutch. Start the engine and turn on the air conditioner. Bring the engine speed up to 2,000 rpm and observe the fan. It should be rotating slowly. Place a piece of cardboard in front of the radiator to speed up the warm-up time. Note the temperature at which the fan begins to rotate faster, generally 15021598F (652608C). Compare this temperature to the manufacturer’s specifications for engagement temperature. If the fan clutch fails any of these tests, it should be replaced. There are no repairs for a faulty fan clutch.

Flexible Fans

Flexible fans are covered in detail in the Classroom Manual. They are subject to the same problems and are tested in basically the same manner as rigid fans.

Electric Fans

Electric cooling fans (Figure 4-32) are used because there is more precise control over their operation. They may be turned on and off by temperature- and pressure-actuated switches, thereby regulating engine coolant and air conditioning refrigerant temperatures at a more precise level.

Working chamber

Silicone oil

Shaft

Clutch plate Fan hub FIGURE 4-31  A typical fan clutch.

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FIGURE 4-32  A typical electric cooling fan.

WARNING: Electric engine cooling fans may start and operate at any time and without warning. This may occur with the ignition switch off or on. Follow the schematic in Figure 4-33 for testing and troubleshooting a typical engine cooling fan system. The fan relay is an electromagnetic switch that controls the cooling and auxiliary fan motors. 1. Start the engine and bring the coolant up to operating temperature. 2. Turn on the air conditioner. 3. Disconnect the cooling fan motor electrical lead connector (Figure 4-34). Verify fan spins freely. 4. Make sure that the ground wire is not disturbed. If the ground wire is a part of the electrical connector, establish a ground connection with a jumper wire (Figure 4-35). 5. Connect a test lamp from ground to the hot wire of the connector (Figure 4-36). Make sure the lamp is good. 6. Did the lamp light? If yes, proceed with step 7. If no, check for a defective fan relay or temperature switch. It is also possible that the engine is not up to sufficient temperature to initiate cooling fan action. 7. Connect a fused jumper wire from the battery positive (1) terminal to the cooling fan connector (Figure 4-37). Make sure the fuse is good.

12-V Batt

F/L

The ground connection must be established to a metal part of the body that is not isolated from electrical ground. The fan relay is an electromagnetic switch that controls the cooling and/or auxiliary fan motors. Make certain that the engine is up to normal operating temperature.

Thermostat*

12-V Ign

Fuse

Fan motor Fan relay Selector switch

Norm Max Off

Bi-level Vent Heat Def

*(Thermostat) engine coolant temperature switch FIGURE 4-33  An electrical schematic of an engine cooling fan system.

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12-V Batt

F/L

Thermostat*

12-V Ign Fan motor Fuse

Fan relay Norm Selector switch

Max Off

Bi-level Vent Heat Def

Disconnect Disconnect

*(Thermostat) engine coolant temperature switch FIGURE 4-34  Disconnect the cooling fan electric motor.

12-V Batt

F/L

Thermostat*

12-V Ign Fan motor Fuse

Fan relay Norm Selector switch

Max Off

Bi-level Vent Heat Def

*(Thermostat) engine coolant temperature switch FIGURE 4-35  Establish ground with a jumper wire.

12-V Batt

F/L

Thermostat*

12-V Ign

Fuse

Fan motor Fan relay Norm Selector switch

Max Off

Bi-level Vent Heat Def

*(Thermostat) engine coolant temperature switch

Test lamp

FIGURE 4-36  Connect a test lamp from ground to the hot wire.

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Fuse

12-V Batt

F/L

Thermostat*

12-V Ign Fan motor Fuse

Fan relay Norm Selector switch

Max Off

Bi-level Vent Heat Def

*(Thermostat) engine coolant temperature switch FIGURE 4-37  Connect a fused jumper wire from the battery positive (1) terminal to the cooling fan connector.

8. Did the fan start and run? If yes, the fan is all right. Check for poor connections at the fan motor and repair them if necessary. If no, proceed with step 9. 9. Again check the fuse in the jumper wire. Is it blown? If yes, the motor is shorted and must be replaced. If no, the motor is open and must be replaced.

Hoses and Clamps Engine cooling system hoses and clamps should be replaced every few years. This should become part of a good preventive maintenance program. If done on a periodic schedule, more expensive repairs, such as those caused by an overheating engine, are not as likely to occur.

Hoses

Carefully check all cooling system hoses when a vehicle is being serviced. The following is a simple checklist for this service: 1. Check for leaks, usually noted by a white, green, or rust color at the point of the leak. 2. Check for swelling, usually obvious when the engine is at operating pressure. 3. Check for chafing, usually caused by a belt or other nearby component. 4. Check for a soft or spongy hose that would indicate chemical deterioration. 5. Check for a brittle hose indicating repeated heating, usually near the coolant pump. 6. Squeeze the hose. If its outer layer splits or flakes away, replace the hose. 7. Squeeze the lower radiator hose. If the reinforcing wire is missing (due to rust or corrosion), replace the hose. Replacing a Hose.  It is a good practice to replace all of the radiator and heater hoses if any of them are found to be defective. It is not always possible to convince the customer that this should be done. 1. Slide the hose clamp back at both ends of the hose (Figure 4-40). 2. Firmly but carefully twist and turn the hose to break it loose from the coolant pump and radiator. Using a box cutter to slice through the hose will help facilitate its removal. 3. Remove the hose (Figure 4-41).

Classroom Manual Chapter 4, page 120

Replace all hoses if any are found to be defective.

SERVICE TIP:

Some engines have additional hoses such as a small bypass hose between the coolant pump and the engine block, hoses used to carry coolant to heat the throttle body on fuel injected engines, and short hoses used to interconnect coolant carrying components on certain engines (Figure 4-38). Do not overlook these hoses when checking the cooling system.

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CAUTION:

Do not use unnecessary force when removing the hose end from the radiator or heater core. Use a razor knife to make a lengthwise incision (Figure 4-39), and peel the hose off the connection.

Gasket Thermal transmitter (for water temperature gauge)

Engine coolant temperature sensor

To cylinder head for right bank

Water outlet

Gasket To intake collector

To cylinder head for left bank

To heater core

Gasket Jiggle valve (Upper aid) Thermostat Water inlet Front

O-ring Liquid gasket

B

Thermostat housing Liquid gasket

A

FIGURE 4-38  Do not neglect interconnecting hoses in the cooling system.

Seal puller

Hose

SERVICE TIP:

Some lower radiator hoses contain a spring. The lower hose is the intake hose to the engine cooling system and under suction the spring prevents the lower hose from collapsing

FIGURE 4-39  To avoid damage to fittings, hose should be slit and loosened with a seal remover or hose tool.

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FIGURE 4-40  Slide the radiator hose clamp back.

FIGURE 4-41  Remove the hose.

Hose Clamps

Many technicians feel that original equipment hose clamps are only good for one-time use. In almost all cases, it is an accepted practice to replace the clamps when replacing a hose. They are inexpensive and are good insurance against an early failure. At least one manufacturer, however, recommends that a constant tension hose clamp, used on many cooling systems (Figure 4-42), be replaced with an original equipment clamp. A number or letter is stamped into the tongue of constant tension clamps

A constant tension hose clamp is a spring tension clamp designed to maintain a consistent clamping tension.

Typical constant tension hose clamp

Radiator hose FIGURE 4-42  A typical constant tension hose clamp.

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Classroom Manual Chapter 4, page 120

The recovery tank is often referred to as an overflow tank or a surge tank. A heat exchanger is an apparatus in which heat is transferred from one medium to another on the principle that heat moves from an object with more heat to an object with less heat.

FIGURE 4-43  A typical hose clamp tool.

for identification. If replacement is necessary, use only an original equipment clamp with matching number or letter. A special clamp tool (Figure 4-43) is available for use in removing and replacing constant tension hose clamps; however, slip joint pliers may also be used. In either case, eye protection should be worn when servicing constant tension clamps.

Recovery Tank The only problem that one may experience with a recovery tank is an occasional leak. Since the recovery tank is not a part of the pressurized cooling system, it can often be successfully repaired with hot glue. If it is found to be leaking, proceed as follows: 1. Remove the tank from the vehicle. 2. Thoroughly clean the tank inside and outside. 3. Use a piece of sandpaper to roughen up the surface at the area of the leak. 4. Use a hot glue gun and make several small beads of hot glue at the point of the leak. Cover the area thoroughly, overlapping each successive bead. 5. If it is accessible, repeat steps 3 and 4 inside the tank.

Classroom Manual Chapter 4, page 122

Heater System

A wet floor carpet can also be caused by a leaking sea around the windshield.

Heater Core

CAUTION:

Do not use force. Take care not to damage the fins of the heater core when removing and replacing it.

The comfort heater system is actually a part of the engine cooling system. The heater core, a small radiator-type heat exchanger, is located in the case/duct system of the heater/air conditioner unit. Most failures of the heater core (Figure 4-44) are due to a leak. This is easily detected by noting a wet floor carpet just below the case on the passenger side of the vehicle or if fogging of the windshield is occurring (moisture coming from ducts). Replacement of the heater core, unfortunately, is not so simple. Because of the many different variations of installation, it is necessary to follow the manufacturer’s shop manual instructions for replacing the heater core. The following is a typical procedure only and is not intended for any particular make or model vehicle: 1. Remove the coolant. 2. Remove the access panel(s) or the split heater/air conditioning case to gain access to the heater core. 3. Loosen the hose clamps and remove the heater coolant hoses. 4. Remove the cable and vacuum control lines (if equipped). 5. Remove the heater core, securing brackets and clamps. 6. Lift the core from the case.

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FIGURE 4-44  A typical heater core.

Control Valve

The control valve is a cable-, vacuum-, or electrically-operated shut-off valve used at the inlet of the heater core to regulate coolant flow through the core. Other than a leak, which is usually obvious, the valve fails due to rust or corrosion. To replace the valve: 1. Remove the coolant to a level below the control valve. 2. Remove the cable linkage, vacuum hose(s), or electrical connector from the control valve (Figure 4-45).

Most control valves are not omnidirectional. Observe proper direction of coolant flow.

FIGURE 4-45  Typical heater flow control valves.

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3. Loosen the hose clamps and remove the inlet hose from the control valve. 4. Remove the heater control valve, as applicable. Remove the outlet hose from the heater core. Remove the attaching brackets or fasteners from the control. 5. Inspect the hose ends removed. If they are hard or split, cut 0.5–1.0 in. (12.7–25.4 mm) from the damaged ends. Better yet, replace the hoses.

Hoses and Clamps If a hose slides onto a fitting very easily, it is probably too large. The fit should require slight resistance.

Classroom Manual Chapter 4, page 120

Heater hoses and clamps are basically about the same as radiator hoses and clamps except they are generally smaller in diameter. It is a practice of some technicians to use a hose that is too large for the application and overtighten the hose clamp to stop the leak. A hose clamp that is too large for the hose is often distorted when tightened sufficiently to secure the hose. Hoses.  Heater hoses are replaced in the same manner as radiator hoses. It is much easier to use the wrong size hose, however. For example, a ¾ in. hose fits very easily onto a ⅝ in. fitting. The hose clamp then must be overtightened (Figure 4-46) to squeeze the hose onto the fitting sufficiently to prevent a leak. It is not so easy to slide a ⅝ in. hose onto a ⅝ in. fitting. The intent, however, is to use the proper size hose for the application. It is good practice to replace all heater hoses if any are found to be defective. The following is a typical procedure: 1. Remove the coolant to a level below that of the hoses to be replaced. 2. Loosen the hose clamp at both ends of the hose. 3. Turn and twist the hoses to break them loose. 4. Remove the hose. Do not use unnecessary force when removing the hose end from the heater core. Clamps.  As with cooling system hose clamps, heater hose clamps should be replaced when a hose is replaced. It is most important that the proper size clamp be used for the hose. If the

FIGURE 4-46  A hose clamp overtightened to compensate for a hose that is too large for the application.

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FIGURE 4-47  A hose clamp that is too large for the hose application.

clamp is too large, it will be distorted before being tightened enough to secure the hose onto the fitting (Figure 4-47). When this occurs, it is extremely difficult to stop a leak.

Antifreeze WARNING: Antifreeze solution is considered a hazardous material. Dispose of antifreeze in an environmentally safe manner. Refer to all applicable federal environmental protection agency (EPA), state and local ordinances and regulations. In general, used antifreeze must be stored in an appropriately labeled bulk container for later recycling or waste pick-up. 1. Make sure that the engine is cool and the cooling system is not under pressure. 2. Place a clean, dedicated container of adequate size under the drain provision of the cooling system. 3. Open the radiator drain provision and drain the cooling system. WARNING: Refer to local ordinances and regulations regarding proper disposal procedures for ethyl glycol-type antifreeze solutions.

Preventive Maintenance

Classroom Manual Chapter 4, page 125

SERVICE TIP:

If the coolant is to be reused, drain it into a clean container. If, however, it is not to be reused, it must be disposed of or recycled in a manner considered to be environmentally safe.

Changing antifreeze/coolant annually helps to prevent cooling system failure, the primary cause of engine-related breakdowns. The antifreeze/coolant, depending on mix ratio, can provide protection for the cooling systems from −84 to 2768F (−64 to 135.68C). The generally recommended ratio of 1:1 (50 percent antifreeze and 50 percent water) provides protection against freezing with an ambient temperature as low as 2348F (236.78C) and provides

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protection from rust and corrosion for the cooling system metals. This includes protection for the thin, lightweight aluminum radiators found in many late-model vehicles.

WARNING: Store used coolant in a properly labeled container. Do not pour used coolant down a drain. Ethylene glycol antifreeze is a very toxic chemical. Do not dispose of coolant into the sewer system or ground water. This is illegal and ecologically unsound.

Extended Life

Extended-life antifreeze generally provides freeze-up and boil-over protection for up to 5 years or 150,000 miles (241,350 kilometers). High-mileage drivers, as well as those who do not have or take the time for regular vehicle preventive maintenance (PM), should rely on the long-lasting protection of an extended-life antifreeze/coolant. Such mixtures are silicate and phosphate free, providing extended protection against rust and corrosion to all metals of the cooling system. Extended-life antifreeze, such as Havolin’s Extended Life DEX-COOLTM, manufactured from ethylene glycol (EG), meets all of the compatibility requirements for the extended-life antifreeze used in most General Motors (GM) vehicles since 1996.

Low Tox

Low-tox antifreeze contains propylene glycol (PG) and is less toxic than EG types. A low-tox antifreeze/coolant mixture offers similar freeze-up and boil-over protection while providing rust and corrosion protection for all cooling system parts, including the aluminum used in radiators. Also, low-tox antifreeze/coolant provides an added margin of safety if accidentally ingested by pets or wildlife. Drain and Flush.  If replacing existing antifreeze/coolant with any other type of antifreeze/ coolant, first completely drain and flush the cooling system. Be aware that if antifreeze solutions are mixed, the intended protection of either solution may be lost, particularly the added margin of safety afforded by the PG formulas. Both types of antifreeze, EG and PG, are biodegradable. It is the rate at which they degrade, however, that is important. EG, though considered more toxic than PG, degrades the fastest. For more specific information, request a material safety data sheet (MSDS) from the manufacturer of the particular product that is being used. All used EG and PG coolants must be recycled for reuse or disposed of in a manner consistent with applicable local, state, and national regulations. Both used EG and PG coolants, though considered toxic, are not considered as a hazardous waste by the Environmental Protection Agency (EPA) unless they contain more than five parts per million (5 ppm) lead (Pb). Lead is a hazardous by-product that leaches out of the solder used to secure the tubes and header tanks. Coolant Recovery/Recycle.  Several companies manufacture antifreeze recovery/recycle/ recharge machines. Some systems connect to the vehicle’s cooling system and inject new or recycled coolant that forces the old coolant out of the system. This type of machine is ideal for field use where electricity is not available. The pump is powered by the vehicle’s battery while the engine is running.

Flush the Cooling System When replacing an existing antifreeze/coolant with an extended-life antifreeze/coolant, the cooling system must first be completely drained and flushed (see Photo Sequence 2). As mentioned earlier, this is necessary to gain the full benefits of the longer-lasting formula. 130 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

PHOTO SEQUENCE 2 Draining and Refilling the Cooling System

P2-1  Ensure that the engine is cold, and slowly remove the radiator cap. CAUTION: If the radiator cap is removed from a hot cooling system, serious personal injury may result.

P2-2  Place a drain pan of adequate size under the radiator drain cock.

P2-3  Install one end of a tube or hose on the draincock and position the other end in the drain pan.

P2-4  Open the radiator draincock and allow the radiator to drain until the flow stops.

P2-5  Place a drain pan of adequate size under the engine.

P2-6  Remove the drain plug from the engine block and allow the engine block to drain until the flow stops. NOTE: There may be more drainage from the radiator at this time.

P2-7  Close the radiator draincock and replace the engine block drain plug.

P2-8  Remove the pans and dispose of the coolant in a manner consistent with local regulations.

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PHOTO SEQUENCE 2

P2-9  Add sealant pellets, if required. Some car lines require that sealant pellets be added to the radiator whenever the cooling system is drained and refilled with fresh coolant. Failure to use the correct sealant pellets may result in premature water pump leakage.

P2-12  Fill the cooling system to within about 1 in. (25.4 mm) below the fill hole.

(CONTINUED)

P2-10  Premix the antifreeze with clear water to a 50:50 ratio. NOTE: Distilled water is required by some manufacturers.

P2-13  Start the engine and let the cooling system warm up. NOTE: When the thermostat opens, the coolant level may drop. After the thermostat opens, add coolant until the level is up to the fill hole.

P2-11  With a large funnel in the radiator fill hole, slowly pour in the coolant mixture. NOTE: Refer to the manufacturer’s specifications for the cooling system capacity.

P2-14  Replace the radiator cap.

P2-15  Check the coolant level in the recovery reservoir and add coolant if needed.

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For example, if an extended-life antifreeze/coolant is currently being used in a vehicle and a regular-type antifreeze is added to the cooling system, the extended-life protection will be lost. When adding antifreeze, always add the same type as that previously used in the cooling system. If the type is unknown, it is generally recommended to drain, flush, and refill the cooling system. The procedure that follows is typical: NOTE: Often instructions are given in the owner’s manual, and one may be told to open an air bleed valve on the engine or to remove a heater hose to purge air that may have entered the engine during draining. 1. Drain the cooling system following steps 1–5 of Job Sheet 7. 2. Close the drain valve. 3. Recycle or dispose of the used coolant according to local laws and regulations. NOTE: Label the container clearly as used antifreeze. Do not use beverage containers to store antifreeze, new or used. If stored, keep the containers away from children and animals. If the antifreeze is to be disposed, do so promptly and properly. 4. Flush the cooling system to clean the engine block of any scale, rust, or other debris before refilling with new antifreeze/coolant. NOTE: A cooling system flush may be used to remove stubborn rust, grease, and sediment, which may not be removed by plain water alone. 5. Remove the radiator cap and fill the radiator with cleaner (if used) and water. 6. Run the engine with the heater on HI and the temperature gauge reading normal operating temperature for the time recommended on the flush product label. NOTE: An infrared (IR) thermometer is a handy tool to use for determining when “normal” engine-operating temperature has been reached. 7. Stop the engine and allow it to cool. 8. Again, open the drain valve and drain the cooling system. 9. Close the drain valve and refill the radiator with plain water. 10. Run the engine for about 15 minutes at normal engine-operating temperature. 11. Stop the engine and allow it to cool, open the drain valve, and redrain the cooling system. 12. Close the drain valve and refill the cooling system, following steps 6–10 of Job Sheet 7. NOTE: Check the owner’s manual for the cooling system capacity, as well as the service manual for any special service instructions. In some cooling systems, the location of the heater core is higher than the cooling system filler neck. These systems are prone to air locks, especially if you are not using an automated cooling system drain and fill machine. One method to lessen the chance of air pockets is to jack up the front of the vehicle until the filler neck is the high point in the cooling system, and then fill the system. Another option is to use a cooling system evacuator and fill adapter. This is an inexpensive, handheld device (Uview Airlift II is one such system) used to place the cooling system under a vacuum, which is then used to draw fresh coolant into the system, thereby eliminating air locks. 13. Once the radiator is filled, run the engine at normal operating temperature with the heater on HI for 15 minutes to mix and disperse the coolant fully throughout the cooling system. 14. Shut off the engine and allow the cooling system to cool. Thermocycling is the process of allowing the cooling system to reach operating temperature and then be allowed to cool down again. Recheck hose clamp tension.

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15. Check the coolant level and concentration. Adjust, if necessary. 16. After a few days of driving, recheck the cooling system. A hydrometer may be used for EG testing, and test strips may be used for PG testing. NOTE: If additional coolant is required, use a premixed 50/50 percent concentrate. If additional coolant is needed, it is suggested that the cooling system be leak tested. Classroom Manual Chapter 4, page 97

Hybrid Electric Cooling System Service Many normal cooling system maintenance procedures on the hybrid electric engine are similar to the conventional service procedures on a nonhybrid platform, but there are exceptions that can become both hazardous and frustrating. One item that is found on a hybrid platform is the coolant heat storage tank that is designed to store hot coolant for up to 3 days (Figure 4-48). In addition to being hot, the coolant is stored under pressure and serious burns may result if manufacturer’s service procedures are not followed during a cooling system service or repair procedure. The cooling system on some platforms is also tied to the inverter assembly, which increases the potential of air being trapped in the cooling system during service. In order to purge air from the cooling system following service, there is a bleed screw and the use of a scan tool is required to cycle the auxiliary electric coolant pump. The service procedure for draining and filling the cooling system of a hybrid electric vehicle is outlined in the manufacturer’s service manual. The following is an outline of the basic steps required but is not intended to substitute for the manufacturer’s recommended procedure: 1. When servicing the cooling system of a hybrid electric vehicle equipped with a coolant heat storage tank and an auxiliary water pump, first disconnect the coolant heat storage auxiliary water pump connector. 2. Remove the radiator cap and drain the engine coolant from both the coolant heat storage tank and the radiator assembly. 3. Perform the required service. 4. Connect the coolant heat storage auxiliary water pump connector.

Heater core A/C water pump

Coolant heat storage tank

Water valve Cylinder head Cylinder block Engine water pump

Radiator

Throttle body

Coolant heat storage water pump

FIGURE 4-48  Hybrid electric vehicle hot coolant storage tank and water pump system.

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5. While refilling the cooling system with the specified coolant, use a scan tool to operate the coolant heat storage auxiliary water pump at 30-second intervals to help the inflow of coolant into the tank to avoid air pockets from being trapped in the cooling system. It will also be necessary to open the cooling system bleed plug during this procedure. Repeat this procedure until no air escapes from the bleed plug. 6. Start and run the engine for 1 to 2 minutes. 7. Turn off the engine and top off the coolant level if necessary.

DTC P1151 Coolant Heat Storage Tank

On a Toyota Hybrid platform, a diagnostic trouble code (DTC) P1151 recommends that the coolant heat storage tank be replaced. But be aware that the service manual also indicates that this code may be set if there is an air bubble in the cooling system. To avoid replacing the coolant storage tank unnecessarily, check for the sound of air bubbles flowing through the heater core from the passenger compartment. If there is no air present in the cooling system, you will not be able to hear the sound of water flowing when the coolant pump is running. If air is present you will hear the sound of rushing water. If air is trapped in the cooling system it will be necessary to bleed the air out of the system as outlined in the manufacturer’s service information. After the air is removed, the DTC must be cleared and the vehicle must be driven for two trips. If the code returns after the air has been bled and the vehicle has been driven for two trips, the coolant heat storage tank must be replaced. WARNING: The coolant heat storage tank is designed to store hot coolant at 1768F (808C) for up to 3 days. Severe burns may result if proper manufacturer service procedures are not followed during service.

Troubleshooting the Heater and Cooling System The following procedure is given as a quick reference to enable the service technician to isolate many of the conditions that can cause improper engine cooling system or heater operation. This procedure is given in three parts: engine overcooling, engine overheating, and loss of coolant. The customer’s complaint would usually be for an overheating condition. If the problem is due to a loss of coolant, the customer may complain that coolant or water must be added frequently. It should be noted that cooling system problems are often caused by, or may cause, airconditioning system problems. Conversely, air conditioning problems may be caused by, or may cause, cooling system problems. ENGINE OVERCOOLING Possible Cause

Possible Remedy

1. Thermostat missing

Replace the thermostat

2. Thermostat defective

Replace the thermostat

3. *Defective temperature sending unit

Replace the sending unit

4. *Defective dash gauge

Replace the dash gauge

5. *Broken or disconnected wire

Repair or replace the wire

6. *Grounded or shorted cold indicator wire (if equipped with a cold lamp)

Repair or replace the wire

*These symptoms indicate overcooling, though the engine temperature may be within safe limits.

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An overheated engine may result in poor to no cooling from the air conditioner. An air-conditioning system malfunction may result in an overheating engine condition.

ENGINE OVERHEATING Possible Cause

Possible Remedy

1. Collapsed radiator hose

Replace the radiator hose

2. Coolant leak

Locate and repair the leak

3. Defective water pump

Replace the water pump

4. Loose fan belt(s)

Torque fan belts to specs

5. Defective fan belt(s)

Replace the fan belts

6. Broken belt(s)

Replace the belt(s)

7. Fan bent or damaged

Replace the fan

8. Fan broken

Replace the fan

9. Defective fan clutch

Replace the fan clutch

10. Exterior of radiator dirty

Clean the radiator

11. Dirty bug screen

Clean or remove the screen

12. Damaged radiator

Repair or replace the radiator

13. Engine improperly timed

Service the engine

14. Engine out of tune

Service the engine

15. Temperature sending unit defective

Replace the sending unit

16. *Dash gauge defective

Replace the dash gauge

17. *Grounded or shorted indicator wire

Repair or replace the wire

*These symptoms indicate overheating, though the engine temperature may be within safe limits.

LOSS OF COOLANT Possible Cause

Possible Remedy

1. Leaking radiator hose

Replace the radiator hose

2. Leaking heater hose

Replace the heater hose

3. Loose hose clamp

Tighten the clamp

4. Leaking radiator (external)

Repair or replace the radiator

5. Leaking transmission cooler (internal)

Repair or replace the radiator

6. Leaking coolant pump shaft seal

Repair or replace the coolant pump

7. Leaking gasket(s)

Replace the gaskets

8. Leaking core plug(s)

Replace the core plug(s)

9. Loose engine head(s)

Re-torque the head(s)

10. Warped head(s)

Replace the head(s)

11. Excessive coolant

Adjust the coolant level

12.Defective radiator pressure cap

Replace the cap

13. Incorrect pressure cap

Replace the cap

14. Defective thermostat

Replace the thermostat

15. Incorrect thermostat

Replace the thermostat

16. Rust in system

Flush the system and add rust protection

17. Radiator internally clogged

Clean or replace the radiator

18. Heater core leaking

Repair or replace the core

19. Heater control valve leaking

Replace the valve

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Terms to Know

case study A customer brings his car into the shop because the temperature gauge does not operate. It remains on cold all of the time, regardless of engine heat conditions. The lead wire to the sending unit is disconnected, and a test light is used to probe for voltage. The test light comes on when the ignition switch is placed in the ON position. When the lead is connected

to ground (−) through a 10 0 resistor, the dash unit needle moves to the full hot position. This is a normal operation according to the service manual. The diagnosis is that the sending unit is defective. It is replaced after approval by the customer and the temperature gauge system is returned to normal operation.

Ambient temperature Constant tension hose clamp Dissipate Drive pulley Fan relay Fill neck Heat exchanger Idler Indexing tab Serpentine belt V-belt

ASE-STYLE REVIEW QUESTIONS 1. Engine overcooling is being discussed: Technician A says that a thermostat stuck open could be the cause of this condition. Technician B says that a missing thermostat could be the cause of this condition. Who is correct? C. Both A and B A. A only B. B only D. Neither A nor B 2. Technician A says that when pressure testing a cooling system, it should hold pressure for 5 minutes. Technician B says that a wet carpet may indicate a heater core leak. Who is correct? C. Both A and B A. A only B. B only D. Neither A nor B 3. All of the following may cause the back side of a ­serpentine belt to separate except: A. Contacting stationary object B. Excessive heat C. Fractured splice D. Pulley misalignment 4. Coolant loss is being discussed: Technician A says that a missing thermostat could be the problem. Technician B says a heater control valve stuck open may be the problem. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

5. Technician A says that as a neoprene serpentine belt ages and wears cracks will form on the belt ribs and that if there are more than three cracks in a 4-inch span, the belt should be replaced. Technician B says that serpentine belts made of EPDM resist cracking and instead exhibit wear to the belt ribs similar to tire wear, and that a depth gauge should be used to assess belt wear. Who is correct? C. Both A and B A. A only B. B only D. Neither A nor B 6. Technician A says that antifreeze should be changed every 2 years. Technician B says that extended-life coolant may last up to 5 years. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 7. An overheating condition is being discussed: Technician A says that replacing the thermostat with one of a lower temperature rating will reduce the ­coolant temperature. Technician B says that replacing the pressure cap with one of a lower rating will reduce the coolant temperature. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

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8. All of the following conditions could cause poor passenger compartment heating system performance except: A. A restricted heater core. B. A heater control valve stuck in the closed position. C. An air pocket in the heater core. D. A thermostat stuck in the closed position. 9. Electric cooling fans are being discussed: Technician A says that they are independent of the ignition switch and may start and run without notice at any time. Technician B says that they are generally protected by a shroud and pose no safety problem. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

10. Cooling system service is being discussed: Technician A says that ethylene glycol antifreeze must be disposed of in a manner prescribed by the Environmental Protection Agency (EPA) and local ordinances. Technician B says that after hoses have been replaced, clamp tension should be rechecked after the cooling system has been allowed to thermocycle. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

ASE CHALLENGE QUESTIONS 1. The tank on a radiator has ruptured: Technician A says that a thermostat that is stuck in the open position could be the cause. Technician B says that a faulty radiator cap could be the cause. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 2. A vehicle is in for repair with a complaint of poor heat output. During testing and diagnosis air is found to be trapped in the heater core. Which of the following is the most likely cause? A. A faulty head gasket B. A stuck open thermostat C. A radiator cap with a failed pressure relief valve D. A faulty water pump

5. If the crankshaft pulley turns clockwise (cw), all of the following statements about the illustration below are true, except: A. The compressor turns clockwise (cw) B. The idler pulley turns counterclockwise (ccw) C. The water pump turns clockwise (cw) D. The alternator pulley turns clockwise (cw)

Alternator pulley

Belt cross section

Idler pulley

Power steering pump pulley

3. The least likely problem associated with a cooling system that had the thermostat removed is: A. Poor heater performance B. Erratic computer engine control C. Lower-than-normal operating temperature D. Loss of coolant 4. The most likely use for an engine coolant temperature switch is to electrically energize the: A. Compressor clutch B. Cooling system fan motor C. Blower motor D. Coolant “hot” warning light

AC compressor pulley Air pump pulley

Water pump pulley Crankshaft pulley

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JOB SHEET

10

Name ______________________________________ Date ________________________

Drain and Fill Coolant Upon completion of this job sheet, you should be able to remove and replace cooling system coolant. NATEF Correlation NATEF AST and MAST Correlations: ENGINE REPAIR: Lubrication and Cooling Systems Diagnosis and Repair; Task #4. Inspect and test coolant; drain and recover coolant; flush and refill cooling system with recommended coolant; bleed air as required. (P-1) Tools and Materials Late-model vehicle Shop manual Two pans Safety glasses or goggles Hazardous waste container Funnel Rubber hose Hand tools, as required Describe the Vehicle being Worked on. Year ____________________ Make _____________________ Model ______________________ VIN _____________________________ Engine type and size ____________________________ Procedure Follow the procedure outlined in the service manual. Photo Sequence 2 may also be used as a guide wherever applicable. 1. Ensure that the engine is cold, and slowly remove the radiator cap. WARNING: If the radiator cap is removed from a hot cooling system, serious personal injury may result. 2. Place a drain pan of adequate size under the radiator draincock and install one end of a tube or hose on the draincock. Position the other end in the drain pan. Open the ­radiator draincock and allow the radiator to drain until the flow stops. 3. Place a drain pan of adequate size under the engine. Remove the drain plug from the engine block and allow the engine block to drain until the flow stops.

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4. Close the radiator draincock and replace the engine block drain plug. 5. Remove the pans and dispose of the coolant in a manner consistent with local regulations. 6. Using your shops service information system such as ALLDATA or similar look up and record the vehicle manufacturer’s cooling system capacity. Record cooling system capacity:  7. Premix antifreeze with clear water to a 50:50 ratio. 8. With a large funnel in the radiator fill hole, slowly pour in the coolant mixture. (Refer to the manufacturer’s specifications for the cooling system capacity.) Fill to about 1.0 in. (25.4 mm) below the fill hole. 9. Start the engine and let the cooling system warm up. When the thermostat opens, the coolant level may drop. If it drops, add coolant until the level is up to the fill hole. At what temperature did the thermostat open?  10. Follow the manufacturer’s recommendation for bleeding air out of the cooling system. When would air-locking in the cooling system be a concern?

11. Replace the radiator cap and check the coolant level in the recovery reservoir. Add coolant if needed. 12. Did the cooling system take the amount specified in the service information listed as cooling system capacity? Why not? 

Instructor’s Response 

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JOB SHEET

11

Name ______________________________________ Date ________________________

Leak Test a Cooling System Upon completion of this job sheet, you should be able to leak test a cooling system. NATEF Correlation NATEF AST and MAST Correlations: ENGINE REPAIR: Lubrication and Cooling Systems Diagnosis and Repair; Task #1. Perform cooling system pressure and dye tests to identify leaks; check coolant condition and level; inspect and test radiator, pressure cap, coolant recovery tank, heater core and galley plugs; determine necessary action. (P-1) Tools and Materials Late-model vehicle Shop manual Safety glasses or goggles Cooling system leak tester Hand tools, as required Describe the Vehicle being Worked on. Year _______________________ Make ____________________ Model ____________________ VIN ________________________________ Engine type and size _________________________ Procedure Follow the procedures typically outlined in the Shop Manual. Ensure that the engine is cold for this procedure. Wear eye protection while pressure testing the cooling system. 1. Note the cooling system operating pressure on the radiator cap. Verify the pressure by referring to the specifications in the manufacturer’s service manual. Record radiator cap pressure:

Does this match manufacturer recommendation? Yes or No 2. Remove the radiator cap and adjust the coolant level to 0.5 in. (12.7 mm) below the bottom of the fill neck. 3. Attach the pressure tester to the filler neck of the radiator. Some radiators require an adapter.

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4. While observing the gauge, pump the tester until it indicates the same pressure noted in the specifications. What is the specifications pressure?  What gauge pressure could you pump in the system?  Explain:  5. If the gauge pressure is not correct in step 4, proceed with step 6. If correct, ­proceed with step 8. Gauge pressure was: Correct _______________ Not correct _______________ 6. Make a visual inspection for coolant leaks. List those areas where a leak is observed.

7. Repair leaks, as required, and repeat leak testing, beginning with step 4. Were any additional leaks defected?  8. Let pressure stand for 5 minutes. If the pressure is the same as in step 4, proceed with step 9. If not, repeat leak testing beginning with step 4. 9. Release the pressure and remove the tester from the cooling system. Attach the tester to the pressure cap. 10. Pump the tester while observing the gauge. What is the maximum pressure?  a.  Does the pressure reach that noted on the radiator cap?  b.  Does the excess pressure release when rated pressure is reached?  c.  What are your conclusions regarding the pressure cap? 

Instructor’s Response 

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JOB SHEET

12

Name ______________________________________ Date ________________________

Replace Thermostat Upon completion of this job sheet, you should be able to replace a cooling system thermostat. NATEF Correlation NATEF AST and MAST Correlations: ENGINE REPAIR: Lubrication and Cooling Systems Diagnosis and Repair; Task #4. Inspect and test coolant; drain and recover coolant; flush and refill cooling system with recommended ­coolant; bleed air as required. (P-1) Task #7. Remove, inspect, and replace thermostat and gasket/seal. (P-1) Tools and Materials Late-model vehicle Service manual Safety glasses or goggles Gasket scraper Hand tools, as required Thermostat and gasket, as required Describe the Vehicle being Worked on. Year _______________________ Make ____________________ Model ____________________ VIN ________________________________ Engine type and size _________________________ Procedure Follow the procedures outlined in the service manual. Ensure that engine is cold and that you wear eye protection. 1. Drain coolant to a level below the thermostat. Follow the appropriate procedures outlined in Job Sheet 7. 2. Is thermostat located near the upper or lower radiator hose?  3. Is this the outlet or inlet for the engine?  4. If required, remove components to gain access to thermostat housing. List components removed. 

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5. Remove retaining bolts or nuts and lift off thermostat housing. 6. Remove the thermostat. Using a gasket scraper, carefully remove any remaining seal or gasket material. 7. Install new thermostat and gasket. CAUTION: Make sure that the thermostat is not installed upside down. Have your instructor initial here at this time. ________________ 8. Replace the thermostat housing and retaining bolts or nuts. a.  Torque specification ______________________ Procedures  9. Replace the components removed in step 2, if any. 10. Replace the coolant removed in step 1. 11. Bleed air out of the cooling system if required by the manufacturer. 12. Test for leaks. Instructor’s Response 

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JOB SHEET

13

Name ______________________________________ Date ________________________

Troubleshoot an Electric Engine Cooling Fan Upon completion of this job sheet, you should be able to troubleshoot and repair electric engine cooling fans. NATEF Correlation NATEF AST and MAST Correlations: ENGINE REPAIR: Lubrication and Cooling Systems Diagnosis and Repair; Task #8. Inspect and test fan(s) (electrical or mechanical), fan clutch, fan shroud, and air dams. (P-1) Tools and Materials Late-model vehicle Service manual Fused jumper wire Hand tools Describe the Vehicle being Worked on. Year _______________________ Make ____________________ Model ____________________ VIN ________________________________ Engine type and size _________________________ Procedure Refer to the appropriate service manual for the specific procedures for troubleshooting an electric engine cooling/condenser fan motor. Failure to do so can result in serious damage to the control system. The following may be used as a guide only. 1. Start the engine and allow the coolant to reach operating temperature. Did the fan turn on? ___________________________________ Explain  2. Turn on the air conditioner. Did the fan turn on? _____________ Explain ____________ 3. Turn the air conditioner OFF and stop the engine. If the fan was running, does it continue to run? ________________________ Explain  4. Carefully disconnect the fan electrical connection. Is this a single-or double-lead connector?

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5. Refer to the wiring diagram. What is the color of the wire that supplies power to the motor? _________________ What is the color of the ground wire? __________________ 6. Using a fused jumper wire, connect between the fan motor lead and positive ­battery terminal. DO NOT connect to the motor ground lead. Does the motor operate? Yes or No Did the fuse “blow?” Yes or No Explain: 

7. If the motor ran in step 6, further testing of the electrical circuit is required. Follow the specific procedure outlined in the service manual. Give your step-by-step procedure and conclusions in the space below. a.   b.   c.   d.  

Instructor’s Response 

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JOB SHEET

14

Name ______________________________________ Date ________________________

Inspect Engine Cooling System Hoses Upon completion of this job sheet, you should be able to visually check the condition of cooling system hoses and perform the necessary action. NATEF Correlation NATEF AST and MAST Correlations: HEATING AND AIR CONDITIONING: Heating, Ventilation, and Engine Cooling Systems Diagnosis and Repair; Task #1. Inspect engine cooling and heater system hoses; perform necessary action. (P-1) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Hoses, as required Describe the Vehicle being Worked on. Year _______________________ Make ____________________ Model ____________________ VIN ________________________________ Engine type and size _________________________ Procedure Follow the procedures outlined in the service manual. Ensure that the engine is cold and that you wear eye protection. 1. Inspect the hoses as outlined on page 99 to determine which hoses require replacement. What were the results of the inspections?  2. Drain the coolant as outlined in Job Sheet 7 to a level below hose connections. 3. If required, remove components to gain access to the hoses and clamps. What components needed to be removed?  4. Loosen the hose clamps at both ends of the hose. Hoses with ferrules on the end may be removed by cutting the ferrules off and using standard hose clamps on replacement hoses. Was it necessary to remove ferrules from any nose ends? 

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5. Firmly but carefully twist and turn the hose to break it loose from the connection point. Use a box cutter to slice through the hose to facilitate its removal. 6. Remove the hose and save for customer inspection if requested (remember, some states require that old parts be saved for customer inspection). Did customer request old parts?  7. Compare the old hose to the new hose for proper fit and shape. Some hoses will need to be trimmed to size. Was it necessary to trim hose length?  8. Apply a small amount of water or coolant to the ends of new hoses to aid in installation. 9. Install the hose clamps. If screw clamps are used, recheck the tension after the cooling system has been allowed to thermal cycle. 10. Refill the cooling system as outlined in Job Sheet 7. 11. Test the cooling system for leaks as outlined in Job Sheet 8. Were any leaks detected?

Instructor’s Response 

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JOB SHEET

15

Name ______________________________________ Date ________________________

Inspect Heater Control Valve Upon completion of this job sheet, you should be able to inspect and test the heater control valve(s) and perform the necessary action. NATEF Correlation NATEF AST and MAST Correlations: HEATING AND AIR CONDITIONING: Heating, Ventilation, and Engine Cooling Systems Diagnosis and Repair. Task #2. Inspect and test heater control valve(s); perform necessary action. (P-2) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Describe the Vehicle being Worked on. Year _______________________ Make ____________________ Model ____________________ VIN ________________________________ Engine type and size _________________________ Procedure Follow the procedures outlined in the service manual. Ensure that the engine is cold and that you wear eye protection. 1. Check the operation of the heater control valve assembly. Proceed to step 2 if replacement is necessary. Is heater control value functioning as designed? _______________ 2. Drain the coolant as outlined in Job Sheet 7 to a level below the hose connections. 3. Remove the cable linkage, vacuum hose(s), or electrical connection from the control valve. How was heater control valve controlled?  4. Loosen the hose clamps and remove the inlet and outlet hoses from the control valve. 5. Inspect the hose ends prior to reinstalling on a new control valve. If the hose ends are hard or split, replace the hoses. Was it necessary to replace hoses?  6. Remove the heater control valve and save it for customer inspection, if requested (remember, some states require that old parts be saved for customer inspection).

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7. Compare the old heater control valve to the new assembly for proper fit and shape and install the control valve assembly. Do the old and new assembly’s match one another?

8. Apply a small amount of water or coolant to the ends of the new hoses to aid in installation. 9. Install the hose clamps. If screw clamps are used, recheck the tension after the cooling system has been allowed to thermal cycle. 10. Reinstall the cable linkage, vacuum hose(s), or electrical connection from the control valve. 11. Refill the cooling system as outlined in Job Sheet 7. 12. Test the cooling system for leaks as outlined in Job Sheet 8. Were any leaks detected? 

Instructor’s Response 

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JOB SHEET

16

Name ______________________________________ Date ________________________

Inspect and Test Fan and Fan Clutch Upon completion of this job sheet, you should be able to inspect and test the fan clutch assembly and perform the necessary action. NATEF Correlation NATEF AST AND MAST Correlations: ENGINE REPAIR: Lubrication and Cooling ­Systems Diagnosis and Repair; Task #8. Inspect and test fan(s) (electrical or mechanical), fan clutch, fan shroud, and air dams. (P-1) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Thermometer Timing light Cardboard Describe the Vehicle being Worked on. Year _______________________ Make ____________________ Model ____________________ VIN ________________________________ Engine type and size _________________________ Procedure Follow the procedures outlined in the service manual. Ensure that the engine is cold and that you wear eye protection. 1. Inspect the fan shroud and air dams. Ensure that they are firmly mounted to the radiator support of the vehicle. Were any faults or failures detected?

2. Inspect the physical condition of the fan blades and the condition of the drive pulley for the fan. Note any faults detected.

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3. If the vehicle is equipped with a fan clutch, inspect the assembly for lateral movement. Maximum allowable movement is ¼ inch as measured at the tip of the fan blades. Also inspect for signs of oil leaking from the clutch assembly. Note any faults or defects.

4. For the fan clutch assembly diagnosis, begin by spinning the fan blade by hand. If the fan blade revolves more than twice when spun by hand, replace the fan clutch. The fan clutch should have a slight drag when spun by hand. Note any faults or failures.

5. Place a thermometer between the fan and the radiator. It may be necessary to drill a small hole in the fan shroud for the thermometer placement. 6. Position a square of cardboard in front of the radiator to limit airflow and to raise the engine temperature. 7. Start the engine and turn on the air conditioning; raise the engine speed to 2,000 rpm. 8. Record the temperature when the fan clutch engages. a.  Engagement temperature  A 52108F (32108C) drop in air temperature should be noticed when the fan clutch engages, along with an increase in fan noise. If the fan clutch does not engage by 15021908F (652908C), replace the assembly. Note any faults or failures.

9. Once the fan clutch has engaged, remove the cardboard blocking the radiator and reduce the engine speed to 1,500 rpm. There may be an increase in fan speed detected. Was there an increase in fan speed?

10. After several minutes of operation, the fan should disengage if it is operating properly. Is the fan clutch operating as designed?

11. If any of the above tests fail, replace the fan clutch assembly. Did the fan clutch fail any of the above tests? Which ones, if any?

Instructor’s Response _____________________________________________________________

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17

JOB SHEET

Name ______________________________________ Date ________________________

Diagnostic Check List Upon completion of this job sheet you should be able to visually check the condition of cooling system and properly fill out a cooling system diagnostic check list. NATEF Correlation NATEF AST and MAST Correlations: HEATING AND AIR CONDITIONING: Heating, Ventilation, and Engine Cooling Systems Diagnosis and Repair. Task #1. Inspect engine cooling and heater systems hoses; perform necessary action. (P-1) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Describe the Vehicle being Worked on. Year _______________________ Make ____________________ Model ____________________ VIN ________________________________ Engine type and size _________________________ Procedure Follow procedures outlined in the service manual. Ensure that the engine is cold and wear eye protection. Inspection

DIAGNOSTIC CHECK LIST OK

Marginal

Faulty

Coolant Level Coolant Color Coolant Freeze Point (2358F) Radiator Cap (–1) No Sign of Coolant in Oil Radiator Condition (1) Expansion Tank Drive Belt(s) Water Pump (1) Hoses (1) Freeze Plugs (1) Head Gaskets (1) Other Leaks (1) 153 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Inspection

OK

Marginal

Faulty

Thermostat Opens at Set Temperature Upper Radiator Hose Hot Lower Radiator Hose Warm Fan Engages Heater Hoses Hot Passenger Compartment Heater Functions Radiator Flow (2) No sign of coolant from exhaust (steam) Comments:

1. Test performed using pressure tester 2. To fully test radiator flow it should be removed from vehicle.

Instructor’s Response 

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18

JOB SHEET Name ______________________________________ Date ________________________

Bench Test Thermostat Upon completion of this job sheet you should be able to visually check the condition of and bench test a thermostat operation and diagnose outcomes of a faulty thermostat. Tools and Materials Hot plate Thermometer Mechanics wire Glass beaker Stirring rod or spoon Safety glasses Procedure 1. Record temperature rating marked on the bottom of thermostat.  Check temperature when thermostat opens

Heat

CAUTION: Do not rest the thermostat or the thermometer on the bottom of the container while heating the water. Contact with the bottom of the container causes the thermostat and the thermometer to be at a higher temperature than the solution. 2. Place thermostat suspended by a wire in a beaker of warm water and place on hot plate with thermometer in water. Agitate the solution with a stirring rod or spoon in order to maintain a uniform temperature of the solution, the thermostat, and the thermometer. 3. Record temperature at which thermostat begins to open. The thermostat should begin to open within 1 / 238F 

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4. Does this temperature match the rating on thermostat? Yes or No 5. Record temperature when thermostat is fully open.  The thermostat valve should start to open at the rated temperature. The thermostat should be fully open after the temperature has increased 258F (118C) above its rated temperature. 6. Is this a good thermostat?  7. If the thermostat opens too soon, what effect would this have on the cooling system? What would the customer complaint be?  8. If the thermostat opens too late, what effect would this have on the cooling system? What would the customer complaint be? 

Instructor’s Response 

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Chapter 5

BASIC TOOLS Manifold and gauge set with hoses

The Manifold and Gauge Set

Safety glasses or goggles Fender cover Basic tool set Thermometer

Upon Completion and Review of this Chapter, you should be able to: ■■

■■

■■

Describe the nomenclature and function of the manifold and gauge set.

■■

Identify the scaling of the low- and high-side gauges in English and metric units.

■■

Connect a manifold and gauge set into an automotive air-conditioning system. Hold a performance test on an automotive air-conditioning system.

Calibrate a gauge.

The Manifold and Gauge Set The manifold and gauge set is to the automotive air-conditioning service technician what the stethoscope and aneroid manometer is to the physician. Both are tools that are essential for the diagnosis of internal conditions that cannot otherwise be observed. The manifold and gauge set is used to diagnose and troubleshoot various system malfunctions based on low- and high-side system pressures. A basic tool for the air-conditioning service technician is the manifold and gauge set (Figure 5-1). The pressure measurement of an air-conditioning system is a means of determining system performance. The manifold and gauge set is an essential tool for making these measurements. The servicing of automotive air-conditioning systems requires the use of a two-gauge manifold set. One gauge is used to observe pressure on the low (suction) side of the system. The second gauge is used to observe pressure on the high (discharge) side of the system. The service technician should have a gauge set for each type of refrigerant serviced and may need additional gauge sets for contaminated refrigerants of each type—one for R-134a, one for R-1234yf, and one for R-12. CFC-12 refrigerants are referred to as R-12 or Freon by service technicians, whereas HFC-134a refrigerants are referred to as R-134a and HFO-1234yf as R-1234yf. There is no significant difference between gauges designated for R-134a refrigerant and those designated for R-12 refrigerant or R-1234yf refrigerants other than the unique service hose coupler that connects to the system service port on the vehicle. However, the three refrigerants are not compatible, and separate gauge sets must be used. The general description, however, is the same for these types.

Low-Side Gauge

The low-side gauge (Figure 5-2), used to monitor low-side system pressure, is called a ­compound gauge. A compound gauge is designed to give both vacuum and pressure indications. This gauge is connected to the low side of the air-conditioning system through the manifold and low-side hose.

The manifold and gauge set is one of the primary service tools for the air-conditioning technician. It contains the gauges and service valve block along with high-side, low-side, and utility hoses and is specific for only one type of refrigerant. Manifold and gauge sets must be dedicated: one for R-12 (CFC-12) and one for R-134a (HFC-134a). Low-side gauge is the left-side refrigerant gauge on the manifold used to read pressures on the low side of the system. 157

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HFC-134a is hydrofluorocarbon refrigerant gas used as a refrigerant and is also known as R-134a. This refrigerant is not harmful to the ozone. It replaced CFC-12 (R-12) in the early to mid-1990s and is the only substitute refrigerant recognized by the major automotive manufacturers.

CFC-12 is dichlorodifluoromethane refrigerant gas (also referred to as R-12) used in automotive air conditioners until the early 1990s. The passage of the Clean Air Act in 1990 banned the production of CFC12 and limited its further use.

FIGURE 5-1  A typical R-134a (HFC-134a) manifold.

A compound gauge registers both pressure and vacuum. The lowside refrigerant gauge is a compound gauge.

Low-side system operating pressures are generally 15–35 psig (103–241 kPa). High-side system operating pressures are generally 160–220 psig (1,103–1,517 kPa).

FIGURE 5-2  A typical low-side gauge.

Calibration of the vacuum scale of a compound gauge is from 30 in. Hg to 0 psig. The pressure scale is calibrated to indicate pressures from 0 psig to 120 psig. The compound gauge is constructed in such a manner so as to prevent any damage to the gauge if the pressure should reach a value as high as 250–350 psig. Low-side pressures above 80 psig are rarely experienced in an operating system. Such pressures may be noted, however, if the low-side manifold service hose is accidentally connected to the high-side fitting of an R-12 system. This can only occur on an R-12 system

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FIGURE 5-3  A typical high-side gauge.

because the service hose coupler is the same size for both high- and low-side pressure on some systems. This cannot occur on R-134a or R-1234yf refrigerant systems because each has unique quick disconnect coupler sizes for both the high-side and the low-side and each refrigerant uses unique sizes that differ greatly from one another. This completely eliminates the possibility of connecting to the wrong service port or refrigerant type. This was done to avoid inadvertent cross contamination since multiple refrigerants have been used on vehicles over the last few decades. The metric gauge used on the low side of the system is scaled in absolute kiloPascal (kPa) units. For conversion, 1 psi is equivalent to 6.895 kPa.

High-Side Gauge

The high-side gauge (Figure 5-3) indicates pressure in the high-pressure side of the system. Under normal conditions, pressures in the high-side seldom exceed 300 psig. As a safety factor, however, it is recommended that the maximum indication of the high-side gauge be 500 psig. The high-side gauge, though not calibrated below 0 psig, is not damaged when pulled into a vacuum. High-side metric pressure gauges are scaled in kPa. The correct conversion is to kPa, whereby 1 psi equals 6.895 kPa. Atmospheric pressure at sea level (14.696 psia) is 101.32892 kPa, rounded off to 101 kPa. 14.696 psi 3 6.895 kPa 5 101.32892

Gauge Calibration

Most quality gauges have a provision for a calibration adjustment. Generally, a gauge is accurate to about 2 percent of its total scale when calibrated so the needle rests on zero with atmospheric pressure applied. To calibrate a gauge: 1. Remove the hose after recovering refrigerant (if applicable). 2. Remove the retaining ring (bezel) and plastic lens cover. 3. Locate the adjusting screw. 4. Use a small screwdriver (Figure 5-4) to turn the adjusting screw in either direction until the pointer is lined up with the zero mark. 5. Replace the plastic lens and bezel.

CAUTION:

Do not force the adjusting screw; to do so may damage the gauge or alter its accuracy.

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FIGURE 5-4  Use a small screwdriver to calibrate a gauge.

Manifold The low- and high-side gauges are connected into the air-conditioning system through a manifold (Figure 5-5) and two high-pressure hoses. The manifold is a cast or machined block with two or more gauges attached and two to four shut-off valves incorporated into it. Some more expensive manifolds also contain a visible sight glass, which allows the service technician to see the flow of liquid refrigerant during charging. The manifold assembly has unique fittings for different refrigerants, and the hoses are not interchangeable between refrigerants of different types. This means that you will need a separate manifold and gauge assembly for each of the different refrigerants (R-134a, R1234yf, and R-12) you service. The Society of Automotive Engineers (SAE) has set standards for automotive refrigerant service equipment. Standard J2197 states that all hose connections on a service manifold for R-134a refrigerant must be a 1 2 in. male ACME fitting and for R-12 refrigerants must be a 7 16 in. 3 20 thread pitch male fitting. Most manifold sets contain two hand valves to provide flow control through the manifold, one for the low-side service hose and one for the high-side service hose, as was shown in ­Figure 5-2 and Figure 5-3. Turning the hand valve clockwise shuts off the common passage in the gauge block, and the gauge will read system pressure. Turning the hand valve counterclockwise opens the common passage for charging or recovery/evacuation. As was noted in Chapter 2, if both valves are closed, both high-side and low-side pressures will be read isolated from one another. However, if either the low- or high-side valve is open, that line pressure gauge circuit will be open to the center service hose port on the manifold set. If the center line is not connected to a charging or recovery station, refrigerant will be vented

20

10 0 10 0 2 0 3

30

40 50 60

100

0

200 300 400 500 600

FIGURE 5-5  Typical manifold gauge set passages.

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to the atmosphere. If the center service port hose is connected to a charge/recovery unit and both hand valves are open, both gauges will read the same pressure due to the common center passage in the gauge block giving inaccurate pressure readings. Some manifolds have a third valve for connecting a vacuum service or refrigerant service hose through the manifold, yet other manifolds may have four valves with: 1. Low-side service hose 2. High-side service hose 3. Vacuum pump service hose 4. Refrigerant service hose

Hoses

Specific requirements for service hoses used in automotive air-conditioning service are given in the SAE standards J2196 and J2197. A refrigeration service hose (Figure 5-6) is constructed to withstand maximum working pressures of 500 psi (3,448 kPa). Some service hoses have a minimum burst pressure rating of up to 2,500 psi (17,238 kPa). The SAE has established different hose specifications for R-134a, R1234yf, and R-12 refrigerants. This is due, in part, to the fact that R-134a has smaller molecules than R-12 refrigerants and tends to more readily leak through hoses and seals. Current service hoses have an impervious barrier to reduce the possibility of refrigerant leakage and are referred to as barrier hoses. The following is a brief overview of those standards as they apply to refrigerants R-134a and R-12. It must be noted that there are no less than nine other alternative refrigerants that have been approved for automotive use by the Environmental Protection Agency (EPA). Each of these alternate refrigerants requires its own unique fittings. The refrigerant manufacturer will supply any information about this requirement on request. The SAE standard J2197 specifies that R-134a service hoses have a 1 2 in.-16 ACME thread for connecting to manifold gauge sets or equipment. The service end connects directly to a quick coupler (Figure 5-7), which has no external threads and a one-way check valve to avoid refrigerant being purged to the atmosphere when disconnected and connects to the vehicle service fitting. The high-side hose includes a 16-mm O.D quick-coupler and the low-side hose includes a 13-mm O.D quick-coupler. If necessary, a M14X1.5 fitting can be used between the hose and quick coupler adapter. The R-12 service hoses have 7 16 in.-20 female refrigerant flare nuts on both ends of all service hoses. The unique service fittings are designed to prevent accidental mixing of refrigerants. For R-1234yf, the SAE standard for service hose, fittings, and couplers is J2888, as specified in J639. The

Barrier hoses have an impervious lining to prevent refrigerant leaking through the walls of the hose. Air-conditioning systems in vehicles have had barrier hoses since 1988.

FIGURE 5-6  Atypical service hose.

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FIGURE 5-7  Quick coupler for R-134a manifold gauge set.

R-1234yf service hoses will bear an “SAE J2888” marking with an adjacent strip. Like R-134a, the high-side hose is red, the low-side hose is blue, and the supply hose is yellow. The service end of the R-1234yf hose also connects directly to a quick-coupler and looks very similar to the R-134a coupler. It has no external threads and a one-way check valve to avoid refrigerant being purged to the atmosphere when disconnected and connected to the vehicle service fitting. The high-side hose includes a 17-mm O.D quick-coupler and the low-side hose includes a 14-mm O.D quick-coupler. The threaded ends of both hoses use an M12 3 1.5-6g male thread. High-Side Service Hose.  The high-side service hose is connected between the system high side and the manifold gauge set or service equipment. Hoses that are designed for R-134a will be labeled SAE J2196/R-134a and are solid red with a black stripe. The high-side service end has a quick disconnect coupler fitting with a 16 mm outside diameter (O.D.) as stipulated by SAE standard J639. The R-1234yf service hoses are also red and will bear an “SAE J2888” marking with an adjacent strip. The high-side service end has a 17-mm O.D quick-coupler. Hoses that are designed for R-12 service are marked SAE J2196 and are available in either solid red or black with a red stripe. A shut-off valve must be placed within 1 ft. or 30 cm of the end connected to the system (Figure 5-8). This valve is intended to help reduce the amount of refrigerant that is vented to the atmosphere during a service procedure and must be on manifold and gauge sets as well as on recovery/recycling station high-/low-side service lines.

FIGURE 5-8  There must be a shut-off valve within 12 in. (30.5 cm) of the service hose end.

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Low-Side Service Hose.  The low-side service hose is connected between the system low side and the manifold gauge set or service equipment. Hoses that are designed for HFC-134a will be labeled SAE J2196/R-134a and are solid blue with a black stripe. The low-side service end has a quick disconnect coupler fitting with a 13 mm OD as stipulated by SAE standard J639. The R-1234yf service hoses are also blue and will bear an “SAE J2888” marking with an adjacent strip. The low-side service end has a 14-mm OD quick-coupler. Hoses that are designed for R-12 service are marked SAE J2196 and are available in either solid blue or black with a blue stripe. A shut-off valve must be placed within 1 ft. or 30 cm of the end connected to the system on manifold and gauge sets as well as on recovery/recycling station high-/lowside service lines. Utility Service Hose.  The utility service hose connects to the center port on the manifold set and is used to connect to external service equipment such as recovery/charging stations, vacuum pumps, or disposable refrigerant tanks. Utility hoses that are designed for R-134a will be labeled SAE J2196/R-134a and are solid yellow with a black stripe. The hose has a 1 2 in. 16 ACME right-hand thread on the end of the hose. The R-1234yf utility hose is also yellow but it has a 1 2 in. 16 ACME left-hand thread on the end of the hose. Utility hoses that are designed for R-12 service are marked SAE J2196, are available in either solid yellow or white or black with a yellow or white stripe, and have 7 16 in. -20 female refrigerant flare nuts on both ends. A shut-off valve must be placed within 1 ft. or 30 cm of the end connected to service equipment for both R-134a and R-12 refrigerants.

Connecting the Manifold and Gauge Set This procedure is used when connecting the manifold and gauge set on the automotive airconditioning system to perform any one of the many operational tests and service procedures. The transition from an ozone-depleting refrigerant (CFC-12) to an ozone-friendly refrigerant (HFC-134a) took place in some car lines during the 1993 model year. In other car lines, the transition took place during the 1994 model year. By the 1995 model year, nearly all vehicles were equipped with the new refrigerant. Before proceeding with the installation of the manifold and gauge set, it is important to identify which type of refrigerant is in the air-conditioning system. Manifold and gauge sets for R-12, R-134a and R-1234yf are not interchangeable. The three refrigerants and their oils are not compatible. Mixing refrigerants, oils, or components could result in serious damage to the air-conditioning system and poor system performance.

The utility hose is often referred to as the service hose.

SERVICE TIP:

The quick disconnect coupler fittings for R-134a high-side and low-side hoses come in various lengths to allow access into tight locations. So if the couplings that came on your manifold set are too long, you can order a compact coupling. As a rule I always use the compact design on my gauge sets.

WARNING: It is important to use extreme care and observe all service and safety precautions when working with refrigerants and refrigeration oil.

Procedure

This procedure is given in three parts that follow. Part I outlines the procedure used when connecting a manifold and gauge set into an R-134a system and is also shown in Photo Sequence 3. It should be noted the procedure for connecting the R-1234yf is the same as the procedure for R-134a. Part II outlines the procedure used when connecting a manifold and gauge set into an R-12 system equipped with Schrader-type service valves. Part III outlines the procedures to follow when connecting a manifold and gauge set into an R-12 system equipped with hand shut-off service valves located on or near compressor assemblies. WARNING: Safety glasses must be worn at all times while working with ­refrigerants. Remember, liquid refrigerant sprayed in the eyes can cause blindness. 163 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 5-9  Remove the protective caps slowly to ensure no refrigerant loss.

WARNING: The EPA requires positive shut-off provisions within 12 in. (30.5 cm) of the service end of each hose. There are various methods of ­accomplishing this; some are manual and some are semiautomatic.

Part I—HFC-134a System and R-1234yf CAUTION:

Place a fender cover on the vehicle to avoid damage to the finish.

1. Remove the protective caps from the high- and low-side service ports (Figure 5-9). WARNING: Remove the caps slowly to ensure that no refrigerant escapes past a defective service valve. NOTE: If a leak is found in the service valve, it should be repaired or replaced. 2. Turn the low-side hose hand valve fully counterclockwise to retract the Schrader ­depressor, before attaching to the system. 3. Connect the low-side hose (Figure 5-10). a. Press a quick-joint-type hose fitting onto a matching system fitting. b. Push firmly until a clicking sound is heard, ensuring that it is locked in place. c. Turn the hand valve clockwise to extend the depressor. 4. Repeat steps 2 and 3 with the high-side hose.

FIGURE 5-10  Connecting the hose fitting to an R-134a system.

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PHOTO SEQUENCE 3 Typical Procedure For Connecting a Manifold And Gauge Set to an R-134a or R1234yf Air-Conditioning System

P3-1  Typical location of the low-side service valve on an R-134a or R-1234yf air-conditioning system.

P3-2  Typical location of the high-side access fittings on an R-134a or R-1234yf air-conditioning system.

P3-3  Ensure that the manifold and gauge set with hoses comply with SAE J2211 for R-134a and SAE J2843 for R-1234yf.

P3-4  Ensure that the manifold lowside hand valve is closed—turned fully clockwise.

P3-5  Ensure that the manifold highside hand valve is closed—turned fully clockwise.

P3-6  Remove the protective cap from the low-side service valve fitting. Repeat this procedure with the high-side service valve fitting.

P3-7  Connect the low-side service hose quick connect adapter to the low-side service valve fitting. Repeat this procedure with the high-side service valve fitting.

P3-8  The manifold and gauge set is ready to be used for servicing the airconditioning system.

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Part II—R-12 System with Schrader-Type Valves CAUTION:

Place a fender cover on the vehicle to avoid damage to the finish.

SERVICE TIP:

Service hoses must be equipped with a Schrader valve depressing pin. If the hoses are not so equipped, a suitable adapter must be used.

1. Remove the protective caps from the high- and low-side service ports. WARNING: Remove the caps slowly to ensure that no refrigerant is leaking past a defective Schrader valve. NOTE: If a leak is found in the service valve, it should be repaired or replaced. 2. Make sure that the manifold hand shut-off valves are closed before the next step. 3. Connect the low-side manifold hose, finger tight, to the suction side of the system. 4. Connect the high-side manifold hose, finger tight, to the discharge side of the system.

Part III—R-12 System with Hand Valves

The high and low-side compressor-mounted hand-operated manual service valves were used on some early air-conditioning systems—both factory and aftermarket installed—and had a cast iron or cast aluminum compressor manufactured by Tecumseh or York.

SPECIAL TOOL High-side adapter, as required

SERVICE TIP:

The high-side fitting on many late-model R-12 car lines (Figure 5-11) requires that a special adapter (Figure 5-12) be connected to the manifold hose before being connected to the system.

FIGURE 5-11  A typical CFC-12 high-side access fitting.

Flexible adapter

45° adapter

90° adapter

Straight adapter

CAUTION:

Place a fender cover on the vehicle to avoid damage to the finish.

FIGURE 5-12  Adapters used to connect a high-side hose into an R-12 system.

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FIGURE 5-13  Remove the protective caps from the service valves.

FIGURE 5-14  Remove the protective caps from the service ports.

Though not used for years for automotive service, they are found in many over-the-road applications, such as Diamond Reo, Kenworth, Mack, and Peterbilt. They are also found in off-road applications such as Allis Chalmers, Caterpillar, International Harvester, and John Deere. The Tecumseh and York compressors, equipped with hand shut-off service valves, are available new or rebuilt for R-12 or R-134a refrigerants having a lubricant charge of mineral oil, ester, or poly-alkaline glycol (PAG), as required. 1. Remove the protective caps from the service valve stems (Figure 5-13), if equipped. 2. Remove the protective caps from the service ports (Figure 5-14).

SERVICE TIP:

Make certain that the hand shut-off valves are closed on the manifold set before the next step.

WARNING: Remove the caps slowly to ensure that no refrigerant is leaking past the service valve. NOTE: If a leak is found in the service valve stem, it should be repaired or replaced. If there is a leak at the service port, the service valve should be replaced. 3. Connect the low-side manifold hose, finger tight, to the suction side of the system. 4. Connect the high-side manifold hose, finger tight, to the high side of the system. 5. Using a service valve wrench (Figure 5-15), rotate the suction-side service valve stem two or three turns clockwise. 6. Repeat step 5 with the discharge service valve stem.

SPECIAL TOOL Service valve wrench

Classroom Manual

Chapter 5, page 143

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FIGURE 5-15  Use a service wrench to turn the service valve stem.

Basic Performance Testing the Air-Conditioning System Moisture in the air is known as relative humidity (RH). Performance testing checks temperature and pressure readings under controlled operating conditions to determine if an air-conditioning system is operating at full efficiency.

The following procedure serves as a guide for the service procedures required for basic ­performance testing of air-conditioning systems. The basic procures are the same regardless of the type of refrigerant gas used in the vehicle. Greater performance testing details are discussed in Chapter 6 of the Classroom Manual; this is meant only as an introduction to become familiar with normal system pressures and temperatures and is not meant to be a diagnostic test procedure. The service technician must always refer to the manufacturer’s service information for specific data for any particular vehicle model. Customer Care: When you are performing repairs or inspection services on a customer’s vehicle, be sure to install disposable paper floor mats and plastic seat covers. The best repair in the world can go unrewarded if you leave a customer’s car dirty.

Preparing and Stabilizing the System

SPECIAL TOOL Large floor fan

1. Ensure that both manifold hand valves are in the closed position to prevent refrigerant venting. 2. Connect the manifold and gauge set into the system. 3. Start the engine; set the speed to about 1,500–1,700 rpm. 4. Place a fan in front of the radiator to assist the ram airflow (Figure 5-16). 5. Turn on the air conditioner; set all controls to maximum cooling or Recirculation mode; set the blower speed on HI. 6. Insert a thermometer in the air-conditioning duct as close as possible to the evaporator core (Figure 5-17). 7. Note the relative humidity levels and refer to Figure 5-19 to determine the approximate duct temperature. The atmospheric relative humidity has a dramatic effect on the effectiveness of the air-conditioning system.

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FIGURE 5-16  A fan is placed in front of the vehicle to provide additional air while performance testing.

An evaporating pressure of 30 psig (207 kPa) corresponds to a temperature of 34.58F (1.48C) for R-134a and 328F (08C) for R-12.

A condensing pressure of 190 psig corresponds to a temperature of 1278F (52.88C) for R-134a and 1348F (33.98C) for R-12. FIGURE 5-17  Need to be able to see low-temperature scale of 0 – 1008F.

Visual Check of the Air Conditioner 1. The average low-pressure gauge reading should be in the range of 20–30 psig (239–310 kPa absolute). NOTE: The term average must be considered: for example, 15–25 psig (103–172 kPa) ­“averages” 20 psig (239 kPa) and 25–35 psig (172–241 kPa) “averages” 30 psig. 2. The high-side gauge should be within the specified range of 160–220 psig (1,103–1,517 kPa) depending on the ambient temperature and humidity. 3. The discharge air temperature should be within the specified range of 402508 F (4.4 – 108C)

Inspect the High and Low Sides for Even Temperatures 1. Feel the hoses and components in the high side of the system to determine if the components are evenly heated.

SERVICE TIP:

When removing the plastic service caps from the R-134a refrigerant lines, inspect the condition of the O-rings inside the caps. These O-rings function as seals for the system and can be the source of refrigerant leaks.

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WARNING: Certain system malfunctions cause the high-side components to become superheated to the point that a serious burn can result if care is not taken when handling these components.

SERVICE TIP:

A slight change in temperature of the inlet and outlet of the accumulator is to be expected and is acceptable.

SERVICE TIP:

Cold or frost at the outlet side is to be expected and is acceptable. Cold or frost at the inlet side, however, is an indication of a defective metering device or that there is excess moisture in the system. Air-conditioning temperature control is by thermostat or low-pressure control.

2. Note the inlet and outlet temperatures of the receiver/drier assembly. A change in the temperature is an indication of a clogged or defective receiver/drier. 3. All lines and components on the high side should be warm to the touch (see the Warning following step 1). 4. All lines and components on the low side of the system should be cool to the touch. 5. Note the condition of the thermostatic expansion valve (TXV) or fixed orifice tube (FOT). The high-pressure inlet should be warmer than the low-pressure outlet.

Test the Thermostats and Control Devices 1. Refer to the service manual for the performance testing of the particular type of control device used. 2. Determine that the thermostat or low-pressure switch engages and disengages the clutch. There should be about a 128F (6.78C) temperature rise between the cut-out (off ) and cut-in (on) point. Many compressors today are of the variable displacement design and do not cycle the compressor clutch, but instead vary the amount of refrigerant flow in the system to regulate evaporator temperature. This is discussed in greater detail in Chapter 9. Guides for determining the proper gauge readings and temperatures are shown in Figure 5-18. The RH at any particular temperature is a factor in the quality of the air (Figure 5-19A and Figure 5-19B). These figures should be regarded as guides only. 3. Complete performance testing. Refer to the manufacturer’s service manual for specific requirements.

70

80

90

100

110

150–190

170–220

190–250

220–300

270–370

38–45

39–47

40–50

42–55

45–60

Ambient Air Temperature, 8F Average Compressor Head Pressure, psig Average Evaporator Temperature, 8F

(A) English 21

27

32

38

43

1,034–1,310

1,172–1,517

1,310–1724

1,517–2,069

1,862–2,551

3.3–7.2

3.9–8.3

4.4–10

5.5–12.8

7.2–15.6

Ambient Air Temperature, 8C Average Compressor Head Pressure, kPa Average Evaporator Temperature, 8C

(B) Metric FIGURE 5-18  Head pressure performance charts: (A) English; (B) metric. 70

Ambient Temperature, 8F

80

90

100

Relative Humidity, %

50

60

90

50

60

90

40

50

60

20

40

50

Discharge Air Temperature, 8F

40

41

42

42

43

47

41

44

49

43

49

55

(A) English 21

Ambient Temperature, 8C Relative Humidity, % Discharge Air Temperature, 8C

50 4.4

60 5

27 90 5.5

50 5.5

60 6.1

32 90 8.3

40 5

50 6.6

38 60 9.4

20 6.1

40 8.3

50 12.7

(B) Metric FIGURE 5-19  Relative humidity performance charts: (A) English; (B) metric.

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Return the System to Service 1. Return the engine speed to normal idle. 2. Back seat the high- and low-side compressor service valves, if equipped. 3. Close the service hose valves. 4. Remove the service hoses. 5. Replace the protective caps to prevent a loss of refrigerant in case the service valve leaks. 6. Turn off the air-conditioning controls. 7. Stop the engine.

case study A customer brings a car, recently purchased from a reputable used car dealer, in for service with a repair authorization to “fix a water leak.” The complaint is that water spills out of the air conditioner onto her feet when she makes a right turn. She also notes that the floor mat on the passenger side is damp most of the time. The technician verifies the damp floor mat and suspects that the heater core is leaking. However, there is no evidence of antifreeze solution on the floor

mat. Further discussion with the customer verifies that the cooling system is apparently “sound.” While talking with the customer, however, the technician notices that there are no familiar drips on the shop floor usually experienced when the air conditioner is operating. Inspection of the drain tube of the evaporator reveals that a recently applied undercoating material has sealed the opening. This causes the water to back up into the evaporator and spill out. Cleaning the drain tube solved the problem.

CAUTION:

If service hoses are equipped with manual shut-off, be sure to close them before disconnecting from the system.

Terms to Know Barrier hoses CFC-12 (R-12) Compound gauge HFC-134a (R-134a) HFO-12334yf (R-1234yf) Low-side gauge Manifold and gauge set Performance testing

ASE-STYLE REVIEW QUESTIONS 1. Technician A says that the performance test ­determines if system pressures are proper. Technician B says that the test determines if the system temperatures are proper. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

3. Technician A says that the blower should be run on high speed for the performance test. Technician B says it does not matter at what speed the fan is run. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

2. Technician A says that humidity has an effect on ­system performance. Technician B says that poor airflow has an effect on system performance. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

4. Technician A says that a slight temperature change at the inlet and outlet of the receiver-drier indicates a restriction. Technician B says that a slight temperature change at the inlet and outlet of an accumulator indicates a restriction. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

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5. Technician A says that a change in temperature from the inlet to the outlet of the thermostatic expansion valve (TXV) is not acceptable. Technician B says that a change in temperature from the inlet to the outlet of a fixed orifice tube (FOT) is acceptable. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 6. Technician A says that an R-12 manifold and gauge set may be used on an R-134a system. Technician B says that an R-134a manifold and gauge set may be used on an R-12 system. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 7. Technician A says that the kPa scale is used to denote pressure on the metric gauges. Technician B says that the Hg/psig scale is used to denote pressure on the English scale. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

8. Technician A says that the maximum working pressure of service hoses should be 500 psig (3,448 kPa). Technician B says that 500 psig (3,448 kPa) is also the burst pressure. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 9. Technician A says that the low-side gauge may be used on the high side, if necessary. Technician B says that the high-side gauge may be used on the low side, if necessary. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 10. Technician A says both hand valves must be closed to read service pressures. Technician B says there is a common passage on a manifold and gauge set. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

ASE CHALLENGE QUESTIONS 1. All of the following statements about a Schrader-type service valve are correct, except: A. The valve may be front seated. B. The valve may be back seated. C. The valve may be midpositioned. D. The valve may be opened. 2. The service valve adapter shown right is turned in The _______________ direction to allow access to the ­air-conditioning system. A. Clockwise (cw) C. Either A or B B. Counterclockwise D. Neither A nor B (ccw)

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3. Technician A says that a manifold and gauge set must have service shut-off valves within 1 ft. (30 cm) of the hose service end. Technician B says that a recovery/recycling station must have service shut-off valves within 1 ft. (30 cm) of the hose service end. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

5. Technician A says that a manifold and gauge set is one of the primary service tools for the air-conditioning service technician. Technician B says that a manifold and gauge set must be dedicated to the type of refrigerant being serviced. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

4. Each type of refrigerant uses a unique set of service fittings that: A. Are designed to prevent accidental loss of refrigerant. B. Are designed to prevent accidental mixing of refrigerants. C. Are more cost effective for manufacturers. D. Are easy to hook up to any system.

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19

JOB SHEET

Name ______________________________________ Date ________________________

Interpreting Gauge Pressure Upon completion of this job sheet, you should be able to troubleshoot an air-conditioning system based on gauge pressure readings. NATEF Correlation NATEF AST and MAST Correlations: HEATING AND AIR CONDITIONING: General: A/C System Diagnosis and Repair. Task #1. Identify and interpret heating and air-conditioning problems; determine necessary action. (P-1) Task #3. Performance test A/C system; identify problems. (P-1) Task #5. Identify refrigerant type; select and connect proper gauge set; record temperature and pressure readings. (P-1) Tools and Materials None required Procedure The gauge pressure reading is given. Identify the problem and suggest the remedy. High-side gauge reading is too high: 1.  2.  3. 

PROBLEM

REMEDY

  

     

High-side gauge reading is too low: 4.  5. 

PROBLEM

 

REMEDY

   

Low-side gauge reading is too high: 6.  7.  8. 

PROBLEM

  

REMEDY

     

Low-side gauge reading is too low: 9.  10. 

PROBLEM

 

REMEDY   175

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Instructor’s Response 

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20

JOB SHEET Name ______________________________________ Date ________________________

Interpreting System Conditions Upon completion of this job sheet, you should be able to troubleshoot an air-conditioning system based on visual, smell, and touch. NATEF Correlation NATEF AST and MAST Correlations: HEATING AND AIR CONDITIONING: General: A/C System Diagnosis and Repair. Task #1. Identify and interpret heating and air-conditioning problems; determine necessary action. (P-1) Tools and Materials None required Procedure The condition is given. Identify the problem and suggest the remedy. Sight glass is clear: 1.  2. 

PROBLEM

REMEDY

 

   

Sight glass is cloudy: 3.  4. 

PROBLEM

REMEDY

 

   

Oily hose or fittings; worn or abraded hose: 5.  6. 

PROBLEM

REMEDY

 

   

Icing condition or temperature change at a component: 7.  8. 

PROBLEM

REMEDY

 

   

Musty smell from evaporator: 9.  10. 

PROBLEM

 

REMEDY

    177

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Instructor’s Response 

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21

JOB SHEET Name ______________________________________ Date ________________________

Identifying Refrigeration System Type Upon completion of this job sheet, you should be able to determine the type of refrigerant in the system. NATEF Correlation NATEF AST and MAST Correlations: HEATING AND AIR CONDITIONING: General: A/C System Diagnosis and Repair. Task #3. Performance test A/C system; identify problems. (P-1) Task #5. Identify refrigerant type; select and connect proper gauge set; record temperature and pressure readings. (P-1) Tools and Materials None required Procedure The refrigerant type is not known. The system condition is given. Identify the probable cause and suggest the remedy. System pressure is higher than expected: 1.  2.  3. 

PROBLEM

  

REMEDY

     

System pressure is lower than expected: 4.  5.  6. 

PROBLEM

  

REMEDY

     

Expected low-side pressure range for a properly operating system: R-12 R-134a 7. _____________ to ______________ psig ______________ to ______________ psig 8. _____________ to ______________ kPa ______________ to ______________ kPa Expected high-side pressure range for a properly operating system: R-12 R-134a 9. _____________ to ______________ psig ______________ to ______________ psig 10. _____________ to ______________ kPa ______________ to ______________ kPa 179 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Instructor’s Response 

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Chapter 6

BASIC TOOLS Mechanic’s basic tool set (English and metric)

Servicing System Components

Fender cover Flare nut wrench set Torque wrench Hacksaw with 32 tpi blade Spring lock coupling tool set Single-edge razor blade FOT remove-replace tool Tube cutter Calibrated container Internal-external snapring pliers Pressure/temperature switch socket

Upon Completion and Review of this Chapter, you should be able to: ■■

■■

■■

■■

■■

Identify and compare the differences between English and metric fasteners. State the purpose of good safety practices when servicing an automotive air-conditioning system. Diagnose air-conditioning system malfunctions based on customer complaints. Identify the different types of automotive air-conditioning systems. Remove the refrigerant (R-134a, R-1234yf, or R-12) from the vehicle air-conditioning system using an approved refrigerant recovery/recycling unit.

■■ ■■

Remove and replace the refrigerant hoses and fittings. Remove and replace the thermostatic expansion valve (TXV).

■■

Remove and replace the fixed orifice tube (FOT).

■■

Remove and replace the accumulator assembly.

■■

Remove and replace the condenser.

■■

Remove and replace the receiver-drier.

■■

Remove and replace the superheat or pressure switch.

English and Metric Fasteners The servicing of automotive air-conditioning systems seems to become more and more ­complex each year. Although basic theories do not change, refrigeration and electrical control are redesigned or modified year to year. To add to the confusion, domestic automotive manufacturers use metric nuts and bolts on many components and accessories. Both English and metric fasteners can be found on the same automobile. Some metric fasteners closely resemble English fasteners in size and appearance. The automotive service technician must be very careful to avoid mixing these fasteners. ­English and metric fasteners are not interchangeable. For example, a metric 6.3 (6.3 mm) capscrew may replace by design an English ¼-28 (¼ in. by 28 threads per in.) capscrew. Note in ­Figure 6-1 that the diameters of the two fasteners differ by only 0.002 in. (0.05 mm). The threads differ by only 2.6 per in. (1 per cm). There are 28 threads per in. (11 threads per cm) for a ¼-28 capscrew, and 30.6 threads per in. (12 threads per cm) for a 6.3 mm capscrew.

Both English and metric fasteners may be found on an assembly. Metric fasteners are any type of fastener with metric size designations, numbers, or millimeters. English fasteners are any type of fastener with English size designations, numbers, decimals, or fractions of an inch.

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#8 #10 1/4

English Series Diameter in mm 0.164 4.165 0.190 4.636 0.250 6.350

5/16 3/8

0.312 0.375

7.924 9.525

18 or 24 16 or 24

7/16

0.437

11.099

14 or 20

1/2 9/16 5/8

0.500 0.562 0.625

12.700 14.274 15.875

13 or 20 12 or 18 11 or 18

Size

3/4

0.750

19.050

Threads Per Inch 32 or 36 24 or 32 20 or 28

Size

Metric Series Diameter in mm

Threads Per Inch (prox)

M6.3 M7 M8

0.248 0.275 0.315

6.299 6.985 8.001

25 25 20 or 25

M10

0.393

9.982

17 or 20

M12

0.472

11.988

14.5 or 20

M14

0.551

13.995

12.5 or 17

M16 M18

0.630 0.700

16.002 17.780

12.5 or 17 10 or 17

M20 M22

0.787 0.866

19.989 21.996

10 or 17 10 or 17

M24

0.945

24.003

8.5 or 12.5

M27

1.063

27.000

8.5 or 12.5

10 or 16

7/8

0.875

24.765

9 or 14

1

1.000

25.400

8 or 14

FIGURE 6-1  A comparison of English and metric fasteners.

While the differences are minor, an English ¼-28 nut will not hold on a metric 6.3 capscrew. Mismatching of fasteners can cause component damage or early failure. Such component failure can result in personal injury. Follow all safety precautions when servicing an automotive air conditioner. Service procedures are suggested routines for the step-by-step act of troubleshooting, diagnosing, and repair contained in your shop repair information system or service manual.

Safety It must be recognized that the skills and procedures of those performing service procedures vary greatly. It is not possible to anticipate all of the conceivable ways or conditions under which service procedures may be performed. It is, therefore, not possible to provide precautions for every possible hazard that may result. The following precautions are basic and apply to any type of automotive service: ■■

Wear safety glasses or goggles for eye protection when working with refrigerant ­(Figure 6-2). This is important while working under the hood of the vehicle.

A

B FIGURE 6-2  Wear safety (A) goggles or (B) glasses when servicing air conditioning components.

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■■

■■

■■

■■

■■

■■

■■

■■

■■

If the engine is to be operated, set the parking brake. a. Place the gear selector in PARK if the vehicle is equipped with an automatic transmission. b. Place the transmission in NEUTRAL if the vehicle is equipped with a manual transmission. Unless required otherwise for the service procedure, be certain that the ignition switch is turned to the OFF position. If the engine is to be operated, be certain that the vehicle is in a well-ventilated area or that provisions are made to vent the exhaust gases. Avoid loose clothing. Roll up long shirt sleeves. Tie long hair securely behind the head. Remove rings, watches, and loose-hanging jewelry. Keep clear of all moving parts when the engine is running. Engine-driven cooling fans have been known to separate. A loose fan blade can cause serious injury. Keep hands, clothing, tools, and test leads away from the engine cooling fan. Electric cooling fans may start without warning even when the ignition switch is in the OFF position. Avoid personal contact with hot parts such as the radiator, exhaust manifold, and highside refrigerant lines. Disconnect the battery when required to do so (Figure 6-3). Follow the recommendations of the manufacturer; Chrysler, for example, requires that the negative (2) cable be disconnected to disable the air bag. General Motors requires the positive (1) cable to be disconnected, and Ford requires both cables be disconnected, first the negative (2), then the positive (1). Batteries normally produce explosive gases. DO NOT allow flames, sparks, or any lighted substances to come near the battery. Always shield your face and protect your eyes when working near a battery. NOTE: When the battery has been reconnected after being disconnected, volatile memory information—such as radio station presets, clock, seat, mirror, and window memory as well as customer input keyless entry codes—will be lost. Also, when the battery is reconnected, some abnormal drive symptoms may occur for the first 10 miles (18 kilometers) or so.

■■

If in doubt, ASK; do not take a chance. If there is no one to ask, consult an appropriate service manual. Again, do not take chances.

FIGURE 6-3  Carefully disconnect the battery cable.

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WARNING: The technician must exercise extreme caution and pay heed to every established safety practice when performing these or any automotive ­air-conditioning service procedures.

Diagnostic Techniques

Noises sound like different things to different people.

Before attempting to service an automotive air-conditioning system, be certain that the diagnosis is based on sound reasoning. Consider the following: ■■ Did you listen carefully to the customer’s complaint? ■■ Does your diagnosis of the problem have merit based on the customer complaint? ■■ What type of system are you working on? a. Cycling or noncycling clutch? b. CFC-12, HFC-134a, or unknown refrigerant? c. Fixed orifice tube or thermal expansion valve? ■■ Do you have the proper tools, equipment, and parts to service the air-conditioning system? a. What tools are required? b. What equipment is required? c. What parts are required? Listen carefully to the customer’s complaint of the problem. If you do not understand, ask questions. Suppose, for example, that the customer complains of a moaning sound. The word moaning means different things to different people, so ask questions. Take a test drive with your customer so the noise can be identified. Assume that you test drive the vehicle and hear nothing. When you return to the shop and tell the customer you heard nothing, the response may be, “Well, you did not start off very fast at the traffic light.” Further discussion will reveal that the noise is only heard when pulling away from a traffic light after stopping. The diagnosis to this problem is a relatively simple one. You are looking for a problem that only occurs during heavy acceleration. The problem can be a defective vacuum check valve or split vacuum hose (Figure 6-4), anything that may cause a vacuum loss during heavy acceleration. NOTE: The loss of a vacuum signal at the control head will generally cause domestic vehicles to “fail safe” in either the heat or defrost mode.

FIGURE 6-4  A split vacuum hose can cause system malfunction.

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FIGURE 6-5  A flare nut wrench set.

Proper Tools, Equipment, and Parts Having and using the proper tools and equipment is an essential part of performing a successful repair procedure. A screwdriver, for example, makes a very poor chisel; an adjustable wrench is a very poor hammer.

Tools

It is important that tools be used for the purpose for which they are designed. For example, a flare nut wrench, not an open-end wrench, should be used on flare nuts (Figure 6-5). A flare nut wrench should not be used to remove a bolt or nut; this service requires either an open, box, combination, or socket wrench.

Equipment

It is equally important that the proper equipment be used for a particular service p ­ rocedure. A vacuum pump, for example, can be constructed using an old refrigerator compressor ­(Figure 6-6). It is neither as attractive nor as efficient as a commercially available vacuum pump, however.

FIGURE 6-6  A typical refrigerator compressor.

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Parts

It is not practical to stock all of the parts that may be required in the course of doing business. The local parts distributors are responsible for that. If, however, a particular customer relies on your shop for a certain service, an adequate stock is suggested. For example, if a local offroad equipment repair facility relies on you for hoses, it would be wise to stock an adequate supply of various types of hose fittings and the several sizes of bulk hose necessary to supply the customer’s needs.

Service Procedures Consult the manufacturer’s service manual for specific guidelines when performing any major automotive airconditioning service.

To disarm is to turn off or disable a device or circuit.

The service procedures given in this chapter are typical and are to be used as a guide only. Due to the great number of variations in automotive air-conditioning system configurations, it is impossible to include all specific and detailed information in this text. When specific and more detailed information is required, the service technician must consult a computer-based information system such as All Data/Mitchell on Demand or the appropriate manufacturer’s service manual for any particular year and model vehicle. General service manuals are available that cover most service procedures in detail for automobiles of a specific year, make, and model. The information is given only as a guide for the student technician to perform basic service procedures that are normally required. Proper service and repair procedures are vital to the safe, reliable operation of the system. Most important, proper service procedures and techniques are essential to providing personal safety to those performing the repair service and to the safety of those for whom the service is provided. Be sure to follow the manufacturer’s recommendations. To disarm the air bag restraint system, for example, Chrysler had suggested disconnecting the battery ground (2) cable; General Motors had suggested disconnecting the positive (1) battery cable; and Ford had suggested disconnecting both cables—first the ground (2) cable, then the positive (1) cable. Since the computers are disabled and often must “relearn” a program, disconnecting the battery is now discouraged. General Motors suggest the following typical procedures: 1. Turn off the ignition switch. 2. Remove the restraint system (air bag) fuse from the fuse panel. 3. Remove the left-side sound insulator. 4. Disconnect the connector position assurance (CPA) and yellow two-way connector found at the base of the steering column. There is no set universal procedure. The best approach is to refer to the specific service manual appropriate for the make and model vehicle being serviced to ensure that proper procedures are followed.

Preparation

SPECIAL TOOLS Battery pliers Recovery equipment Take extreme care when disconnecting a battery.

There are certain basic procedural steps that must be taken before attempting to perform any service procedure. Whenever applicable, this procedure will be referenced in the various service procedures that follow. 1. Place the ignition switch in the OFF position. 2. Place a fender cover on the car to protect the finish. 3. Disconnect the battery cable. Follow procedures as outlined in the appropriate manufacturer’s service manual. 4. Recover the system refrigerant. Use the proper recovery equipment and follow the instructions outlined in the next section. 5. Locate the component that is to be removed for repair or replacement. 6. Remove access panel(s) or other hardware necessary to gain access to the component.

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Refrigerant Recovery To purge an air-conditioning system, in general terms, is to remove all of its contents, primarily refrigerant. While the term is generally understood to refer to refrigerant, it may also include air and moisture. Purging a system of refrigerant is usually necessary when a component is to be serviced or replaced. Until recently, to “purge” was to vent refrigerant into the atmosphere. The Federal Clean Air Act Amendments of 1990, however, required that after July 1, 1992, no refrigerants could be intentionally vented. The EPA requires that service equipment hoses have shut-off valves within 12 inches (30 cm) of the service end coupler. These valves must be closed before removing the coupler from the air-conditioning system service fitting. R-134a manifold and gauge sets as well as Recovery/Recycling/Recharging equipment generally have service hoses with an automatic check valve in the coupler to avoid the venting of refrigerant into the atmosphere. It is required that a refrigerant recovery system (Figure 6-7) be used to purge an airconditioning system of refrigerant. Manufacturers’ specifications and procedures should be followed to ensure safe and adequate performance. The following procedure is typical and should be used only as a guide. WARNING: Adequate ventilation must be maintained during this procedure.

Procedure for R-134a and R-12 Refrigerant Systems 1. Determine what type of refrigerant is in the system being serviced (i.e., R-134a or R-12) in order to select the correct recovery/recycling/recharge unit to be used. a. On some vehicles, it may be advisable to test the purity of the refrigerant in the vehicle’s air-conditioning system with a refrigerant identifier and to test the system for sealant contamination prior to attaching the refrigerant recovery unit. The procedures for using both these devices are outlined in Chapter 6 of this manual. NOTE: Some units are dual refrigerant recovery/recycling stations and have separate gauges and lines for both R-134a and R-12 refrigerants.

To purge is to remove refrigerant, moisture, and air from a system or by flushing with a dry gas such as nitrogen (N) to remove all moisture from a system. The Federal Clean Air Act, Title 6, is an amendment signed into law in 1990 that established national policy relative to the reduction and elimination of ozone-depleting substances. To recover refrigerant is to remove it, in any condition, from the system. A recovery system refers to the circuit inside the recovery unit used to recycle and transfer refrigerant from the air-conditioning system to the recovery cylinder.

FIGURE 6-7  Typical refrigerant recovery/ recycling/recharging machine.

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The term purge is used to refer to the removal of refrigerant.

SERVICE TIP:

Any time a major air-conditioning component is replaced or if the refrigerant system has been open to the atmosphere (moisture contamination) or empty for an extended period it is advisable that the receiver-drier/ accumulator be replaced, along with other necessary repairs. The desiccant contained inside acts to absorb unwanted moisture from the refrigerant system, and heavy contamination particles may settle to the bottom of the container. Most compressor manufacturers will not honor the warranty on a new or rebuilt compressor if the receiver-drier/ accumulator is not also replaced at the time of service.

Classroom Manual Chapter 6, page 173

2. Connect the recovery unit high- and low-side lines to the vehicle’s refrigerant service fittings and note the system pressures. a. If you are using a unit that is not equipped with gauges on the control console, it will be necessary to connect a manifold and gauge set to the vehicle system and attach the yellow service hose of the manifold and gauge set to the stand-alone recovery/recycling unit. 3. Start the engine and set the air-conditioning system controls to the MAX cold position with the blower on HI. NOTE: Some system malfunctions, such as a defective compressor or low system ­refrigerant charge level, may make the next four steps impossible to perform, in which case proceed with step 8. 4. Raise the engine speed to 1000–1200 rpm and operate for approximately 10 minutes to allow the system to stabilize and to allow most of the refrigerant oil to return to the compressor assembly. 5. Return the engine speed to normal idle. 6. Turn off the air-conditioning controls. 7. Shut of the engine. 8. Start the recovery unit, following the instructions for the recovery/recycling/recharge unit being used, and begin the recovery process. a. In general, this requires the opening of the valves on the refrigerant recovery tank and turning on the recovery switch located on the recovery unit console. b. If a manifold and gauge set is being used it will be necessary to open the hand valves on the manifold set high side and low side. 9. When the recovery process is complete, note the gauge readings; the low-side gauge should read 4 in. Hg (102 mm) of vacuum or lower. 10. Wait 2 minutes and observe the gauge readings again. If a positive pressure is noted, the recovery process will need to be repeated again. If a vacuum or 0 psig is noted, the recovery process is complete. See Photo Sequence 4 for a typical procedure for recovering (purging) refrigerant from the system.

Refrigerant Recovery For R-1234yf The procedure for recovering R-1234yf refrigerant is similar, with the following exceptions. R-1234yf refrigerant recovery/recycling/recharge (R/R/R) equipment must meet SAE J2843, and an integrated internal J2927 refrigerant identifier (Figure 6-8) or external J2912 refrigerant identifier must be attached for the machine to operate. An acceptable reading that must be received prior to recovery/recycling is 98 percent pure or greater. If an unacceptable reading is detected, such as contamination by another gas (R-134a) the refrigerant is considered contaminated and the equipment will not allow recovery to proceed. If a system is contaminated a separate recovery-only machine must be used to recover and store the contaminated refrigerant for either reclamation or disposal at an EPA-approved facility. The J2843 equipment is a little more time-consuming to use but it is intended to be as environmentally conscious as possible and force technicians to follow proper protocol.

Servicing Refrigerant Hoses and Fittings There are many types of fittings used to join refrigerant hoses to the various components of the air-conditioning system. Some of these fittings are (Figure 6-9) as follows: ■■ Male and female SAE flare ■■ Male and female upset flange, commonly called O-ring ■■ Male and female spring lock

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SAE is the Society of Automotive Engineers.

Courtesy of Robinair, Bosch Automotive Service Solutions

An O-ring is a synthetic rubber or plastic gasket with a round- or squareshaped cross section used as seals on line fittings. A spring lock is a special fitting used to form a leak-proof joint.

FIGURE 6-8  The R-1234yf recover/recycle/ recharge equipment must meet SAE J2843 and looks very similar to a conventional R-134a machine but has an integrated refrigerant identifier that meets SAE J2927.

Garter spring Cage

Nut

A B C Male (left) and female (right) SAE flare fittings: (A) straight, (B) 45° elbow, and (C) 90° elbow

A B C Male (left) and female (right) O-ring fittings: (A) straight, (B) 45° elbow, and (C) 90° elbow

Male fitting Female fitting

O-rings

Stud

Female fitting O-ring

Guide

Details of a "Peanut" fitting

Cage Garter spring Details of spring lock (garter) connector

A Hose B C Male barb fittings: (A) straight, (B) 45° elbow, and (C) 90° elbow

Insert

Ferrule

Fitting

A typical "beadlock" fitting. A male O-ring connector is illustrated.

FIGURE 6-9  Various types of fittings used in automotive air condition service.

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■■ ■■

An insert fitting is a fitting designed to fit inside a hose, such as a barb fitting or beadlock fitting. Use caution when using a razor blade. Always cut away from the body.

■■

Male barb Peanut Beadlock This procedure will be given in three parts:

1. Repairing a hose using a beadlock insert fitting 2. Servicing spring lock fittings 3. O-ring service WARNING: R-1234yf is considered a mildly flameable refrigerant and as such refrigerant hoses and fittings should not be repaired. If a hose or fitting failure is found, the hose and fitting assembly should be replaced as an assembly. Seals and O-rings may be serviced.

Part 1. Hose Repair Using a Beadlock Fitting

A barb fitting is a fitting that slips inside a hose and is held in place with a gear-type clamp. Ridges (barbs) on the fitting prevent the hose from slipping off.

In order to meet new SAE refrigerant leakage specifications, a beadlock ferrule fitting with a captive metal shell (Figure 6-10) must be used for R-134a hose repairs. Barb fittings and screw (worm gear) style hose clamps are not acceptable repair methods for barrier-type hoses and do not meet current SAE standards. To repair lines using a beadlock fitting, follow the steps below and refer to Photo Sequence 5 for beadlock hose assembly repair. 1. Measure and mark the required length of replacement hose, or determine how much hose must be cut ahead of the damaged fitting. 2. Use a single-edge razor blade knife (utility knife) to cut the hose. 3. Trim the end of the hose to be used to ensure that the cut is at a right angle (square).

BEADLOCK FITTING CRIMP STYLE

Beadlock fitting before crimp

Hose locating hole

Grooved stem for nylon barrier hose FIGURE 6-10  To meet current SAE leaking standards, a beadlock fitting with a captive sheel must be used or R-134a line or fitting repairs.

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PHOTO SEQUENCE 4 Typical Procedure for Recovering (Purging) Refrigerant from the System

P4-1  Attach the service hoses of the refrigerant recovery/recycling/charging system to the vehicle high- and low-side service fittings.

P4-2  Open all hose shut-off valves.

P4-4  Turn on the main switch.

P4-5  Turn on the recovery (compressor) switch.

P4-7  Observe the gauges for at least 5 minutes. If the vacuum does not rise, complete refrigerant recovery. If the vacuum rises but remains at 0 psig (0 kPa) or below, a leaking system is indicated. Complete refrigerant recovery and repair the system.

P4-3  Connect the refrigerant recovery system to an approved electrical power supply.

P4-6  Operate until a vacuum pressure is indicated. The recovery system will automatically shut off. If it is not equipped with an automatic shut-off, turn the compressor switch to OFF after achieving a vacuum pressure.

P4-8  If the vacuum rises to a positive pressure, above 0 psig (0 kPa), the refrigerant was not completely removed from the system. Repeat the recovery procedure, starting with step P4-5 of this procedure.

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PHOTO SEQUENCE 4

P4-9  Repeat step P4-6 until the system holds a stable vacuum for at least 2 minutes.

CAUTION:

Use the proper oil for the refrigerant used in the system; that is, mineral oil for R-12 and PAG or Ester oil for R-134a (Figure 6-12). Some service information indicated that mineral oil may be used on seals and O-rings because it aids in forming a natural barrier to R-134a leaks.

(CONTINUED)

P4-10  After all of that refrigerant has been recovered from the system, close all valves. Close the service hose shut-off valves, the low- and high-side manifold valves, and the recovery system inlet valve. Disconnect all the hoses from the system service valves or fittings. Cap all fittings and hoses prevent dirt, foreign matter, or moisture from entering the system. This is most important for an R-134a system. The lubricant used in this system is very hygroscopic.

4. Select the correct fitting outside diameter (OD) for the hose inside diameter (ID). See Figure 6-11 for beadlock fitting sizes. 5. Apply clean refrigerant oil to the inside of the hose to be used. 6. Be sure that the beadlock ferrule fitting is free of nicks and burrs, and coat the fitting end to be inserted with clean refrigerant oil. 7. Slip the beadlock ferrule fitting into the refrigerant line in one constant, deliberate twisting motion.

Fitting for #6 hose

5/16"

Fitting for #8 hose

13/32"

Fitting for #10 hose

1/2"

Fitting for #12 hose

29/32" O.D.

3/4" O.D. No. 6

1" O.D.

No. 8

1-3/32" O.D.

5/8" No. 10

No. 12

FIGURE 6-11  Select the correct beadlock fitting size to be used for R-134a line or fitting repairs.

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PHOTO SEQUENCE 5 Assemble Beadlock Hose Assembly

P5-1  Measure the hose and mark the proper length.

P5-2  Cut the hose, ensuring that the end is “squared.”

P5-3  Liberally lubricate the beadlock fitting with mineral oil.

P5-4  Shake off excess oil.

P5-5  Insert the hose with the ferrule into the fitting.

P5-6  Crimp the ferrule.

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FIGURE 6-12  Containers of mineral and PAG oil.

SPECIAL TOOLS Flare nut wrench set ¼ in. drive socket set Torque wrench Hacksaw with 32 tpi blade Pliers Beadlock crimp set Spring lock coupling tool set Single-edge razor blade

8. Position the hose and beadlock ferrule fitting into the crimping tool clamp, verifying that proper crimping die was selected. 9. Apply clamping pressure as directed by the tool manufacturer to achieve proper crimp, generally until the die halves almost touch. 10. Reinstall the hose assembly on the vehicle.

Part 2. Servicing Spring Lock Fittings

For simplicity, this procedure is given in two parts: To Separate, steps 1 through 4, and To Join, steps 5 and 6.

To Separate 1. Install the special tool onto the coupling so it can enter the cage to release the garter spring (Figure 6-13). 2. Close the tool and push it into the cage to release the female fitting from the garter spring (Figure 6-14).

Tool

Tool

Push tool into cage Cage FIGURE 6-13  Installing the special spring lock coupling tool.

FIGURE 6-14  Close the tool and push it into the cage to release the coupling.

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O-rings Female fitting

Cage Male fitting

Garter spring

FIGURE 6-15  Pull the coupling apart.

3. Pull the male and female coupling fittings apart (Figure 6-15). 4. Remove the tool from the disconnected spring lock coupling.

To Rejoin

5. Lubricate two new O-rings with clean refrigeration oil and install them on the male fitting. NOTE: The O-ring material is of a special composition and size. To avoid leaks, use the proper O-rings. Also, see the caution following step 4 of Part 1. Always use new O-rings. 6. Insert the male fitting into the female fitting and push them together to join.

Part 3. Servicing O-rings

O-rings must be replaced whenever a component fitting is removed for any reason. They do not usually leak if not disturbed. On occasion, however, an O-ring may be found to be leaking and must be replaced. If it becomes necessary to replace an O-ring, be aware that there are several different types available for different applications. For example, in addition to spring lock fittings, there are two different types of O-ring fittings used on systems (Figure 6-16): 1. Captive 2. Standard Although R-134a O-rings are similar to R-12 O-rings, they are made of a different material. Most R-12 and R-134a O-rings are not compatible. When replacing them, it is important to use the proper O-ring for the fitting. The ID as well as the OD are also important considerations to ensure a leak-free connection.

A

Use the proper O-ring.

SERVICE TIP:

Coat O-ring seals with mineral oil to form an improved barrier seal.

B FIGURE 6-16  Captive (A) and standard (B) O-ring fittings.

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Replacing Air-Conditioning Components The following procedures may be considered typical for step-by-step instructions for the replacement of air-conditioning system components. For specific replacement details, however, refer to the manufacturer’s shop service manual for the particular year, model, and make of the vehicle.

Removing and Replacing the Thermostatic Expansion Valve (TXV) SPECIAL TOOL Flare nut wrench set

This procedure will be given in two parts: 1. Servicing the Standard TXV 2. Servicing the H-Block TXV

Part 1. Servicing the Standard TXV Classroom Manual Chapter 6, page 184

Take care not to damage the capillary tube or remote bulb.

1. Follow the procedures outlined in “Preparation.” 2. Remove the insulation tape from the remote bulb. 3. Loosen the clamp to free the remote bulb. 4. Disconnect the external equalizer, if the TXV is so equipped. 5. Remove the liquid line from the inlet of the TXV. 6. Remove and discard the O-ring, if equipped. 7. Inspect the inlet screen (Figure 6-17). a. If it is clogged, clean and replace the screen. Skip to step 14. b. If it is not clogged, proceed with step 8. 8. Remove the evaporator inlet fitting from the outlet of the TXV. 9. Remove and discard the O-ring, if equipped. 10. Remove the holding clamp (if provided on the TXV), and carefully lift the TXV from the evaporator. 11. Carefully locate the new TXV in the evaporator. 12. Insert new O-ring(s) on the evaporator inlet, if equipped. 13. Attach the evaporator inlet to TXV outlet. Tighten to the proper torque. 14. Install the new O-rings on the liquid line fitting, if so equipped. 15. Attach the liquid line to the TXV inlet. Tighten to the proper torque. 16. Reconnect the external equalizer tube, if equipped.

FIGURE 6-17  Inspect the inlet screen of the thermostatic expansion valve.

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17. Position the remote bulb and secure it with a clamp. 18. Tape the remote bulb to prevent it from sensing ambient air. 19. Proceed with step 14 of Part 2.

Part 2. H-Valve TXV 1. Follow the procedures outlined in “Preparation.” 2. Disconnect the wire connected to the pressure cut-out or pressure differential switch, as applicable. 3. Remove the bolt from the line sealing plate found between the suction and liquid lines. 4. Carefully pull the plate from the H-valve. 5. Cover the line openings to prevent the intrusion of foreign matter. 6. Remove and discard the plate to the H-valve gasket. 7. Remove the two screws from the H-valve. 8. Remove the H-valve from the evaporator plate. 9. Remove and discard the H-valve to the evaporator plate gasket. 10. Install a new H-valve with the gasket (Figure 6-18). 11. Replace the two screws. Torque to 1702230 in.-lb (20226 N ? m). 12. Replace the line plate to the H-valve gasket. 13. Hold the line assembly in place and install the bolt. Torque to 1702230 in.-lb (20226 N ? m). 14. Replace the access panels and any hardware previously removed. 15. Reconnect the battery following the instructions given in the manufacturer’s shop manual. 16. Leak-test, evacuate, and charge the system with refrigerant as outlined in Chapter 6 of this manual. 17. Complete the system performance test job sheet.

Be careful not to mar or nick the mating surface(s).

Classroom Manual Chapter 6, page 188

Low-pressure switch Thermostat

To evaporator

Liquid line Suction line

Expansion valve

Capillary tube Well FIGURE 6-18  A typical H-valve.

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Removing and Replacing the Fixed Orifice Tube (FOT)

Although orifice tubes may look alike, they are not interchangeable.

SPECIAL TOOLS Flare nut wrench set FOT removal tool Extractor tool Torque wrench Tube cutter

The fixed orifice tube (FOT) is also known as: ■■ Cycling clutch orifice tube (CCOT) ■■ Fixed orifice tube/cycling clutch (FOTCC) ■■ Variable displacement orifice tube (VDOT) It should be noted that orifice tubes are not interchangeable. An orifice tube used on Ford car lines may not be used on GM car lines. The same service tool may be used, however, to remove and replace any of them. When replacing the orifice tube, it is most important that the correct replacement part be used. Some car lines have a nonaccessible orifice tube in the liquid line. Its exact location, anywhere between the condenser outlet and the evaporator inlet, is determined by a circular depression or three indented notches in the metal portion of the liquid line. An orifice tube replacement kit is used to replace this type orifice tube and 2.5 in. (63.5 mm) of the metal liquid line. This service procedure is given in two parts: 1. Servicing the Accessible FOT 2. Replacing the Nonaccessible FOT NOTE: On some models, a service kit is not available for replacement of the orifice tube and the liquid line will have to be replaced. In addition, a manufacturer may require the replacement of the liquid line that houses the orifice tube if service is indicated.

Part 1. Servicing the Accessible FOT

The procedure (Photo Sequence 6) is given in two parts: Removing the FOT, steps 1 through 9, and Replacing the FOT, steps 10 through 14.

Removing the FOT 1. Perform the procedures outlined in “Preparation.” NOTE: It may not be necessary to disconnect the battery for this procedure.

CAUTION:

Use an oil that is proper for use with the system refrigerant; that is, mineral oil for CFC-12 and PAG for HFC-134a.

2. Using the proper flare nut wrenches, remove the liquid line connection at the inlet of the evaporator to expose the FOT. 3. Remove and discard the O-ring(s) from the liquid line fitting, if equipped. 4. Pour a very small quantity of clean refrigeration oil into the FOT well to lubricate the seals. 5. Insert the FOT removal tool onto the FOT (Figure 6-19). 6. Turn the T-handle of the tool slightly clockwise (cw) only enough to engage the tool onto the tabs of the FOT. 7. Hold the T-handle and turn the outer sleeve or spool of the tool clockwise to remove the FOT. Do not turn the T-handle. NOTE: If the FOT breaks during removal, proceed with step 8. If it does not break, proceed with step 10. 8. Insert the extractor into the well and turn the T-handle cw until the threaded portion of the tool is securely inserted into the brass portion of the broken FOT (Figure 6-20). 9. Pull the tool. The broken FOT should slide out. NOTE: The brass tube may pull out of the plastic body. If this happens, remove the brass tube from the puller and reinsert the puller into the plastic body. Repeat steps 8 and 9.

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Hold

Removal and installation tool

Evaporator inlet

A FIGURE 6-19  Insert the FOT removal tool.

Broken orifice tube extractor tool Fixed orifice tube Evaporator inlet FIGURE 6-20  Insert the extractor tool to remove the broken FOT.

Installing the FOT

10. Liberally coat the new FOT with clean refrigeration oil. 11. Place the FOT into the evaporator cavity and push it in until it stops against the evaporator tube inlet dimples. 12. Install a new O-ring, if equipped. 13. Replace the liquid line and tighten it to the recommended torque. 14. Replace the accumulator as outlined in this chapter. 199 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

PHOTO SEQUENCE 6 Typical Procedure for Replacing a Fixed Orifice Tube This service procedure presumes that all of the refrigerant has been properly removed from the air-conditioning system.

P6-1  Using the proper open end or flare nut wrenches, remove the liquid line from the evaporator inlet fitting.

P6-4  Hold the T-handle and turn the outer sleeve clockwise to remove the orifice tube. Do not turn the T-handle. NOTE: If the orifice tub broke, proceed with P6-5. If not broken, proceed with P6-6.

P6-7  Coat the new orifice tube liberally with clean refrigeration lubricant.

P6-2  Pour a small quantity of refrigerant lubricant into the orifice tube well to lubricate the O-rings.

P6-3  Insert an orifice tube removal tool and turn the T-handle slightly clockwise to engage the orifice tube.

P6-5  Insert the broken orifice tube extractor into the orifice tube well and turn the T-handle clockwise several turns until the tool has been threaded into the orifice tube.

P6-6  Pull the tool. The orifice tube should slide out.

P6-8  Slide the new orifice tube into the evaporator until it stops against the tube inlet dimples.

P6-9  Slide a new O-ring onto the evaporator or liquid, as applicable.

P6-10  Connect the liquid line to the evaporator and tighten the nut with the proper wrenches.

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Part 2. Servicing the Nonaccessible FOT 1. Follow the procedures outlined in “Preparation.” NOTE: It may not be necessary to disconnect the battery. 2. Remove the liquid line from the evaporator inlet. Remove and discard the O-rings, if equipped. 3. Remove the liquid line from the condenser outlet. Remove and discard the O-rings, if equipped. 4. Locate the orifice tube. The outlet side of the orifice tube can be identified by a circular depression or three notches (Figure 6-21). 5. Use a tube cutter to remove a 2.5 in. (63.5 mm) section of the liquid line (Figure 6-22). 6. Slide a compression nut onto each section of the liquid line. 7. Slide a compression ring onto each section of the liquid line with the taper portion toward the compression nut. 8. Lubricate the two O-rings with clean refrigeration oil of the proper type and slide one onto each section of the liquid line. See the warning following step 4 of part 1. 9. Attach the orifice tube housing, with the orifice tube inside, to the two sections of the liquid line (Figure 6-23). 10. Hand tighten both compression nuts. Note the flow direction indicated by the arrows. The flow should be toward the evaporator. 11. Hold the orifice tube housing in a vise or other suitable fixture to tighten the compression nuts.

To evaporator Orifice tube outlet Liquid line

From condenser FIGURE 6-21  Locate the FOT.

A

CAUTION:

Note how the liquid line was routed, steps 2 and 3, so it can be replaced in the same manner.

SERVICE TIP:

Allow at least 1 in. (25.4 mm) of exposed tube at either side of any bend. Also, do not use excessive pressure on the feed screw of the tube cutter to avoid distorting the liquid line. A hacksaw should not be used if a tube cutter is available. If a hacksaw must be used, however, flush both pieces of the liquid line with clean refrigeration oil to remove contaminants such as metal chips. Be sure that all flushing residue is removed from the tubes before reassembly.

B

A – 2 1 /2 in. (63.5 mm) B – 1 in. (25.4 mm) Liquid line FIGURE 6-22  After locating the FOT, remove 2.5 in. (63.5 mm) of the liquid line.

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Compression ring (2)

Compression nut (2)

O-ring (2)

Orifice tube housing

Orifice tube Liquid line

FIGURE 6-23  The replacement orifice tube housing assembly.

SERVICE TIP:

Be sure that the hose bends are in the same position as when removed for ease in replacing the liquid line.

2. Tighten each compression nut to 65270 ft.-lb (87294 N ? m) torque. 1 13. Insert new O-rings on both ends of the liquid line, if equipped. 14. Install the liquid line: a. Attach the condenser end of the liquid line to the condenser and tighten to the proper torque. b. Repeat step 14a with the evaporator end of the liquid line. 15. Leak-test, evacuate, and charge the system as outlined in Chapter 6 of this manual. 16. Repeat or continue performance testing.

Removing and Replacing the Accumulator

SPECIAL TOOLS Flare nut wrench set ­Calibrated container Torque wrench

The accumulator contains the desiccant in a fixed orifice tube system.

CAUTION:

Use the proper oil for the refrigerant in the system; for example, mineral oil for R-12 and PAG for R-134a. Do not reuse oil that was removed from the system.

If the refrigerant system is suspected of being contaminated with moisture, it is recommended that the accumulator/receiver dryer be replaced since it contains moisture absorbing desiccant material. It is also recommended that the accumulator/receiver dryer be replaced when any major component in the refrigerant system is replaced (i.e., compressor, metering device, evaporator, and condenser) since debris and contaminants may be trapped in the container. In addition, most compressor manufacturers/rebuilders will not honor their warranty if the accumulator/receiver is not replaced at the same time. 1. Follow the procedures outlined in “Preparation.” 2. Disconnect the electrical connection on the pressure control switch. 3. Remove the accumulator inlet fitting. 4. Remove and discard the O-ring. 5. Remove the accumulator outlet fitting. 6. Remove and discard the O-ring. 7. Remove the bracket attaching screw and bracket. 8. Remove the accumulator from the vehicle (Figure 6-24). 9. Remove the pressure switch. 10. Remove and discard the O-ring from the pressure switch. 11. Pour the oil from the accumulator into a calibrated container. 12. With a new O-ring, install the pressure switch on the new accumulator. 13. Add a like amount of oil, as removed in step 11, to a new accumulator or 0.2 fl. oz. (5 mL) to 0.5 fl. oz. (15 mL) if no fluid was recovered from the old accumulator. 14. Position the new accumulator. 15. Using new O-rings, attach the evaporator outlet line to the accumulator inlet and finger tighten. 16. Using new O-rings, attach the suction line to the accumulator outlet and finger tighten. 17. Replace the retainer bracket, removed in step 7.

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FIGURE 6-24  Removing the accumulator from the vehicle.

18. Using appropriate flare nut wrenches, torque the inlet and outlet fittings, steps 15 and 16, as specified. 19. Reattach the electrical connector to the pressure switch. 20. Connect the battery, if removed in step 1, according to the manufacturer’s recommendations. NOTE: For steps 20 through 22, refer to Chapter 7. 21. Leak-test the system. 22. Evacuate the system. 23. Charge the system. 24. Complete the system performance test job sheet.

Removing and Replacing the Condenser 1. Follow the procedures outlined in “Preparation.” NOTE: It is not generally necessary to disconnect the battery for this procedure. 2. Remove the hood hold-down mechanism and any other cables or hardware that inhibit access to the condenser. 3. Remove the hot-gas line at the top of the condenser. 4. Remove and discard any O-rings. 5. Remove the liquid line at the bottom of the condenser. 6. Remove and discard any O-rings. 7. Remove and retain any attaching bolts or nuts holding the condenser in place. 8. Lift the condenser from the car. 9. Install the new condenser by reversing the procedure given in steps 2, 3, 5, and 7 and 1.0 fl. oz. (30 mL) of clean refrigerant oil. NOTE: Be sure to install new O-rings, if equipped, on the hot gas and liquid lines. 10. Leak-test the system. 11. Evacuate the system. 12. Charge the system with refrigerant.

Removing and Replacing the Receiver-Drier 1. Recover the air-conditioning system refrigerant as outlined earlier in this chapter. 2. Remove the low- or high-pressure switch wire, if applicable. 3. Remove the inlet and outlet hoses (liquid lines) from the receiver-drier.

Classroom Manual Chapter 6, page 198

SPECIAL TOOLS Flare nut wrench set Torque wrench Do not reuse O-rings.

Classroom Manual Chapter 6, page 176

SPECIAL TOOLS Flare nut wrench set Torque wrench The receiverdrier contains the desiccant in a TXV system.

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FIGURE 6-25  Remove the receiver-drier from the vehicle.

Classroom Manual Chapter 6, page 180

4. Remove and discard O-rings or gaskets, if applicable. 5. Loosen and remove the mounting hardware. 6. Remove the receiver-drier from the vehicle (Figure 6-25). 7. Drain and measure the amount of refrigerant oil that was removed from the receiverdrier. Add the same amount of new manufacturer recommended refrigerant oil to the replacement receiver-drier to be installed in step 9. If no oil is removed, add 0.2 fl. oz. (5 mL) to 0.5 fl. oz. (15 mL) of new refrigerant oil to the new receiver-drier. 8. Remove the pressure switch from the drier, if applicable. Discard the gasket or O-ring. 9. Install a new receiver-drier. Reverse the order of removal, steps 2, 3, and 5–7. NOTE: Most receiver-driers are marked with an arrow (→) or the word(s) “IN” and “OUT” to denote the direction of refrigerant flow. Remember, flow is away from the condenser and toward the metering device. 10. Leak-test, evacuate, and charge the air-conditioning system. Customer Care: It is becoming a more common practice today for technicians to leave a small personalized business card with the technician’s name on it ­thanking the customer for the opportunity to serve them.

SPECIAL TOOLS Internal snapring pliers, if applicable Appropriate wrench for the type pressure/ temperature switch

Superheat or Pressure Switch Determine the location of the switch to be replaced. If it is the superheat switch on the rear head of a Harrison compressor, follow the applicable steps in the procedure for replacing the compressor. If it is a pressure switch on the accumulator, follow the appropriate steps in the procedure for replacing the accumulator. If it is a drier pressure switch, follow the appropriate steps in

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the procedure for replacing the drier. If it is anywhere else in the system, the following general procedures may apply: 1. Recover the refrigerant as outlined earlier in this chapter. 2. Using the proper tool, remove the defective component. 3. Remove and discard the gasket or O-ring. 4. Place a new gasket or O-ring on the new component. 5. Install the new component, again using the proper tool. 6. Leak-test, evacuate, and charge the system with refrigerant. 7. Hold the performance test, if indicated.

In Conclusion ■■

■■ ■■ ■■ ■■ ■■

■■

Note the amount of refrigerant and oil removed from the system during refrigerant recovery process. Use only components and parts designated for a particular system: R-12 or R-134a. Use new gaskets or O-rings when replacing a component or removal of a line or fitting. Liberally coat all components with clean refrigeration oil before reassembly. For reassembly, reverse the removal procedure. Do not overfill or underfill the A/C system with refrigerant oil. When replacing refrigerant components refer to manufacturers recommendation on how must refrigerant oil needs to be added back into the refrigerant system and include this amount to the amount that was removed during the recovery and evacuation process. The pie chart in Figure 6-26 gives an example of refrigerant system oil distribution. Only use fresh clean oil recommended by manufacturer. Recharge the system with the specified amount of refrigerant.

Fluid container 10%

Evaporator 20%

Compressor 50%

Condenser 10%

Suction hose 10% FIGURE 6-26  This pie chart roughly represents the distribution of oil throughout the refrigerant system. When replacing refrigerant components, refer to manufacturer’s recommendation on how much refrigerant oil needs to be added back into the refrigerant system.

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Other problems may cause an airconditioning system to malfunction.

Terms To Know Barb fitting Disarm English fasteners Federal Clean Air Act Insert fitting Metric fasteners O-ring Purge Recovery system SAE Service procedures Spring lock

case study A customer complains of a chattering noise that occurs only when driving home. Technician: “The noise occurs only on the way home, never on the way to work?” Customer: “That’s right, only on the way home.” Technician: “What time do you go home?” Customer: “Usually seven or eight o’clock. I’ve even tried to take different routes. The chatter always happens about 5 miles from work.” Technician: “Do you operate your air conditioner in the evening?” Customer: “I seldom turn it off. I like to avoid the road fumes whenever I can.” Technician: “Are you sure that it is the air conditioner?” Customer: “Yes. When it makes a noise, I turn the air conditioner off. The noise stops.” Technician: “Only on the way home from work. Does it ever happen when you’re on the way home from a movie or the grocery store?” Customer: “When we go out later, I take my wife’s car.”

Technician: “Why?” Customer: “I have a bad generator (alternator) and use my little battery charger to keep the battery up. An overnight charge is just enough to get me to work and back.” Based on what you have learned, you know that low voltage will cause the clutch to chatter. By the time the customer drove approximately 5 miles toward home with his headlamps on, the battery voltage was reduced to a level that caused this chatter. The problem is a defective alternator; it is not an airconditioning problem at all. Get to know your customers. The more you communicate, the more effective you are when performing troubleshooting and diagnosis of needed service. Be it a groan, chatter, squeak, or bang, the customer will eventually reveal the problem. Often, the customer will hear a noise that you may not identify as being a problem. The customer hears it as a noise that is different than those experienced since owning the vehicle. Questioning the customer will often reveal when, why, and how.

ASE-STYLE REVIEW QUESTIONS 1. Before installation: Technician A says refrigerant system O-rings can be coated with a gasket sealant. Technician B says that refrigerant system O-rings should be coated with new refrigerant oil. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 2. Before attempting to service an automotive air-­ conditioning system consider all of the following except: A. Listen to customer complaint. B. Does your diagnosis make sense based on customer complaint? C. Can customer afford the repair? D. Do you have the proper tools and equipment to ­service the system?

3. Technician A says that it is permissible, according to the EPA, to release refrigerant from the hoses of a manifold and gauge set because it is such a small amount. Technician B says that, to minimize refrigerant loss, shut-off valves are required by the EPA within 12 in. (30 cm) of the service end of the manifold and gauge set hoses. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 4. Technician A says that desiccant is found in the receiver-drier. Technician B says that desiccant is found in the accumulator. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

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5. Technician A says that fixed orifice tubes are interchangeable in order to tailor system performance. Technician B says that fixed orifice tubes may be located anywhere between the evaporator outlet and the compressor inlet. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

8. When removing the accessible orifice tube: Technician A says that both the T-handle and the outer sleeve are turned. Technician B says that either the T-handle or the outer sleeve may be turned. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

6. The term “purge an air-conditioning system” in general terms means to: A. Remove the refrigerant from the system. B. Flush the refrigerant system. C. Recharge the refrigerant system. D. Add sealant to the refrigerant system.

9. Technician A says that all orifice tubes are the same size, but they are not interchangeable. Technician B says that all orifice tubes are not the same size, but they are interchangeable. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

7. Technician A says that the accumulator should be replaced if there is moisture in the system. Technician B says that the accumulator must be replaced if the fixed orifice tube (FOT) is replaced. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

10. Technician A says that mineral oil may be used to lubricate O-rings used on an R-134a system. Technician B says that PAG lubricants may be used on O-rings for an R-134a system. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

ASE CHALLENGE QUESTIONS 1. A leaking evaporator is being replaced on a vehicle. Technician A says that some additional refrigerant oil should be added to the air-conditioning system prior to recharging it. Technician B says that the new O-rings or seals should be coated with clean refrigerant oil. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 2. After the refrigerant has been recovered from an airconditioning system, which of the following should a technician do? A. Change the recovery unit filters. B. Record the amount of refrigerant oil removed from the system.

C. Check the purity of the refrigerant in the recovery tank. D. Measure the acidity level of the refrigerant in the recovery tank. 3. The refrigerant is being recovered from an air-conditioning system. Technician A says that both the vapor and liquid tank valves on the recovery unit storage tank valves must be opened. Technician B says that the high- and low-pressure valves on the manifold and gauge set must be opened. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

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4. Most vendors will not honor the warranty on a new or rebuilt compressor if the _______________ is not also replaced at the time of service. A. Accumulator or receiver-drier B. Expansion valve or orifice tube C. O-ring seals or gaskets D. Oil or lubricant

5. The illustration below shows: A. A spring lock coupling being removed. B. An O-ring seal or gasket being removed. C. Both A and B D. Neither A nor B

Removal and installation tool

Evaporator inlet

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JOB SHEET

22

Name ______________________________________ Date ________________________

Determining the Type of Air-Conditioning System Upon completion of this job sheet, you should be able to identify the type of air-­ conditioning system: cycling clutch or noncycling clutch. NATEF Correlation NATEF AST and MAST Correlations: HEATING AND AIR CONDITIONING: General: A/C System Diagnosis and Repair. Task #3. Performance test A/C system; identify problems. (P-1) Task #5. Identify refrigerant type; select and connect proper gauge set; record temperature and pressure readings. (P-1) Tools and Materials An air-conditioned vehicle Manufacturer’s service manual Describe the Vehicle being Worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure 1. Visually inspect the air-conditioning system and describe its overall condition.

2. In a well-ventilated area, start the engine, place the transmission in PARK, and turn on the air-conditioning system to MAX cooling. If a standard transmission, place in ­NEUTRAL and chock the wheels. Describe your procedure for accomplishing this step.     3. Move the cold control from one extreme to the other. a.  Does the compressor cycle off and on? Describe your findings.     b.  Does the heater control valve change positions? Describe your findings.     209 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

4. What is the type of system? Cycling clutch or noncycling clutch?     5. How did you make this determination?     6. Locate the temperature control information in the shop manual. Where is this information located?     7. Does the information presented in step 6 verify your determination of step 5?     Instructor’s Response     

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JOB SHEET

23

Name ______________________________________ Date ________________________

Determining the Refrigerant Type Upon completion of this job sheet, you should be able to identify the type of refrigerant used in the air-conditioning system. NATEF Correlation NATEF AST and MAST Correlations: HEATING AND AIR CONDITIONING: General: A/C System Diagnosis and Repair. Task #3. Performance test A/C system; identify problems. (P-1) Task # 5. Identify refrigerant type; select and connect proper gauge set; record temperature and pressure readings. (P-1) Tools and Materials An air-conditioned vehicle Manufacturer’s shop manual Describe the Vehicle being Worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure 1. Visually inspect the air-conditioning system and describe its overall condition.     2. Inspect the low-side service fitting. Is it an R-12,R-134a, R-1234yf, or other type of fitting? Describe.     3. Inspect the high-side service fitting. Is it an R-12, R-134a, R-1234yf, or other type of fitting? Describe.     4. Are there any decals under the hood to identify the refrigerant type? Describe your findings.    

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5. What type of refrigerant is in the system?     6. Does the shop manual verify your findings?     7. What special precautions would you take when recovering this refrigerant?     Instructor’s Response     

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JOB SHEET

24

Name ______________________________________ Date ________________________

Component Temperature Testing Upon completion of this job sheet, you should be able to determine the normal external temperature of various air-conditioning system components and determine if repairs are required. NATEF Correlation NATEF AST and MAST Correlations: HEATING AND AIR CONDITIONING: General: A/C System Diagnosis and Repair. Task #1. Identify and interpret heating and air-conditioning problems; determine necessary action. (P-1) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Thermocouple on a digital multimeter or an infrared noncontact thermometer Describe the Vehicle being Worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure Always wear eye protection when working on or around refrigerant system components. 1. Start the engine and turn the air-conditioning system on. Allow the vehicle to run for several minutes. 2. Using a contact thermocouple on a digital multimeter or an infrared noncontact thermometer, measure the temperature of each component listed below. 3. If the temperature is in a safe range, you may touch the hoses and components on the high side of the system to determine if the components’ temperature is ­consistent throughout. A refrigerant pressure of 199 psig corresponds to a temperature of approximately 1308F for R-134a and R-1234yf. Measure or touch the entire length of the hose or component and note any temperature differential. All high-side system components should be warm.

CAUTION:

Be aware that ­system malfunctions can cause the highside components to become superheated to the point that a serious burn may result. Care must be taken when handling any high-side system components.

  a. High-side discharge refrigerant line from the compressor to the condenser: Temperature recorded 

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b. On the graph below, record the condenser surface temperature at various grid ­locations to show how heat flows through the condenser.

c. High-side liquid line leaving the condenser to the receiver-drier (if equipped): Condenser outlet temperature  d. If equipped, record the receiver-drier inlet and outlet temperatures: Receiver-drier inlet temperature  Receiver-drier outlet temperature  4. Record the inlet and outlet temperatures of the expansion valve or fixed orifice tube (FOT). Expansion valve (FOT) inlet temperature  Expansion valve (FOT) outlet temperature  Frost on the outlet side of the metering device is acceptable. But frost on the inlet side of the metering device may be an indication of a defective metering device or a sign of excessive moisture in the refrigerant system. 5. If the temperature is in a safe range, you may touch the hoses and components on the low side of the system to determine if the components’ temperature is consistent throughout. A refrigerant pressure of 27 psig corresponds to a temperature of 318F for R-134a and 278F for R-1124yf. Measure or touch the entire length of the hose or ­component and note any temperature differential. All low-side system components should be cool.   a.  Record the evaporator inlet and outlet temperatures. Evaporator inlet temperature  Evaporator outlet temperature  b.  Record the evaporator suction line-to-compressor inlet temperature.  c.  If equipped, record the accumulator inlet and outlet temperatures. Accumulator inlet temperature  Accumulator outlet temperature  Instructor’s Response      214 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

JOB SHEET

25

Name ______________________________________ Date ________________________

Identifying Hose Fittings Upon completion of this job sheet, you should be able to identify the type of hose fittings used in the air-conditioning system. NATEF Correlation NATEF AST and MAST Correlations: HEATING AND AIR CONDITIONING: ­Refrigeration System Component Diagnosis and Repair. Task #6. Remove and inspect A/C system mufflers, hoses, lines, fittings, O-rings, seals, and service valves; perform necessary action. (P-2) Tools and Materials An air-conditioned vehicle Manufacturer’s shop manual Describe the Vehicle being Worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure 1. Visually inspect the air-conditioning system and describe its overall condition.     2. Inspect the hose-to-condenser inlet fitting. Describe its type.     3. Inspect the high-side liquid line-to-evaporator inlet fitting. Describe its type.     4. Are the two hose fittings (steps 2 and 3) interchangeable? Explain.     5. Why do you think that a barb-type fitting should not be used with a barrier hose?    

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6. Locate hose fittings in the shop manual. Does the shop manual verify your findings?     7. What special precautions would you take when servicing hoses and fittings?     Instructor’s Response     

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JOB SHEET

26

Name ______________________________________ Date ________________________

Recover and Recycle Refrigerant Upon completion of this job sheet, you should be able to recover and recycle refrigerant. NATEF Correlation NATEF AST and MAST Correlations: HEATING AND AIR CONDITIONING: Refrigerant Recovery, Recycling, and Handling. Task #2. Identify and recover A/C system refrigerant. (P-1) Task #3. Recycle, label, and store refrigerant. (P-1) Tools and Materials Vehicle with air-conditioning system in need of service Selected air-conditioning system service tools Manifold and gauge set with hoses Refrigerant recovery/recycle machine Recovery tank Describe the Vehicle being Worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure

1. What type of refrigerant does the under-hood label identify in the system?  2. Do the vehicle refrigerant service fittings match the refrigerant listed on the ­identification label?  3. Attach the refrigerant purity identifier to the system. a.  Type of refrigerant identified  b.  Does refrigerant identified match refrigerant label on vehicle?  c.  Purity of refrigerant tested  d.  Was the presence of contamination detected?  4. Connect the gauge manifold hoses to the air-conditioning system service ports.   5. What type connectors are found? On the low-side service port?  On the high-side service port? 

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6. Observe the gauges. The low-side gauge reads  The high-side gauge reads  NOTE: If zero (0 psig or 0 kPa) or below pressure is observed in step 6, it may be assumed that there is no refrigerant in the system. If it is presumed that there are residual traces of refrigerant in the lubricant, proceed with step 7. 7. Connect the manifold gauge hose to the recovery unit. 8. What type connector is found on the recovery unit?     NOTE: The procedure for recovering R-1234yf refrigerant is similar, with the following exceptions. R-1234yf refrigerant recovery/recycling/recharge (R/R/R) equipment must meet SAE J2843, and use an integrated internal J2927 refrigerant identifier or external J2912 refrigerant identifier and must be attached for the machine to operate. An acceptable reading that must be received prior to recovery/recycling is 98 percent pure or greater. If an unacceptable reading is detected, such as contamination by another gas (R-134a), the refrigerant is considered contaminated and the equipment will not allow recovery to proceed. If a system is contaminated, a separate recoveryonly machine must be used to recover and store the contaminated refrigerant for either reclamation or disposal at an EPA-approved facility. 9. Start the recovery unit, open the appropriate hand valves, and recover air-conditioning system refrigerant following instructions provided by the recovery equipment manufacturer. 10. Close the hand alves (opened in step 9) and turn off the recovery unit. Observe the gauges. What is the reading in psig or kPa?

Low Side High Side

Now After 5 Min. After 10 Min. After 15 Min. _____________  _____________  _____________  _____________  _____________  _____________  _____________  _____________ 

11. Explain the conclusion of the results of step 10.     12. Carefully remove the manifold and gauge set hoses ensuring that no ambient air enters the system. Instructor’s Response     

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JOB SHEET

27

Name ______________________________________ Date ________________________

Replacing the Receiver-Drier/Accumulator Upon completion of this job sheet, you should be able to identify a receiver-drier/ accumulator and describe how to replace it. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: ­Refrigeration System Component Diagnosis and Repair. Task #8. Remove, inspect, and reinstall receiver-drier or accumulator-drier; determine recommended oil quantity. (P-2) Tools and Materials An air-conditioned vehicle with a defective receiver-drier/accumulator Refrigerant recovery station Set of mechanic’s hand tools Manufacturer’s shop manual Describe the Vehicle being Worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure 1. Visually inspect the air-conditioning system and describe its overall condition.     2. Locate the receiver-drier/accumulator. Describe its location.     3. Troubleshoot the receiver-drier/accumulator following procedures outlined in the shop manual. Is it defective? Explain your findings.     4. Are there decals under the hood to identify the refrigerant type? Describe your findings. What type of refrigerant is in the system?    

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5. Does the shop manual verify your findings?     6. What procedure would you follow to replace the receiver-drier/accumulator?     Instructor’s Response     

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JOB SHEET

28

Name ______________________________________ Date ________________________

Replacing the Superheat or Pressure Switch Upon completion of this job sheet, you should be able to troubleshoot and replace a highpressure release device. NATEF Correlation NATEF MAST Correlation: HEATING AND AIR CONDITIONING: Refrigeration System Component Diagnosis and Repair. Task #11. Diagnose A/C system conditions that cause the protection devices (pressure, ­thermal, and PCM) to interrupt system operation; determine necessary action. (P-2) NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING Operating Systems and Related Controls Diagnosis and Repair. Task #2. Diagnose A/C compressor clutch control systems; determine necessary action. (P-2) Tools and Materials An air-conditioned vehicle with pressure switch Refrigerant recovery station Set of mechanic’s hand tools Manufacturer’s shop manual Describe the Vehicle being Worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure 1. Visually inspect the air-conditioning system and describe its overall condition.     2. Locate the pressure switch(es). Describe its/their location.     3. Troubleshoot the low-/high-pressure switch following procedures outlined in the shop manual. Is it defective? Explain your findings.    

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4. Can the pressure switch be replaced without recovering the refrigerant? Explain your answer.     5. Are there decals under the hood to identify the refrigerant type? Describe your findings. What type of refrigerant is in the system?     6. Does the shop manual verify your findings?     7. What procedure would you follow to replace the low-/high-pressure switch?     Instructor’s Response     

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JOB SHEET

29

Name ______________________________________ Date ________________________

Air-Conditioning System Performance Test Upon completion of this job sheet, you should be able inspect and test the air-conditioning system for normal operation. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: General: A/C System Diagnosis and Repair. Task #3. Performance test A/C system; identify problems. (P-1) NATEF MAST Correlation: HEATING AND AIR CONDITIONING: General: A/C System Diagnosis and Repair; Identify refrigerant type; conduct a performance test of the A/C system; determine necessary action. (P-1) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Manifold and gauge set Thermometer Describe the Vehicle being Worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure Follow the procedures outlined in the service manual. Ensure that the engine is cold and wear eye protection. NOTE: The following procedures outlined are for an R-134a refrigerant system. 1. Place a fender cover on the vehicle to protect the finish. 2. Remove the protective caps from the high- and low-side service ports. NOTE: Remove the caps slowly to ensure that no refrigerant escapes past a defective service valve, and inspect the O-ring seal on the cap. 3. Ensure that all manifold valves are closed (clockwise) to prevent refrigerant venting from service ports. 4. Turn the low-side hose hand valve fully counterclockwise to retract the Schrader depressor into the service port.

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5. Clip on the low-side hose; push firmly until it clicks in place. a. Turn the low-side hose hand valve fully clockwise to extend the Schrader depressor. 6. Clip on the high-side hose; push firmly until it clicks on. b. Turn the high-side hose hand valve fully clockwise to extend the Schrader depressor. 7. Place a fan in front of the vehicle to assist in cooling the A/C condenser. 8. Start the engine. 9. Turn on the air conditioner; set all controls to control settings listed in table and note the blower motor operation. Control Setting LO LO-MED HI-MED HI

OK/NOT OK

10. Turn on the air conditioner; set all controls to maximum cooling; set the blower speed on HI. 11. Insert a thermometer in the air-conditioning duct as close to the evaporator core as possible and note which duct this is. Also record the following duct temperatures. 12. Duct Outlet Temperature

Right Duct

Center Duct

Left Duct

13. If equipped with a sight glass on the receiver-drier, note the refrigerant flow.







a. Clear 

b. Bubbles  c. Foggy 

14. Record pressure levels on gauges. System pressure Outside air temperature System expected pressure based on Pressure/Temperature Chart Class Manual

Low Side

High Side

Instructor’s Response     

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JOB SHEET

30

Name ______________________________________ Date ________________________

Replace AC Expansion Valve Upon completion of this job sheet, you should be able to recover refrigerant from an A/C system, remove and replace the expansion valve assembly, evacuate and recharge the system, as well as perform a leak test of the system. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Heating, Ventilation, and Engine Cooling Systems Diagnosis and Repair. Task #1. Inspect engine cooling and heater system hoses; perform necessary action. (P-1) Tools and Materials Test vehicle Refrigerant recovery and recycling unit Manifold and gauge set Basic hand tools Safety glasses Describe the Vehicle being Worked on. Year _____________________ Make _____________________ Model _____________________ VIN _____________________________ Engine type and size ____________________________ Procedure

1. Determine the type of refrigerant and expansion valve used in the system. a. Refrigerant   b. Expansion valve   2. Connect the gauge set to the system. Note the high-side and low-side pressures with the system off. a. High-side pressure   b. Low-side pressure   3. Connect the manifold gauge set-to-recovery unit. Start the unit following unit manufacturer instructions. 4. Wait 5 minutes and note if pressure is detected (if pressure is present rerun the recovery process). System should hold a vacuum for 2 minutes. Did it? _______________________ 225 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

5. Follow manufacturer’s recommended procedure for removal and replacement of component. Standard Valve

6. Remove the bulb from the insulation. Describe the location and the method of holding the bulb and external equalizer, if equipped, in place. _____________________________             7. Disconnect the inlet side from the line. Which line is this one and which tool is required to disconnect?        8. Inspect the screen. Describe its condition and your actions to correct any problems.              9. Disconnect the valve from the evaporator. Which tool is required to disconnect?        10. Remove the valve from the evaporator. Explain the procedures and the tools used.             

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11. Remove all O-rings. Install all new O-rings. Lube the rings with the proper lubricant. 12. Position the valve in the evaporator and tighten the clamp, if equipped. 13. Connect the valve to the evaporator. Torque  14. Connect the line to the valve inlet. Torque  15. Position and secure the equalizer and bulb. How is the bulb secured? _______________       H-block Expansion Valve

16. Complete steps 1 and 2. 17. Are there any electrical connections? If so, what circuit(s) is (are) involved? Disconnect as needed.              18. Disconnect the line-sealing plate from the valve. Explain the procedures and the tools used.              19. Remove the valve from the evaporator. Explain the procedures and the tools used.              20. Remove all gaskets and clean the mating surfaces as needed. 21. Install the valve/evaporator gasket.

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22. Mount the valve to the evaporator. Torque    23. Install the line plate/valve gasket. 24. Connect the line-sealing plate to the valve. Torque  25. Evacuate the system. Did the system hold a vacuum?  26. Recharge the system. a. Record the amount of refrigerant added.  27. Check the system for leaks using a halon leak detector. 28. Record the system running pressure. a. High-side pressure  b. Low-side pressure  Instructor’s Response     

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JOB SHEET

31

Name ______________________________________ Date ________________________

Replace A/C Orifice (Expansion) Tube Upon completion of this job sheet, you should be able to recover refrigerant from an A/C system, remove and replace the orifice (expansion) tube assembly, evacuate and recharge the system, as well as perform a leak test of the system. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Refrigeration System Component Diagnosis and Repair. Task #9. Remove, inspect, and install expansion valve or orifice (expansion) tube. (P-1) Tools and Materials Test vehicle Refrigerant recovery/recycling/recharge unit Manifold and gauge set Basic hand tools Safety glasses FOT and O-ring seal Describe the Vehicle being Worked on. Year _____________________ Make _____________________ Model _____________________ VIN _____________________________ Engine type and size ____________________________ Procedure

1. Determine the type of refrigerant used in the system. a. Refrigerant  2. Connect both the high- and low-side gauges to the vehicle refrigerant system. Note the high-side and low-side pressures with the system off. a. High-side pressure  b. Low-side pressure  3. Begin the refrigerant recovery process as outlined in Job Sheet 21, Recover and Recycle Refrigerant, by initializing the recovery unit. Start the unit following unit manufacturer’s instructions. 4. Wait 5 minutes and note if pressure is detected (if pressure is present, rerun the recovery process). System should hold a vacuum for 2 minutes. Did it?  5. Record the amount of refrigerant recovered, if the service unit you are using has this feature. 

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6. Locate the fixed orifice tube (FOT) in the high-side liquid refrigerant line between the condenser outlet and the evaporator inlet. There is usually a visible dimple in the liquid line where the FOT is located and a line connection point. a. Where was the FOT in relation to the condenser outlet and the evaporator inlet?   7. Disconnect the line fitting where the FOT is located. Which line is this one and which tool is required to disconnect?  8. Remove and discard the O-ring(s) from the liquid line fitting, if equipped. 9. Insert the FOT removal tool onto the FOT. 10. Turn the T-handle and turn the outer sleeve or spool of the tool clockwise to remove the FOT. Do not turn the T-handle. NOTE: If the FOT breaks during removal, proceed with step 11. If it does not break, proceed to step 13. 11. Insert the extractor tool into the line where the remaining piece of the FOT is located and turn the T-handle clockwise until the threaded portion of the tool is securely inserted into the brass portion of the broken FOT. 12. Pull the tool. The broken FOT should slide out. NOTE: If the FOT brass tube pulls out of the plastic body, remove the brass tube and repeat steps 11 and 12. 13. Inspect the screen on the FOT. Describe its condition and your actions to correct any problems.   14. Verify that the replacement FOT is the same color as the one that was removed. 15. Liberally coat the new FOT with clean refrigerant oil. 16. Place the FOT into the refrigerant line and push it until it stops against the dimples on the line. 17. Install all new O-rings. Lube the rings with the proper lubricant. 18. Connect the line connection and torque to specifications. Torque  19. Evacuate the system. Did the system hold a vacuum?  20. Recharge the system. a. Record the amount of refrigerant added.  21. Check the system for leaks using a halon leak detector. 22. Record the system running pressure. a. High-side pressure  b. Low-side pressure  Instructor’s Response      230 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

JOB SHEET

32

Name ______________________________________ Date ________________________

Replace Air-Conditioning Condenser Upon completion of this job sheet, you should be able to recover refrigerant from an A/C system, remove and replace the condenser assembly, evacuate and recharge the system, as well as perform a leak test of the system. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Refrigeration System Component Diagnosis and Repair. Task #7. Inspect A/C condenser for airflow restrictions; perform necessary action. (P-1) Tools and Materials Test vehicle Refrigerant recovery and recycling unit Manifold and gauge set Basic hand tools Safety glasses Describe the Vehicle being Worked on. Year _____________________ Make _____________________ Model _____________________ VIN _____________________________ Engine type and size ____________________________ Procedure

1. Connect the gauge set to the system. Note the high-side and low-side pressures with the system off. a. High-side pressure   b. Low-side pressure   2. Connect the manifold gauge set to the recovery unit. Start the unit following the unit manufacturer’s instructions. 3. Wait 5 minutes and note if pressure is detected (if pressure is present, rerun the recovery process). The system should hold a vacuum for 2 minutes. Did it? _______________ 4. Follow the procedures outlined earlier in “Removing and Replacing the Condenser” and refer to the manufacturer’s recommended procedure for removal and replacement of the component. 5. Evacuate the system. Did the system hold a vacuum? 

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6. Follow the manufacturer’s recommended procedure for the removal and replacement of the component. 7. Recharge the system. a. Record the amount of refrigerant added.  8. Check the system for leaks using a halon leak detector. 9. Record the system running pressure. a. High-side pressure   b. Low-side pressure   Instructor’s Response     

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JOB SHEET

33

Name ______________________________________ Date ________________________

Replace the A/C Refrigerant Line Upon completion of this job sheet, you should be able to recover refrigerant from an A/C system, remove and replace a refrigerant line assembly, evacuate and recharge the system, as well as perform a leak test of system. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Refrigeration System Component Diagnosis and Repair. Task #6. Remove and inspect A/C system mufflers, hoses, lines, fittings, O-rings, seals, and service valves; perform necessary action. (P-2) Tools and Materials Test vehicle Refrigerant recovery/recycling/recharge unit Manifold and gauge set Basic hand tools Safety glasses Refrigerant line and O-ring seals Describe the Vehicle being Worked on. Year _____________________ Make _____________________ Model _____________________ VIN _____________________________ Engine type and size ____________________________ Procedure

1. Determine the type of refrigerant used in the system. a. Refrigerant  2. Connect both the high- and low-side gauges to the vehicle refrigerant system. Note the high-side and low-side pressures with the system off. a. High-side pressure  b. Low-side pressure  3. Begin the refrigerant recovery process as outlined in Job Sheet 21, Recover and Recycle Refrigerant, by initializing the recovery unit. Start the unit following the unit manufacturer’s instructions. 4. Wait 5 minutes and note if pressure is detected (if pressure is present rerun the recovery process). System should hold a vacuum for 2 minutes. Did it?  5. Record the amount of refrigerant recovered, if the service unit you are using has this feature. 

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6. Locate the refrigerant line to be replaced. a. What other components will have to be removed to gain access to the refrigerant line requiring replacement?      b. What is the name of the line being replaced and is it located on the high- or low-side of the refrigerant system?      c. Does the line normally transport refrigerant in the liquid or gaseous state?  7. Disconnect the line fittings using the appropriate service tools. Which tool is required to disconnect the line and fittings?  8. Remove the old line from the vehicle. 9. Remove and discard the O-ring(s) from the line fittings, if equipped. 10. Position the new line into mounting brackets, if equipped. 11. Install all new O-rings. Lube rings with the proper lubricant. 12. Connect the line connection and torque to specifications. Torque  13. Evacuate system. Did system hold a vacuum?  14. Recharge system. a. Record the amount of refrigerant added.  15. Check the system for leaks using a halon leak detector. 16. Record the system running pressure. a. High-side pressure  b. Low-side pressure  17. Record the system vent temperature.   Instructor’s Response     

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Chapter 7

BASIC TOOLS Manifold and gauge set (R-12 or R-134a, as applicable)

Air-Conditioning System Servicing and Testing

Refrigerant recovery system (R-12 or R-134a, as applicable) Vacuum pump (oil-less, R-12 or R-134a, as applicable) Charging cylinder (R-12 or R-134a, as applicable) Scales (if using refrigerant cylinders) Can tap (if using small cans of refrigerant) Dye injector Halogen leak detector Safety glasses Fender cover Small brush

Upon Completion and Review of this Chapter, you should be able to: Determine refrigerant system contamination by performing a refrigerant purity test with a refrigerant analyzer.

■■

■■

Perform an unloaded refrigerant system performance test.

■■

■■

Analyze performance test results.

■■

■■

■■

■■

Determine if the refrigerant system is contaminated with refrigerant sealant. Leak-test an air-conditioning system using a soap solution. Leak-test an air-conditioning system using a halogen leak detector.

■■

Leak-test an automotive air-conditioning system using a dye solution. Evacuate an air-conditioning system using the single evacuation method. Evacuate an air-conditioning system using the triple evacuation method.

■■

Charge the system with refrigerant R-134a.

■■

Charge the system with refrigerant R-1234yf.

■■

Charge the system with refrigerant R-12.

■■

Test the refrigerant for noncondensable gas contamination.

Generally, the first piece of equipment that a service technician reaches for is the manifold and gauge set (Figure 7-1). The manifold and gauge set to the technician is much the same as a blood pressure test kit is to a physician. It provides a means to “see” what is happening inside the system. Pressures inside an air-conditioning system are as important to the system as pressures inside the body are to the human. Procedures for the proper use of the manifold and gauge set are given in Chapter 5 of this manual. Review of Chapter 5 would be a good idea at this time.

Some systems also have a sight glass.

WARNING: Safety glasses must be worn while working with refrigerants. Remember, liquid refrigerant splashed in the eyes can cause blindness. 235 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 7-1  Manifold and gauge set.

Contaminated refrigerant refers to any refrigerant that is not 98 percent pure. Refrigerant may be contaminated if it contains excess air or another type of refrigerant.

Classroom Manual Chapter 7, page 205

Refrigeration Contamination Before servicing an air-conditioning system, it should first be determined what type of refrigerant is in the system and, perhaps more important, if the refrigerant is contaminated. Recent studies indicate that, on average, 23 out of every 1000 motor vehicles tested contained some form of contaminated refrigerant. That amounts to over 450,000 contaminated systems out of the 20 million vehicles serviced each year. A system is considered to be contaminated if it contains more than 2 percent of a “foreign” substance. Since the average system contains less than 2 lb. (907 grams) of refrigerant, contaminants may not exceed 0.32 oz. (9 grams). There are actually several types of contamination to be found in the automotive air-conditioning system. In order of occurrence, these contaminants include air, moisture, mixed refrigerant types, and illegal refrigerants. A refrigerant identifier should be used to determine the purity of the refrigerant before servicing an air-conditioning system. Failure to do so may result in personal injury if it contains a flammable substance or in a contaminated recovery cylinder if it contains other types of refrigerant. The refrigerant gas analyzer measures and displays the purity of the refrigerant being tested as a percentage along with the percentage of air (noncondensable gas) and the presence of hydrocarbons (HC) in the sample being tested. The following procedure is for the GA500-Plus Gas Analyzer (Figure 7-2). Procedures may vary for other models. Always follow the operating instructions that accompany the equipment being used: 1. Connect the purity test unit power cable to the vehicle’s battery. 2. Attach the sample hose to the vehicle’s refrigerant system service fitting. a. Select the R-134a or R-1234yf (or the R-12) hose and push the quick-connect coupler onto the fitting on the bottom of the analyzer. Turn the fitting knob to the left to retract the valve activating pin. b. Connect the sample hose service port coupler to the low side (vapor port) of the airconditioning system and turn the knob to the full right position to open the valve port. 3. Fully depress the purity test unit pump button four times to start the test cycles.

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FIGURE 7-2  The refrigerant gas analyzer measures and displays the purity of the refrigerant being tested.

4. Evaluate the sample using light-emitting diode (LED) indicators and liquid crystal display (LCD). a. Record the refrigerant purity: _________ R-134a _________ R-1234yf _________ R-12 _________ HC _________ R-22 _________ Air b. Percent of air contamination  NOTE: Because air is a noncondensable gas, the analyzer ignores its presence in calculating gas concentrations. Consequently, the total of all displays may be greater than 100 percent. 5. To repeat the test, pump the button four times to restart the test cycles. 6. Disconnect the sample hose attached to the vehicle’s air-conditioning system; push the pump button to purge the refrigerant in the analyzer. Refrigerant systems should be tested with a refrigerant identifier because crosscontamination of refrigerant will also affect the temperature-pressure relationship of the refrigerant gas. Cross-contamination is when a system designed and containing one refrigerant is partially charged with another refrigerant on top of the existing refrigerant. An example of this can occur when a system containing R-12 is not properly recovered, evacuated, and recharged with R-134a with proper service fittings and labels installed but instead is partially charged with another refrigerant such as R-134a on top of the R-12 that remains in the original system. Unfortunately with retrofit kits for R-12 to R-134a readily available at all parts and discount retailers, any consumer can purchase and incorrectly service his or her pre-1994 R-12 vehicle. Be wary of retrofitted R-12 vehicles that do not have a retrofit label installed by a reputable service facility. It could also occur if someone intentionally installs R-134a into an R-1234yf system due to the higher cost of R-1234yf. This would be in violation of EPA laws. Noncondensable (air) or cross-contaminated refrigerant can cause reduced system performance, lack of lubrication issues, and chemical breakdown. If recovery/recycling equipment is connected to a cross-contaminated system the unit will have to be cleaned out and all the filters and dehydrator element will have to be replaced. If the cross-contaminated equipment is 237 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

unknowingly connected to other vehicle air-conditioning systems being serviced, the resulting performance issues can spread like a virus, creating a service nightmare for the repair shop as well as extremely high repair costs to fix the issues created. If a system or portable recovery container is cross-contaminated or contains an unknown refrigerant, it must be disposed of properly. The Environmental Protection Agency (EPA) does not allow venting of any automotive refrigerant into the atmosphere no matter what is in the system. The acceptable method is to recover the refrigerant into a dedicated recovery-only unit for unknown or cross-contaminated refrigerants. The contaminated refrigerant should be recovered into a Department of Transportation (DOT) approved gray-with-yellow-top recovery tank. When full it must be disposed of with a local recycler in accordance with local, state, and federal laws. In addition, check with local ordinances that govern the storage of combustible or hazardous materials. Because of the many requirements and additional service equipment required, many shops will not service contaminated refrigerant systems.

Unloaded System Performance Testing When a customer complains of poor air-conditioning performance an air-conditioning system unloaded performance test should be the initial test to determine if the refrigerant system is operating as designed. As a service technician you should always follow the manufacturer’s service and diagnostic information to determine if the air-conditioning system is operating as designed. A thorough diagnosis of the air-conditioning system begins with a comparison of the temperature-pressure relationship (Figure 7-3) data of system performance. The role of this 320 280 High-side pressure (psig)

240 200 160 120 60

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Ambient temperature (°F) 50

45 Center vent temperature (°F)

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35 32 10

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25 20 Low-side pressure (psig)

30

FIGURE 7-3  R-134a air-conditioning system unloaded performance test data chart requires that the vehicle’s windows and doors be closed and that the recirculation vent control mode be selected for accurate test results.

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type of chart is to provide a performance test platform that is reliable and easy to understand. The relative humidity of any given day has no effect on the unloaded performance test. It will not affect the high-side system pressure unless the Fresh Air mode is selected instead of the Recirculation mode, which should be selected. The unloaded performance test takes into account system pressures and temperatures in analyzing system condition. During the unloaded performance test, you are required to select the Recirculation mode, which dries the air as it is recirculating during system stabilization. The unloaded performance test’s use of recirculated dry air allows for consistent achievement of the lowest possible vent temperatures and provides a consistent performance comparison of similar vehicles regardless of ambient air temperatures or humidity levels on a particular day. Thus, preconditioning the vehicle in the pretest procedure that follows is critical to accurate system testing.

Pretest Procedure

It is important to prepare and inspect the vehicle prior to beginning the test: 1. Move the vehicle to a shaded area not in direct sunlight and allow it to cool down. The performance test should not be performed until the vehicle has reached ambient air temperature. 2. Inspect the condenser fins and clean them with a soft brush and nonpressurized running water. A condenser that restricts airflow can give the appearance, based on pressure readings, that the system is fully charged when it is actually low on refrigerant. 3. Close all windows and doors. 4. Open the vehicle hood. 5. Turn the vent fan on high and activate the air-conditioning system in the Recirculation mode. 6. Next, run the engine at 1000 rpm and allow the system to stabilize for a minimum of 15 minutes. Measure the air temperature leaving the center vents. The unloaded test strips the air in the passenger compartment of heat and humidity as it is recirculated through the evaporator, allowing the lowest possible vent temperatures to be achieved. The performance chart in Figure 7-3 for the unloaded performance test requires that the engine speed be 1000 rpm (650 rpm) to be accurate.

Test Procedure

1. Determine the type of refrigerant in the air-conditioning system and connect an R-134a recovery/recycling/recharge station or an R-1234yf recovery/recycling/recharge station to the air-conditioning system high-side and low-side pressure test fittings. 2. Record the ambient air temperature approximately 12 in. in front of the vehicle’s condenser. 3. With the engine running at 1000 rpm check both the high- and low-side system pressures. If the vehicle is equipped with a rear air-conditioning system ensure that the rear blower is off and record the result. 4. Place a thermometer in the center dashboard vent and record the outlet air temperature. 5. If the vehicle is equipped with a rear air-conditioning system, turn the rear blower on high and place a thermometer in the rear outlet vent and record the outlet air temperature. With the engine running at 1000 rpm check both the high- and low-side system pressures and record the result. 6. Increase the engine speed to 3000 rpm and measure the low-side system pressure as well as the dashboard center vent outlet air temperature and record the results. NOTE: The pressure gauge readings at 1000 rpm are not comparable to the observations at 3000 rpm. 7. Compare the readings recorded to the temperature pressure graph in Figure 7-3. 239 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

320 280 High-side pressure (psig)

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(Example 185 to 210 psig)

200 160 120 60

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Ambient temperature (°F) Ambient temperature taken 12 in. in front of the condenser (Example shows 95 °F) FIGURE 7-4  The high-side performance chart for R-134a allows the technician to determine if the vehicle’s air-conditioning system high-side pressure is in the normal range for current ambient air temperature.

To interpret the high-side performance chart, first determine the shop temperature (step 2) and draw a vertical line on the graph (Figure 7-4). Next, draw horizontal lines from both the top and bottom of the black pressure band on the chart across to the high-side ­pressures on the left of the graph. The high-side pressure reading (step 3) should be between the two horizontal pressure marks for a normally operating system. Next, interpret the low-side performance chart. First, determine the low-side system ­pressure (step 3) and draw a vertical line on the graph (Figure 7-5). Next, draw a horizontal line from the point where the vertical line meets the top of the black pressure band on the chart across to the center vent temperature on the left of the graph. The center vent temperature in the passenger compartment (step 4) should be at or below the temperature indicated on the graph for a normally operating system. As long as the evaporator is not icing, the ­temperature may be colder than the chart indicates but the temperature should never be lower than 338F (0.68C). In general, to obtain 408F (4.48C) center vent temperature air, the air-conditioning low-side temperature generally needs to be 20 psig (137.9 kPa).

50 Example 41°F 45 Center vent temperature (°F)

40

35 32 10

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30

Low-side pressure (psig) (Example shows 20 psig) FIGURE 7-5  The low-side performance chart for R-134a allows the technician to determine if the vehicle’s air-conditioning system vent temperature is correct for the current low-side operating pressure.

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Test Results

This table shows the possible causes for test results being out of specifications. Test Results

Possible Causes

Outlet air temperature from the center dashboard vent is higher than normal.

•• Air mix door is out of adjustment.

Outlet air temperature from the corner dashboard vents varies by more than 108F.

•• Air mix door is out of adjustment.

Refrigerant system low-side pressure is too low, and the outlet air temperature from the right corner dashboard vent is at least 108F cooler than the left corner dashboard vent.

•• Low refrigerant charge. •• Restricted refrigerant flow through the evaporator.

Pressure on the high side of the refrigerant system is too high.

•• Restricted airflow through the condenser. •• Condenser/radiator fan is inoperative. •• Restricted refrigerant flow through the system.

Pressure on the high side of the refrigerant system is too low.

•• System is low on refrigerant charge.

Sealant Contamination Detection Refrigerant systems contaminated with air-conditioning system sealant additives can cause irreparable damage to air-conditioning service equipment and void manufacturer warranties of both service equipment and vehicle. These sealants are carried through the system by the refrigerant and as the refrigerant and sealant escape through a leak point (hole) the sealant reacts with moisture and air, solidifying to form a seal. These sealants will also enter the airconditioning service equipment and can cause serious damage to the solenoids, valves, and tubing in there cover/recycle/recharge units and manifold and gauge sets. A sealant detection kit like the “Neutronics QuickDetect A/C Sealant Detection Kit” (Figure 7-6) is an invaluable

Classroom Manual Chapter 7, page 206

FIGURE 7-6  A simple-to-use Neutronics Inc. refrigerant system sealant identifier will determine if an airconditioning system has been contaminated by sealant.

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tool for today’s service technician and shop owner. It is important to gather information from the customer about past vehicle service history to determine if you should test the system for sealant contamination. If the system was ever serviced by a noncertified person (backyard mechanic) or shop, always test refrigerant purity and test the system for sealant contamination before proceeding with any air-conditioning system service or repair.

Procedure 1. Prepare the sensing plug by injecting water into both ends with the syringe. After injecting water, shake the sensing plug once to remove excess water. 2. Insert the nonribbed end of the sensing plug into the quick-disconnect adapter coupling for the type of refrigerant being tested. 3. Install the safety cap (steel washer) over the sensing plug to prevent accidental release of the plug from the coupler during testing. 4. Insert one end of the rubber hose over the ribbed end of the sensing plug, ensuring that the hose is fully seated onto the plug. 5. Attach the other end of the rubber hose onto the graduated flowmeter, ensuring that the hose is fully seated. 6. Start the vehicle and turn the air-conditioning system on, selecting MAX cooling, lowest temperature setting, and high blower speed. 7. Allow the air-conditioning system to run and circulate refrigerant for a minimum of 2 minutes. 8. Shut off the air-conditioning system and turn off the engine. Allow the refrigerant system 3 minutes to stabilize and equalize pressures. 9. Suspend the flowmeter in a vertical position (Figure 7-7). 10. Attach the flowmeter assembly refrigerant system service coupler to the vehicle’s airconditioning system high-side service port.

FIGURE 7-7  The flowmeter of the sealant identifier must be in a vertical position in order to obtain accurate results if the air-conditioning system has been contaminated by sealant.

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11. Measure the flow rate coming from the air-conditioning high side on the graduated flowmeter scale and slide a rubber O-ring on the graduated flowmeter scale to the reading observed. If the flow rate is above 1.5 proceed to step 12. If the flow rate is below 1.5 repeat steps 1 through 11. If the flow rate is still below 1.5 see “Troubleshooting low flow” in step 11a. a. Troubleshooting low flow during initial installation. Low flow may be caused by: i. An inoperable service port ii. Reusing a sensing plug iii. A clogged tube iv. Low refrigerant system charge. If the first three steps were checked and deemed okay and a low refrigerant charge is suspected, add a small amount of refrigerant to the system and retest. 12. Monitor the reading on the flowmeter for 3 minutes. During the first 30–60 seconds, the flow rate may rise as water is pushed through the sensing bulb. 13. Note the highest reading recorded during the first 60 seconds and compare it to the reading after 3 minutes. If the final flow rate drops by more than 30 percent of the highest initial flow rate observed, then refrigerant system sealant is present. If the final reading is within 30 percent of the initial reading, then sealant is not present. 14. After the test is complete, disconnect the tester from the vehicle and replace the vehicle service cap on the service fitting. Throw away the used sensing plug and return the rest of the components to the kit.

Leak Testing the System Before undertaking any leak-detection procedures, perform a visual inspection of all system components, fittings, and hoses for signs of lubricant leakage, damage, wear, or corrosion. Note that R-134a and R-1234yf refrigerant polyalkaline glycol (PAG) lubricant may evaporate and therefore not be visible, whereas R-12 refrigerant mineral oil, on the other hand, does not evaporate and will leave a visible stain. To prevent an inaccurate or false reading with an electronic leak detector, make sure that there is no refrigerant vapor or tobacco smoke in the vicinity of the vehicle being checked. Also, because there could be more than one leak in the air-conditioning system, when a leak has been found, continue to check for additional leaks. Perform the leak test in a relatively calm area so the leaking refrigerant is not dispersed in air movement. With the engine not running: 1. Connect a proper manifold and gauge set to the air-conditioning system’s low- and highside service ports. 2. Ensure that the refrigerant pressure in the air-conditioning system is at least 50 psig (345 kPa) and that the ambient temperature is 608F (15.68C) or above. NOTE: If less than specified, recover, evacuate, and recharge the system with enough refrigerant to perform the leak test. NOTE: At temperatures below 608F (15.68C), leaks may not be detected since the system pressure may not reach 50 psig (345 kPa). 3. Conduct the leak test from the high side to the low side at points shown in Figure 7-8, as follows.

Compressor Check the high- and low-side hose fittings, relief valve, gaskets, and shaft seal. Check the service valves, if compressor-mounted, with the protective covers removed.

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Suction tube Suction tube Liquid tube

Suction hose

Liquid tube Expansion valve Receiver Compressor Condenser

Evaporator Liquid tube

Discharge hose Discharge hose

Suction hose

Discharge hose

FIGURE 7-8  Test points for leak detection.

Accumulator

Check the inlet and outlet fittings, pressure switch, weld seams, and low-side service fitting (with cap removed), if equipped.

Receiver-Drier

Check the inlet and outlet hose fittings, pressure switch, weld seams and the fusible plug, and sight glass, if equipped.

Service Valves

Check all around the low- and high-side service valves with the caps removed. Ensure that the service valve caps are secured on the service valves after testing to prevent future leaks. NOTE: After removing the manifold gauge hoses from the service valves, wipe away residue to prevent any false readings by the leak detector. Blowing low-pressure air across the service valve should clear any refrigerant residue vapor. If a service valve port is found to be leaking, repair it as required before replacing the valve cap.

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Evaporator

In some systems, the blower motor resistor block may be removed to gain access to the evaporator core for testing. Since refrigerant is heavier than air, however, the leak may be best detected at the evaporator condensate drain hose. If using an electronic leak detector, place the probe near the drain hose for 10 to 15 seconds immediately after stopping the engine. Take care not to contaminate the end of the test probe. If it is a dual air-conditioning system, do not forget to check both evaporators, front and rear.

Condenser

Check all around the discharge (inlet) line and liquid (outlet) line connections. Check the front (face) of the condenser for any leaks that may be due to road damage. If the air-conditioning system has an auxiliary condenser, check it for leaks as well.

Metering Device

Carefully check all connections, inlet and outlet, of the metering device if a thermostatic expansion valve (TXV) or the spring lock coupling if an orifice tube. In a dual air-conditioning system, check both front and rear metering devices.

Hoses

Although barrier-type refrigeration hoses, now required by the EPA, are relatively leak proof, they may on occasion develop a pinhole leak. Visually inspect all hoses carefully for telltale traces of lubricant or dye that indicate a leak. Leaks are not so easily detected visually since PAG lubricant may evaporate from the surface of the hose. Any of the leak test methods may be employed if a leak in a hose is suspected and is not visually detected. If it is a dual airconditioning system, check all hoses, front to back, of the vehicle.

Pressure Controls

Check all around a pressure control. Though rare, a pressure control has been known to leak past the seal of the electrical connector. Remove the connection and thoroughly check the control.

Methods

The three most popular methods of leak detection today use soap bubbles, electronic halogen, and ultraviolet dye. They are covered in the following sections. The once popular halide (gas) leak detector is not recommended. It is only effective for detecting CFC refrigerants and is considered hazardous in view of the danger of encountering flammable refrigerants.

Soap Solution The soap solution is used as a method of leak detection when it is impractical or impossible to pinpoint the exact location of a leak by using the halogen leak detector methods. A commercial soap solution is available that is generally more effective than a homemade solution. A good grade of sudsing liquid dishwashing detergent may be used, however, if a prepared commercial solution is not available.

Preparing the System 1. Connect the manifold and gauge set to the system. 2. Make certain that the high- and low-side manifold hand valves are in the closed (cw) position.

The least expensive method is by soap bubbles.

Classroom Manual Chapter 7, page 216

Some detergents may be used undiluted.

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FIGURE 7-9  Leaks are detected when a bubble forms.

Charge refers to a specific amount of refrigerant or oil by volume or weight.

3. If the system is equipped with manual service valves, place the high- and low-side valves in the cracked position. 4. Open the low- and high-side hose shut-off valves. 5. Determine the presence of refrigerant in the system. A minimum value of 50 psig (348 kPa) is needed. 6. If there is an insufficient charge of refrigerant in the system, continue with the next step, “Adding Refrigerant for Leak Testing.” If the charge is sufficient, omit the next step and proceed with leak testing.

Adding Refrigerant for Leak Testing SPECIAL TOOL Refrigerant identifier

CAUTION:

Use a ­refrigerant identifier to ­determine that the source refrigerant is the same type— R-12 or R-134a— that is used in the air-conditioning system. A minimum of 50 psig (348 kPa) is required for leak testing. The hose shut-off valve is provided to reduce emissions.

1. Attach the center manifold service hose to a source of refrigerant. 2. Open the refrigerant container service valve. 3. Open the high-side manifold hand valve until a pressure of 50 psig (348 kPa) is reached on the low-side gauge. Then close the high-side hand valve. 4. Close the refrigerant container service valve. 5. Close the service hose shut-off valve. 6. Remove the hose from the refrigerant container.

Procedure 1. Apply soap solution to all joints and suspected areas by using the dauber supplied with the commercial solution or by using a small brush with household solution. 2. Leaks are exposed when a bubble forms (Figure 7-9). 3. Repair any leaks found.

Tracer Dye Leak Detection As a rule of thumb, the presence of oil at a fitting or connection generally indicates a refrigerant leak. This is not always the case, however, because oil is used on fittings as an aid in assembly procedures and PAG oil often does not leave significant residue behind. If a leak is suspected, the area should be wiped clean and the leak verified. This may be accomplished by either of the several methods discussed in this chapter. A popular method of refrigerant leak detection is with the use of a fluorescent tracer dye that is easily detected with an ultraviolet (UV) lamp (Figure 7-10). Ultraviolet Leak Detection: Stability and Compatibility Criteria of Fluorescent Refrigerant Leak Detection Dyes for Mobile R-134a and R-1234yf (HFO-1234yf) Air-Conditioning Systems must meet J2297 standards (revised 2/2011).

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FIGURE 7-10  Ultraviolet (UV) lamp used for leak testing.

Some manufacturers install fluorescent tracer dye in the factory fill of the air-conditioning system. To inject dye into the system, the system pressure must be above 80 psig (551.6 kPa). For proper use and accurate results, always follow the instructions included with the tracer dye. The refrigerant dye must be approved for automotive air-conditioning systems. A specific dye for an electric motor-driven air-conditioning compressor that is nonconductible is required and there are dyes specific to the type of refrigerant in the system. The dye is generally available in either yellow or red and after a few days of being added to a system the point of the leak should be visible. To pinpoint the leak, scan all the air-conditioning system components, fittings, and hoses with the UV lamp. The exact location of a leak will be revealed by a bright yellow-green glow of the tracer dye. Leaks are best detected in low ambient-light conditions. In areas where the lamp cannot be used, such as where the ambient light is high, a mechanic’s mirror may be used. The technician may also wipe the suspected area with a disposable, nonfluorescent towel, which is then examined with the lamp for traces of the dye. After the leak has been repaired, the dye can be removed from the exterior of the ­leaking area by using an oil solvent. To verify that the repair has been made, operate the air-­ conditioning system for about 5 minutes and reinspect the area with the UV lamp. Since more than one leak may occur, it is wise to check the entire system. Many technicians prefer to add a dye trace solution to the refrigerant any time the air-­ conditioning system is opened for service. Refrigerant is also available in both small disposable cans and bulk tanks that already contain dye for use in system recharging. With the high cost of refrigerant and technician labor, this practice is well worth the additional cost at the time of repairs.

Halogen (Electronic) Leak Detection The halogen (electronic) leak detector (Figure 7-11) is the most sensitive of all types of leak detectors. These leak detectors must comply with SAE standard SAE J-2791 standard for R134a leak detecting equipment. For R-1234yf detection, they must meet the new SAE J2913 standard and if they are both J2791 and J2913 they can be used to detect leaks in both types of systems. Verify that your leak analyzer meets these standards as older equipment may have been manufactured before this requirement. This SAE standards were created to improve leak detection equipment sensitivity requirements to a sensitivity level of 0.15 oz./year (4 g/y).

Classroom Manual Chapter 7, page 217

Classroom Manual Chapter 7, page 218

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A

B

FIGURE 7-11  Electronic leak detectors: (A) cordless; (B) corded.

CAUTION:

Do not keep the probe in contact with refrigerant any longer than is ­necessary to locate the leak. Do not deliberately place the probe in a stream of raw refrigerant or in an area where a severe leak is known to exist. The sensitive components of the leak detector can be severely damaged.

SERVICE TIP:

If a leak is located, the electronic leak detector reacts in the same manner as it does when placed by the reference leak.

Leak detectors that meet this standards will have at least three sensitivity scales that can be selected manually: (A) 0.15 oz./year (4 g/y), (B) 0.25 oz./year (7 g/y), and (C) 0.5 oz./year (14 g/y). It must be calibrated to detect a refrigerant leak within 2 seconds from a distance of 3/8 in. (9.5 mm) moving at a rate of 3 in. (75 mm) per second and must be able to self-clear itself within 2 seconds once moved away from the leak. This type of leak detector can be of great value in detecting the “impossible” leak. When using an electronic leak detector, ensure that the instrument, if required, is calibrated and set properly according to the operating instructions provided by the manufacturer. In order to use the leak detector properly, read the operating instructions and perform any specified maintenance. Other vapors in the service area or any substances on the components—such as antifreeze, windshield washing fluid, or solvents and cleaners—may falsely trigger the leak detector. Make sure that all surfaces to be checked are clean. Do not permit the detector sensor tip to come into contact with any substance; a false reading can result, and the leak detector can be damaged. WARNING: A halogen electronic leak detector must be used in well-ventilated areas only. It must never be used in spaces where explosive gases may be present. Those meeting SAE J2913 standards are safe to use to detect R-1234yf even though it is a mildly flammable refrigerant. The following list and Photo Sequence 7 illustrate typical procedures for using an e­ lectronic leak detector: 1. Hold the probe in position about 3/16 in. (5 mm) from the area to be checked (Figure 7-12). 2. When testing, circle each fitting with the probe (Figure 7-13). 3. Move the probe along the component about 1–2 in. (25–50 mm) per second (Figure 7-14). 4. If a leak is detected, verify it by fanning or blowing compressed air into the area of the suspected leak, then repeat the leak check.

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PHOTO SEQUENCE 7 Typical Procedure for Checking for Leaks

P7-1  Turn the control or sensitivity knobs to OFF or ZERO. If the leak detector is corded, connect it to an approved voltage source. Skip this step if it is cordless.

P7-2  Turn on the switch. Allow a warm-up period of about 5 minutes. There is usually no warm-up period required for cordless models.

P7-3  Place the probe at the reference leak. Adjust the control or sensitivity knobs until the detector reacts.

P7-4  Remove the probe. The reaction should stop.

P7-5  If the reaction continues, the sensitivity control is adjusted too high. Repeat the procedure of step P7-3. If the reaction stops, the sensitivity adjustment is adequate.

P7-6  Slowly move the search hose under and around all of the joints and connections.

P7-7  Check all seals and screw-in pressure control devices.

P7-8  Check the service fittings. It will be necessary to remove the service cap for this test.

P7-9  Check the evaporator at the outlet duct drain, or in some cases the blower motor resistor block may be removed to gain access.

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Approx. 5 mm (3/16 in.)

1 sec. 25–50 mm (1–2 in.) FIGURE 7-12  Hold the probe about 3/16 in. (5 mm) away.

FIGURE 7-13  Circle each fitting. 

FIGURE 7-14  Move the probe 1–2 in. (25–50 mm) per second.

Repair System To evacuate is the process of creating a vacuum within a system to remove all traces of air and moisture. Be sure to use the proper refrigerant, only R-12 or R-134a, as appropriate.

Classroom Manual Chapter 7, page 212

1. After the leak is located, recover the system refrigerant as outlined in this chapter. 2. Repair the leak as indicated. 3. Add or change oil, if required. 4. Evacuate the system. 5. Charge the system with refrigerant. 6. Recheck the system for leaks; verify the repair.

Evacuating the System An important step in the repair of an automotive air-conditioning system is proper evacuation. The air-conditioning system must be evacuated whenever it is serviced to the extent that the refrigerant was recovered. Proper evacuation rids the system of all air and most moisture that may have entered during repair service. Photo Sequence 8 illustrates the typical procedure for evacuating the system. The following procedure assumes that the system has been serviced and does not contain refrigerant.

Checking for Leaks

A standing vacuum test may be made to leak test the system. Proceed as follows: A standing vacuum test is a leak test performed on an air-conditioning system by pulling a vacuum and then determining, by observation, if the vacuum holds for a predetermined period of time to ensure that there are no leaks. Only enough refrigerant to increase the system pressure to 50 psi (345 kPa) is required.

1. Evacuate the systems outlined in Photo Sequence 8. 2. Close the manifold hand valves and turn off the vacuum pump. 3. Note the low-side gauge reading; it should be 29 in. Hg. (3.4 kPa absolute) or lower. 4. Allow the system to “rest” for 5 minutes, then again note the low-side gauge reading. NOTE: The low-side gauge needle should not raise faster than 1 in. Hg. (3.4 kPa absolute) in 5 minutes. If the system does not meet the requirement of step 4, a leak is indicated. A partial charge of refrigerant must be installed, and the system must be leak checked. After the leak is detected, the refrigerant must be recovered. After the leak is repaired, again perform the standing vacuum test, starting with step 1 above.

Triple Evacuation Method The basic steps in the triple evacuation method are given here. The procedures assume that the system is sound after the refrigerant has been removed and repairs, if any, have been made.

Procedure

As previously detailed, connect the manifold and gauge set into the system. Be sure that all hoses and connections are tight and sound and that all appropriate valves are in the closed position.

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PHOTO SEQUENCE 8 Typical Procedure for Evacuating the System

P8-1  Connect the manifold and gauge set low- and high-side service hoses to the system.

P8-2  Make sure that the high- and lowside manifold hand valves are in the closed position and both gauges read zero or less.

P8-3  Connect the service hoses to the vehicle refrigerant system high- and lowside fittings.

P8-4  Remove the protective caps from the inlet and exhaust of the vacuum pump.

P8-5  Connect the center manifold service hose to the inlet of the vacuum pump.

P8-6  Open the shut-off valve of the three service hoses.

P8-7  Connect the power cord of the vacuum pump to an approved power source.

P8-8  Turn on the vacuum pump.

P8-9  Open the low-side manifold hand valve and observe the low-side gauge needle. The needle should be immediately pulled down to indicate a slight vacuum.

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PHOTO SEQUENCE 8

(CONTINUED)

P8-10  After about 5 minutes, the low-side gauge should indicate 20 in. Hg (33.8 kPa absolute) or less. The high-side gauge needle should be slightly below the zero index of the gauge.

P8-11  If the high-side needle does not drop below zero, unless restricted by a stop, a blockage in the system is indicated. If the system is blocked, discontinue the evacuation. Repair or remove the obstruction. If the system is clear, continue the evacuation.

P8-12  Operate the pump for another 15 minutes and observe the gauges. The system should be at a vacuum of 24–26 in. Hg (20.3–13.5 kPa absolute). If it is not, close the low-side hand valve.

P8-13  Observe the compound (low-side) gauge. If the needle rises, indicating a loss of vacuum, there is a leak that must be repaired before the evacuation is continued. If no leak is evident, continue the evacuation.

P8-14  Reopen the low-side manifold hand valve.

P8-15  Open the high-side manifold hand valve.

P8-16  Allow the vacuum pump to operate for a minimum of 30 minutes, longer if time permits. After pump-down, close the high- and low-side manifold hand valves. Turn off the vacuum pump and close the service hose shut-off valves. Turn off the vacuum pump valve, if equipped. Then, disconnect the manifold service hose from the vacuum pump. Replace the protective caps, if any.

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First Stage 1. Pump a vacuum to the highest efficiency for 25–30 minutes. 2. Close the manifold hand valves. 3. Close the service hose shut-off valves. 4. Close the vacuum pump shut-off valve, if equipped. If the system is not equipped with a shut-off valve, turn off the pump. 5. Disconnect the service hose from the vacuum pump. 6. Connect the service hose to a dry nitrogen (Figure 7-15) source. 7. Open the service hose shut-off valve. 8. Open the nitrogen supply valve. 9. Open the low- and high-side service hose shut-off valves. 10. Open the low-side manifold hand valve to break the vacuum: a. Slowly increase the pressure to 1–2 psig (6.8–13.7 kPa). b. Close all valves: the manifold low-side hand valve, service hose shut-off valve, lowand high-side hose shut-off valves, and the nitrogen supply valve. 11. Disconnect the service hose from the nitrogen supply.

Second Stage 1. Allow one-half hour, which is sufficient time for the dry nitrogen to “stratify” the system. 2. Reconnect the service hose to the vacuum pump. 3. Open the vacuum pump shut-off, if equipped. If not equipped, turn on the pump. 4. Open the service hose shut-off valve. 5. Open the manifold low- and high-side hand valves. 6. Pump a vacuum to the highest efficiency for 25–30 minutes. 7. Repeat steps 2 through 11 as outlined in “First Stage” procedures.

Third Stage 1. Follow steps 1 through 6 as outlined in “Second Stage” procedures. 2. Close all valves: the service hose shut-off valve, vacuum pump shut-off valve, if equipped (if not equipped, turn off the pump), low- and high-side service hose shut-off valves, and manifold low- and high-side hand valves. 3. Turn off the vacuum pump (if not previously done). 4. Remove the service hose from the vacuum pump. 5. The system is now ready for charging. Follow the appropriate procedure outlined in this chapter.

Triple evacuation is the process of evacuation that involves three pump downs and two system purges with an inert gas such as dry nitrogen (N). Dry nitrogen is the element nitrogen (N) that has been processed to ensure that it is free of moisture. Several different types of service hose shut-off valves are available.

CAUTION:

Make sure that the nitrogen supply has proper regulators and that supply pressure does not exceed 75 psig (517 kPa). Be sure the nitrogen pressure is regulated before opening the valve. To stratify is the process of arranging or forming into layers to fully blend. Air contains moisture in the form of humidity.

FIGURE 7-15  Typical dry nitrogen setup.

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CAUTION:

The system is now under a vacuum. Opening any valves or fittings, even momentarily, will allow moistureladen air to enter the system. Pound cans is a term used when referring to a small disposable can of refrigerant. A “pound” can of R-134a actually contains 12 ounces (0.355 liters).

CAUTION:

Above 1308F (54.48C), ­liquid refrigerant ­completely fills a container. ­Hydrostatic pressure builds up rapidly with each degree of temperature added. Never heat a refrigerant ­container above 1258F (51.78C).

Classroom Manual Chapter 7, page 223

Eye protection should include side shields.

Customer Care: While under the hood servicing a vehicle, make a point of checking all fluid levels and topping them off as needed. Customers may never say anything, but when they push the washer button and there is always fluid, they appreciate it.

Charging the System The typical methods of charging an automotive air-conditioning system refrigerant are given in this service procedure: from a recovery/recycling/recharge unit, from pound cans with the system off, from pound cans with the system operating, and from a bulk source. For R-1234yf refrigerant only recovery/recycling/recharging units meeting SAE J2927 can be used to recharge the refrigerant system and special charging procedures must be followed. The following additional safety precautions must also be followed when handling refrigerant. ■■ Do not deliberately inhale refrigerant. ■■ Do not apply a direct flame to a refrigerant container. ■■ Do not place an electric resistance heater close to a refrigerant container. ■■ Do not abuse a refrigerant container. ■■ Do not use pliers or vice grips to open and close refrigerant valves. Use only approved wrenches. ■■ Do not handle refrigerant without suitable eye protection. ■■ Do not discharge refrigerant into an enclosed area. ■■ Do not expose refrigerant to an open flame. ■■ Do not lay cylinders flat. Store containers in an upright position only. Secure large cylinders with a chain to prevent them from tipping over.

Preparing the System

This procedure assumes that the system has been evacuated. If it has not been evacuated, refer to the proper procedure for evacuation before attempting to charge the system. If charging from pound cans, set up the refrigerant recovery system according to the equipment manufacturer’s instructions to be used to recover any residual refrigerant that remains in a can while charging the system.

Recharging System with a Recovery/Recycling/Recharge Unit

A service facility must have a recovery/recycling/recharge unit (Figure 7-16) for each type of refrigerant serviced (i.e., R-134a, R-1234yf, and R-12). This unit is used to charge refrigerant systems after the repair has been completed in most instances, though some shops also use manifold and gauge sets and bulk refrigerant containers and separate scales for the charging process, except on R-1234yf systems. Some units are dual system and designed to service both R-134a and R-12 refrigerants or R-134a and R-1234yf. Refrigerant is generally less expensive per unit in larger packages. Charging the refrigerant system with the correct amount of refrigerant is one of the most critical aspects of air-conditioning service. Close is not good enough, especially with today’s small capacity systems. A 1.2 lb. (0.54 kg) system is overcharged or undercharged by almost 10 percent with an error of only 62 oz. (0.06 kg). Efficient system operation depends on proper charge level of refrigerant. Too little or too much refrigerant can lead to poor cooling complaints or system failure. Partial charging a refrigerant system is no longer an acceptable practice except for the purpose of adding refrigerant to determine the location of a leak during the diagnostic process. In addition, with the speed and accuracy of today’s recovery/recycling/ recharge units, there is no need for the guesswork involved in a partial charge. If the charge

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FIGURE 7-16  A typical air-conditioning system recovery/recycling/recharge unit.

level of a refrigerant system is in doubt, then recover, evacuate, and recharge the system before proceeding with refrigerant system diagnosis. An undercharged system will result in poor or inadequate cooling under high heat loads. Slightly undercharged systems may provide satisfactory cooling under moderate heat loads, but cooling performance will be poor under high ambient temperatures and heat loads due to lack of reserve refrigerant. This can lead to improperly diagnosed systems and either unneeded repairs or no repair at all. In addition, a low refrigerant charge level will cause the clutch cycling switch to cycle the compressor more often than normal. An overcharged system will also result in poor or inadequate cooling. The higher than designed level of refrigerant can also lead to compressor failure. An overcharged system will generally have higher than normal system pressures. In addition, the refrigerant system may also exhibit noise coming from the compressor assembly due to liquid refrigerant entering the compressor and higher system-operating pressures. The following is an outline of the basic charging procedures for a recovery/recycling/ recharge unit for R-134a or R-12. Always follow the specific instructions that are provided by the equipment manufacturer when using a charging station. Though systems are similar in operation each unit has specific steps that must be followed.

Procedure 1. Connect both the high- and low-side service lines from the recovery/recycling/recharge unit to the vehicle refrigerant system high- and low-side service fittings, respectively. 2. Ensure that the vehicle refrigerant system has been properly evacuated prior to proceeding with the recharging of the refrigerant system. 3. Open the refrigerant tank valve(s) on the recharge station (Figure 7-17). 4. Set the unit to deliver the required amount of either new or recycled refrigerant for the vehicle refrigerant system being charged (Figure 7-18). Remember, refrigerant charge level is system specific. Refer to the refrigerant label located in the engine compartment or refer to the appropriate service information for system refrigerant capacity. 255 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 7-17  Open the refrigerant tank valve(s) on the recovery/recycling/recharge unit.

FIGURE 7-18  A typical air-conditioning system recovery/recycling/recharge console control panel.

5. Start the recharge process; most systems are capable of recharging the refrigerant system with the vehicle off. 6. Once the charging process is complete, the unit may be disconnected from the vehicle and the vehicle service fitting caps may be reinstalled on the vehicle high- and low-side access fittings. 7. After the system has been recharged, perform an unloaded air-conditioning performance test to verify proper function of the system. Photo Sequence 9 illustrates a typical procedure for system charging. 256 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

PHOTO SEQUENCE 9 Typical Procedure for Completing the System Charge

P9-1  Connect both the high- and low-side service lines from the recovery/recycling/ recharge unit to the vehicle refrigerant system high- and low-side service fittings, respectively.

P9-2  Open the service hose shut-off valve on the quick-disconnect coupling.

P9-3  Open the refrigerant tank valve(s) on the charge station.

P9-4  Set the unit to deliver the required amount of either new or recycled refrigerant for the vehicle refrigerant system being charged.

P9-5  Start the recharge process; most systems are capable of recharging the refrigerant system with the vehicle off.

P9-6  Once the charging process has been completed, start the vehicle engine.

P9-7  Turn the blower motor control on high speed.

P9-8  Activate the air-conditioning system in the Recirculation mode and set the temperature control to the coldest setting.

P9-9  Place a fan in front of vehicle to assist in cooling the air-conditioning condenser.

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PHOTO SEQUENCE 9

(CONTINUED)

P9-10  With the engine running at 1000 rpm check both the high- and lowside gauge pressures.

P9-11  Place a thermometer in the center dashboard vent and record the outlet air temperature.

P9-13  Disconnect the recovery/recycling/ recharge unit from the vehicle and shut the refrigerant tank valve(s) on the charge station.

P9-14  Replace the vehicle service fitting caps on the high- and low-side access fittings.

P9-12  Compare both gauge and thermometer readings to the temperature/ pressure chart for the vehicle being serviced.

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WARNING: R-1234yf is a mildly flammable refrigerant. Never smoke or expose refrigerant to an open flame, hot surface, high-energy ignition source, sparks, or secondary ignition components.

Charging the R-1234yf System Charging an R-1234yf refrigerant system is essentially the same as charging an R-134a system except that the system requires a leak test be performed during system charging. If a leak is detected, the system will not continue with the recharge procedure. The equipment is intended to be as environmentally conscious as is possible and force technicians to follow proper protocol. Before the recovery/recycling/recharge equipment can recharge a vehicle’s refrigerant system, it must first pass an automated precharge leak test to detect the possibility of a gross system leak greater than 0.3 g/s before the system is charged. During the pressurized portion of the test, the technician must turn the vehicle’s HVAC system blower motor to high, turn off the A/C, and set the air distribution to floor discharge. Next, the technician must use a J2913-compliant leak detector set to low sensitivity (14 g/y) into the center duct of the floor discharge. Once the technician has set up the vehicle and leak detection equipment, the R/R/R machine will install 15 percent of the programmed charge into the vehicle’s refrigerant system. The technician must then monitor the leak detector for the next 5 minutes or until a leak is detected, whichever comes first. After 5 minutes, the sytem will ask a series of questions: 1. Was the leak test performed? Y/N 2. If yes, Was a leak found? Y/N If the technician answers yes, then the machine will only allow recovery and evacuation. 3. If no, Is there an auxiliary evaporator? If no, then the machine will allow the recharge procedure to continue and will complete the system recharge. If the technician answered yes, then the machine will instruct the technician to perform a rear evaporator leak test as was performed for the front evaporator. 4. Next, was an auxiary evaporator leak test performed? If yes, was a leak found? Again, if a leak was noted, then only recovery and evacuation will be allowed. If no, then the machine will complete the system recharge.

Operation and Maintenance of Refrigerant Recover/Recycling Equipment

It should be a routine practice to verify the correct operation and to determine the required maintenance of refrigerant handling equipment in every shop. In some shops, one individual is assigned the task of maintaining equipment, whereas in many other shops, this task is not assigned but rather becomes the responsibility of all the technicians using the equipment. It is important to remember that refrigerant system operation after the repair depends on the accuracy of the service equipment being used. Improperly maintained equipment creates diagnostic and performance issues that lead to lost time and productivity for the vehicle owner, the repair shop, and the individual technician. Procedure.  Always follow the procedures outlined in the service manual for the specific refrigerant recovery/recycling unit being used. 1. Based on the service information for the unit, follow the replacement service interval for the filter(s) and desiccant (Figure 7-19). Often, this is every 20 hours of unit operation. Also, make note if the unit is equipped with a filter change indicator. 2. Does the vacuum pump require routine oil change maintenance or is the unit equipped with a oil-less pump? 259 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 7-19  Replace the recovery/recycling/ recharge unit filters at the recommended maintenance interval to provide optimum system performance.

3. Locate and record the recovery tank date code stamped on the tank’s collar (Figure 7-20). 4. Refrigerant recovery tanks require recertification every 5 years. Verify that the recovery tank is the correct color for the refrigerant it contains: sky blue for R-134a, white with a red strip on top portion of tank for R-1234yf, white for R-12, or gray with a yellow top for unknown refrigerants. The U.S. DOT, under Title 49 as well as SAE standard J2296, requires that every 5 years a recovery tank be both externally and internally inspected and a hydrostatic pressure test be performed. The date code indicates when the tank was produced or recertified and must not be older than 5 years. Using a tank that is out of date can subject the owner to a $25,000 fine. Use only DOT-certified Title 49 or UL-approved containers with a stamp of DOT-4BA or DOT-4BW on the tank as proof.

FIGURE 7-20  Note and record the recovery tank date code.

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FIGURE 7-21  Attach the can tap valve.

Install the Can Tap Valve on a “Pound” Container This procedure may be followed prior to servicing an R-134a system using small disposable cans. 1. Be sure that the can tap valve stem is in the fully counterclockwise (ccw) position. 2. Attach the valve to the can (Figure 7-21). Secure the valve with the locking nut, if so equipped. Secure the valve with the clamping lever, if so equipped. 3. Make sure that the manifold service hose shut-off valve is closed. 4. Connect the manifold service hose to the can tap port. 5. Pierce the can by turning the valve stem all the way in the clockwise (cw) direction. 6. Back the can tap valve out, turning in a counterclockwise (ccw) direction. 7. The center (service) hose is charged with refrigerant to the shut-off valve and is under a vacuum between the manifold and shut-off valve. WARNING: Do not open the high- or low-side hand valves at this time.

Checking the System for Blockage

This procedure may be followed when charging the system from pound cans. 1. Open the service hose shut-off valve. 2. Open the low- and high-side service hose shut-off valves. 3. Open the high-side gauge manifold hand valve. Observe the low-side gauge pressure. Close the high-side hand valve. 4. Close the hose shut-off valves. Close the service hose and the low- and high-side hoses.

A can tap valve is a valve found on a can tap used to control the flow of refrigerant. There are two basic types of can tap valve: locking nut and clamping ring. If the discharge valve and plate are in good condition, refrigerant must circulate through the system to impress pressure on the lowside gauge.

Using Pound Cans (System Off) 1. Open the service hose shut-off valve. 2. If not previously done, fully open the can tap valve. 261 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

SERVICE TIP:

If the low-side gauge does not move from the vacuum range into the pressure range, a system blockage is indicated. Correct the blockage, then evacuate and continue with the appropriate service procedure. FIGURE 7-22  Invert the container to allow liquid refrigerant to flow.

CAUTION: Charging liquid refrigerant into a compressor while it is running may cause damage to the compressor and injury to the technician.

The ¼ in. (6.4 mm) service hose acts like a capillary tube. At 40 psig (276 kPa), the refrigerant will vaporize by the time it travels the 6 ft. (1.8 m) of hose.

CAUTION:

Regulate the lowside manifold hand valve so that low-side pressure remains under 40 psig (276 kPa) to ensure that liquid refrigerant does not enter the system.

3. Open the high-side gauge manifold hand valve. 4. Observe the low-side pressure gauge. If the gauge indication does not move from the vacuum range to the pressure range, a system blockage is indicated. If the system is not blocked, proceed with step 5. If the system is blocked, correct the condition and evacuate the system before continuing with step 5. 5. Invert the container (Figure 7-22) and allow the liquid refrigerant to enter the system. 6. Tap the refrigerant container on the bottom. An empty can produces a hollow ringing sound. The system generally requires 10 percent less R-134a than was required for R-12 when retrofitting. 7. Use the recovery system to remove any residual refrigerant from the empty can. 8. Repeat steps 5, 6, and 7 with additional cans of refrigerant as required to charge the air conditioner. Refer to the manufacturer’s specifications for system capacity.

Using Pound Cans (System Operational) 1. Start the engine and adjust the speed to about 1250 rpm by turning the idle screw or the setting on the high cam. 2. Make sure that both the manifold hand valves are closed. 3. Adjust the air-conditioning controls for MAX cooling with the blower on HI. 4. Open the service hose shut-off valve. 5. Open the low- and high-side hose shut-off valves. 6. If not previously done, open the can tap valve. 7. With the can in an upright position, open the low-side manifold hand valve. 8. After the pressure on the low side drops below 40 psig (377 kPa absolute), the can may be inverted to allow more rapid removal of the refrigerant. 9. Tap the can on the bottom to determine if it is empty. An empty refrigerant can will give a hollow ringing sound. One may also shake the can to determine if refrigerant is “sloshing around” inside. 10. Repeat steps 7, 8, and 9 with additional cans of refrigerant as required to charge the system completely. Refer to the manufacturer’s specifications regarding system capacity.

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11. Close all valves: the can tap valve (if refrigerant remains in the can), service hose shut-off valve, low- and high-side service hose shut-off valves, low- and high-side manifold hand valves. 12. Remove the refrigerant container. If refrigerant remains in the can, close the charging hose shut-off valve and remove the can tap from the center service hose. If the can is empty, use the recovery system to remove any residual refrigerant from the manifold, hoses, and can. 13. Remove the manifold and gauge set. 14. Replace all protective caps and covers.

Take care not to overcharge the airconditioning system.

Charging from a Bulk Source with a Manifold and Gauge Set Shops that perform a large volume of air-conditioning service can obtain bulk refrigerant in 10-, 15-, 25-, 30-, 50-, and 145-pound (4.5-, 6.8-, 11.3-, 13.6-, 22.7-, and 65.8-kilogram) cylinders. The use of bulk containers requires a set of scales or other approved measuring device to determine when the proper system charge is obtained. This is not an acceptable procedure for small-volume refrigerant systems or for R-1234yf systems due to its lack of accuracy. The high cost of refrigerant, particularly R-12, has prompted many service facilities to charge for it by the ounce. An ounce (29.6 mL) of R-12 now generally costs more than 10 times what a pound (473 mL) did before the federal restrictions on refrigerants. Regulations by the Bureau of Weights and Measures, in most states, require that certified scales be used to ensure that the costs of refrigerant to the customer are proper. Two types of scales easily meet this requirement: electronic and beam. An electronic scale (Figure 7-23) is more properly referred to as an electronic charging meter. Some charging meters display refrigerant weight as it is being charged from the tank; others may be programmed to automatically charge a selected amount of refrigerant and will shut off when the programmed amount has been reached. Some charging meters measure refrigerant in increments of 0.5 oz. (14.8 mL), while other; are accurate to and measured in 0.25 oz. (7.4 mL) increments. Charging meters can generally

Hanging scales are often used to weigh refrigerant.

FIGURE 7-23  Typical electronic charging meter (scale).

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accept cylinders having a gross weight of 100 lbs. (45.4 kg) or more. When buying refrigerant in any size container, it is suggested that the cylinder be checked for weight and a sample of its contents be tested for purity. At today’s prices, one cannot be too careful. Electronic charging scales are compatible with all refrigerants and have a tare function that may be zeroed (0.00 oz.). Some meters have a digital display in either pounds (lbs.) or kilograms (kg). Battery-powered charging meters generally include an AC adapter and have a “sleep mode” to ensure extended battery life. The following procedure assumes that the system has been properly prepared for charging procedures. If not, consult the appropriate heading for the proper procedure before continuing.

Connecting the Refrigerant Container Be sure to use the correct refrigerant. R-12 and R-134a are not compatible.

CAUTION:

Keep the refrigerant cylinder in an upright position at all times. Liquid refrigerant must not be allowed to enter the compressor. This can cause ­serious ­damage and ­possible injury. Gross weight is the weight of a substance or matter that includes the weight of the container.

1. Make sure that all service valves are in the OFF or closed position. Check the service hose shut-off valves, manifold hand valves, compressor service valves, if equipped, and refrigerant source valve. 2. Connect the center manifold service hose to the supply refrigerant cylinder. 3. Open the refrigerant cylinder hand valve. 4. The system is now under a vacuum from the manifold to the service hose shut-off valve, and under a refrigerant charge from the cylinder to the hose shut-off valve.

Charging the System 1. Open the service hose shut-off valve. 2. Open the low- and high-side manifold hose shut-off valves. 3. Briefly open the high-side manifold hand valve. Observe the low-side gauge. 4. System blockage is indicated if the low-side gauge needle does not move from the vacuum range into the pressure range. If the system is not blocked, proceed with step 5. If the system is blocked, correct the blockage and reevaluate the system before continuing with step 5. 5. Start the engine and adjust the speed to about 1250 rpm. 6. Adjust the air-conditioning controls for MAX cooling with the blower on HI. 7. Place the refrigerant cylinder on an approved scale and note the gross weight. 8. Open the low-side manifold hand valve to allow refrigerant to enter the system. 9. When the system is fully charged, close the low-side manifold hand valve. 10. Close the refrigerant cylinder service valve. 11. Close the service hose shut-off valve. 12. Remove the service hose from the refrigerant cylinder. 13. Note the gross weight now shown on the scale. Refrigerant used, by weight, is the difference between what the cylinder weighed in step 7 and what it now weighs. 14. Conduct performance tests or other tests as required. 15. Return the engine to its normal idle speed. 16. Turn off all air-conditioning system controls. 17. Shut off the engine. 18. Close all valves. Close the low- and high-side service hose shut-off valves. Back seat the compressor service valves, if equipped. 19. Use the recovery system to remove any residual refrigerant from the manifold and hoses. 20. Remove the manifold and gauge set. 21. Replace all protective caps and covers.

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Testing Refrigerant for Noncondensable Gas Recycled refrigerant in portable storage containers should be periodically checked for noncondensable gas (air) contamination. This includes recycled storage containers that are on recovery/ recycle/recharge units. To determine if the refrigerant is contaminated the temperature/pressure relationship of the refrigerant gas is analyzed. The best time to proceed with this test procedure is at the beginning of the workday before beginning any refrigerant system service. The procedure that follows outlines the steps for testing for noncondensable gases.

Classroom Manual Chapter 7, page 207

Procedure

Prior to checking a recovery tank of recycled refrigerant for noncondensable gases, the tank must first sit at room temperature above 658F (18.38C) for at least 12 hours to stabilize out of direct sunlight. 1. Identify the type of recycled refrigerant based on tank color (sky blue 5 R-134a; white with a red band 5 R1234yf; white 5 R-12). 2. Verify that the manifold set control knobs and hose shut-off valves are closed. 3. Connect the manifold gauge set auxiliary hose (yellow) to the recovery tank low-side (vapor) outlet (blue). 4. Using a contact or infrared thermometer, record the tank temperature within 4 in. (10 cm) of the tank. 5. Open the low-pressure valve on the tank and the low-pressure valve on the manifold line and manifold; record the recovery tank pressure. 6. Go to the chart in Figure 7-24 for R-134a and R-12 refrigerant being tested, or the chart in Figure 7-25 for R-1234yf refrigerant, and compare the tank temperature to the chart. a. Based on the chart, determine the acceptable tank pressure. b. Tank pressure should be at or below the listed pressure. c. If pressure is above the temperature/pressure chart, attach the refrigerant identifier and test for impurities. If no impurities are identified (i.e., alternative refrigerant or HC) proceed to the next step. If the refrigerant pressure is at or below the chart pressure, the refrigerant contains no noncondensable gases and may be put back into service. Note that higher pressures indicate the presence of noncondensable gases. 7. Slowly vent the vapor from the top of the recovery tank into the recovery/recycling unit until pressure falls below the limit shown in the charts. If the recycled refrigerant is R-134a and the pressure is high after purging, shake the container and wait several minutes, then retest. 8. If the pressure still exceeds the pressure limits in the chart, recycle the entire contents of the container. 9. Label and store the refrigerant. Some recycling equipment have either an automatic or a manual air purge operation that can take place during the normal unit recycling or evacuation process.

Freon is a generic term used to refer to R-12.

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STANDARD PRESSURE TEMPERATURE CHART FOR R-134A Temperature Fahrenheit

Pressure kPa

Temperature Fahrenheit

PSIG

70

76

71 72

Pressure PSIG

524

86

102

77

531

87

79

545

88

73

80

551

74

82

75

83

76 77

kPa

Temperature Celsius

Pressure PSIG

Temperature Celsius

kPa

703

21.1

524

103

710

21.7

105

724

22.2

89

107

738

565

90

109

572

91

111

85

586

92

86

593

93

78

88

607

79

90

621

80

91

81 82

Pressure kPa

PSIG

76

30.0

703

102

531

77

30.5

710

103

545

79

31.1

724

105

22.8

551

80

31.7

738

107

752

23.3

565

82

32.2

752

109

765

23.9

572

83

32.8

765

111

113

779

24.4

586

85

33.3

779

113

115

793

25.0

593

86

33.9

793

115

94

117

807

25.6

607

88

34.4

807

117

95

118

814

26.1

621

90

35.0

814

118

627

96

120

827

26.7

627

91

35.6

827

120

93

641

97

122

841

27.2

641

93

36.1

841

122

95

655

98

125

862

27.8

655

95

36.7

862

125

83

96

662

99

127

876

28.3

662

96

37.2

876

127

84

98

676

100

129

889

28.9

676

98

37.8

889

129

85

100

690

101

131

903

29.4

690

100

38.3

903

131

STANDARD PRESSURE TEMPERATURE CHART FOR R-12 Temperature Fahrenheit

Pressure kPa

Temperature Fahrenheit

PSIG

70

80

71 72

Pressure kPa

Temperature Celsius

PSIG

551

86

103

82

565

87

83

572

88

73

84

579

74

86

75

87

76 77

Pressure PSIG

Temperature Celsius

kPa

710

21.1

551

105

724

21.7

107

738

22.2

89

108

745

593

90

110

600

91

111

88

607

92

90

621

93

78

92

634

79

94

648

80

96

81 82

Pressure kPa

PSIG

80

30.0

710

103

565

82

30.5

724

105

572

83

31.1

738

107

22.8

579

84

31.7

745

108

758

23.3

593

86

32.2

758

110

765

23.9

600

87

32.8

765

111

113

779

24.4

607

88

33.3

779

113

115

793

25.0

621

90

33.9

793

115

94

116

800

25.6

634

92

34.4

800

116

95

118

814

26.1

648

94

35.0

814

118

662

96

120

827

26.7

662

96

35.6

827

120

98

676

97

122

841

27.2

676

98

36.1

841

122

99

683

98

124

855

27.8

683

99

36.7

855

124

83

100

690

99

125

862

28.3

690

100

37.2

862

125

84

101

696

100

127

876

28.9

696

101

37.8

876

127

85

102

703

101

129

889

29.4

703

102

38.3

889

129

FIGURE 7-24  Compare the refrigerant static storage tank temperature to the chart above. Refrigerant gas pressure should be below the pressure listed for the given tank pressure. Higher pressures indicate contamination.

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R-1234yf Fahrenheit Pressure/Temperature Chart 77 80 83 86 89 92 96 99 102 106 110 113 117 121 125 129 133 137 142 146 148 150 155 160 164 169 174 179 184 190 195

200 206 212 218 223 229 236 242 248 255 261 268 275 282 289 296 304 311 319 326 334 342 351 359 368 376 385 394 403 413

0 4 8 12 16 17 18 22 23 24 28 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70

72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 102 104 106 108 110 111 112 114 116 118 120 122 124 126 128 130

132 134 136 138 140 142 144 146 148 150 152 154 156 158 160 162 164 166 168 170 172 174 176 178 180 182 184 186 188 190

°C

kPa

°C

kPa

°C

-18 -16 -14 -12 -10 -8 -6 -4 -2 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

544 562 581 601 620 641 661 682 704 726 748 771 794 818 842 866 891 917 943 970 997 1024 1052 1081 1110 1140 1170 1201 1232 1264 1297 1330

23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54

1363 1398 1432 1468 1504 1541 1578 1616 1654 1694 1733 1774 1815 1857 1900 1943 1987 2032 2078 2124 2171 2219 2267 2317 2367 2418 2523 2631 2743 2859 2979

55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 82 84 86 88 90

Condenser

9 11 14 16 19 19 20 23 24 25 28 31 33 35 37 38 40 42 44 47 49 51 53 56 58 61 63 66 68 71 74

62 75 90 105 120 137 155 174 194 214 225 236 248 260 272 284 297 309 323 336 350 364 379 394 409 425 440 457 473 490 508 526

Evaporator

PSIG °F

Condenser

PSIG °F

Evaporator

PSIG °F

R-1234yf Celsius Pressure/Temperature Chart kPa

FIGURE 7-25  R-1234yf pressure/temperature chart.

Terms to Know

case study A customer complained of an inoperative air conditioner and requested that Freon be added. The ­technician advised the customer that if refrigerant were needed, there must be a leak in the system. The customer responded “I have to add Freon every couple of months—just put it in.” The technician attempted to explain the problems with just adding refrigerant, such as loss of oil, harm to the environment, and possible damage to the air-conditioning system components, such as the compressor. The customer still insisted that he only wanted Freon.

Politely and tactfully, the technician refused the service. “You have come to the wrong place,” she told the customer. “This service facility employs only ­A SE-certified technicians who are dedicated to their profession. To perform a service in an improper ­manner violates the essence of ASE certification.” The somewhat surprised, but impressed, customer left the facility without further ado. He returned the next day and had the air conditioner properly repaired.

Can tap valve Charge Contaminated refrigerant Dry nitrogen Evacuate Gross weight Pound cans Standing vacuum test Stratify Triple evacuation

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ASE-STYLE REVIEW QUESTIONS 1. Technician A says that a system is contaminated if it contains more than 2 percent of a foreign substance. Technician B says that air is considered a contaminant if it exceeds 2 percent of the system capacity. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 2. Technician A says that tobacco smoke will not affect refrigerant leak detection. Technician B says that an electronic halogen leak detector is the best method of leak detection. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 3. Technician A says that special electronic leak detectors are available that are used for halogen gases. Technician B says that there are electronic leak ­detectors available that will detect CFCs as well as HFCs. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 4. All of the following statements about injecting a dye solution into the air-conditioning system are true, except: A. Dye is approved for automotive air-conditioning system use. B. Dye is available in either yellow or red. C. A few days after injection, the dye will be visible at the point of the leak. D. The dye affects the overall performance of the system. 5. Technician A says that one need not evacuate the ­system if the “sweep and purge” method is used. Technician B says that one need not evacuate the ­system if it has been “opened” for less than 5 minutes. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

­ 6. After a repair that required opening the ­refrigerant system the system should be evacuated (pumped down) for a minimum of how many minutes? A. 5 minutes. C. 30 minutes B. 10 minutes D. 60 minutes 7. Technician A says that the air-conditioning system can be charged from the low side while the system is running. Technician B says that the air-conditioning system can be charged from the high side while the system is not running. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 8. Technician A says that the minimum pressure ­recommended for leak testing an R-12 system is 60 psig (414 kPa). Technician B says the minimum recommended ­pressure for leak testing an R-134a system is 50 psig (414 kPa). Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 9. Technician A says that fluorescent tracer dye is easily detected using an ultraviolet lamp. Technician B says that the dye should be removed from the system after leak detection. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 10. Technician A says that a standing vacuum test may be held to check an air-conditioning system for leaks. Technician B says that a standing vacuum test does not reveal how many leaks there are in the system. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

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ASE CHALLENGE QUESTIONS 1. When an air-conditioning system is opened for repairs or service, there is a possibility that  will enter system. A. Air C. Both A and B B. Moisture D. Neither A nor B 2. During initial system evaluation an unknown refrigerant is identified. Which of the following should a ­technician do? A. Treat it like R-134a and recover and recycle it. B. Treat it like R-1234yf and recover and recycle it. C. Purge it into the atmosphere D. Treat it as a contaminated refrigerant. 3. Technician A says that the evacuation process will remove dirt and debris from the refrigerant system. Technician B says that the evacuation process will remove moisture and air from the refrigerant system. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

4. Technician A says that when testing for a refrigerant leak, the electronic leak detector probe should be held against the suspected leak area. Technician B says that the electronic leak ­detector requires routine calibration and probe tip maintenance. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 5. Technician A says that comparing the temperaturepressure relationship of recycled refrigerant is a reliable method for finding noncondensable gas contamination. Technician B says that if the recovery tank pressure is higher than the temperature-pressure relationship chart indicates, the refrigerant is OK to use. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

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JOB SHEET

34

Name ______________________________________ Date ________________________

Analyzing Refrigerant Gas Sample Purity Upon completion of this job sheet, you should be able to diagnose the purity of a vehicle’s refrigerant system. The analyzer measures and displays the purity percentage of the refrigerant being tested, as well as the percentage of air in the sample being tested. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Refrigerant Recovery, Recycling, and Handling. Task #2. Identify - and recover A/C system refrigerant. (P-1) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Yokogawa GA500-Plus Refrigerant Gas Analyzer or similar device Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure The following procedure is for the GA500-Plus Gas Analyzer. Procedures may vary for other models. Always follow the operating instructions that accompany the equipment being used. 1. Connect the purity test unit power cable to the vehicle’s battery. 2. Attach the sample hose to the vehicle’s refrigerant system service fitting. a. Select the R-134a (or the R-12) hose and push the quick-connect coupler onto the fitting on the bottom of the analyzer. Turn the fitting knob to the left to retract the valve activating pin. b. Connect the sample hose service port coupler to the low side (vapor port) of the air-conditioning system and turn the knob to the full right position to open the valve port. 3. Fully depress the purity test unit pump button four times to start the test cycles.

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4. Evaluate the sample using LED indicators and the LCD display. a.  Record refrigerant purity: __________ R-134a __________ R-12 __________ HC __________ R-22 _________ AIR b.  Percent of air contamination  NOTE: Because air is a noncondensable gas, the analyzer ignores its presence in calculating gas concentrations. Consequently, the total of all displays may be greater than 100 percent. 5. To repeat the test, pump the button four times to restart the test cycles. 6. Disconnect the sample hose attached to the vehicle’s R-134a system; push the pump button to purge the refrigerant in the analyzer. 7. Based on the results of this test, what procedure will you use to recover the refrigerant? 

Instructor’s Response 

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JOB SHEET

35

Name ______________________________________ Date ________________________

Refrigerant Leak Detecting with Electronic Leak Detector Upon completion of this job sheet, you should be able to use an electronic leak detector to leak test an air-conditioning system. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: General: A/C System Diagnosis and Repair Task #6. Leak test A/C system; determine necessary action. (P-1) NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING Refrigerant Recovery, Recycling, and Handling. Task # 2. Identify and recover A/C system refrigerant. (P-1) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Manifold and gauge set Dye injector kit Electronic leak detector Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure 1. Locate the vehicle refrigerant system information label under the hood of the test ­vehicle. Determine the type of refrigerant that is used in this system, the recommended charge volume, and the type and amount of refrigerant oil. a.  Type of refrigerant  b.  Refrigerant charge amount  c.  Lubricant type  d.  Lubricant amount 

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2. If label(s) are not present or are unreadable, explain how to identify the refrigerant. Identify the refrigerant. 

3. Explain why this system is being checked for leaks.  4. Operate the air conditioning for approximately 5 minutes. 5. Shut down the system and engine. 6. Review all the instructions supplied with the electronic leak detector. 7. If applicable, connect the detector to a power source. 8. Inspect the system, starting with the compressor discharge line. 9. Move the detector probe over as much of the condenser as possible. Record the results.  10. Move the detector probe over and around each fitting and along the bottom of each hose and line. Record the results.  11. Move the detector probe over the evaporator area, internal and external, as much as possible. If the case duct drain is accessible move the sensor probe to the drain outlet. Record the results.  12. Record the results of any leak detected and list the name of the line or component.     13. Recommend and discuss any repairs that must be made. 

Instructor’s Response     

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JOB SHEET

36

Name ______________________________________ Date ________________________

Air-Conditioning System Unloaded Performance Test Upon completion of this job sheet, you should be able to perform an unloaded air-­ conditioning system performance test and determine whether the system is operating as designed. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: General: A/C System Diagnosis and Repair. Task #3. Performance test A/C system; identify problems. (P-1) Task #5. Identify refrigerant type; select and connect proper gauge set; record temperature and pressure readings. (P-1) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Manifold and gauge set Thermometer Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________Engine type and size _____________________________ Procedure

NOTE: The following procedures outlined are for an R-134a refrigerant system. If this procedure is being performed on a cycling clutch system, all observations should be made as close to the end of the compressor on cycle as possible. Pretest Procedure It is important to prepare and inspect the vehicle prior to beginning the test. 1. Move the vehicle to a shaded area not in direct sunlight and allow it to cool down. The performance test should not be performed until the vehicle has reached ambient air temperature. 2. Inspect the condenser fins and clean them with a soft brush and nonpressurized running water. A condenser that restricts airflow can give the appearance, based on pressure readings, that the system is fully charged when it is actually low on refrigerant. 3. Close all windows and doors. 275 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

4. Open the vehicle hood. 5. Place a fender cover on the vehicle to protect the finish. 6. Remove the protective caps from the high- and low-side service ports. NOTE: Remove the caps slowly to ensure that no refrigerant escapes past a defective service valve, and inspect the O-ring seal on the cap. 7. Ensure that all manifold valves are closed (clockwise) to prevent refrigerant venting from service ports. 8. Turn the low-side hose hand valve fully counterclockwise to retract the Schrader depressor into the service port. 9. Clip on the low-side hose; push firmly until it clicks into place. a.  Turn the low-side hose hand valve fully clockwise to extend the Schrader depressor. 10. Clip on the high-side hose; push firmly until it clicks on. a.  Turn the high-side hose hand valve fully clockwise to extend the Schrader depressor. 11. Place a fan in front of the vehicle to assist in cooling the air-conditioning condenser. 12. Turn the vent fan on high and activate the air-conditioning system in the MAX ­Recirculation mode and set the temperature control to the coldest setting. 13. Next run the engine at 1000 rpm and allow the system to stabilize for 15 minutes. Measure the air temperature leaving the center vents. The unloaded test strips the air in the passenger compartment of heat and humidity as the passenger compartment air is recirculated through the evaporator, allowing for the lowest possible vent temperatures to be achieved. The performance chart (see Figure 7-3) for the unloaded performance test requires that the engine speed be at 1000 rpm (650 rpm) to be accurate. Test Procedure 1. Connect an R-134a recovery/recycling station to the air-conditioning system high-side and low-side pressure test fittings. Record the ambient air temperature approximately 12 in. in front of the vehicle on the R-134a Air Conditioning Work Sheet. 2. With the engine running at 1000 rpm check both the high- and low-side system pressures. If the vehicle is equipped with a rear air-conditioning system, ensure that the rear blower is off and record the result on the R-134a Air Conditioning Work Sheet. 3. Place a thermometer in the center dashboard vent and record the outlet air temperature on the R-134a Air Conditioning Work Sheet. 4. If the vehicle is equipped with a rear air-conditioning system, turn the rear blower on high and place a thermometer in the rear outlet vent and record the outlet air temperature. With the engine running at 1000 rpm check both the high- and low-side system pressures and record the result on the R-134a Air Conditioning Work Sheet. 5. Increase the engine speed to 3000 rpm and measure the low-side system pressure as well as the dashboard center, left, and right corner vent outlet air temperatures and record the results on the R-134a Air Conditioning Work Sheet. NOTE: The pressure gauge readings at 1000 rpm are not comparable to the observations at 3000 rpm. 6. Compare the readings recorded on the R-134a Air Conditioning Work Sheet to the temperature pressure chart in Figure 7-3 on page 236. 276 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

R-134a Air Conditioning Work Sheet Initial Air-Conditioning System Evaluation

NOTE: The following procedures outlined are for an R-134a refrigerant system. If this procedure is being performed on a cycling clutch system, all observations should be made as close to the end of the compressor on cycle as possible. 1. Record the following information obtained with the vehicle running at 1000 rpm Ambient air temperature 12 in. in front of the vehicle High-side pressure (rear air OFF, if equipped) High-side pressure (rear air ON, if equipped) Low-side pressure (rear air OFF, if equipped) Low-side pressure (rear air ON, if equipped) Center duct vent outlet air temperature Left corner duct vent outlet air temperature Right corner duct vent outlet air temperature Rear duct vent outlet air temperature 2. Record the following information obtained with the vehicle running at 3000 rpm: Low-side pressure (rear air OFF, if equipped) Low-side pressure (rear air ON, if equipped) Center duct vent outlet air temperature Left corner duct vent outlet air temperature Right corner duct vent outlet air temperature Rear duct vent outlet air temperature

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After Air-Conditioning System Repair Comparison

NOTE: The following procedures outlined are for an R-134a refrigerant system. If this procedure is being performed on a cycling clutch system, all observations should be made as close to the end of the compressor on cycle as possible. 1. Record the following information obtained with the vehicle running at 1000 rpm Ambient air temperature 12 in. in front of the vehicle High-side pressure (rear air OFF, if equipped) High-side pressure (rear air ON, if equipped) Low-side pressure (rear air OFF, if equipped) Low-side pressure (rear air ON, if equipped) Center duct vent outlet air temperature Left corner duct vent outlet air temperature Right corner duct vent outlet air temperature Rear duct vent outlet air temperature 2. Record the following information obtained with the vehicle running at 3000 rpm: Low-side pressure (rear air OFF, if equipped) Low-side pressure (rear air ON, if equipped) Center duct vent outlet air temperature Left corner duct vent outlet air temperature Right corner duct vent outlet air temperature Rear duct vent outlet air temperature Instructor’s Response     

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JOB SHEET

37

Name ______________________________________ Date ________________________

Maximum Heat Load System Diagnostic Work Sheet Upon completion of this job sheet, you should be able to test the air-conditioning system under maximum heat load while monitoring system pressures and temperatures and be able to analyze system efficiency and identify marginal or failed components in the air-­ conditioning system. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: General: A/C System Diagnosis and Repair. Task #3. Performance test A/C system; identify problems. (P-1) Task #5. Identify refrigerant type; select and connect proper gauge set; record pressure ­readings. (P-1) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Refrigerant manifold and gauge set Thermometer Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure Follow the procedures outlined in the service manual and wear eye protection. 1. Place the vehicle outside in direct sunlight. 2. Start the engine and run it at idle speed. Allow the engine to reach normal operating temperature. 3. Turn on the air conditioning and set the air-conditioning control panel to MAX AC, or select AC and Recirculation mode. 4. Open all doors and set the blower motor speed to HIGH. 5. Allow the air-conditioning system to stabilize for a minimum of 5 minutes. 6. Record the ambient air temperature approximately 1 ft. in front of the condenser in the table that follows.

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7. Record the relative humidity in the table that follows. 8. Connect a refrigerant identifier and determine the type and purity of the sample. a.  Refrigerant identified  b.  Purity of sample  c.  Percent of noncondensable gas (air)  9. Connect the manifold and gauge set to the high and low sides of the air-conditioning system. Measurement Ambient air temperature Relative humidity AC center duct temperature Ambient air temperature to duct outlet temperature difference High-side pressure Low-side pressure Condenser inlet temperature Condenser outlet temperature Condenser temperature difference Evaporator inlet temperature Evaporator outlet temperature Evaporator temperature difference

Specification

Before Repair

After Repair

Minimum 308F*

208F Min 508F Max**

258F Min 158F Max***

*Ambient air to duct air temperature drop1Min 308F **Condenser inlet to outlet temperature drop 5 208F Min 508F Max ***Evaporator inlet to outlet temperature drop 5 258F Min 1 58F Max

Instructor’s Response     

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JOB SHEET

38

Name ______________________________________ Date ________________________

System Evacuation Upon completion of this job sheet, you should be able to evacuate an air-conditioning system. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Refrigerant Recovery, Recycling, and Handling. Task #4. Evacuate and chargeA/C system; add refrigerant oil as required. (P-1) Tools and Materials Vehicle with air-conditioning system in need of evacuation Gauge and manifold set Vacuum pump Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure

1. Connect the gauge manifold hoses to the air-conditioning system service ports. 2. What type connectors are found: On the low-side service port?  On the high-side service port?  3. Observe the gauges. The low-side gauge reads  The high-side gauge reads  NOTE: If pressure is observed in step 2, perform Job Sheet 24 before proceeding with this job sheet. 4. Connect the manifold gauge hose to the vacuum pump. 5. What type connector is found on the vacuum pump?    

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6. Turn on the vacuum pump, open the appropriate hand valves, and evacuate the airconditioning system for the length of time suggested in the service manual,  hr/min. 7. Close the hand valves (opened in step 6) and turn off the vacuum pump. Observe the gauges. What is the reading in psig or kPa? Low Side High Side

Now After 5 Min. After 10 Min. After 15 Min. _____________ _____________ _____________ _____________ _____________  _____________  _____________  _____________ 

8. Explain the conclusion of the results of step 7.     9. Carefully remove the manifold and gauge set hoses, ensuring that no ambient air enters the system, or proceed with Job Sheet 34. Charge A/C system with refrigerant. Instructor’s Response     

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JOB SHEET

39

Name ______________________________________ Date ________________________

Charge Air-Conditioning System with Refrigerant Upon completion of this job sheet, you should be able to charge or recharge an air-­ conditioning system. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Refrigerant Recovery, Recycling, and Handling. Task #4. Evacuate and charge A/C system; add refrigerant oil as required. (P-1) Tools and Materials Manifold and gauge set with hoses Source of refrigerant Small “pound” cans Bulk source Recovery/recycle/recharging system Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure

1. Connect the blue hose from the RRR machine to the low-side port on the vehicle and connect the red hose to the high-side service port of the vehicle’s air-conditioning system. 2. What type connectors are found (R-134a. R-1234yf, or R-12): On the low-side service port?  On the high-side service port?  3. Observe the gauges. The low-side gauge reads  The high-side gauge reads  NOTE: If pressure is observed in step 3, there is refrigerant in the system. Either perform refrigerant recovery before proceeding, or “top off ” the refrigerant as instructed by your instructor following this job sheet if it is a large R-134a system. 4. Connect the yellow service hose to the refrigerant source if required by the type of equipment you are using.

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5. What type of refrigerant are you using as the source? 6. Record the amount of refrigerant that is required for filling the system. This ­information may be found on the vehicle’s refrigerant system information label or in the factory service information for the vehicle. a.  Amount of Refrigerant to be installed in system:  7. Is additional refrigerant oil going to be injected into the system? Yes or No: a.  If yes, what type and amount of oil?  8. Following the equipment manufacturer’s instructions or those outlined in the service manual, as applicable for the type of charging equipment you are using, begin charging procedure with the proper amount of refrigerant required by the manufacturer that was determined in step 6. 9. Once the charging process has completed, observe the gauges. What is the reading in psig and kPa? Low Side High Side

psig _______________  _______________ 

kPa _______________  _______________ 

10. Explain the resultant low- and high-side pressures noted in step 9. (Are they normal?)

11. Carefully remove the service hoses ensuring that no refrigerant is allowed to escape. Instructor’s Response 

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JOB SHEET

40

Name ______________________________________ Date ________________________

Air-Conditioning System Diagnosis Upon completion of this job sheet, you should be able to make basic air-conditioning ­system diagnostic checks. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: General: A/C System Diagnosis and Repair. Task #4. Identify abnormal operating noises in the A/C system; determine necessary action. (P-2) NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Heating, Ventilation, and Engine Cooling Systems Diagnosis and Repair. Task #1. Inspect engine cooling and heater systems hoses; perform necessary action. (P-1) NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Operating Systems and Related Controls Diagnosis and Repair. Task #4. Inspect and test A/C-heater control panel assembly; determine necessary action. (P-3) Tools and Materials A vehicle with an air-conditioning system Selected air-conditioning service tools Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure The following observations are to be made with the engine OFF. Record your procedure and findings in the spaces provided. 1. Inspect the compressor drive belt for condition and tightness. Type belt __________________________ Number of belts __________________________ Procedure  Findings  2. Inspect the water pump direct drive fan (if applicable). Procedure  Findings  3. Inspect all coolant carrying hoses, fittings, and shut-off valve. Procedure  Findings  285 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

4. Inspect all refrigerant-carrying hoses and fittings. Procedure  Findings  5. Inspect all vacuum hoses, fittings, and components. Procedure  Findings  Make the following checks with the engine running and the air-conditioning system controls to MAX cool. Give your procedure and findings in the spaces provided. 6. Check the operation of the compressor clutch. Procedure  Findings  7. Check the operation of the electric cooling fan, if applicable. Procedure  Findings  8. Check blower motor operation; LO, LO-MED, HI-MED, and HI. Procedure  Findings  9. Check for proper airflow from outlets. Procedure  Findings  10. Check refrigerant flow in sight glass, if applicable. Procedure  Findings  11. Carefully check suction and liquid line temperature. Procedure  Findings  12. Check temperature of airflow from dash outlets. Procedure  Findings _______________  _______________  _______________ 

OUTLET Right Center Left

TEMP8F _______________  _______________  _______________ 

TEMP8C _______________  _______________  _______________ 

On conclusion of testing, turn the air-conditioning system OFF and stop the engine. Remove all tools, such as the thermometer used in step 12. Instructor’s Response 

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JOB SHEET

41

Name ______________________________________ Date ________________________

Operation and Maintenance of Refrigerant Recovery/Recycling Equipment Upon completion of this job sheet, you should be able to verify the correct operation and determine the required maintenance of refrigerant-handling equipment. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Refrigerant Recovery, Recycling, and Handling. Task #1. Perform correct use and maintenance of refrigerant handling equipment according to equipment manufacturer’s standards. (P-1) Tools and Materials Owner’s manual for refrigerant recovery/recycling unit Safety glasses or goggles Hand tools, as required Refrigerant recovery/recycling unit Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size ____________________________ Procedure Follow procedures outlined in the service manual for the Refrigerant Recovery/Recycling Unit. 1. Based on the service information for the unit, what is the recommended service interval for the filter(s) and desiccant?    a.  Is the unit equipped with a filter change indicator? Yes or No b.  Does the filter require maintenance? Yes or No 2. Briefly explain the service steps involved in replacing the filter(s).    

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3. Does the vacuum pump require routine oil change maintenance, or is it an oilless pump?    

4. What is the recommended interval for changing vacuum pump oil and how is an oil change performed?    

5. Locate and record the recovery tank date code. a.  What is the current date code on the tank?  b.  What is the date the tank requires recertification?  c.  What color is the tank?  Instructor’s Response     

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JOB SHEET

42

Name ______________________________________ Date ________________________

Check Stored Refrigerant for Noncondensable Gases and Label Container Upon completion of this job sheet, you should be able to test recycled refrigerant for noncondensable gases. Label and store refrigerant. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Refrigerant Recovery, Recycling, and Handling. Task #3. Recycle, label, and store refrigerant. (P-1) Tools and Materials Refrigerant recovery tank containing recycled refrigerant Safety glasses or goggles Hand tools, as required Manifold gauge set or Refrigerant Recovery/Recycling Unit Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size ____________________________ Procedure Prior to checking a recovery tank of recycled refrigerant for noncondensable gases, the tank must first sit at room temperature above 658F (18.38C) for at least 12 hours to stabilize out of direct sunlight. 1. Identify the type of recycled refrigerant.     2. Verify that the manifold set control knobs and hose shut-off valves are closed. 3. Connect the manifold gauge set auxiliary hose (yellow) to the recovery tank low-side outlet (blue).

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4. Using a contact or infrared thermometer, record the tank temperature within 4 in. (10 cm) of the tank. a.  Tank temperature _______________ 8F _______________ 8C 5. Open the low-pressure valve on the tank and low-pressure valve on the manifold line and manifold. Record the recovery tank date code. a.  Tank Pressure _______________ psig _______________ kPa 6. Go to the chart below for the type of refrigerant being tested; compare the tank temperature to the chart. a.  What is the chart pressure listed? b.  Is the tank pressure at or below listed pressure? Yes or No c.  If the pressure is above the limit, attach the refrigerant identifier and test for ­impurities. If no impurities are identified (i.e., alternative refrigerant or HC), proceed to the next step. If the refrigerant pressure is at or below the chart pressure, the ­refrigerant contains no noncondensable gases and may be put back into service. NOTE: Higher pressures indicate the presence of noncondensable gases. 7. Slowly vent the vapor from the top of the recovery tank into the recovery/recycling unit until pressure falls below the limit shown in charts. If the recycled refrigerant is R-134a and the pressure is high after purging, shake the container and wait several minutes, then retest. 8. If the pressure still exceeds the pressure limits in the chart, recycle the entire contents of the container. 9. Label and store refrigerant.

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STANDARD PRESSURE TEMPERATURE CHART FOR R-134A Temperature Pressure Temperature Pressure Fahrenheit PSIG kPa Fahrenheit PSIG kPa

Temperature Pressure Temperature Pressure Celsius Celsius kPa PSIG kPa PSIG

70

76

524

86

102

703

21.1

524

76

30.0

703

102

71

77

531

87

103

710

21.7

531

77

30.5

710

103

72

79

545

88

105

724

22.2

545

79

31.1

724

105

73

80

551

89

107

738

22.8

551

80

31.7

738

107

74

82

565

90

109

752

23.3

565

82

32.2

752

109

75

83

572

91

111

765

23.9

572

83

32.8

765

111

76

85

586

92

113

779

24.4

586

85

33.3

779

113

77

86

593

93

115

793

25.0

593

86

33.9

793

115

78

88

607

94

117

807

25.6

607

88

34.4

807

117

79

90

621

95

118

814

26.1

621

90

35.0

814

118

80

91

627

96

120

827

26.7

627

91

35.6

827

120

81

93

641

97

122

841

27.2

641

93

36.1

841

122

82

95

655

98

125

862

27.8

655

95

36.7

862

125

83

96

662

99

127

876

28.3

662

96

37.2

876

127

84

98

676

100

129

889

28.9

676

98

37.8

889

129

85

100

690

101

131

903

29.4

690

100

38.3

903

131

STANDARD PRESSURE TEMPERATURE CHART FOR R-12 Temperature Pressure Temperature Pressure Fahrenheit PSIG kPa Fahrenheit PSIG kPa

Temperature Pressure Temperature Pressure Celsius Celsius kPa PSIG kPa PSIG

70

80

551

86

103

710

21.1

551

80

30.0

710

103

71

82

565

87

105

724

21.7

565

82

30.5

724

105

72

83

572

88

107

738

22.2

572

83

31.1

738

107

73

84

579

89

108

745

22.8

579

84

31.7

745

108

74

86

593

90

110

758

23.3

593

86

32.2

758

110

75

87

600

91

111

765

23.9

600

87

32.8

765

111

76

88

607

92

113

779

24.4

607

88

33.3

779

113

77

90

621

93

115

793

25.0

621

90

33.9

793

115

78

92

634

94

116

800

25.6

634

92

34.4

800

116

79

94

648

95

118

814

26.1

648

94

35.0

814

118

80

96

662

96

120

827

26.7

662

96

35.6

827

120

81

98

676

97

122

841

27.2

676

98

36.1

841

122

82

99

683

98

124

855

27.8

683

99

36.7

855

124

83

100

690

99

125

862

28.3

690

100

37.2

862

125

84

101

696

100

127

876

28.9

696

101

37.8

876

127

85

102

703

101

129

889

29.4

703

102

38.3

889

129

Instructor’s Response      291 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

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Chapter 8

BASIC TOOLS Basic mechanic’s tool set Manifold and gauge set Flare nut wrench set Springlock coupling tool set Vacuum pump Refrigerant recovery system Test lamp Jumper wire Thermometers (2) Large fan (if required)

Diagnosis of the Refrigeration System

Upon Completion and Review of this Chapter, you should be able to: ■■

■■

■■

Determine if the air-conditioning malfunction is due to an electrical or a mechanical failure.

■■

Determine the “state-of-charge” of refrigerant in the air-conditioning system.

■■

Perform functional testing of the electrical and mechanical systems. Understand general troubleshooting procedures and practices.

Determine if the air conditioner is a cycling clutch or noncycling clutch system.

Air-Conditioning Diagnosis Servicing the automotive air-conditioning system requires a good working knowledge of the purpose and function of the individual components that make up the total system. This includes the action and reaction of both the mechanical and electrical systems and subsystems. Air-conditioning systems vary from vehicle to vehicle by year and model; therefore, no standard diagnostic procedures are possible. All automotive air-conditioning system diagnostics, however, share a few common prerequisites. These prerequisites include: ■■ Determine if the problem is electrical or mechanical, or both. ■■ Determine that the system is properly charged with refrigerant, that it is not undercharged or overcharged. ■■ Determine the type system: cycling clutch or noncycling clutch type. ■■ Perform a functional test of the air-distribution system to determine proper operation. This should be accomplished before proceeding with the diagnosis procedures. The components of the air-distribution system include the blower motor, switches, vacuum lines, air ducts, and mode doors. ■■ Perform an unloaded performance test of the system to verify correct low- and high-side pressures based on the temperature–pressure chart discussed in Chapter 7. NOTE: Consider the ambient temperature and relative humidity conditions.

System Inspection If the air-conditioning system malfunction is due to abnormally high or low system pressures, inspect the following (Photo Sequence 10): 1. Visually check the condenser. Make certain that the airflow is not blocked by dirt, debris, or other foreign matter.

When in doubt, refer to the manufacturer’s specifications. A functional test is another term used for a system performance test that compares readings of the temperature and pressure under controlled conditions to determine if an air-conditioning system is operating at full efficiency. Ducts are tubes or passages used to provide a means to transfer air from one point to another.

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PHOTO SEQUENCE 10

P10-1  Visually check for signs of a refrigerant leak as may be noted by an oil stain.

P10-2  Inspect the hoses for cuts or other obvious damage.

P10-3  Inspect the condenser for debris or other foreign matter.

P10-4  Carefully feel the hoses to determine if there is a temperature differential. Caution: Some hoses may become extremely hot.

P10-5  A restriction will often result in frosting at the point of restriction on the high side.

P10-6  Ensure that the fan(s) are operating properly.

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SERVICE TIP:

This determination may be made by performing a procedure known as an “insufficient cooling quick check.”

FIGURE 8-1  Check for refrigerant leaks.

SPECIAL TOOLS Electronic leak detector Belt tension gauge

A visual inspection often reveals a problem.

FIGURE 8-2  Using a belt tension gauge to check for proper belt tension.

2. Inspect between the condenser and radiator. Check for any foreign matter. Clean, if necessary. 3. Visually check for bends or kinks in the tubes and lines that may cause a restriction. Check the condenser, refrigerant hoses, and joining tubes. 4. Using a proper leak detector (Figure 8-1), check for refrigerant leaks. It is good practice to leak check the air-conditioning system any time it has a low charge or a leak is suspected. It should also be checked for leaks whenever service operations have been performed that require “opening” the system. 5. Check the air-distribution duct system for leaks, restrictions, or binding mode doors. Insufficient airflow may also indicate a clogged or restricted evaporator core. 6. Visually check for proper clutch operation. A slipping clutch may be caused by low voltage due to a loose wire, a defective control device, or improper clutch air gap. 7. Use a belt tension gauge to check for proper drive belt tension. Consult the manufacturer’s specifications for proper belt tension (Figure 8-2).

Air-Conditioning Pressure Diagnostics If you are able to verify a customer complaint of poor passenger compartment cooling, compare the refrigerant system gauge readings to a manufacturer’s published diagnostic information. In some cases a manufacturer may provide a diagnostic graph broken into the pressure zones for the refrigerant system high- and low-side pressures (Figure 8-3). In the following

A tension gauge is a tool for measuring the tension of a belt based on deflection rate.

CAUTION:

Follow specific instructions when using a leak detector.

Remove rings, watches, and jewelry when working on electrical components.

295 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

690 100 620 90

3

550 80 480 70 Low-side

2

415 60 345 50 275 40

1

213 30

4

140 20 70 10 100 700

200 1400

300 2100

400 2750

(psi) (kPa)

High-side FIGURE 8-3  Refrigerant system high- and low-side pressure zone diagnostic graph.

Wires separated inside a connector are not easily detected by visual inspection.

sections conditions 1 through 7, discussed in the Class Manual, may be condensed into four major system operation pressure zones. The following procedure will determine in which zone condition the system is operating. Perform an air-conditioning system performance test and measure the operating efficiency under the following conditions: The ambient air temperature must be at least 608F (168C), no additional air should be flowing across the front of the vehicle during the test, and the vehicle should be parked in the shade or inside the shop. The vehicle windows should be opened to ventilate the interior during the first part of the test. The following test is valid for both R-134a and R-1234yf systems. 1. Connect manifold and gauge set to high-side and low-side service ports on the vehicle. After the vehicle has sat for at least 5 minutes with the engine off, record system static pressures and ambient air temperature. 2. Compare temperature and pressure reading observed to the below data. ■■ Temperature above 608F (168C) and at least 50 psi (345 kPa). ■■ Temperature above 758F (248C) and at least 70 psi (483 kPa). ■■ Temperature above 908F (338C) and at least 100 psi (690 kPa). 3. If the system conditions above were met, proceed to step 4. If the pressures were lower than the above, leak test the system. 4. Close the vehicle doors and windows, but leave the driver’s-side window open approximately 6 inches. Start the engine, turn the A/C ON, set the blower speed to high and select panel (face) discharge, and set the temperature to the coldest setting. Install thermometer in center duct discharge. 5. Allow system to operate for 5 minutes while observing for conditions such as abnormal frost areas and unusual noses. 6. Record: ■■ Dust outlet air temperature ■■ High-side pressure reading ■■ Low-side pressure reading ■■ Relative humidity level 7. Compare data recorded to performance table (Figures 8-4 and 8-5). If the data falls within the ranges specified, the system operation is normal. If the data does not fall within the specified ranges, proceed to the next step.

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Refrigerant Service Port Pressure Ambient Air Temperature

Relative Humidity

Low Side

High Side

Maximum Center Discharge Air Temperature

552658F(132188C)

0–100%

22–29 psi (151–199 kPa)

129–168 psi (888–1157 kPa)

438F ( 68C)

662758F(192248C)

Below 40%

22–28 psi (151–192 kPa)

149–215 psi (1026–1481 kPa)

438F ( 68C)

Above 40%

22–34 psi (151–234 kPa)

152–210 psi (1047–1446 kPa)

468F ( 78C)

Below 35%

22–32 psi (151–220 kPa)

179–220 psi (1233–1515 kPa)

488F ( 88C)

35–50%

22–33 psi (151–227 kPa)

179–225 psi (1233–1550 kPa)

508F (108C)

Above 50%

24–37 psi (165–254 kPa)

179–212 psi (1233–1460 kPa)

558F (138C)

Below 30%

24–36 psi (165–248 kPa)

202–241 psi (1391–1660 kPa)

558F (138C)

30–50%

25–38 psi (172–261 kPa)

202–238 psi (1391–1639 kPa)

658F (188C)

Above 50%

28–40 psi (192–275 kPa)

200–235 psi (1378–1619 kPa)

668F (198C)

Below 20%

28–40 psi (192–275 kPa)

231–270 psi (1591–1860 kPa)

648F (178C)

20–40%

29–42 psi (199–289 kPa)

231–267 psi (1591–1839 kPa)

668F (198C)

Above 40%

31–43 psi (213–296 kPa)

228–270 psi (1570–1860 kPa)

708F ( 218C)

762858F( 252298C)

862958F( 302358C)

9521058F( 362418C)

FIGURE 8-4  An example of an air conditioning performance table of normal operating ranges for R-134a under various ambient temperatures and humidity levels.

AJC Performance Table Ambient Temperature

Relative Humidity

Low-Side Service Port Pressure

High-Side Service Port Pressure

Maximum Left Center Discharge Air Temperature

132188C (552658F)

0–100%

199–261 kPa (29–38 psi)

1233–1481 kPa (179–215 psi)

108C ( 508F)

Less than 40%

220–296 kPa (32–43 psi)

1288–1543 kPa (187–224 psi)

128C ( 528F)

Greater than 40%

227–310 kPa (33–45 psi)

1336–1612 kPa (194–234 psi)

138C ( 558F)

Less than 35%

241–316 kPa (35–46 psi)

1419–1639 kPa (206–238 psi)

138C ( 558F)

35–60%

254–323 kPa (37–47 psi)

1460–1667 kPa (212–242 psi)

148C ( 578F)

Greater than 60%

254–344 kPa (37–50 psi)

1481–1729 kPa (215–251 psi)

178C ( 618F)

Less than 30%

261–337 kPa (38–49 psi)

1522–1750 kPa (221–254 psi)

158C ( 598F)

30–50%

268–358 kPa (39–52 psi)

1550–1798 kPa (225–261 psi)

178C ( 618F)

Greater than 50%

282–385 kPa (41–56 psi)

1591–1860 kPa (231–270 psi)

188C ( 648F)

Less than 20%

275–351 kPa (40–51 psi)

1632–1853 kPa (237–269 psi)

178C ( 618F)

20–40%

289–378 kPa (42–55 psi)

1646–1901 kPa (239–276 psi)

188C ( 648F)

Greater than 40%

310–399 kPa (45–58 psi)

1688–1949 kPa (245–283 psi)

208C ( 688F)

Less than 20%

296–372 kPa (43–54 psi)

1743–1949 kPa (253–283 psi)

188C ( 648F)

Greater than 20%

310–399 kPa (45–58 psi)

1770–1998 kPa (257–290 psi)

208C ( 688F)

Below 30%

330–406 kPa (48–59 psi)

1867–2080 kPa (271–302 psi)

228C ( 708F)

192248C (662758F)

252298C (762858F)

302358C ( 862958F)

362418C ( 9621058F)

422468C (10621158F) 472498C (11621208F)

FIGURE 8-5  An example of an air conditioning performance table of normal operating ranges for R-1234yf under various ambient temperatures and humidity levels.

297 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

A defective ground wire accounts for a high percentage of electrical failures.

Be sure that the test lamp is not defective; that it will light when it is expected to do so.

8. If the high-side and low-side pressures are within the specified ranges but the outlet duct temperature does not, see the Pressure Zone 1 description below for additional information. 9. If the low-side pressure is greater than the specified range, but the high side pressures are within the specified ranges or lower, see the Pressure Zone 2 description below for additional information. 10. If the high-side and low-side pressures are both higher than the specified ranges, see the Pressure Zone 3 description below for additional information. 11. If the low-side pressure is less than the specified range, but the high-side pressure is greater than or within the specified ranges or lower, see the Pressure Zone D description below for additional information.

Pressure Zone 1

SERVICE TIP:

Digital multimeters have internal fuses to protect their circuits. Never connect a meter to a circuit in a series if the possible current level in the circuit could exceed the amperage rating of the internal meter fuse. If in doubt, use a fused jumper lead with a fuse rated at less than the internal meter fuse. This way, if the current draw is higher than expected, the jumper lead fuse will blow.

If the high- and low-side refrigerant pressures fall into the Zone 1 area, the following should be checked. The high- and low-side pressures may be normal or slightly less than normal based on ambient air temperature. If the refrigerant system is not functioning as designed, the following items should be checked for proper operation: ■■ Refrigerant system slightly undercharged ■■ Refrigerant gas contamination ■■ Air duct delivery problem

Pressure Zone 2

If the high- and low-side refrigerant pressures fall into the Zone 2 area, the following should be checked. If the low-side pressure is higher than normal and the high-side pressure is lower than normal, the following items should be checked: ■■ Refrigerant system undercharged ■■ Defective or malfunctioning compressor ■■ Defective or malfunctioning thermal expansion valve

Pressure Zone 3

If the high- and low-side refrigerant pressures fall into the Zone 3 area, the following should be checked. If the low- and the high-side pressures are both higher than normal, the following items should be checked: ■■ Refrigerant system overcharged ■■ Thermostatic expansion valve defective ■■ Condenser cooling fan operation ■■ Restricted airflow across the condenser ■■ Noncondensable air contamination

Pressure Zone 4

If the high- and low-side refrigerant pressures fall into the Zone 4 area, the following should be checked. If the low-side pressure is lower than normal and the high-side pressure is higher than normal, the following items should be checked: ■■ A restriction in the air-conditioning system ■■ Refrigerant system undercharged ■■ Thermostatic expansion valve restricted/defective ■■ Debris in the system, desiccant bag failed

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Defective Components The following is an overview of what the technician may expect if a component of the airconditioning system is found to be defective.

Evaporator

A defective evaporator produces an insufficient supply of cool air. This symptom is often the result of a leak in the evaporator core. Other causes include: ■■ Dirt- or debris-plugged core (clean the core) ■■ Cracked or broken case (replace or caulk the case) ■■ Leaking seal or O-ring (replace the seal or O-ring) ■■ Restricted refrigerant passage ways through the core

Compressor

A malfunctioning compressor will be indicated by one or more of the following symptoms: ■■ Noise, indicating premature failure ■■ Seizure, usually due to oil loss ■■ Leakage, due to defective seals, gaskets, or O-rings ■■ Low suction and low high-side pressure caused by an undercharge of refrigerant or a restriction in the low side of the system ■■ High suction and low discharge pressure usually caused by a defective compressor valve plate or gasket assembly Some noise is to be expected from most compressors and may be considered normal during regular operation. Irregular rattles and noises, however, are an indication of early failure due to loss of oil or broken parts. When the air-conditioning system control calls for cooling and the compressor is inoperative, verify that 12 volts are present at the clutch terminals. To check for compressor seizure: 1. Turn off the engine. 2. De-energize the compressor clutch. 3. Try to rotate the drive plate by hand (Figure 8-6).

Classroom Manual Chapter 8, page 257

Inspect the compressor for visual indications of a loss of oil.

FIGURE 8-6  Rotate the drive plate (armature) by hand.

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NOTE: Compressors that have not been used for a long period of time may “stick.” If this is the case, turning it four or five times in both directions should free it up. If it will not rotate or takes great effort, the compressor may have an internal defect. Also, if there is no resistance to turning, the shaft may be broken internally.

Classroom Manual Chapter 8, page 256

Look for a “frost patch,” indicating a restriction.

SERVICE TIP:

A restricted condenser may also result in excessive compressor discharge pressure. A partial restriction can cause a temperature change and even frost or ice to form immediately after the restriction. In this case, the restriction is serving as a metering device.

If the compressor clutch is slipping, it may be due to an internal compressor problem or it may be due to an incorrect clutch air gap. Before condemning the compressor, determine if the air gap is correct. Low voltage or a defective clutch coil may also cause clutch slipping problems. First, check to ensure that there are at least 12 volts available at the clutch coil. Next, disconnect the clutch coil and one side of the diode, if applicable, then check its resistance. Refer to the manufacturer’s specifications for specific values; however, the resistance should generally be between 3 and 4 ohms (3–4 Ω). Refer to Job Sheet 49 for procedures. Low discharge pressure can be caused by poor internal compressor sealing, such as the valve plate or valve plate gasket set. It can also be caused by a restriction in the compressor or in the low side of the system. Yet another cause of low discharge pressure is an insufficient charge of refrigerant. All possibilities should be explored before diagnosing the problem as a defective compressor.

Condenser

There are three possible malfunctions of a condenser: 1. A leak due to rust and corrosion or by being struck by a sharp object or stone. 2. A restriction if a tube has been bent when struck with an outside object, such as a stone, with insufficient force to cause a leak but sufficient to kink or collapse a tube. 3. Restricted airflow through the condenser caused by dirt, debris, or foreign matter. When the airflow through the condenser is restricted or blocked, high discharge pressures will result. This high discharge pressure may or may not be noticeable on a high-side gauge connected to the vehicle service port depending on the location of the service port. If the gauge is connected before the restriction, high-side gauge pressure will be higher than normal. But if the gauge is connected after the restriction, the high-side gauge reading may be in the low to normal range. Always think about where the gauges are physically connected to the system and what these readings are telling you. Improper gauge reading interpretation can lead to a lengthy and often incorrect diagnosis. NOTE: Though not easily detected, the outlet tube of the condenser may be slightly cooler than the inlet tube. Carefully feel the temperature by hand. It should go from a hot inlet at the top to a warm outlet at the bottom. A proper heat exchange should result in an even gradient across the surface of the condenser. Some technicians prefer the use of a laser-sighted, digital readout (DRO), infrared (IR) thermometer (Figure 8-7) for taking temperature measurements. This type of thermometer provides an immediate and accurate indication of the surface temperature of any object, in 8F or 8C, simply by pointing the thermometer at the object. See Job Sheet 47 at the end of this chapter entitled “Heat Transfer through the Condenser.”

Orifice Tube

Orifice tube failures are often indicated by low suction and discharge pressures. This condition results in insufficient cool air from the evaporator. The common cause of orifice tube failure is a restriction. A less common cause is a clogged inlet screen due to contamination, corrosion particles, or refrigerant desiccant loose in the refrigerant system due to a defective accumulator. Regardless of the cause, the recommended repair is to replace the orifice tube (Figure 8-8) and the defective parts that caused the problem. Moisture contamination can also have similar symptoms and poor performance complaints such as a restricted orifice tube. If a refrigerant system is contaminated with moisture, 300 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 8-7  Using a laser-sighted, digital thermometer for measuring temperature gradient.

A B FIGURE 8-8  An (A) orifice tube with a (B) clogged screen.

the pressure in the system will swing between a vacuum to normal on the low-side gauge and between low to normal on the high-side gauge. The air-conditioning system may operate normally at first, but as the system runs, a no cooling condition may exist. This condition is often described as intermittent air-conditioning operation by the driver. The moisture in the system freezes in the fixed orifice tube (FOT) or thermostatic expansion valve (TXV) and causes a temporary blockage. If moisture is suspected the accumulator assembly must be replaced and the system must be evacuated.

Thermostatic Expansion Valve

Most TXV failures are indicated by the same symptoms as orifice tube failures. Many TXV failures, however, are due to a malfunctioning of the power element. This failure usually results in a closed valve that will not allow refrigerant to enter the evaporator. Regardless of the cause of failure, except for a clogged inlet screen, replacement of the valve is the recommended repair.

Classroom Manual Chapter 8, page 254

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Screen

FIGURE 8-9  Inlet screen of a thermostatic expansion valve (TXV).

The inlet screen of the TXV can also become plugged due to contamination, corrosion particles, or refrigerant desiccant loose in the system due to a defective receiver-drier (Figure 8-9).

Refrigerant Lines

The suction line is usually the largest hose or tube.

The liquid line is usually the smallest hose or tube.

Refrigerant line restrictions are generally indicated by one or more of the following symptoms: ■■ Suction line: A restriction of the suction line causes low suction pressure, low discharge pressure, and little or no cooling. The evaporator is starved of refrigerant. ■■ Discharge line: A restricted discharge line generally causes the pressure relief valve to open to release excess pressure to the atmosphere. Pressure relief valves are generally selfreseating whenever the pressure drops to a predetermined safe level. ■■ Liquid line: A liquid line restriction has the same general symptoms as a suction line restriction—low suction pressure, low discharge pressure, and little or no cooling from the evaporator.

Causes of Failure Following are some of the common causes of failure found in an automotive air-conditioning system: ■■ Leaks; undercharge of refrigerant ■■ High pressure; overcharge of refrigerant in the system, air in the system, excess oil in the system ■■ Poor connections ■■ Restrictions ■■ Contaminants ■■ Moisture ■■ Defective component

Functional Testing A functional test may be performed to determine the operating conditions of the air-­ conditioning control head (Figure 8-10) as well as the air-distribution system. The functional test consists of checking the operation of the blower, heater, and air-conditioning control assembly mode lever. This test also includes comparing mode lever and switch positions in relation to air delivery. 302 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 8-10  A typical air-conditioning system control head.

Diagnosing H-Block Thermostatic Expansion Valve System The ideal ambient temperature to be testing expansion valves is 702858F (212278C). The f­ ollowing test procedure will quickly detect expansion valve malfunctions such as stuck open, stuck closed, or loss of gas charge in the power dome. 1. Connect the manifold and gauge set or charging station to the vehicle refrigerant system service ports and verify the refrigerant charge level. 2. Verify that all vehicle windows and doors are closed. 3. Start the engine and allow the vehicle to idle. 4. Activate the air-conditioning system, set the temperature control to the highest heat setting, turn the blower motor on high, and select Recirculation mode. 5. Allow the vehicle to run until the passenger compartment warms up. This is to put maximum heat load on the refrigerant system and create the need for maximum refrigerant flow through the evaporator (expansion valve will open). 6. If the refrigerant system has a sufficient charge, the high-pressure gauge should be 120–240 psig (827–1655 kPa) and the low-side gauge should read 30–50 psig (207–345 kPa). If pressure levels are correct, go to step 7. If pressures are out of range, replace the expansion valve. 7. If the low-side gauge reading is within the specified range, cool the TXV for 30 seconds by flowing liquid CO 2 (or another suitable super-cold substance) over the exterior of the TXV housing.

WARNING: When working with liquid CO2, wear eye protection, insulated protective gloves, and long sleeves to protect the skin and eyes from serious injury. NOTE: Liquid CO 2 is the preferred method of super cooling the expansion valve and is available from welding supply shops. Ensure that you specify liquid CO 2; otherwise you may receive low-pressure CO 2 gas for beverage dispensing. 8. The low-side gauge reading should drop to 10 psig (69 kPa). If pressure does not drop, replace the expansion valve. 9. Allow the system to stabilize and the TXV to thaw. The low-side pressure should return to 30–50 psig (207–345 kPa). If pressure does not return to these levels, replace the expansion valve. NOTE: If the expansion valve appears to be intermittently sticking, it may be caused by moisture contamination. If moisture contamination is suspected, the receiver-drier needs to be replaced, not the TXV, and the system needs to be thoroughly evacuated. 10. Perform an unloaded system performance test.

Classroom Manual Chapter 8, page 254

Interpreting gauge readings will become “second nature” to the technician.

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Diagnosing Thermostatic Expansion Valve Systems

SPECIAL TOOL Large floor fan

SERVICE TIP:

Gauge readings vary and their application is often a matter of “professional opinion.” Gauge readings should, then, only be used as a guide in diagnostic procedures. Proceed with step 5 for abnormally low lowside gauge readings. Go to step 9 for abnormally high lowside gauge readings.

The following procedure may be followed to diagnose the TXV system performance: 1. Connect the manifold gauge set to the system. 2. Start the engine and adjust the engine speed to fast idle, 1000–1200 rpm. 3. Place a large fan in front of the condenser to substitute for normal ram airflow (Figure 8-11). 4. Operate the air conditioner to “stabilize” the system: a. Adjust all controls for MAX cooling. b. Operate the system for 10–15 minutes. 5. Observe and note the gauge readings. 6. If the low-side gauge reading is abnormally low, place a warm rag (1258F [528C]) around the valve body (Figure 8-12). 7. Observe the low-side gauge. a. If the pressure rises, there is moisture in the system. Correct as required. b. If the pressure does not rise, proceed with step 8. 8. Remove the remote bulb and place it in a warm (1258F [528C]) rag (Figure 8-13).

FIGURE 8-11  Place a fan in front of the vehicle to provide ram air.

FIGURE 8-12  Place a warm rag around the TXV body.

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SERVICE TIP:

FIGURE 8-13  Place the remote bulb in a warm rag.

9. Observe the low-side gauge. a. If the pressure rises, the remote bulb was probably improperly placed. Reposition the bulb, tighten it, and retest the system. b. If the pressure does not rise, proceed with step 10. 10. If the low-side gauge reading, step 4, was abnormally high, remove the remote bulb from the evaporator outlet tube and place it in an ice water (H 2 O) bath. 11. If the low-side pressure drops to normal or near normal, the problem may be: a. Lack of insulation of the remote bulb. Reinstall, insulate, and retest. b. Improperly placed remote bulb. Reposition the remote bulb, insulate, and retest. 12. Conclude the test. a. Turn off all air-conditioning controls. b. Reduce the engine speed and turn off the engine. c. Remove the manifold and gauge set.

Refrigerant System Charge Level Determination Temperature Method There are several methods available for determining the proper charge level of the vehicle refrigerant system. The following test procedure for an FOT air-conditioning system determines the proper refrigerant charge level based on system pressures and the temperature of the high-pressure liquid line. This test procedure is for FOT systems only and is not designed to be used with expansion valve systems. The technician will compare system pressures and monitored line temperature to the FOT charge determination chart (Figure 8-14). Both the procedure and the chart are based on ambient air temperature range of 702858F (212298C) in the service facility.

A CO2 pressure tank equipped with a low-pressure liquid regulator and a venting hose may be used to chill the remote bulb or the internally regulated H-Block TXV by bleeding low-pressure liquid CO2 over the valve or bulb.

SERVICE TIP:

Replace the TXV if it fails the bulb warming/cooling test. If the problem in step 4 was low pressure, check the inlet screen for foreign matter before replacing the valve.

Rock salt (sodium chloride, NaCl) in ice water (H2O) will produce a freezing (328F [08C]) liquid temperature for testing purposes.

Procedure

1. Attach the manifold and gauge set or recovery/recycling/charge station to the vehicle refrigerant service ports. Ambient air temperature must be in the range of  702858F (212298C). 2. Attach a clamp-on thermocouple onto the vehicle high-pressure liquid line just before the FOT inlet point. The closer the temperature is recorded to the FOT inlet, the more accurate the temperature reading will be. 3. Start the engine and run it at idle speed. Turn on the air conditioning and set the A/C control panel to Fresh-Air mode and the temperature level to the coldest setting. 4. Open all doors and set the blower motor speed to HI. 305 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

˚F 200 180 UNDERCHARGED Anything in this area

160 140 120

OP PR

100

ER

A CH

RG

GE AN R E

OVERCHARGED Anything in this shaded area

80 60 40 50

100

150

200

250

300

350

400

450

500

Liquid line pressure (psi) FIGURE 8-14  Fixed orifice tube (FOT) charge determination chart is based on ambient air temperature range of 70 – 858F (21 – 298C).

5. Allow the air-conditioning system to stabilize for a minimum of 5 minutes. 6. Increase the high-pressure liquid line pressure to 260 psig (1793 kPa) by restricting airflow across the air-conditioning system condenser. a. Place a piece of cardboard in front of the air-conditioning condenser. Cover only enough of the condenser to raise and maintain the liquid line pressure at the level specified above. 7. Record the high-pressure gauge reading. 8. Record the high-pressure liquid line inlet temperature just before the FOT. 9. Referring to the Charge Determination Chart, record the ideal high-pressure range for the line temperature recorded in step 8. 10. Compare the pressure recorded in step 7 to the idle pressure range determined in step 9. a. If the refrigerant system is operating in the proper charge range, the refrigerant system is functioning correctly. b. If the refrigerant system is operating in the undercharge range, add 2 oz. of refrigerant (0.057 kg) R-134a to the refrigerant system and repeat steps 5–10. c. If the refrigerant system is operating in the overcharge range, reclaim 2 oz. of refrigerant (0.057 kg) R-134a from the refrigerant system using the recovery/recycling/ charge station and repeat steps 5–10.

Insufficient Cooling: Cycling Clutch Orifice Tube (CCOT) Classroom Manual Chapter 8, page 252

Idle speed is the speed (rpm) at which the engine runs while at rest (idle).

The quick test procedure in CCOT systems helps to determine if the air-conditioning system is properly charged with refrigerant. This test can only be performed if the ambient temperature is above 708F (218C). The quick test can simplify system diagnosis by verifying the problem of insufficient refrigerant. This quick test also eliminates a low refrigerant charge as a source of the problem. The quick test is performed as follows: 1. Start the engine. Allow it to warm at normal idle speed. 2. Open the hood and doors. 3. Select the NORM mode. 4. Move the lever to the full COLD position.

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FIGURE 8-15  Feel the evaporator inlet after the orifice tube.

5. Select HI blower speed. 6. Feel the temperature of the evaporator inlet after the orifice tube (Figure 8-15). 7. Feel the temperature of the accumulator surface when the compressor is engaged. a. Both surfaces (steps 6 and 7) should be at the same temperature. If they are not the same, check for other problems. b. If the inlet of the evaporator is cooler than the suction line accumulator surface or if the inlet has frost accumulation, a low refrigerant charge is indicated. 8. If a low refrigerant charge is indicated, add 4 oz. (113 g) of refrigerant and repeat steps 6 and 7. 9. Add 4 oz. (113 g) at a time until both surfaces feel the same temperature. NOTE: It is normal for an accumulator to sweat if the system is properly charged with refrigerant. It means that the evaporated refrigerant is absorbing heat from the ambient air surrounding the accumulator and suction line. This heat, added to the heat adsorbed in the evaporator, is called superheat and does not cause a change in pressure. Overall sweating, then, does not indicate that there is a restriction in the accumulator.

SERVICE TIP:

If the compressor is cycling, wait until the clutch is engaged.

SERVICE TIP:

Allow the system sufficient time, 5 minutes or so, to stabilize between each addition of refrigerant.

Diagnosing Orifice Tube Systems If the indication is “no cooling” or “insufficient cooling” from the air-conditioning system, inspect the air-conditioning and cooling systems for defects as follows:

Preliminary Checks (All Models)

Inspect the system components before connecting the manifold and gauge set. Procedures for diagnosing the General Motors Cycling Clutch Orifice Tube (CCOT) and Ford Fixed Orifice Tube (FFOT) systems follow. Diagnosing TXV systems is covered later in this chapter.

General Motors CCOT Diagnosis

1. Check to verify that the temperature door strikes both stops when the lever is moved rapidly from hot to cold and cold to hot. 2. Check for a loose, missing, or damaged compressor drive belt. 3. Check for loose or disconnected wiring or connectors.

CAUTION:

Adding refrigerant in this manner should only be done if the system is known to be sound and free of leaks. Adding refrigerant to a leaking system does more harm than good.

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Flexible trailing edge

Radiator support (upper)

Rigid leading edge

Water pump pulley

Front

Spacer

Flex fan assembly Front cross member

A

Motor coolant fan

B

FIGURE 8-16  A typical engine cooling fan: (A) engine driven; (B) electrically driven.

4. Check to see if the cooling fan (Figure 8-16) is running continuously in all air-conditioning modes. NOTE: Make repairs as necessary, and recheck cooling.

Classroom Manual Chapter 8, page 251

5. If items checked in steps 1 through 4 are satisfactory and the system still does not cool: a. Set the temperature lever to full (MAX) cold. b. Move the selector lever to NORMAL A/C. c. Set the blower switch to HI. d. Open the doors and hood. e. Warm the engine at 1500 rpm. 6. Perform a visual check for compressor clutch operation. a. If the clutch does not engage, proceed with the “Compressor Clutch Test.” b. If the clutch engages or cycles, feel the liquid line before the orifice tube (Figure 8-17). c. If the tube is warm, proceed with step 7. d. If the tube is cold, check the high-side tubing for a restriction. NOTE: A restriction will be marked with a drop in temperature or frost spot. If the tubing is restricted, repair, evacuate, and recharge the system.

FIGURE 8-17  Feel the liquid line before the orifice tube.

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7. If the system is equipped with variable displacement compressor, proceed with “Diagnosing Variable Displacement Compressor Orifice Tube Systems.” For all other models, feel the evaporator inlet and outlet tubes. a. If the inlet is colder than the outlet, the system may be undercharged. Check for and repair any leaks; evacuate, charge, and retest the system. If no leaks are found, proceed with “System Charge Test.” b. If the outlet tube is colder than the inlet tube or both tubes are the same temperature, proceed with “Pressure Switch Test.” 8. Normal system performance ranges for a cycling clutch system are 15–35 psig (103.42– 241.32 kPa) on the low side, 145–200 psig (999.74–1378.95 kPa) on the high side, and the center duct vent output temperature should be in the range of 352558F (1.7212.88C).

System Charge Test This test may be performed if cooling is not adequate and the static pressure of both the high and low side are below 50 psig (344.74 kPa) with the system off. While performing the system charge test, watch the high-side gauge for any indication of overcharging, such as excessively high pressure. Discontinue the test if the system pressure exceeds that expected for any given ambient temperature condition. Compare system pressure to the manufacturer’s specifications. The Delta-T method described in Chapter 8 of the Class Manual may also be useful for FOT system diagnosis. (See Job Sheet 45 on “Refrigerant System Charge Level Temperature Method [Delta-T].”) 1. Add a “pound” of refrigerant. Check the clutch cycle rate. a. If the clutch cycles more than eight times per minute (less than every 7 seconds), discharge the system and check for a plugged orifice tube or some other restriction. b. If the clutch cycles less than eight times per minute (more than every 8 seconds), proceed with step 2. 2. Feel the accumulator inlet and outlet tubes (Figure 8-18). a. If the inlet tube is warmer or the same temperature as the outlet tube, add 3–4 oz. (85–113 g) more refrigerant. b. If the inlet tube is colder than the outlet tube, add 3–4 oz. (85–113 g) more refrigerant. Baffle

Refrigerant vapor inlet

Inlet

Outlet

Desiccant bag

Internal tube

Filter assembly Oil bleed hole in tube FIGURE 8-18  A typical accumulator showing inlet and outlet tubes.

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CAUTION:

When adding refrigerant, never exceed the recommended capacity of the system.

Classroom Manual Chapter 8, page 258

3. Feel the inlet and outlet tubes of the accumulator. a. If the inlet tube is, again, warmer or if it is the same temperature as the outlet tube, add 3–4 oz. (85–113 g) more refrigerant. b. If the inlet tube is still colder than the outlet tube, add 3–4 oz. (85–113 g) more refrigerant. 4. Again, feel the accumulator inlet and outlet tubes. a. If the inlet tube is still warmer or at the same temperature as the outlet tube, add 3–4 oz. (85–113 g) more refrigerant. b. If the inlet tube is still colder than the outlet tube, recover the refrigerant and check for a clogged or restricted orifice tube. WARNING: While performing this test, watch for any indication of overcharging, such as excessively high discharge pressure. If high pressures occur, discontinue the test.

Pressure Switch Test

This test may be performed whenever the inlet and outlet tube temperatures are acceptable, but cooling is not sufficient. 1. Using a manifold and gauge set (Figure 8-19), check to determine if the clutch cycles on between 41 and 51 psig (283 and 352 kPa), and cycles off between 20 and 28 psig (138 and 193 kPa). (Refer to Figure 8-33.) a. If cycling is correct, proceed with “Performance Test.” b. If the clutch cycles at pressures too low or too high, replace the pressure cycling switch. 2. If the clutch runs continuously, disconnect the evaporator blower motor wire (Figure 8-20). The clutch should cycle off between 20 and 28 psig (138 and 193 kPa). a. If the pressure drops to below 20 psig (138 kPa), replace the pressure cycling switch. b. If the clutch cycles off, proceed to “Performance Test.” On

Off

FIGURE 8-19  The clutch should cycle (A) on and (B) off within a specified range.

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FIGURE 8-20  Disconnect the blower motor.

Performance Test

To conduct the performance test: 3. Set the temperature lever to full cold, selector to MAX A/C, and place the blower motor switch in the HI position. 4. Start the engine. Allow it to run at 2000 rpm. 5. Close the doors and windows. 6. Place an auxiliary fan in front of the condenser. 7. Allow the system to stabilize, 5-10 minutes. 8. Place a thermometer in the register nearest the evaporator and check the temperature (Figure 8-21). The temperature should be 352458F (1.727.28C) with an ambient temperature of 808F (278C).

An overcharge of refrigerant is generally accompanied by excessive high-side pressure.

FIGURE 8-21  Measure discharge air temperature at the center register.

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Cycling time is a term used to describe the total time from when the clutch engages until it disengages and engages again.

SERVICE TIP:

If none of these conditions exist, the system was overcharged. Recover, evacuate, and recharge following approved procedures.

Slight compressor noises are to be expected.

9. If the outlet temperature is high, check the compressor cycling time. a. Check the cycling clutch switch operation. NOTE: Many of today’s air-conditioning systems use an ambient air temperature sensor that will not allow the compressor to engage if outside temperatures are below a predetermined level, generally 508F (108C). b. If the clutch is energized continuously, discharge the system and check for a missing orifice tube, plugged inlet screen, or other restriction in the suction line. c. If the clutch cycles on and off or remains off for an extended period, discharge the system and check for a plugged orifice tube. Replace the tube, and evacuate, charge, and retest the system. Refer to Figure 8-25 and the manufacturer’s cycling clutch rate for the vehicle.

Diagnosing Variable Displacement Compressor Orifice Tube Systems 1. Connect the gauge set to the system. 2. Use a jumper wire to bypass the cooling fan switch. 3. Start and run the engine at about 1000 rpm. 4. Set the selector lever to NORM A/C and the blower motor switch to the HI position. 5. Measure the discharge air temperature at the center register as shown in Figure 8-21. 6. If the temperature is less than 608F (168C), proceed with step 8; if it is more than 608F (168C), check the pressure at the accumulator (low side). a. If this pressure is 35–50 psig (241–345 kPa), proceed with step 8 (Figure 8-22). b. If the pressure is greater than 50 psig (345 kPa), proceed to step 11. 7. If the accumulator pressure in step 6 was less than 35 psig (241 kPa), add a “pound” can of refrigerant. a. If the pressure is now more than 35 psig (241 kPa), leak test the system. b. If the pressure is still low, discharge the system and examine the orifice tube for a restriction. If it is plugged or otherwise defective, replace the orifice tube, and evacuate, charge, and retest the system. 8. Set the selector lever to the DEF mode. Disconnect the engine cooling fan and allow the compressor to cycle on the high-pressure cut-out switch. a. If a compressor knocking noise is noted on clutch engagement, the system oil charge is high. If this is the case, discharge the system, flush all components, and charge with the appropriate amount of refrigerant and oil.

FIGURE 8-22  Pressure between 35 and 50 psig (241 and 345 kPa).

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FIGURE 8-23  Pressure at the accumulator of 29–35 psig (200–241 kPa).

b. If no compressor noise was heard in step 8a, set the selector lever to MAX cooling. Adjust the blower control to its LO setting. 9. Idle the engine for 5 minutes at 1000 rpm. If the pressure at the accumulator is now 29–35 psig (200–241 kPa), the system is operating properly (Figure 8-23). 10. If the pressure at the accumulator is below 28 psig (193 kPa), discharge the system. Replace the compressor control valve, and evacuate, charge, and retest the system. a. If the pressure is above 36 psig (248 kPa), discharge the system. Replace the compressor control valve, and evacuate, charge, and retest the system. b. If step 10a did not prove effective—the pressure is still above 36 psig (248 kPa)— replace the compressor. 11. In step 6, if the pressure at the accumulator (Figure 8-24) was above 50 psig (345 kPa) and below 160 psig (1103 kPa), discharge the system and check for a missing orifice tube. a. If the orifice tube is not missing, replace the compressor control valve. Evacuate, charge, and retest the system.

CAUTION:

Ra

Replace any lubricant that may have been removed from the air-conditioning system during the refrigerant recovery process plus any that may have been lost due to a leak. One of the major causes of compressor failure is lack of lubricant.

nge FIGURE 8-24  Pressure range of 50–160 psig (345–1103 kPa).

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b. If the condition is not corrected with a new control valve, replace the compressor. 12. If the pressure in step 6 was higher than 160 psig (1103 kPa), the system is overcharged. Discharge, evacuate, charge, and retest the system.

Diagnosing Ford’s fot System FFOT is an acronym for Ford Fixed Orifice Tube.

Proper diagnosis of Ford’s FOT system may be accomplished by observing the clutch cycle rate, time on plus time off, and system pressures. Low and high pressure will vary somewhat between the low and high points as the clutch cycles on and off. Prepared charts (Figure 8-25) are used to compare the system pressures and clutch cycle rate to determine if the system pressures and clutch cycle rate are as specified. Most Ford lines with an electric cooling fan use an electronic module to control the fan and clutch circuits. For electrical troubleshooting and repairs, refer to the manufacturer’s appropriate wiring diagrams for specific model year vehicles. The following diagnosis assumes that the cooling fan and clutch electrical circuits are functioning properly. The accuracy of clutch cycle timing for the FFOT system depends on the following conditions: 1. The in-car temperature must be stabilized at 702808F (212278C). 2. MAX air conditioning with RECIR (recirculating) air must be selected. 3. MAX blower speed must be selected. 4. The engine should be running at 1500 rpm for a minimum of 10 minutes. The lowest pressure noted on the low-side gauge, as observed as the clutch is disengaged, is the low-pressure setting of the clutch cycling pressure switch. Conversely, the pressure

Seconds 30 25

Normal clutch on-time

Total clutch cycle time 100 80

20

60

15

40

10 5

20 60

Seconds 30

80 70 90 100 °F Ambient temperatures

60

80 70 90 Ambient temperatures

100 °F

Normal clutch cycle rate per minute

Normal clutch off-time

Seconds 3

25 20

2

15 10

1

5 60

80 70 90 Ambient temperatures

100 °F

60

80 100 °F 70 90 Ambient temperatures

FIGURE 8-25  Typical diagnostic and testing charts for a cycling clutch system.

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recorded when the clutch first engages is the high-pressure setting for the clutch cycling pressure switch. Compressor clutch cycling will not normally occur if the ambient temperature is above 1008F (388C), and in some instances above 908F (218C), depending on conditions such as relative humidity and engine speed. Also, clutch cycling does not usually occur when the engine is operating at curb idle speed. If the system contains no refrigerant or is extremely low on refrigerant, the clutch may not engage. If, on the other hand, a clutch cycles frequently, it is an indication that the system is undercharged or the orifice tube is restricted.

FFOT System Diagnosis

If poor or insufficient cooling is noted and the system does not have an electrodrive engine cooling fan, proceed to step 2. If it is equipped with an electrodrive engine cooling fan as shown in Figure 8-16, check to determine if the clutch energizes. If the clutch does not energize, check the electrical clutch circuit. 1. If the clutch energizes, determine if the cooling fan operates when the clutch is engaged. a. If it does not, check the cooling fan electrical circuit. b. If the fan operates properly, proceed to step 2. 2. Check for a loose, missing, or damaged compressor drive belt. 3. Inspect for loose, disconnected, or damaged clutch, clutch cycling wires, or connectors. 4. Check the resistor connections, if equipped. 5. Check the connections of all vacuum hoses (Figure 8-26). 6. Check for blown fuses and proper blower motor operation. 7. Be sure all vacuum motors and temperature doors provide full travel. 8. Inspect all control electrical and vacuum connections. NOTE: Repair all items as necessary and recheck the system. 9. If cooling is still inadequate, refer to the pressure-cycle time charts. a. Hook up a manifold gauge set. b. Set the selector lever to MAX A/C and the blower switch to HI. c. Set the temperature lever to full cold. d. Close all doors and windows. 10. Insert a thermometer in the center grille outlet. a. Allow the engine to run for 10–15 minutes at approximately 1500 rpm with the compressor clutch engaged. b. Check and note the discharge temperature. c. Check and record the outside ambient temperature.

Ambient: surrounding air. Ambient temperature refers to surrounding air temperature.

FIGURE 8-26  A vacuum leak can be a source of trouble.

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Ambient air contains moisture in the form of “humidity.”

11. With a watch, time the compressor on and off time. Compare the findings with the appropriate chart. a. If the clutch does not cycle rapidly, proceed with step 15. b. If the clutch cycles rapidly, bypass the clutch cycling switch with a jumper wire. The compressor should now operate continuously. 12. Feel the evaporator inlet and outlet tubes. a. If the inlet tube is warm or if the outlet tube is colder after the orifice tube, leak test the system. Repair leaks, and evacuate, charge, and retest the system. b. If no leaks are found, add approximately 4 oz. (113 g) of refrigerant. 13. Again, feel the inlet and outlet tubes. a. If the inlet tube is colder, add 4 oz. (113 g) of refrigerant. b. Once more, check the inlet and outlet tubes. Continue to add refrigerant in 4 oz. (113 g) increments until the tubes feel equal in temperature and are about 282408F (22 to 48C). c. If, in step 12, the inlet tube was equal to the outlet tube (approximately 282408F [22 to 48C], add 8–12 oz. (226–339 g) of refrigerant (Figure 8-27). d. Check the outlet discharge temperature for a minimum of 508F (108C). 14. If, in step 11, the outlet tube temperature was equal to the inlet tube temperature, 282408F [22 to 48C], replace the clutch cycling switch and retest the system. 15. Feel the evaporator inlet and outlet tubes. a. If the inlet tube is warm or if the outlet tube is colder after the orifice tube, perform steps 12 and 13 to restore the system. b. If the inlet and outlet tubes are at the same temperature, 282408F [22 to 48C], or if the outlet tube after the orifice tube is slightly colder than the inlet tube, check for normal system pressure requirements. 16. If the compressor cycles within limits, the system is functioning properly. a. If the compressor cycles on high or low pressures, on above 52 psig (359 kPa) and off below 21 psig (145 kPa), replace the clutch cycling switch and retest the system.

FIGURE 8-27  Typical “pound” cans actually contain 12 oz. (339 g) of refrigerant.

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FIGURE 8-28  Compressor cycles off at 21–26 psig (145–179 kPa).

b. If the compressor runs continuously, disconnect the blower motor wire. Check for the compressor cycling OFF at 21–26 psig (145–179 kPa) suction pressure (Figure 8-28). c. If so, reconnect the blower motor wire. The system is functioning properly. d. If the suction pressure fell below 21 psig (145 kPa) when the blower motor wire was disconnected, replace the clutch cycling switch and retest the system.

Poor Compressor Performance Refer to the FFOT chart (see Figure 8-25). Some of the other problems relating to poor compressor performance include: ■■ Clutch slippage ■■ Loose drive belt ■■ Clutch coil open ■■ Dirty control switch contacts ■■ High resistance in clutch wiring ■■ Blown fuse or open circuit breaker Additional problems associated with compressors include: ■■ Cycling switch ■■ Clutch seized ■■ Accumulator refrigerant oil bleed hole-plugged refrigerant leaks

Classroom Manual Chapter 8, page 258

Customer Care: Customers often want a “quick fix” at the lowest possible price. Do not sacrifice your integrity as a technician and succumb to customer demands. One example of this is the use of refrigerant stop-leak products to seal refrigerant leaks that are difficult to find or expensive to repair. These products can potentially damage service equipment and system components. In the end, neither the technician nor the customer will be satisfied.

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case study

Terms to Know Cycling time Ducts Functional test Idle speed Tension gauge

The customer complains that the air conditioning blows warm air. Recent service history shows that the air-conditioning compressor, receiver dryer, and condenser had been replaced. The technician attached a manifold and gauge set to the air-conditioning system and found low-side pressure to be 40 psi and high-side pressure to be 450 psi after the air conditioning was operated for a few minutes. First the technician recovered and recharged the system with the amount of refrigerant specified by the manufacturer to verify that the system had not been overcharged during the previous services. But the pressures did not change. The technician inspected for debris in front of the condenser and between the condenser and the radiator. Next the technician placed a shop fan in front of the vehicle and sprayed the condenser with water. The high-side

pressure immediately dropped to 260 psi. The technician checked to see if the cooling fan was being commanded on and determined that the cooling fan was not coming on when a high-pressure condition existed in the airconditioning high side. Upon further diagnosis the fan control module was found to be faulty and was replaced. Once the repair was made the system pressures were 26 psi on the low side and 220 psi on the high side and the air-conditioning system functioned properly. This case is an example of how something as simple as checking the operation of the electric cooling fan can be overlooked. If all the causes of a system malfunction condition are not checked it may lead to the misdiagnosis, as was indicated by the previous repairs. This was a summary of an actual case posted on http://www.iATN.net.

ASE-STYLE REVIEW QUESTIONS 1. The high- and low-side pressures may be normal or slightly less than normal based on ambient air temperature. If the refrigerant system is not functioning as designed, the following items should be checked for proper operation: A. Air duct delivery C. Refrigerant gas problem contamination B. Refrigerant system D. Refrigerant slightly overcharged system slightly undercharged 2. A technician is diagnosing a system with a poor cooling complaint and both the high-side and low-side pressure readings are much higher than normal. Technician A says that this could be the result of leaves or debris blocking air flow through the condenser. Technician B says that the vehicle’s air-conditioning system may be undercharged. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 3. Technician A says that low suction and discharge pressure may indicate a low refrigerant charge. Technician B says that low suction and discharge pressure may indicate a restriction in the system.

Who is correct? A. A only B. B only

C. Both A and B D. Neither A nor B

4. Technician A says that a liquid line restriction has the same general symptoms as a suction line restriction. Technician B agrees, adding, “An undercharge of refrigerant also has the same symptoms.” Who is correct? C. Both A and B A. A only B. B only D. Neither A nor B 5. Technician A says that air is a noncondensable gas. Technician B says that air collects in the evaporator during the OFF cycle of the air-conditioning system. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 6. Technician A says that moisture in the system can cause poor or no cooling. Technician B says that moisture in the system can cause harmful acids. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

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7. Technician A says that a restriction in the suction line will cause excessive high-side pressure. Technician B says that a restriction will result in a pressure change, usually marked by frost or ice. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 8. Technician A says that if the orifice tube is missing, the low-side pressure will be low. Technician B says that if the orifice tube is plugged with debris, low-side pressure will be high. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

9. A manifold and gauge set is attached to an operating air conditioner. The low-side gauge reading is too high and the high-side reading is too low. What could be the problem? A. Refrigerant overcharge B. Insufficient refrigerant C. Expansion valve stuck open D. Defective compressor 10. Technician A says that the minimum flow test on a TXV is made by wrapping the remote bulb in a warm rag. Technician B says that a maximum flow test may be made on a TXV by immersing the remote bulb in ice water (H 2 O). Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

ASE CHALLENGE QUESTIONS 1. Which of the following could cause very low pressures on the low side of a system equipped with an expansion valve? A. Expansion valve stuck closed B. Expansion valve stuck open C. Compressor valves not sealing D. Compressor clutch inoperative

4. An R-134a system has excessively high low-side and normal to low high-side system pressures. Which of the following is the most likely cause? A. A restricted expansion valve B. A defective compressor C. Restricted air flow across condensor D. The refrigerant system is overcharged

2. All of the following may cause a low-pressure gauge to go into a vacuum, except: A. Clogged screen in the metering device B. Clogged screen in the accumulator C. Clogged screen in the receiver-drier D. Thermostatic expansion valve stuck closed

5. An R-134a expansion valve system that is properly charged has the following gauge readings, high-side 165 psig and low-side 40 psig and the ambient air temperature is 858F . Which of the following is the most likely cause? A. A restricted receiver drier B. A restricted condenser C. An out of adjustment temperature blend door D. A stuck open expansion valve

3. An R-134a system has both excessively high low-side and high-side system pressures. Which of the following is the most likely cause? A. An air dust delivery system problem B. The refrigerant system is undercharged C. A restriction in the evaporator core D. The refrigerant system is overcharged

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43

JOB SHEET Name ______________________________________ Date ________________________

Inspect the V-Belt Drive Upon completion of this job sheet, you should be able to visually check the compressor drive V-belt and check its tension. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: ­Refrigeration System Component Diagnosis and Repair. Task #1. Inspect and replace A/C compressor drive belts, pulleys, and tensioners; determine necessary action. (P-1) Tools and Materials A vehicle with V-belt drive Service manual Belt tension gauge Describe the vehicle being worked on. Year ______________________ Make ______________________ Model ______________________ VIN ______________________________ Engine type and size _____________________________ Procedure

1. List the different belts, and their purpose.    2. Visually inspect the belts and describe the condition of each.    3. Check the tension of the A/C belt. According to specifications, the tension should be _______________. The tension is _______________. 4. Based on the inspection above, what is your recommendation?    5. What procedure would you follow to adjust the belt tension?    Instructor’s Response  

 



  321

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44

JOB SHEET Name ______________________________________ Date ________________________

Inspect the Serpentine Drive Belt Upon completion of this job sheet, you should be able to visually check the compressor ­serpentine drive belt and check its tension. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: ­Refrigeration System Component Diagnosis and Repair. Task #1. Inspect and replace A/C compressor drive belts, pulleys, and tensioners; determine necessary action. (P-1) Tools and Materials A vehicle with serpentine drive belt Service manual Belt tension gauge Describe the vehicle being worked on. Year _______________________ Make ____________________ Model ____________________ VIN ________________________________ Engine type and size _________________________ Procedure

1. If more than one belt, list the different belts and their purpose(s). __________________   2. Visually inspect the belt(s) and describe its (their) condition. _______________________   3. Check the tension of the belt(s). According to specifications, the tension should be _______________. The tension is _______________. 4. Based on the above inspection, what is your recommendation? _____________________   5. What procedure would you follow to adjust the belt tension?   Instructor’s Response  

 



  323

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JOB SHEET

45

Name ______________________________________ Date ________________________

Refrigerant System Charge Level Temperature Method (Delta-T) Upon completion of this job sheet, you should be able to test the air-conditioning system for proper refrigerant charge level while monitoring system pressures and temperatures. The following procedure is for a fixed orifice tube (FOT) system only and is not designed to be used with an expansion valve system. FOT charge determination chart is based on ambient air temperature range of 702858F (212298C). NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: General: A/C System Diagnosis and Repair. Task #3. Performance test A/C system; identify problems. (P-1) Task #5. Identify refrigerant type; select and connect proper gauge set; record temperature and pressure readings. (P-1) Tools and Materials Late-model vehicle with an FOT refrigerant system Service manual or information system Safety glasses or goggles Hand tools, as required Refrigerant manifold and gauge set Clamp-on thermocouple and Charge Determination Chart Digital multimeter Thermometer Describe the vehicle being worked on. Year _______________________ Make ____________________ Model ____________________ VIN ________________________________ Engine type and size _________________________ Procedure

1. Attach manifold and gauge set or recovery/recycling/charge station to vehicle refrigerant service ports. Ambient air temperature must be in the range of 702858F (212298C). 2. Attach a clamp-on thermocouple onto the vehicle high-pressure liquid line just before the FOT inlet point. The closer the temperature is recorded to the FOT inlet the more accurate your temperature reading will be. 3. Start engine and run at idle speed. Turn on air conditioning and set AC control panel to Fresh-Air mode and temperature level to the coldest setting. 4. Open all doors and set blower motor speed to HI.

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5. Allow air-conditioning system to stabilize for a minimum of 5 minutes. 6. Increase high-pressure liquid line pressure to 260 psig (1793 kPa) by restricting airflow across air-conditioning system condenser. a. Place a piece of cardboard in front of the air-conditioning condenser. Cover only enough of the condenser to raise and maintain the liquid line pressure at the level specified above. 7. Record the high-pressure gauge reading.    8. Record the high-pressure liquid line inlet temperature just before the FOT.   9. Referring to the Charge Determination Chart, record the ideal high-pressure range for the line temperature recorded in step 8.  10. Compare the pressure recorded in step 7 to the idle pressure range determined in step 9. a. If the refrigerant system is operating in the proper charge range, the refrigerant system is functioning correctly. b. If the refrigerant system is operating in the undercharge range, add 2 oz. of refrigerant (0.057 kg) R-134a to the refrigerant system and repeat steps 5–10. c. If the refrigerant system is operating in the overcharge range, reclaim 2 oz. of ­refrigerant (0.057 kg) R-134a from the refrigerant system using the recovery/­ recycling/charge station and repeat steps 5–10. Measurement A/C center duct temperature High-side pressure Low-side pressure High-pressure liquid line inlet Temperature just before FOT Low-pressure liquid line outlet Temperature just after FOT FOT inlet temperature minus FOT Outlet temperature Refer to the Charge Determination Chart. Record the ideal high-pressure range

Specification

Before Repair

After Repair

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Charge Determination Chart Deg. F 200˚ 180˚ UNDERCHARGED Anything in this area

160˚ 140˚ 120˚

OP PR

100˚

ER

A CH

RG

GE AN R E

OVERCHARGED Anything in this shaded area

80˚ 60˚ 40˚ 50

100

150

200

250

300

350

400

450

500

Liquid line pressure (psi)

Instructor’s Response  

 



 

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JOB SHEET

46

Name ______________________________________ Date ________________________

Inspect the Condenser Upon completion of this job sheet, you should be able to visually check the air-conditioning system condenser for proper airflow. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Refrigeration System Component Diagnosis and Repair. Task #7. Inspect A/C condenser for airflow restrictions; perform necessary action. (P-1) Tools and Materials An air-conditioned vehicle Contact thermometer or infrared thermometer Describe the vehicle being worked on. Year ______________________ Make _____________________ Model _____________________ VIN ________________________________ Engine type and size _________________________ Procedure

1. Visually inspect the air-conditioning system and describe its overall condition.   2. In a well-ventilated area, start the engine, place the transmission in park, and turn on the air-conditioning system to MAX cooling. If a standard transmission, place in ­NEUTRAL and chock the wheels. Describe your procedure for accomplishing this step.   WARNING: Take care not to come into contact with moving parts, such as fan blades or belts, and heated metal, such as the exhaust manifold, when performing steps 3 through 5. In addition, air-conditioning lines may be very hot. 3. Carefully place your hand on the condenser near the refrigerant inlet. Describe what you feel. Check and record the temperature.    4. Carefully place your hand on the condenser near the refrigerant outlet. Describe what you feel. Check and record the temperature.    329 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

5. When moving your hand across the condenser, refrigerant inlet to outlet, do you feel a change in temperature? If so, describe the change. Check and record the temperature at various locations.    6. Based on the inspection above, what is your recommendation?    7. What procedure would you follow to increase the airflow across the condenser?   Instructor’s Response  

 



 

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47

JOB SHEET Name ______________________________________ Date ________________________

Heat Transfer through the Condenser Upon completion of this job sheet, you should be able to test heat transfer through the airconditioning condenser assembly and determine if there is an internal blockage. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: General: A/C System Diagnosis and Repair. Task #1. Identify and interpret heating and air-conditioning concerns; determine necessary action. (P-1) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Test vehicle Infrared noncontact thermometer DMM and temperature probe Describe the vehicle being worked on. Year ______________________ Make _____________________ Model _____________________ VIN ________________________________ Engine type and size _________________________ Procedure

1. First, record all the temperatures at the condenser locations listed in the chart below before starting the vehicle. 2. Next, start the engine and run it at about 1000 rpm. 3. Turn the vent fan on high and activate the air-conditioning system in the MAX “Recirculation” mode; set temperature control to the coldest setting. 4. Record the temperatures at the various locations across the condenser and time intervals indicated. Temperature prior to Starting

Temperature after 1 Minute

Temperature after 5 Minutes

Temperature after 10 Minutes

Condenser upper left corner Condenser lower left corner Condenser center Condenser upper right corner Condenser lower left corner Condenser upper hose (compressor discharge line) Condenser lower hose (liquid line)

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5. What kind of heat transfer process does the condenser use?    6. Which condenser hose becomes hot first?  Why?    7. How does heat flow through the condenser?    8. On the graph below show how heat flows through the condenser and indicate where the refrigerant inlet and outlet lines are located.

9. Were any blockages to the refrigerant flow through the condenser noted?      Instructor’s Response  

 



 

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JOB SHEET

48

Name _______________________________________ Date ________________________

Remove and Replace Condenser Assembly Upon completion of this job sheet, you should be able to remove and reinstall the condenser, measure oil quantity, and determine the necessary action. NATEF Correlation NATEF MAST Correlation: HEATING AND AIR CONDITIONING: Refrigeration System Component Diagnosis and Repair. Task #13. Remove, inspect, and reinstall condenser; determine required oil quantity. (P-2) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Describe the vehicle being worked on. Year _______________________ Make ____________________ Model ____________________ VIN ________________________________ Engine type and size _________________________ Procedure Access to the condenser assembly is gained by following the procedures outlined in the appropriate service manual. The following procedure is typical and assumes the procedure for access to the condenser is available. Ensure that the engine is cold and wear eye protection. 1. Recover the refrigerant. 2. Remove the hood hold-down mechanism and any other cables or hardware that inhibit access to the condenser. 3. Remove the hot-gas line at the top of the condenser. 4. Remove and discard any O-rings. 5. Remove the liquid line at the bottom of the condenser. 6. Remove and discard any O-rings. 7. Remove and retain any attaching bolts or nuts holding the condenser in place. 8. Lift the condenser from the car. 9. Drain the oil from the evaporator into a calibrated cup. How much if any oil was removed?

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10. For replacement, reverse the preceding procedure. How much oil does the manufacturer service information recommend adding to the system as part of the repair? 11. Evacuate the system, does it hold a vacuum for 5 minutes after the vacuum pump is turned off? What does this tell you? 12. Charge the system with refrigerant. How much refrigerant does the system require?

Instructor’s Response  

 



 

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Chapter 9

BASIC TOOLS Basic technician’s tool set

Compressors and Clutches

Refrigerant recovery equipment Manifold and gauge set with hoses Safety glasses/goggles Graduated container Funnel Fender covers

Upon Completion and Review of this Chapter, you should be able to: ■■

■■

■■

Identify the various makes and models of compressors used in automotive air-conditioning service.

■■

Check and correct the oil level in various models of compressors.

■■

Leak test and replace shaft seals in various models of compressors.

■■

Leak test and correct shell and fitting leaks of various models of compressors. Troubleshoot and replace various types of compressors. Troubleshoot and make mechanical repairs to clutch coils and rotor assemblies.

The compressor (Figure 9-1) is thought of as the heart of the automotive air-conditioning system. Without the compressor, the system would not function. Actually, all five components of the system are essential if the system is to function properly. In addition to the connecting hoses and fittings, these five components are the compressor, condenser, metering device, evaporator, and accumulator or receiver-drier. This chapter covers the compressor and clutch. The other components of the system are covered in detail in other chapters of this manual as well as the Classroom Manual. Refer to the index of either manual for further reference.

Proper refrigerant is also essential for an air-conditioning system.

Compressor There are over a dozen manufacturers of compressors with hundreds of different models and configurations available for use on the modern automobile. Some that are still in use date back to 1961. Others, which are seldom found, have been discontinued generally because of size and weight.

Compressor Clutch There are various designs and manufacturers of compressor clutch assemblies today. This chapter highlights some of the models available and how to service the compressor clutch and coil assembly on those models. It is important, however, to cover in general terms how to inspect and diagnose a compressor clutch assembly, regardless of the model of compressor you are working on.

Testing Compressor Clutch Electrical Circuit Air-conditioning compressor clutch electrical circuits incorporate a clamping diode to save the electrical circuit from voltage spikes. It is imperative that this diode be checked any time a compressor or clutch assembly is replaced or if a fault was found on the electrical engagement circuit. A faulty diode will lead to the premature failure of the control module if not detected (Figure 9-2).

Classroom Manual Chapter 9, page 281

Classroom Manual Chapter 9, page 285

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SERVICE TIP:

Prior to testing the compressor clutch operation you should verify that the compressor is not seized. One way to do this is with the engine off; grasp the front of the compressor clutch and see if you can turn it by hand, and do not forget to wear safety glass. Also, if the compressor has not been operated for some time a layer of rust may form between the clutch halves and may become dislodged when the compressor engages creating an eye injury hazard.

FIGURE 9-1  Some of the many compressors that have been used over the years.

A digital storage oscilloscope or a digital multimeter with a MIN/MAX function may be used to detect excessive voltage spikes when the compressor is shut off. Generally, the voltage spike should not exceed 60 volts. WARNING: If the vehicle is equipped with an air bag, refer to the appropriate service information under the supplemental passive restraint system to avoid accidental air bag deployment and the possible bodily harm that could result.

Clutch Test

If the clutch is not operational, check the condition of the wiring and verify that the ­system contains the proper amount of refrigerant. Connect a jumper wire with an in-line fuse ­(Figure 9-3) between the positive (1) battery terminal and the clutch coil lead. If the clutch does not energize, proceed with step 1. If the clutch energizes, proceed with step 2. 1. Connect a jumper wire from the clutch coil to an engine ground (2). If the clutch does not energize, remove and repair it as necessary.

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Fuse

Fuse 30 A/C compressor clutch relay 87

PCM Relay control circuit

Bidirectional zener diode A/C compressor clutch coil

FIGURE 9-2  Wiring diagram for an air-conditioning clamping diode.

FIGURE 9-3  A typical jumper wire. The in-line fuse guards against an accidental short circuit.

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FIGURE 9-4  Jump across the pressure switch connector.

2. If the clutch operates but cooling is not sufficient, allow the system to operate for a few minutes and check the low-side pressure at the accumulator access fitting. a. If the pressure is above 50 psig (345 kPa), proceed with step 3. b. If the pressure is below 50 psig (345 kPa), proceed with step 4. 3. Connect a jumper wire across the pressure switch connector (Figure 9-4). a. If the compressor operates, the switch is defective. Replace the switch and retest the system. b. If the compressor does not operate, check for an open or a short circuit between the switch and clutch. 4. Connect a high-pressure gauge and check the high-side pressure. a. If the high-side pressure is above 50 psig (345 kPa), discharge the system and check for a plugged orifice tube or a restriction in the high side. b. If the high-side pressure is below 50 psig (345 kPa), the refrigerant charge is lost. Leak test, repair, evacuate, recharge, and retest the system. Clutch Diode.  A strong electromagnetic field is generated when electrical power is applied to the clutch. When this power is disconnected, the magnetic field collapses and creates highvoltage spikes. These spikes, harmful to the delicate electronic circuits, must be eliminated. A diode, across the clutch coil, provides a path to ground for the electrical spikes as power is interrupted. This diode is usually taped inside the wiring harness across the 12-volt and ground leads (Figure 9-5). Typical procedures for testing a diode are given in Photo Sequence 11. The diode may also be tested using a digital multimeter (DMM) following the procedures outlined in the instructions included with the meter. From clutch control Clutch coil

Diode

FIGURE 9-5  A diode in the clutch circuit prevents electrical spikes.

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PHOTO SEQUENCE 11 Bench Testing the Compressor Clutch Coil and Diode The following procedure may be followed by technicians using a digital ohmmeter. Many digital ­multimeters (DMM), however, have a “short cut” method for testing a diode. Follow instructions included with the DMM. If either the clutch coil or the diode fails the test, it is defective and must be replaced.

P11-1  Before bench testing an inoperative clutch coil, check for voltage present at the connector with the coil disconnected and controls set for COOL. NOTE: If 12 volts are available, proceed with the bench test, step 2. If 12 volts are not present, the problem is probably neither the clutch coil nor the diode.

P11-2  Carefully cut and remove the tape to expose the diode leads to the clutch coil.

P11-3  Isolate the diode by disconnecting one lead from the clutch coil.

P11-4  Connect an ohmmeter to the clutch coil leads or from the coil lead to ground, as applicable. Note the resistance. NOTE: 0 Ω indicates that the coil is shorted. Infinite (O.L.) Ω indicates that the coil is open.

P11-5  Connect an ohmmeter to the diode. Note the resistance. NOTE: If your meter is equipped with a diode test setting, use this setting instead of the ohm’s setting for more accurate results. The diode setting reading is generally 0.7 volt in one direction and 0 volts or open in the other direction.

P11-6  Reverse the ohmmeter leads to the diode and, again, note the resistance. NOTE: There should be low ohms (due to internal resistance of the diode) when the ohmmeter is connected in one direction and infinite ohms resistance when connected in the other direction.

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Compressor Clutch Amperage Draw and Resistance Test

SERVICE TIP:

If the frictional surface of the clutch plate or rotor shows signs of warpage due to excessive heat, that part should be replaced. Slight scoring is normal; if either assembly is heavily scored, however, it should be replaced. Compressors are designed to pump vapor only. Liquid may cause severe damage. A shaft seal refers to the compressor shaft seal, which is an assembly consisting of springs, snaprings, O-rings, and ceramic seal. They allow the shaft to turn without the loss of refrigerant or oil.

SERVICE TIP:

Check component prices. It is often less expensive to replace the compressor assembly than to replace only the compressor clutch assembly.

1. Visually check the coil for loose connections or cracked insulation. 2. Inspect the clutch plate and hub assembly. Check for signs of looseness between the plate and hub. 3. Check the rotor and bearing assembly. With the belt removed, the clutch pulley should spin smoothly without roughness. 4. Check the bearing for signs of excessive noise, binding, or looseness. Replace the bearing, if necessary. 5. Check for oil on the friction surface. If oil is present, the compressor shaft seal is leaking and the compressor or seal must be replaced. 6. Check for a proper clutch air gap. Some compressor clutches use spacer shims to adjust this air gap. 7. Locate the air-conditioning compressor clutch wiring diagram for the vehicle you are servicing, as well as the amperage draw and resistance specifications for the compressor clutch coil. 8. Ensure the ignition switch is in the OFF position and remove the air-conditioning compressor clutch relay. 9. Using a digital multimeter (DMM) set to the DC ampere scale, connect the meter leads in series across the contact point circuit of the relay connector (these are the larger cavities). On an ISO relay connector this would be terminal #30 and terminal #87. 10. Start the engine and select air-conditioning MAX mode. Record the amperage (I) draw and compare it to specifications, generally 2–3 amperes at 12 volts. 11. Turn the engine off and replace the relay. 12. Set your DMM to the DV volt scale and connect it in parallel across the compressor clutch connector. 13. Start the engine and select air-conditioning MAX mode. Record the voltage drop and compare it to the battery voltage. The voltage drop and battery voltage should be within 0.5 volts of each other. Example: voltage drop 12.1 volts and battery voltage of 12.6 volts. If the voltage drop to battery voltage comparison is greater than specified, inspect for high circuit resistance. It should be noted that a clutch failure may be due to other system failures such as a compressor that is binding, higher-than-normal high-side system pressure, excessive oil in the air-conditioning system, as well as a loose drive belt or faulty belt tensioner.

Compressor Identification When servicing a compressor, it is important to be able to identify its type, manufacturer, and model number. This is especially true for identifying replacement parts, such as a compressor shaft seal. It is, perhaps, equally important if it is necessary to replace the compressor. Following is a brief overview, in alphabetical order, of most of the compressors that are currently available, new or rebuilt. Customer Care: While under the hood servicing a vehicle, make a point of using a shop towel to wipe off information labels and major components and shrouds. If a customer opens the hood to inspect the vehicle after he picks it up, it is a sign to him that someone who cares has worked on it.

Diagnosis of Compressor Noise

When attempting to diagnose air conditioning–related noises, it is important to know when the noise occurs and under what operating and temperature conditions. Noises related to the air-conditioning compressor are often misleading. Conditions that effect compressor noise 340 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

are vehicle speed, engine speed, engine temperature, weather conditions, and engine load, to name a few. Drive belt noise is speed sensitive and depending on belt tension can often be misdiagnosed as compressor noise. Drive belt tension can cause a noise when the compressor clutch is engaged, which may not be present when the compressor clutch is disengaged. Always check drive belt condition and tension before proceeding with compressor noise diagnosis. It is important to select a quiet area and to duplicate the complaint conditions in order to precisely locate the source of the noise. Turn the air conditioning on and off several times and listen to the compressor. Use an engine stethoscope (Figure 9-6), an electronic ear, or a long screwdriver with the handle held to your ear to aid in localizing the area that the noise is emanating from. Verify that the compressor clutch air gap (Figure 9-7) is set to specifications and that the pulley and clutch plate is properly aligned. In addition, make sure that the compressor clutch field coil is securely mounted to the compressor assembly. It is possible to duplicate high ambient air temperature conditions by restricting airflow across the condenser and listening for unusual noises. By restricting airflow across the condenser with a piece of cardboard, high-side discharge pressure can be increased. Do not allow high-side pressure to increase above 400 psig (2760 kPa) or system damage may result. Sometimes a high-pressure relief valve will open prior to its designed pressure relief point, generating a very loud high-pitched noise. If the relief valve is the source of the noise, the refrigerant will have to be recovered from the system and the valve will have to be replaced. If the valve still does not seat properly after being replaced, the compressor assembly will have to be replaced. Inspect the refrigerant hose and line routing and points of interference, and verify that the mounting brackets are secure to eliminate line vibration as a cause of noise concern ­(Figure 9-8). At this time also inspect the lines for kinks and sharp bends that could cause a point of restriction and increased operational noise. Internal compressor noises come from a variety of sources. Swash plate compressors can develop excessive internal clearance due to lack of lubrication, refrigerant overcharge, or from normal wear over time. It is possible to check for abnormal wear between the swash

SERVICE TIP:

Some service procedures, such as replacing the air-conditioning compressor clutch coil assembly and bearing, can be performed on the vehicle if space permits.

SERVICE TIP: A running design change

is a design change made during a current model/year production.

FIGURE 9-6  An engine stethoscope can aid in localizing the area the noise is emanating from.

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FIGURE 9-7  Verify that the AC compressor clutch air gap is set to specifications and pulley is aligned correctly.

FIGURE 9-8  Inspect refrigerant hose and line routing.

plate and the shoe discs without removing the compressor from the vehicle by following the following procedure: ■■ Attach a recovery/recycle/charge station to the vehicle and recover all the refrigerant from the system. ■■ Disconnect both the suction and the discharge hoses from the compressor assembly. ■■ Rotate the compressor clutch hub in a clockwise direction for several turns and note the resistance to rotation. 342 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Now rotate the compressor clutch hub in a counterclockwise direction for several turns and note the resistance to rotation. The compressor should immediately have the same resistance to rotation as it did in the clockwise direction. ■■ Any free play (backlash) noted on the initial reverse of direction indicates excessive free play clearance between the swash plate and shoe discs. The compressor will need to be replaced. Compressor piston noise is often caused by excessive internal pressure on the piston head. The internal pressure on the piston head can be up to 30 percent higher than the high pressure recorded on the manifold and gauge set. An example of this would be if the high-side discharge pressure is 300 psig (2068 kPa), the internal head pressure could be 390 psig (2689 kPa). The typical R-134a compressor is designed to withstand up to an 8 to 1 ratio (8:1) or pressure differential. When the ratio goes above that point, a compressor may develop a piston knock and over time complete compressor failure. A crude method for calculating compressor compression ratios is to take the low-side gauge reading and add 15 psig (103 kPa) to the reading (i.e., 30 psig 1 15 psig 5 45). Next, measure and record the high-side discharge (not liquid line) pressure and add 15 psig (103 kPa) to the reading. If the service port is located on the refrigerant liquid line after the condenser, you will need to use a thermocouple temperature probe and record the line temperature. After recording the line temperature, use a refrigerant temperature to pressure conversion chart to obtain the pressure for the recorded temperature. Next, add 15 psig (103 kPa) to this determined pressure. The final step is to divide the calculated low-side pressure number by the calculated high-side pressure number. In the preceding example, if the pressure recorded on the high-side discharge line is 400 psig (2758 kPa) and the low-side pressure is 30 psig (207 kPa), what would the compressor ratio be? ■■

400 psig 1 15 5 415 (2758 kpa 1 103 5 2861) 30 psig 1 15 5 45 (207 kpa 1 103 5 310) 415/45 5 a ratio of 9.2 : 1 (2861/310 5 9.2 : 1), which is an excessively high ratio for continuous compressor operation. This is why maintaining proper system function and pressures as well as accurate charge levels is critical to overall system performance and life. Leaves and road debris clogging the condenser airflow can have a devastating impact on compressor life. In addition, even slight refrigerant overcharging errors on small-capacity systems or air (noncondensable gas) contaminated systems may dramatically affect system performance.

Cause of Compressor Failure

Service technicians need to determine the root cause of compressor failures or leaks, whenever possible. Compressor seals can develop leaks due to excessive system pressure and heat, system contamination, improper mounting torque, or compressor-to-mounting bracket alignment errors. The following questions need to be answered when determining the root cause of a failure: ■■ Did compressor damage result from previous service work, such as prying against the case or pulley (Figure 9-9), failure to properly torque down the case to the mounting bracket, or a warped case or mounting bracket? ■■ Was a high refrigerant system temperature caused by lack of refrigerant system lubrication, incorrect refrigerant oil, excessive refrigerant oil, poor heat transfer at the condenser (physical blockage or excessive oil volume), or refrigerant overcharge? In addition, a slipping compressor clutch or clutch bearing failure will also generate excessive heat buildup, resulting in compressor shaft seal leaks and possibly compressor failure. ■■ Is there refrigerant system contamination such as Type I system sealant additive, which causes seals to soften and swell; moisture, causing oxidation at the sealing areas; solid particulate contamination circulating with the refrigerant (desiccant, metal); blended refrigerants; or air contamination, causing high-operating pressures? 343 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Flange is another term used for mounting boss. It is a protective rim, collar, or edge on an object used to keep the object in place or secure it to another object. A mounting boss is another term used for a mounting flange. It is a protective rim, collar, or edge on an object used to keep the object in place or secure it to another object.

FIGURE 9-9  AC compressor damage can result from prying against compressor case or pulley assembly.

It is essential to follow manufacturer-recommended torque and mounting procedures for refrigerant system compressors. This is especially critical with today’s alloy composite compressor housing, which can easily be distorted during mounting. When a compressor flange or mounting boss is installed in the mounting bracket, check for wobbling by gently shaking the assembly back and forth (Figure 9-10). The compressor should fit snugly against the bracket and not rock back and forth prior to being torqued into place. If a wobbling condition is detected, check for warpage; the acceptable range for bracket or compressor housing mounting point warpage is 0.0–0.030 in. A feeler gauge may be used to measure the amount

FIGURE 9-10  The AC compressor should fit snuggly against bracket and not rock back and forth prior to being torqued into place.

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of warpage. The compressor should be torqued into place in stages. If the torque specification for the mounting bolts is 40 lb. (13.5 N·m), first tighten all bolts in a circular pattern at 10 lb. (13.5 N·m), repeat the procedure at 20 lb. (27 N·m), and finally repeat the process again at the final torque setting of 40 lb. (54 N·m). This procedure should prevent case distortion and seal failure.

Refrigerant Lubricant The lubricant in the air-conditioning compressor circulates through the system with the refrigerant when the system is in operation. Most manufacturers specify PAG oil for R-134a systems with a specific viscosity number, whereas a few manufacturers call for ester oil as the factory-recommended lubricant. Older R-12 air-conditioning systems called for mineral oil as the system lubricant. Refrigerant oil should be added to a system any time a major component (e.g., compressor, condenser, etc.) is replaced or after a large leak has been repaired. It is important to maintain the manufacturer-specified amount of lubricant in the system and not to overfill the system. Too little oil in the refrigerant system will lead to compressor failure. Too much refrigerant oil may cause poor cooling performance due to thermal exchange interference. Always refer to the specific vehicle manufacturer’s service information and service bulletins when selecting refrigerant lubricant. When servicing the hybrid electric vehicle refrigerant system do not assume that it takes the same refrigerant oil as the nonhybrid vehicle refrigerant system. When servicing a hybrid vehicle’s refrigerant system it is imperative that the correct refrigerant oil be used. The hybrid electric vehicle uses insulated refrigerant oil designed to minimize the conductivity of electricity through the compressor case in the event of a circuit failure. Many Toyota hybrid electric vehicles call for ND-11 refrigerant oil. In addition, it is even more critical than ever to properly evacuate the refrigerant system after service to the required vacuum levels for proper moisture removal. Always refer to vehicle manufacturers’ recommendations for correct refrigerant oil. Always select the correct lubricant and amount for the system being serviced. The amount of refrigerant oil contained in a refrigerant system varies according to the design and size of the system. As a rough guideline the distribution of oil throughout the refrigerant system is 50% in the compressor, 10% in the condenser, 10% in the fluid container (receiver-drier/­accumulator), 20% in the evaporator, and 10% in the suction hose. When a refrigerant component is replaced always refer to the service information for the recommended amount of oil that should be added to the system.

Refrigerant Oil Return Operation

A lubricant return operation should be performed prior to replacing any major ­refrigerant system component or compressor assembly. The intent of this operation is to allow the majority of the system oil to be returned to the air-conditioning compressor assembly. In order to perform the refrigerant return operation, the air-conditioning system must be operating and there must be no evidence of a large amount of refrigerant oil loss.

Procedure 1. Start the engine and allow it to idle at 1500 rpm. 2. Turn on the air-conditioning system and set it to MAX, or select the Recirculation mode. 3. Set the blower motor speed to HI. 4. Allow the engine to idle at 1500 rpm for 10 minutes. 5. Turn off the engine. 6. Recover the refrigerant and record the amount of refrigerant oil removed from the system by the refrigerant recovery/recycle station. Add this amount of refrigerant oil back into the system along with the amount specified with the specific component being replaced.

The term logo refers to a company trademark, such as the Ford Motor Company “FORD” or General Motors’ “GM.”

CAUTION:

If excessive refrigerant oil loss has occurred, never perform the lubricant return operation because compressor damage may result. Some compressors have little or no oil reserve. Since oil is often lost with refrigerant, it is unwise to “top off” a system without determining the cause.

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An “off-road” vehicle is one that is not licensed for street travel, such as a harvester or thrasher.

Compressors, like most other components with moving parts, require oil for lubrication to prevent damage. Remove any other wires, such as superheat switch wire, from the compressor, if equipped.

Special procedures for determining the amount of refrigerant oil to be added to the ­system when the compressor is replaced are detailed at the end of this section. 7. Replace the system component and evacuate and recharge the system according to ­manufacturer service procedures. Add the specified amount of refrigerant oil for the component being replaced plus the amount of refrigerant oil recorded during the recovery process in step 6. After replacing the evaporator, condenser, or refrigerant storage container (receiver-drier/ accumulator), add the manufacturer-specified amount of refrigerant oil. An example of the amount of lubricant to be added is listed in the following table. Part Replaced

Refrigerant Oil to Be Added to System

Condenser

1.2 fl. oz. (35 mL)

Refrigerant storage container (receiver-drier/accumulator)

0.3 fl. oz. (10 mL)

Evaporator

2.5 fl. oz. (75 mL)

When the air-conditioning system compressor is replaced, it is necessary to d ­ etermine how much refrigerant oil was in the old compressor assembly and the amount removed ­during the refrigerant recovery process in order to determine how much clean fresh oil must be added to the system along with the new compressor. The total of these two amounts is added to the refrigerant system when the new compressor is installed ­(Figure 9-11). It is critical that just the right amount of refrigerant be added to the air-conditioning system. If too little oil is added the replacement compressor will fail, and if too much oil is added system performance will be affected. Always use fresh oil when adding lubricant to the system.

Recovery recycling equipment

Old compressor

Record amount

Record amount

“X” mL

“Y” mL

New compressor

Drain lubricant from new compressor into clean container

Reinstall “X” mL + “Y” mL of new lubricant New compressor

New lubricant Add another 5 mL (0.2 US fl. oz.) of new lubricant when replacing liquid tank.

FIGURE 9-11  Before a replacement compressor is installed, you must first determine how much refrigerant oil was recovered during the recovery process, plus how much refrigerant was drained from the old compressor assembly. The total of these two amounts is added to the refrigerant system when the new compressor is installed.

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The following procedure covers removing refrigerant oil from an old compressor assembly. 1. Follow the steps in “Refrigerant Oil Return Operation” detailed earlier and recover/­recycle the refrigerant from the air-conditioning system. Record the amount of refrigerant oil removed during this process. 2. Once the old air-conditioning compressor is removed, drain the old lubricant from the compressor into a graduated container and record the amount removed. 3. Drain the lubricant from the new compressor that is going to be installed into the vehicle into another clean container. 4. Add fresh, clean lubricant through the suction port of the new compressor. The amount to add is the amount recorded in step 1 plus the amount recorded in step 2. 5. Install the new compressor on the vehicle. Once the refrigerant lines have been connected, rotate the compressor clutch plate by hand several times to distribute the lubricant.

Pin-type connectors are single or multiple electrical connectors that are round-or pin shaped and fit inside a matching connector. Modern connectors outside the passenger compartment use weather pack seals.

Refrigerant Lubricant Diagnosis To avoid repeated compressor failure, always inspect the condition of the refrigerant lubricant and take the appropriate corrective action. If the oil is clean and free of debris no corrective action is required. But, if the oil is clean but there is debris present inspect the following: ■■ Replace component containing the desiccant. ■■ Remove and inspect the high-pressure filter if equipped. ■■ Remove, inspect, and clean the thermostatic expansion valve or replace the fixed orifice tube if contaminated. ■■ If equipped with a rear auxiliary compressor, replace rear auxiliary line filter of install one if not present. ■■ Inspect the suction port of the replacement compressor and install a suction screen if one is not present. If the oil is dark brown/black or if the oil has an unusual or a pungent odor but no debris is present, inspect the following: ■■ Replace component containing the desiccant. ■■ Flush the refrigerant system. If the oil is dark brown/black or if the oil has an unusual or a pungent odor with debris present, inspect the following: ■■ Replace component containing the desiccant. ■■ Flush the refrigerant system ■■ Remove and inspect the high-pressure filter if equipped. ■■ Remove, inspect, and clean the thermostatic expansion valve or replace the fixed orifice tube if contaminated. ■■ If equipped with a rear auxiliary compressor, replace rear auxiliary line filter or install one if not present. ■■ Inspect the suction port of the replacement compressor and install a suction screen if one is not present. If the refrigerant system was overcharged with oil or if the wrong oil had been installed in the system or the refrigerant was contaminated, flush the refrigerant system.

Removing and Replacing the Compressor 1. Follow all of the required procedures as outlined in “Refrigerant Oil Return Operation.” 2. Remove the inlet and outlet hoses or service valves from the compressor. NOTE: The suction and discharge lines of many systems are connected to the compressor with a common manifold.

Spade-type connectors are single or multiple electrical connectors that are flat spade shaped and fit inside a matching connector. Modern connectors outside the passenger compartment use weather pack seals.

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SERVICE TIP:

A magnetic parts tray to hold nuts and bolts under the hood while servicing a vehicle will save you both time and aggravation.

3. Remove the clutch lead wire. 4. Loosen and remove the belt(s). 5. Remove the mounting bolt(s) from the compressor bracket(s) and brace(s). 6. Remove the compressor from the vehicle (Figure 9-12). 7. Drain the old compressor into a graduated cylinder and record amount drained (Figure 9-13). 8. Position the new or rebuilt compressor. 9. Install the mounting bolt(s) into the compressor bracket(s) and brace(s). 10. Position and reinstall the belt(s). 11. Replace the clutch lead wire. 12. Using new gaskets or O-rings, replace the suction and discharge lines in the reverse order as removed in step 2. NOTE: Steps 12 through 14 procedures are found in Chapter 7 of this manual.

High-side switches include high pressure and superheat. An undercharge of oil will result in early compressor failure; an overcharge in inadequate performance. FIGURE 9-12  Remove the compressor from the vehicle.

FIGURE 9-13  Drain the compressor oil into a graduated container.

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13. 14. 15. 16.

Leak-test the system. Evacuate the system. Charge the system with refrigerant. Complete the system performance test job sheet.

Stretch to Fit Belts

Provided by The Gates Corporation

If the compressor that you are removing is equipped with a stretch to fit belt be identified by looking at the part number, if the last letters are “SF,” as in K030195SF, then it is a stretch to fit belt requiring special service instruction for replacement. In addition it is recommended that any time a component is removed that is driven by a stretch to fit belt that a new belt be installed to maintain optimal load tensioning. There are special service instruction that must be followed in order to replace the belt to avoid damage to the belt or component. There are eight different service procedures depending on the application. Special service instructions are identified on the new belt packaging sleeve with an Alpha (letter) character, as in Instruction E (Figure 9-14). Specific instructions can be found in the manufacturer service information or by visiting the Gates website and searching for “Stretch Fit belt installation” (www.gates.com/utility/micro-v-stretch-fit-beltinstallation-instructions). A screw driver, pry bar, or plyers should never be used to install a new belt. Stretch to fit belt removal is achieved by simply cutting the belt (Figure 9-15). There are two special tools available from Gates for installation of the stretch to fit belt, depending on the application. One tool is for general installation (Figure 9-16) part number Gates 91030 and one is designed for Subaru AC compressor belt replacement (Figure 9-17) part number Gates 91031.

FIGURE 9-14  Special service instructions are identified on the new belt packaging sleeve with an Alpha (letter) character, as in “Instruction E.”

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Provided by The Gates Corporation Provided by The Gates Corporation

FIGURE 9-15  Stretch to fit belt removal is achieved by simply cutting the belt.

Provided by The Gates Corporation

FIGURE 9-16  A special stretch to fit belt installation tool is available from Gates to avoid belt damage.

FIGURE 9-17  For Subaru applications a special stretch to fit belt installation tool is available for replacing the AC compressor belt from Gates to avoid belt damage.

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FIGURE 9-18  Stretch Fit Belt style A

Provided by The Gates Corporation

FIGURE 9-19  Stretch Fit Belt style B

Provided by The Gates Corporation

FIGURE 9-20  Stretch Fit Belt style C

Provided by The Gates Corporation

Provided by The Gates Corporation

The following images (Figures 9-17 through 9-25) detail replacement procedures for the eight different configurations.

FIGURE 9-21  Stretch Fit Belt style D

351

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Provided by The Gates Corporation

Provided by The Gates Corporation

FIGURE 9-22  Stretch Fit Belt style E

FIGURE 9-24  Stretch Fit Belt style G

Provided by The Gates Corporation

Provided by The Gates Corporation

FIGURE 9-23  Stretch Fit Belt style F

FIGURE 9-25  Stretch Fit Belt style H

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Installing Inline Filter After a catastrophic compressor failure there will be small metal particles left in the refrigerant system. Many manufacturers do not recommend chemical flushing of their refrigerant system. Instead of chemical flushing some manufacturers recommend flushing with clean refrigerant (recover, charge, and then recover again). This process is generally ineffective in removing all the particles left behind. A more practical alternative to protect the system is to install an inline auxiliary filter into the refrigerant system to trap debris and contaminants that may remain in the system after a compressor or desiccant failure. Auxiliary inline filters may be installed downstream in the liquid line or at the suction port to the compressor inlet or in both locations for maximum protection. The liquid line inline filter is connected in series to the high-pressure refrigerant line between the condenser outlet and the restriction device (i.e., TXV or FOT) to trap small particles of debris (Figure 9-26) that may be left in the system after component failure. Instruction for installing an auxiliary filter may be found in the job sheet at the end of this chapter entitled “Installation of Auxiliary Liquid Line Filter.” An additional inline filter may be installed in low-pressure suction line at the compressor inlet to trap any remaining small particles of debris from entering the air-conditioning compressor (Figure 9-27). This filter screen is mechanically pressed into the suction line with a special service tool kit. After the air-conditioning system has been operated for a few hours, the filter should be checked and the system retested. The quickest method for testing the filter is to perform a temperature drop test across the inlet and outlet of the filter assembly. A clamp-on thermocouple is the simplest and most accurate method of checking line temperature. If the filter is unrestricted the filter inlet and outlet temperatures should be the same; the allowable range of temperature drop across the filter is 0268F (0238C). If the temperature drop exceeds 108F (68C) the filter will need to be cleaned or replaced. NOTE: If the filter becomes clogged, air-conditioning system performance will be negatively affected. The restricted filter will also restrict the flow of refrigerant oil through the system, which could cause premature compressor failure.

Filter screen Hose manifold FIGURE 9-26  Inline filter may also be connected in series to the high-pressure refrigerant line to trap small particles of debris.

FIGURE 9-27  Inline filter installed in low-pressure suction line at the compressor inlet will trap small particles of debris from entering the air-conditioning compressor.

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Nippondenso

Compressors must be identified by model number, not just by appearance.

SPECIAL TOOLS Bearing remover/pulley installer External snapring pliers Graduated container Hub remover Three-jaw puller Shaft key remover Shaft protector Shaft seal seat installer Shaft seal seat remover

Nippondenso has, perhaps by far, the greatest number of makes and models of compressors available for automotive air-conditioning service. They are used on many car lines, such as Acura, BMW, Chevrolet, Chrysler, Corvette, Dodge, Ford, Honda, Toyota, Lexus, Lincoln, Mazda, Mercedes-Benz, Mercury, Merkur, Mitsubishi, Plymouth, and Porsche. There are over 25 different models and more than 100 styles of Nippondenso compressors in current use. Other models, such as Ford’s FX6 and FX15 and Chrysler’s A590 and C171, are also manufactured by Nippondenso. Other models no longer in current production have been replaced, generally by improved design models. Most compressors, which are designated for particular applications, cannot be interchanged. A replacement compressor, then, is best identified by giving the supplier information such as: ■■ OEM number from identification tag ■■ Make, model, and year of vehicle ■■ Grooves in pulley: 1, 2, 4, 5, or 6 ■■ Accessories, such as power steering ■■ Series and date of manufacture (VIN) Before attempting any installation, it is always wise to make a visual inspection to determine if the supplied replacement compressor is comparable to the defective unit. If the supplied compressor is without a clutch assembly, pull the clutch assembly from the defective compressor to make a comparison. Check the shaft size and length. Also, determine if it is a splined or keyed shaft. Many clutches are not interchangeable.

Servicing the Nippondenso Compressor The procedures for servicing the Nippondenso compressor are given in three sections: replacing the shaft seal, checking and adding oil, and servicing the clutch. These procedures assume that the compressor has been removed from the vehicle and that the services are to be performed “on the bench.”

Replacing the Shaft Seal Seal replacement for the Nippondenso compressor is somewhat different from most other compressors in that the front head assembly must first be removed. See Photo Sequence 12 for a typical procedure for removing and replacing the Nippondenso shaft seal assembly.

Checking and Adding Oil to the Nippondenso Compressor The Nippondenso compressor is factory charged with 13 oz. (384 mL) of refrigeration oil. It is not recommended that the oil level be checked as a matter of routine unless there is evidence of a severe loss. The following procedure assumes that the suction and discharge service valves have been removed from the compressor. Do not attempt to remove the service valves before the refrigerant has been removed from the system.

Draining the Compressor 1. Drain the compressor oil through the suction and discharge service ports into a graduated container. 2. Rotate the crankshaft one revolution to be sure that all oil is drained. 3. Note the quality and quantity of the oil drained. Inspect the drained oil for brass or metallic particles, which indicate a compressor failure. Record (in ounces or milliliters) the amount of oil removed. 4. Discard the old oil as required by local regulations.

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PHOTO SEQUENCE 12 Typical Procedure for Removing and Replacing the Nippondenso Compressor Shaft Seal Assembly

P12-1  After removing the clutch and coil assemblies, use the shaft key remover to remove the shaft key.

P12-2  Remove the felt oil absorber and retainer from the front head cavity.

P12-3  Clean the outside of the compressor with pure mineral spirits and air dry. Do not submerge the compressor into mineral spirits. Drain the oil into a graduated measure.

P12-4  Remove the six through bolts from the front head. Use the proper tool; some require a 10 mm socket and others require a 6 mm Allen wrench. Discard the six brass washers (if so equipped) and retain the six bolts.

P12-5  Gently tap the front with a plastic hammer to free it from the compressor housing. Remove and discard the headto-housing O-ring and the head-to-valve plate gasket.

P12-6  Place the front head on a piece of soft material, such as cardboard, cavity side up. Use the shaft seal seat remover to remove the seal seat.

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PHOTO SEQUENCE 12

(CONTINUED)

P12-7  Using both hands, remove the shaft seal cartridge.

P12-8  Liberally coat all seal parts, compressor shaft, head cavity, and gaskets with clean refrigeration oil. Carefully install the shaft seal cartridge, making sure to index the shaft seal on the crankshaft slots.

P12-9  Install the seal seat into the front head using the seal seat installer.

P12-10  Install the head-to-valve plate gasket over the alignment pins in the compressor housing. Install the head-tohousing O-ring. Carefully slide the head onto the compressor housing, making sure that the alignment pins engage in the holes in the head.

P12-11  Using six new brass washers (if required), install the six compressor through bolts. Using a 10 mm socket or a 6 mm Allen wrench, as required, tighten the bolts to a 260 in.-lb. (29.4 N?m) torque. SERVICE TIP: Use an alternate pattern when torquing the bolts.

P12-12  Replace the oil with clean refrigeration oil. Install the crankshaft key using a drift. Align the ends of the felt and its retainer and install them into the head cavity. Be sure the felt and retainer are fully seated against the seal plate. Replace the clutch and coil assembly.

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Refilling the Compressor 1. Add oil, as follows: a. If the amount of oil drained was 3 oz. (89 mL) or more, add an equal amount of clean refrigeration oil. b. If the amount of oil drained was less than 3 oz. (89 mL), add 5–6 oz. (148–177 mL) of clean refrigeration oil. 2. If the compressor is to be replaced, drain all of the oil from the new or rebuilt compressor and replace the oil as outlined in step 1 (a or b, as applicable).

SERVICE TIP:

Servicing the Nippondenso Compressor Clutch The Nippondenso compressor may be equipped with either a Nippondenso or Warner clutch assembly. Though these two clutches are similar in appearance, their parts are not interchangeable. Complete clutch assemblies are, however, interchangeable on this compressor. The apparent difference in the two clutches is that the Nippondenso pulley (Figure 9-28) has two narrow single-row bearings that are held in place with a wire snapring. The Warner clutch (Figure 9-29) has a single wide double-row bearing that is staked or crimped in place. Clutch pulley

Compressor Snapring

Field coil

Snapring

Clutch hub Hub key

Snapring Pulley bearings

Shims

Snapring

Field coil

SERVICE TIP: Clutch hub

Hub key

Snapring Dust shield

Classroom Manual Chapter 9, page 288

Locknut

Clutch pulley

Pulley bearing

Oil is added into the suction or discharge port(s). Rotate the compressor crankshaft at least five revolutions by hand after adding oil.

A snapring is a spring steel ring used to secure and retain a component to another component.

FIGURE 9-28  Exploded view of a Nippondenso compressor with Nippondenso clutch.

Compressor

Be sure to use the proper type and grade of oil to ensure refrigerant compatibility.

The shaft/hub key need not be removed. Take care not to lose the shim washer(s).

Shims Locknut

FIGURE 9-29  Exploded view of a Nippondenso compressor with a Warner clutch.

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Tools that are not properly secured and used may cause damage to the part.

CAUTION:

Make certain that the puller jaws are firmly and securely located behind the pulley to avoid damage.

Removing the Clutch 1. Remove the hub nut. 2. Use the hub remover and remove the clutch hub (Figure 9-30). 3. Use the snapring pliers to remove the pulley retainer snapring. 4. With the shaft protector in place (Figure 9-31), remove the pulley and bearing assembly with the three-jaw puller. 5. Use the snapring pliers to remove the field coil retaining snapring (Figure 9-32). 6. Note the location of the coil electrical connector and lift the field coil from the compressor.

Replacing the Pulley Bearing 1. Support the pulley with the proper clutch pulley support. 2. Drive out the bearing(s) using a hammer and bearing remover (Figure 9-33). 3. Lift out the dust shield and retainer or leave them in place. Make sure that the dust shield is in place before installing the bearing(s).

Hub remover tool

FIGURE 9-30  Use the hub removal tool to remove the clutch hub.

Puller tool

Electrical connector Snapring

Shaft protector

FIGURE 9-31  With the shaft protector in place, use a three-jaw puller to remove the pulley and bearing assembly.

Field coil FIGURE 9-32  Use a snapring pliers to remove the clutch coil assembly.

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Bearing remover tool

Bearing

Pulley hub

Pulley support tool FIGURE 9-33  Use a hammer (not shown) and bearing remover tool to drive out the bearing after placing the hub on a pulley support.

Bearing installer tool

Pulley hub

Bearing

FIGURE 9-34  Use a bearing installer and hammer to drive the new bearing(s) into the pulley hub.

SERVICE TIP: 4. Install the new bearing(s) using the bearing installer and the hammer (Figure 9-34). The bearing(s) must be fully seated in the rotor. 5. Replace the wire snapring if the clutch is a Nippondenso. If it is a Warner clutch, stake the bearing in place using the prick punch and the hammer.

Installing the Clutch 1. Install the field coil. Be sure the locator pin on the compressor engages with the hole in the clutch coil. 2. Install the snapring. Be sure the bevel edge of the snapring faces out. 3. Slip the rotor/bearing assembly squarely on the head. Using the bearing remover/pulley installer tool, gently tap the pulley onto the head (Figure 9-35). 4. Install the rotor/bearing snapring. The bevel edge of the snapring must face out. 5. Install shim washers or be sure they are in place. Check the shaft/hub key to ensure proper seating. 6. Align the hub keyway with the key in the shaft. Press the hub onto the compressor shaft using the hub replacer tool (Figure 9-36).

Before reassembly, use pure mineral spirits to clean all parts, including the pulley bearing surface and the compressor front head.

If index pins are not engaged properly, misalignment occurs.

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Tool

A snapring installed backward will not hold properly.

FIGURE 9-35  Gently tap the pulley assembly onto the compressor head.

Hub damage may occur if the key is not properly aligned.

Hub replacer tool FIGURE 9-36  Press the hub onto the shaft sing the hub replacer tool.

CAUTION: Do not drive ­(hammer) the hub on; to do so will damage the compressor.

7. Using a nonmagnetic feeler gauge, check the air gap between the hub and rotor ­(Figure 9-37). The air gap should be 0.021–0.036 in. (0.53–0.91 mm). 8. Turn the shaft (hub) one-half turn and recheck the air gap. Change the shim(s) as ­necessary to correct the air gap. 9. Install the locknut and tighten to 10–14 ft.-lb. (13.6–19.0 N·m). 10. Recheck the air gap. See steps 7 and 8.

Feeler gauge

FIGURE 9-37  Check the air gap between the hub and rotor using a nonmetallic feeler gauge.

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Shaft seals

Felt dust seal

Clutch hub Snapring

Classroom Manual Chapter 9, page 281

CAUTION:

Shims

Snapring Field coil

Compressor

Clutch pulley

The use of proper refrigerant is important. Do not mix refrigerants.

FIGURE 9-38  Panasonic’s rotary vane compressor.

Panasonic (Matsushita) The Panasonic rotary vane-type compressor (Figure 9-38) was first introduced in 1993 by Ford Motor Company on the Probe. The compressor, which is belt driven off the engine, uses HFC-134a as a refrigerant.

Servicing the Panasonic Vane-Type Compressors The main components of the Panasonic vane-type compressor are the rotor with three vanes, a sludge control valve, a discharge valve, and a thermal protector. The only service that may be accomplished is checking and adjusting oil, servicing the clutch, replacing the shaft seal, and servicing the thermal protector, sludge control, and discharge valve. All service procedures assume that the compressor has been removed from the vehicle and is being worked with on the bench.

Checking and Adjusting Compressor Oil Level A new Panasonic Rotary compressor contains 6.78 oz. (200 mL) of a special paraffin-base refrigeration oil, designated as YN-9. It is necessary to adjust the oil any time the compressor is serviced or when being replaced, as outlined in the following procedure.

Procedure 1. Drain the oil from the defective compressor into a calibrated container and note the amount removed. Allow the compressor to drain thoroughly. 2. Drain the oil from the replacement compressor into a second calibrated container. Allow the compressor to drain thoroughly. 3. Add the same amount of clean refrigeration oil to the replacement compressor that was removed from the defective compressor. 4. Add an additional 0.68 oz. (20 mL) of oil.

Servicing the Clutch Assembly

Removing the Clutch and Coil 1. Using an Allen wrench, remove the clutch armature Allen bolt. 2. Remove the clutch armature.

The rotary compressor is not sensitive to an overcharge of oil. An overcharge, however, may reduce overall system capacity and efficiency.

CAUTION:

Use the proper oil and the correct amount of oil. Too much oil will reduce the system capacity, and too little oil will result in insufficient lubrication. Oil removed from an air-conditioning system or component must be discarded in accordance with EPA regulations.

SPECIAL TOOLS External snapring pliers Internal snapring pliers

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Clutch field coil

Clutch field coil screws (3) FIGURE 9-39  Using a driver remove/install the three clutch field coil screws.

An internal snapring is a retaining device used to retain or hold a component inside a cavity or case.

3. Remove the shim(s) and set aside. 4. Using internal snapring pliers, remove the clutch rotor/pulley snapring. 5. Remove the clutch rotor/pulley. 6. Using a screwdriver, remove the three clutch field coil screws. Remove the clutch field coil (Figure 9-39).

Replacing the Coil and Clutch 1. Replace the clutch field coil and secure with three screws (see Figure 9-39). 2. Replace the clutch rotor/pulley and secure with the internal snapring. 3. Replace the shim(s). 4. Replace the clutch armature and secure with the Allen bolt.

Servicing the Compressor Shaft Seal To service the compressor shaft seal, proceed as follows:

Removing the Shaft Seal 1. Remove the clutch. It is not necessary to remove the clutch coil for seal service. 2. Remove the felt dust seal from the seal cavity (Figure 9-40). 3. Using internal snapring pliers, remove the shaft seal snapring (Figure 9-41). 4. Using the seal remover, remove the seal seat (Figure 9-42). 5. Using the seal remover/installer, remove the shaft seal (Figure 9-43).

Installing the Shaft Seal A seal, if installed backward, is almost impossible to remove.

1. Coat all seal parts with clean refrigeration oil. 2. Install the shaft seal, using the remover/installer tool. 3. Install the shaft seal, using the seal remover tool. 4. Replace the shaft seal snap ring. 5. Replace the felt dust seal. 6. Replace the clutch assembly.

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Remover/replacer tool

Felt dust seal

FIGURE 9-40  Remove/replace the felt dust seal.

Shaft seal snapring

FIGURE 9-41  Remove/replace the shaft seal snapring.

Shaft seal seat

FIGURE 9-42  Remove/install the shaft seat.

Remover/replacer tool Compressor shaft seal

FIGURE 9-43  Remove/install the shaft seal.

Servicing the Compressor The thermal protector, sludge control, and discharge valve are the only components that may be serviced in the Panasonic rotary compressor. It is not necessary to remove the clutch assembly or the shaft seal assembly for this service. For the disassembly of the Panasonic vane rotary compressor to service the internal parts, follow the procedure listed below. The procedure may be followed in reverse order for reassembly.

Before reassembly, liberally coat all parts with clean refrigeration oil that is compatible with the refrigerant requirements of the system.

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Procedure 1. Replace the discharge valve and stopper. 2. Secure the discharge valve and stopper with the two bolts removed in disassembly. 3. Install the thermal protector and secure it with the snapring. 4. Replace the thermal protector housing with a new gasket and secure it with four capscrews. 5. Secure the thermal protector hold-down bracket with the screw previously removed. 6. Replace the two compression springs and spring stoppers. 7. With a new gasket in place, install the oil control valve with three bolts. 8. Install the housing cover. Secure the housing cover with two Allen bolts and six hex nuts. 9. Replace the refrigeration oil.

Sanden SERVICE TIP:

Sanden’s compressors are equipped with Buna-N O-rings for R-12 service and neoprene O-rings for R-134a service. Sanden’s Buna-N O-rings are black, while their neoprene O-rings are blue.

There are about 20 models of the Sanden compressor, formally known as Sankyo. These compressors are used by Chevrolet, Chrysler, Dodge, Fiat, Ford, Honda, Jeep, Mazda, Peugeot, Renault, Subaru, and Volkswagen. The considerations for selecting a replacement Sanden compressor are: ■■ Head style: horizontal or vertical O-ring; horizontal or vertical pad; vertical flare ■■ Clutch diameter: from 3.8 in. (96.5 mm) to 5.6 in. (142 mm) ■■ Number of grooves in clutch rotor: either 1 or 2 V-groove or 4, 5, 6, 7, or 10 poly-groove ■■ Mounting boss measurement, front to rear, outside to outside: from 2.85 in. (72.4 mm) to 4.41 in. (112 mm) ■■ Type of refrigerant: R-12 or R-134a

WARNING: Do not mix refrigerants.

Servicing the Sanden (Sankyo) Compressor

SPECIAL TOOLS Air gap gauge set Front plate installer Face puller Hammer, small soft O-ring remover Seal protector Seal remover and installer Seal seat remover Seal seat retainer Spanner wrench

Servicing the Sanden/Sankyo compressor is limited in this manual to: replacing the shaft oil seal, checking and adjusting the proper oil level, and servicing the clutch. This procedure assumes that the compressor has been removed from the vehicle and is being serviced on the bench.

Replacing the Compressor Shaft Oil Seal The following procedures may be followed when replacing the compressor shaft seal.

Removing the Shaft Seal 1. Using a ¾ in. hex socket and spanner wrench (Figure 9-44), remove the crankshaft hex nut. 2. Remove the clutch front plate (Figure 9-45) using the clutch front plate puller. 3. Remove the shaft key and spacer shims and set them aside. 4. Using the snapring pliers (Figure 9-46), remove the seal retaining snapring. 5. Remove the seal seat using the seal seat remover and installer (Figure 9-47). 6. Remove the seal (Figure 9-48) using the seal remover tool. 7. Remove the shaft seal seat O-ring (Figure 9-49) using the O-ring remover. 8. Discard all parts removed in steps 5, 6, and 7.

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FIGURE 9-44  Remove the crankshaft hex nut.

FIGURE 9-45  Remove the clutch front plate.

FIGURE 9-46  Remove the seal seat snapring.

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FIGURE 9-47  Remove the seal seat.

FIGURE 9-48  Remove the seal.

FIGURE 9-49  Remove the O-ring.

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FIGURE 9-50  Use the air gap gauge to check the rotor-to-hub clearance.

Installing the Shaft Seal 1. Clean the inner bore of the seal cavity by flushing it with clean refrigeration oil. 2. Coat the new seal parts with clean refrigeration oil. 3. Install the new shaft seal seat O-ring. Make sure it is properly seated in the internal groove. Use the remover tool to position the O-ring properly. 4. Install the seal protector on the compressor crankshaft. Liberally lubricate the part with clean refrigeration oil. 5. Place the new shaft seal in the seal installer tool, and carefully slide the shaft seal into place in the inner bore. Rotate the shaft seal clockwise (cw) until it seats on the compressor shaft flats. 6. Rotate the tool counterclockwise (ccw) to remove the seal installer tool. 7. Remove the shaft seal protector. 8. Place the shaft seal seat on the remover/installer tool and carefully reinstall the shaft seal in the compressor seal cavity. 9. Replace the seal seat retainer. 10. Reinstall the spacer shims and shaft key. 11. Position the clutch front plate on the compressor crankshaft. 12. Using the clutch front plate installer tool, a small hammer, and an air gap gauge, reinstall the front plate (Figure 9-50). 13. Draw down the front plate with the shaft nut. Use the air gap gauge for go at 0.016 in. (0.4 mm) and no-go at 0.031 in. (0.79 mm). 14. Using the torque wrench, tighten the shaft nut to a torque of 25–30 ft.-lb. (33.0–40.7 N·m).

Checking Compressor Oil Level The compressor oil level should be checked at the time of installation and after repairs are made when it is evident that there has been a loss of oil. The Sankyo compressor is factory charged with 7 fl. oz. (207 mL) of oil. A special angle gauge and dipstick are used to check the oil level. The oil chart (Figure 9-51) compares the oil level with the inclination angle of the compressor. This procedure may also be followed with the compressor in the vehicle after first ensuring that the refrigerant has been recovered.

CAUTION:

Do not touch the carbon ring face with your fingers. Normal body acids will etch the seal and cause early failure. Do not discard parts that may be reused, such as shaft keys, spacers, nuts, bolts, clamps, snaprings, and so on. Some seal faces are made of a ceramic material. These seals may be damaged if care is not taken during handling.

Use nonmetallic feeler gauges to determine clutch air gap.

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Inclination Angle In Degrees

Acceptable Oil Level In Increments

0 10 20 30 40 50 60

6–10 7–11 8–12 9–13 10–14 11–16 12–17

FIGURE 9-51  Dipstick reading vs. inclination angle.

(Top view)

Aluminum planet plate

Thrust bearing

Oil filler hole Do not attempt to remove the oil plug until after ensuring that the refrigerant has been removed from the system.

Cast-iron cam rotor at top dead center position FIGURE 9-52  Position the rotor to top dead center (TDC).

TDC is an acronym for “top dead center.”

SERVICE TIP:

The dipstick tool for this procedure is marked in eight increments. Each increment represents 1 oz. (29.57 mL) of oil. An overcharge of oil has basically the same effect as an overcharge of refrigerant.

Preparing the Compressor 1. Position the angle gauge tool across the top flat surfaces of the two mounting ears. 2. Center the bubble and read the inclination angle. 3. Remove the oil filler plug. Rotate the clutch front plate to position the rotor at TDC ­(Figure 9-52). 4. Face the front of the compressor. If the compressor angle is to the right, rotate the clutch front plate ccw by 110 degrees. If the compressor angle is to the left, rotate the plate cw by 110 degrees (Figure 9-53).

Checking the Oil Level 1. Insert the dipstick until it reaches the stop position marked on the dipstick. 2. Remove the dipstick and count the number of increments of oil. 3. Compare the compressor angle and the number of increments with the table (see Figure 9-51). 4. If necessary, add oil to bring the oil to the proper level. Do not overfill. Use only clean refrigeration oil of the proper grade.

Servicing the Clutch Although this procedure presumes that the compressor is removed from the vehicle, if ample clearance is provided in front of the compressor for clutch service, it need not be removed for this service.

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FIGURE 9-53  Rotate the clutch front plate.

Removing the Clutch 1. Use a ¾ in. hex socket and spanner wrench to remove the crankshaft hex nut as shown in Figure 9-44. 2. Remove the clutch front plate, using the clutch front plate puller as shown in Figure 9-45. 3. Using the snapring pliers, remove the internal and external snaprings (Figure 9-54 and Figure 9-55). 4. Using the pulley puller (Figure 9-56), remove the rotor assembly. 5. If the clutch coil is to be replaced, remove the three retaining screws and the clutch field coil. Omit this step if the coil is not to be replaced.

Replacing the Rotor Bearing 1. Using the snapring pliers, remove the bearing retainer snapring. 2. From the back (compressor) side of the rotor, knock out the bearing using the bearing remover tool and a soft hammer. 3. From the front (clutch face) side of the rotor, install the new bearing using the bearing installer tool and a soft hammer. Take care not to damage the bearing with hard blows of the hammer (Figure 9-57). 4. Reinstall the bearing retainer snapring.

FIGURE 9-54  Remove the internal snapring.

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FIGURE 9-55  Remove the external snapring.

FIGURE 9-56  Remove the rotor assembly.

FIGURE 9-57  Install the rotor bearing.

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CAUTION:

Alignment is essential in order to prevent damage to mating surfaces.

FIGURE 9-58  Drive the front plate onto the shaft.

Replacing the Clutch 1. Reinstall the field coil (or install a new field coil, if necessary) using the three retaining screws. 2. Align the rotor assembly squarely with the front compressor housing. 3. Using the rotor two-piece installer tools and a soft hammer, carefully drive the rotor into position until it seats on the bottom of the housing. 4. Reinstall the internal and external snaprings using the snapring pliers. 5. Align the slot in the hub of the front plate squarely with the shaft key. 6. Drive the front plate on the shaft using the installer tool and a soft hammer (Figure 9-58). Do not use unnecessary hard blows. 7. Check the air gap with go and no-go gauges. 8. Replace the shaft nut and tighten it to a torque of 25–30 ft.-lb. (33.9–40.7 N·m) using the torque wrench. WARNING: Careful handling of all seal parts is important. The carbon seal face and the steel seal seat must not be touched with the fingers because of the ­etching effect of the acids normally found on the fingers.

Electrically-Driven Air-Conditioning Compressor Many hybrid electric vehicles are equipped with a high-voltage three phase alternating current air-conditioning compressor which has specific safety and service requirements. These are easily identifiable by the bright orange electrical cables connected to the AC compressor. This section is meant only as an overview for system service. Always refer to specific vehicle manufacturer service information for specific service procedures. An electrically-driven air-conditioning compressor (Figure 9-59) does not have a drive belt but is instead connected to the high-voltage harness by an orange colored wire and connector harness. The compressor requires special ND-11 insulating refrigerant oil (Figure 9-60). This specially formulated polyolester (POE) oil is used because of its high dielectric qualities. Avoid oil cross contamination during system evacuation and recharging by using hoses designed for ND-11. Using incorrect lubricant can set diagnostic trouble codes (DTC) and may cause damage to the electrically-driven compressor and may result in the leakage of electrical power.

A BIT OF HISTORY Tecumseh was one of the first manufacturers of automotive air-conditioning compressors. A large, heavy, cast-iron flywheelpulley compressor was used from the late 1940s through the late 1950s. Known as Tecumseh’s Model HH, it was discontinued in 1958 in favor of a smaller, somewhat lighter model LB. The model LB, which was also made of cast iron, was soon discontinued, however and was replaced by the popular HA and HG series, which are still found on limited applications. A carbon seal face is made of a carbon composition rather than another material, such as steel or ceramic. Etching is the unintended erosion of a metal surface generally caused by acid exposure.

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FIGURE 9-59  Typical electronic inverter air-conditioning compressor found on hybrid electric vehicles.

CAUTION REFRIGERANT UNDER HIGH PRESSURE Improper service methods may cause injury. Air-conditioning system should be serviced by qualified personnel. See Repair Manual. Refrigerant

Classroom Manual Chapter 9, page 301

HFC134a Max. 0.58kg(1.29Ibs.) USE ONLY Min. 0.48kg(1.06lbs.)

Oil

ND-OIL OR EQUIVALENT

11

SAE J-639

MFD, BY DENSO MANUFACTURING MICHIGAN INC. FIGURE 9-60  Typical refrigerant system label for electronic inverter air-conditioning compressor system.

There is a risk that high voltage could find a path to ground through the oil if it is contaminated. If a system is contaminated the recommendation is frequently to replace all components that refrigerant flows through. Just 1% of PAG oil contamination could compromise the dielectric properties in the POE oil. You should only use refrigerant service equipment that meets SAE specification J2788H, the H suffix designates “hybrid” and is designed to avoid hybrid high voltage air-conditioning system cross contamination through service hoses and refrigerant routing in the internal passages. Oil must be discarded in a manner consistent with the Environmental Protection Agency (EPA) guidelines.

Electronic Inverter Compressor Removal and Service 1. Disconnect the negative cable from high-voltage battery pack. 2. Remove high-voltage service plug. 3. Attach R/R/R equipment and recover refrigerant from the system. 4. Disconnect discharge hose and subassembly from compressor (Figure 9-61). 5. Seal the opening on the discharge hose using vinyl tape to prevent foreign matter and moisture from entering the system.

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FIGURE 9-61  Electronic inverter air-conditioning compressor discharge hose.

FIGURE 9-62  Electronic inverter air-conditioning compressor suction hose.

6. Disconnect suction hose and subassembly from compressor (Figure 9-62). 7. Again seal the opening on the suction hose using vinyl tape to prevent foreign matter and moisture from entering the system. 8. Wearing insulated lineman gloves remove electric inverter compressor connector and three harness hold-down clamps. Release the green-colored lock (1) and disconnect the connector (2) (Figure 9-63). Insulate the end of the vehicle harness connector with vinyl tape.

An overcharge of oil will reduce system capacity.

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1 2

FIGURE 9-63  Electronic inverter air-conditioning compressor electrical connector and harness.

Crayon or chalk temporarily marks component locations. A scribe or file is used to permanently mark the location.

FIGURE 9-64  Electronic inverter air-conditioning compressor mounting points.

9. Remove the three mounting bolts and remove compressor from vehicle (Figure 9-64). 10. Check for debris in the discharge port of the compressor and drain the old compressor and inspect condition of the oil. If any particles or debris is present in either the oil or the discharge port, the dryer must also be replaced.

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11. Ready the new compressor for installation. Gradually remove the service valves from the suction and discharge ports to release the inert gas (helium) from the new compressor. The new compressor is shipped charged with 4.05 fl. oz. (115 cc) of new ND-11 oil. To determine the amount of oil to remove from the new compressor follow the following formula: 115 cc 2 (Amount drained from old compressor) 5 (Amount of oil to remove from new compressor before installation) 12. If a new compressor is installed without adjusting the oil volume the refrigerant system will be overcharged with oil reducing the effectiveness of the heat exchangers and may cause refrigerant system failure and abnormal vibration. 13. Install the new compressor mounting it with only 2 bolts (bolts 1 and 2) as indicated in Figure 9-65 first. Torque bolts to 18 ft. lbs. (25 N·m). 14. Install remaining bolt (3) (Figure 9-66) and torque bolt to 18 ft. lbs. (25 N·m). 15. Wearing insulated lineman gloves reinstall electric inverter compressor connector and three harness hold-down clamps and lock the green-colored lock. 16. Install new O-rings lubricated with ONLY new ND-11 oil on both discharge and suction hose assemblies and reconnect hoses. Torque retaining bolts to 87 in. lbs. (9.8 N·m). 17. Install the high-voltage service plug. 18. Reconnect the negative cable from high-voltage battery pack. 19. Review manufacturer service information to see if a system initialization needs to be performed after battery disconnect. 20. Recharge the system with the proper amount of refrigerant. 21. Warm-up compressor. 22. Inspect for refrigerant leaks and perform a system performance test.

1

2

FIGURE 9-65  Mount electronic inverter air-conditioning compressor with only two of the three bolts.

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3

FIGURE 9-66  Mount electronic invert air-conditioning compressor three bolt and torque to specification.

Terms to Know Carbon seal face Etching Flange Internal snapring Mounting boss Running design change Shaft seal Snapring

case study A customer brings her vehicle into the shop because the air conditioner does not work. Initial inspection reveals that the clutch does not energize when the air conditioner is turned on, but the blower motor is operative. The technician checks all of the fuses and circuit breakers that may affect the clutch circuit and finds that all are good. Next, the technician uses a voltmeter to check the available voltage at the clutch

coil connector. The test indicates that 12.6 volts are available. The technician then performs a voltage drop test across the ground side of the clutch coil. The voltmeter indicates 12.6 volts. The conclusion is that the ground provision of the clutch coil is defective and must be repaired. After the ground wire, which is bonded to body metal, is cleaned and reconnected, the clutch functions properly and the air conditioner is fully operational.

ASE-STYLE REVIEW QUESTIONS 1. A slipping compressor clutch may be due to all of the following, except: A. Incorrect clutch air gap B. Internal compressor problem C. Excessively high refrigerant pressure D. Low refrigerant charge

2. The electromagnetic clutch is being discussed: Technician A says that the clutch will slip if the air gap is too close. Technician B says that the clutch will slip if the belt is close. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

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3. There are signs of oil spray on the compressor clutch hub and nearby underhood areas. Technician A says that a leaking compressor shaft seal could be the cause. Technician B says that a faulty compressor clutch bearing could be the cause. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 4. Technician A says that it is virtually impossible to insert the seal seat backward when using the ­appropriate tool. Technician B says that it is almost impossible to remove a seal seat that has been installed backward. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 5. Most air-conditioning systems that have R-134a as the refrigerant also use _______________ as a lubricant. A. Polyalkaline glycol (PAG) B. Polyolester (POE) C. Mineral oil D. Alkylbenzene oil 6. The compressor clutch circuit is being tested. Technician A says if the compressor clutch coil ­voltage drop is equal to source voltage (battery) then the clutch coil is defective. Technician B says if the test lamp does not light when connected across the clutch’s harness terminals, then the problem is probably a shorted clutch coil. A. A only C. Both A and B B. B only D. Neither A nor B

7. O-rings are being discussed. Technician A says that R-134a O-rings are usually black. Technician B says that R-12 O-rings are blue or green. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 8. Technician A says that the seal cavity may be flushed with clean refrigeration oil. Technician B says that the seal cavity may be flushed with clean mineral spirits. Both agree that the residue must be disposed of in a proper manner. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 9. To measure and adjust compressor clutch air gap, a _______________ feeler gauge should be used. A. nonmetallic C. carbon steel B. soft steel D. metallic 10. A vehicle returns to the shop for a repeat failure of the compressor system due to compressor clutch slippage and overheating. Which of the following is the most likely cause? A. A loose drive belt. B. A low refrigerant charge level. C. A faulty compressor clutch diode. D. High resistance in the compressor clutch electrical circuit.

ASE CHALLENGE QUESTIONS 1. During the compression stroke of an air-conditioning compressor, the suction valve is closed by the: A. Discharge valve. C. Valve spring. B. Discharge pressure. D. Suction pressure. 2. If the compressor oil has been drained and it shows signs of metallic particles, all of the following should be done, except: A. All system inlet screens should be cleaned after flushing. B. The receiver-drier or accumulator should be replaced after flushing.

C. The entire system should be flushed. D. A full charge of heavier refrigeration oil should be added after flushing. 3. The angle of the swash plate in a variable displacement compressor is controlled by: A. Suction pressure differential in the crankcase. B. Pressure differential between the low and high sides. C. Both A and B. D. Neither A nor B.

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4. The shims shown in the illustration are used to: C. Back up the locknut. A. Align the clutch pulley. D. Adjust the air gap. B. Secure the hub key.

5. The purpose of the compressor is to: A. Pump low-pressure vapor to a high-pressure vapor. B. Pump low-pressure vapor to a low-pressure liquid. C. Pump low-pressure liquid to a high-pressure liquid. D. None of the above.

Clutch pulley

Compressor Snapring

Field coil

Hub key

Snapring

Pulley bearing Dust shield

Clutch hub

Shims Locknut

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JOB SHEET

49

Name ______________________________________ Date ________________________

Compressor Identification Upon completion of this job sheet, you should be able to identify the different types of ­compressors used in automotive air-conditioning systems. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: General: A/C System Diagnosis and Repair. Tools and Materials Several vehicles equipped with air-conditioning systems Describe the vehicle being worked on.

Vehicle 1 Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Vehicle 2 Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Vehicle 3 Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Vehicle 4 Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure 1. Visually inspect the air-conditioning system and describe its overall condition.

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Vehicle

One

Compressor: Type

  

Cylinders



Two

Three

Four

_____/_____ ___________

_____/_____

_____/_____

___________

___________

Refrigerant: Type



Charge: Lb./oz

_____/_____

mL

___________

Lubricant: Type



Charge: oz.

_____/_____

_____/_____

_____/_____

_____/_____

mL

___________

___________ 

___________ 

___________ 

Belt Type



Instructor’s Response 

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JOB SHEET

50

Name ______________________________________ Date ________________________

Refrigerant Oil Return Operation and Compressor Oil Selection/Replacement Upon completion of this job sheet, you should be able to determine the approved lubricant for the refrigerant system and add the proper amount. Lubricant is added to the refrigerant system when a component is replaced or after a large leak has been repaired. It is important to maintain the specified amount of lubricant in the system and not to overfill it. A lubricant return operation should be performed prior to replacing any major refrigerant system component or compressor assembly. The intent of this operation is to allow the majority of the system oil to be returned to the air-conditioning compressor assembly. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: General: A/C System Diagnosis and Repair Task #7. Inspect condition of refrigerant oil removed from A/C system; determine necessary action. (P-2) Task #8. Determine recommended oil and oil capacity for system application. (P-1) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Refrigerant recovery/recycling/charge station Describe the vehicle being worked on. Year_____________________ Make _____________________ Model ______________________ VIN ____________________________ Engine type and size _____________________________ Procedure In order to perform the refrigerant return operation, the air-conditioning system must be operating and there must be no evidence of a large amount of refrigerant oil loss. 1. Start the engine and allow it to idle at 1500 rpm. 2. Turn on the air-conditioning system and set it to MAX or select the Recirculation mode.

CAUTION:

If excessive refrigerant oil loss has occurred, never perform the lubricant return operation because compressor damage may result.

3. Set the blower motor speed to HI.

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4. Allow the engine to idle at 1500 rpm for 10 minutes. 5. Turn off the engine. 6. Recover the refrigerant and record the amount of refrigerant oil removed from the system by the refrigerant recovery equipment. Add this amount of refrigerant oil back into the system along with the amount specified with the specific component being replaced. a.  Record amount of oil removed.  b.  Record amount of refrigerant removed.  7. Replace the system component and evacuate and recharge the system according to manufacturer’s service procedures. Add the specified amount of refrigerant oil for the component being replaced, plus the amount of refrigerant oil recorded during the recovery process. a.  Amount of oil removed in step 6a  b. Amount of oil specified to be added to the system for the component replaced  c. Total amount of refrigerant to be added to the system prior to charging (a 1 b) 5  After replacing the evaporator, condenser, or refrigerant storage container (receiver-drier/accumulator), add the manufacturer-specified amount of refrigerant oil. An example of the amount of lubricant to be added is listed in the following table. Part Replaced

Refrigerant Oil to Be Added to System

Condenser

1.2 fl. oz. (35 mL)

Refrigerant storage container (receiver-drier/accumulator)

0.3 fl. oz. (10 mL)

Evaporator

2.5 fl. oz. (75 mL)

Instructor’s Response 

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JOB SHEET

51

Name ______________________________________ Date ________________________

Check and Correct Compressor Oil Level Upon completion of this job sheet, you should be able to check and correct compressor lubricant levels. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: General: A/C System Diagnosis and Repair. Select oil type; measure and add oil to the A/C system as needed. (P-1) Tools and Materials An air-conditioning system compressor Service manual Selected air-conditioning tools Lubricant, if required Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size ____________________________ Procedure 1. What type of refrigerant is the compressor designed for? 2. What type of lubricant is the compressor designed for? 3. What is the lubricant capacity? oz. ____________ mL____________ 4. Following procedures outlined in the service manual, drain the lubricant from the compressor. 5. How much lubricant was drained from the compressor? oz. ____________ mL ____________

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6. When refilling, how much clean, fresh lubricant should be added to the compressor? oz. ____________ mL ____________ 7. Should the lubricant removed in step 4 be reused?  Why?

Instructor’s Response 

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JOB SHEET

52

Name ______________________________________ Date ________________________

Replace A/C Compressor Assembly Upon completion of this job sheet, you should be able to recover refrigerant from an A/C system, remove and replace a compressor assembly, evacuate and recharge a system, as well as perform a leak test of the system. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: General: A/C System Diagnosis and Repair. Task #6. Leak test A/C system; determine necessary action. (P-l) Task #7. Inspect condition of refrigerant oil removed from A/C system; determine necessary action. (P-2) Task #8. Determine recommended oil and oil capacity for system application. (P-l) NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Refrigeration System Component Diagnosis and Repair. Task #3. Remove, inspect, and reinstall A/C compressor and mountings; determine recommended oil quantity. (P-2) Tools and Materials Test vehicle Refrigerant recovery and recycling unit Manifold and gauge set Refrigerant leak detector Hand tools, as required Safety glasses Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure 1. Connect the gauge set to the system. Note the high-side and low-side pressures with the system off. a.  High-side pressure  b.  Low-side pressure  2. Connect the manifold gauge set to the recovery unit. Start the unit following the unit manufacturer’s instructions.

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3. Wait 5 minutes and note if pressure is detected (if pressure is present, rerun the recovery process). The system should hold a vacuum for 2 minutes. Did it?  4. Follow the steps “Removing and Replacing the Compressor” listed in Chapter 5, and refer to the manufacturer’s recommended procedure for the removal and replacement of the component. 5. Evacuate the system. Did the system hold a vacuum?  6. List the amount and type of oil used: a.  Type of oil:  b.  Amount of oil required:  7. Recharge the system. a.  Record the amount of refrigerant added.  8. Check the system for leaks using a halon leak detector. 9. Record the system running pressure. a.  High-side pressure b.  Low-side pressure

Instructor’s Response

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JOB SHEET

53

Name ______________________________________ Date ________________________

Compressor Clutch Amperage Draw and Resistance Test Upon completion of this job sheet, you should be able to inspect air-conditioning compressor clutch amperes draw and resistance and compare it to a calculated value, as well as perform a voltage drop test across the coil assembly. You should also be able to diagnose unusual operating noises in the air-conditioning system and determine necessary action. NATEF Correlation NATEF AST and MAST Correlation: General: HEATING AND AIR CONDITIONING: General: A/C System Diagnosis and Repair. Task #4. Identify abnormal operating noises in the A/C system; determine necessary action. (P-2) NATEF AST and MAST Correlation: General: HEATING AND AIR CONDITIONING: Operating Systems and Related Controls Diagnosis and Repair Task #1. Inspect and test A/C-heater blower, motors, resistors, switches, relays, wiring, and protection devices; perform necessary action. (P-l) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Digital multimeter (DMM) T-pins Describe the vehicle being worked on. Year _____________________ Make _____________________ Model_____________________ VIN ____________________________ Engine type and size ____________________________ Procedure Follow procedures outlined in the service manual. Ensure that the engine is cold and wear eye protection. 1. Visually check the coil for loose connections or cracked insulation. Were any faults detected?

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2. Inspect the clutch plate and hub assembly. Check for signs of looseness between the plate and hub. Were any faults detected?

3. Check the rotor and bearing assembly. 4. Check the bearing for signs of excessive noise, binding, or looseness. Replace the ­bearing if necessary. Were any faults detected?

5. Locate the air-conditioning compressor clutch wiring diagram for the vehicle you are servicing, as well as the amperage draw and resistance specifications for the compressor clutch coil. a.  Record resistant specifications. b.  List amperage draw specifications. 6. Ensure the ignition switch is in the OFF position. Remove the A/C compressor clutch relay. 7. Using a digital multimeter (DMM) set to the DC ampere scale, connect the meter leads in series across the contact point circuit of the relay connector (these are the larger cavities). On an ISO relay connector, this would be terminal #30 and ­terminal #87. 8. Start the engine and select A/C. Record amperage (I) draw and compare it to specifications. a.  Record Amperes (I) (Current) b.  Is this recorded reading within specifications? 9. Turn the engine off and replace the relay. 10. Set the DMM to ohms and disconnect the connector from the compressor clutch. 11. Measure the resistance of the compressor clutch coil. a.  Ω Resistance (R) b.  Is this recorded reading within specifications?

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12. Reconnect the A/C compressor clutch connectors. Set the DMM to read DC volts. Restart the vehicle and measure the battery voltage at the compressor clutch by back probing the connector. Shut the vehicle off. a.  Voltage (E) 1. Using Ohm’s law, calculate the current, I 5 E/R 5 ___________ vs. ___________ Actual (reading from 8a). 13. Were the actual and the calculated results the same? If not, why?  14. Using Ohm’s law, calculate the resistance of the A/C compressor clutch, E/I 5 R. a. Using Ohm’s law, calculate the current, R 5 E/I 5 ___________ vs. ___________ Actual (reading from 11a). 15. Were the actual and the calculated results the same? If not, why? 

16. Set your DMM to the DV volt scale and connect it in parallel across the compressor clutch connector. 17. Start the engine and select air-conditioning MAX mode. Record the voltage drop and compare it to source voltage. a.  Voltage drop  b.  Source voltage  18. If the voltage drop is not within 0.1 volt of the source voltage, what could be the cause of this difference? 

Instructor’s Response 

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JOB SHEET

54

Name ______________________________________ Date ________________________

Inspect and Test the Clutch Coil and Diode Upon completion of this job sheet, you should be able to inspect and test the compressor clutch coil and diode assembly. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: ­Refrigeration System Component Diagnosis and Repair. Task #2. Inspect, test, service, or replace A/C compressor clutch components and/or ­assembly; check compressor clutch air gap; adjust as needed. (P-2) Tools and Materials An air-conditioned vehicle Service manual Digital multimeter (DMM) Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size ____________________________ Procedure 1. Gain access to the compressor clutch area. Describe its location.  2. Visually inspect wiring and describe its condition.  3. With the engine not running but the ignition switch ON and A/C controls to MAX cooling, check the available voltage at the clutch coil connector. According to specifications, the voltage should be _______________. The voltage is _______________. 4. Turn the ignition OFF. Disconnect the clutch coil and isolate the diode, if equipped. Check the resistance of the clutch coil. According to specifications, the resistance should be _______________. The resistance is _______________. 5. With the diode isolated, connect it to an ohmmeter. What is the resistance?  Reverse the leads on the ohmmeter. What is the resistance? 

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6. Select the diode test setting on the DMM. First, connect the leads to the diode, placing the positive lead on one side and the negative lead on the opposite side of the diode; note the reading. Then reverse the leads and note the reading. Forward bias reading  Reverse bias reading  NOTE: The DMM should read 0.7–0.5 volt in one direction (forward bias) and ­infinity or out of limits in the other direction (reverse bias) if the diode is functioning correctly. 7. Based on the inspection above and tests, what is your recommendation? 

Instructor’s Response 

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JOB SHEET

55

Name ______________________________________ Date ________________________

Removing and Replacing a Compressor Clutch Upon completion of this job sheet, you should be able to remove and replace a typical compressor clutch. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: ­Refrigeration System Component Diagnosis and Repair. Task #1. Inspect and replace A/C compressor drive belts, pulleys, and tensioners; determine necessary action. (P-1) Task #2. Inspect, test, service, or replace A/C compressor clutch components and/or ­assembly; check compressor clutch air gap; adjust as needed. (P-2) Tools and Materials Compressor with clutch Service manual Selected air-conditioning tools Clutch components, as required Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure Following procedures outlined in the service manual, perform the following tasks. 1. Remove the clutch hub and plate assembly. 2. Visually inspect the hub and plate assembly. Note any problems.

3. Remove the pulley and bearing assembly. 4. Carefully inspect the bearing for signs of wear or roughness. Note any problems.

5. Make an electrical resistance check of the coil. Coil resistance should be: ________ ohms. Coil resistance is: ________ ohms.

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6. Replace parts, as needed. List additional parts required.  7. Reassemble the clutch. Instructor’s Response 

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JOB SHEET

56

Name ______________________________________ Date ________________________

Installation of Auxiliary Liquid Line Filter Upon completion of this job sheet, you should be able to determine the need for an airconditioning system filter and perform the necessary action. The focus of this job sheet is on the installation of an auxiliary filter to trap debris and contaminants that may remain in a system after a compressor or desiccant failure. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: ­Refrigeration System Component Diagnosis and Repair. Task #5. Determine need for an additional A/C system filter; perform necessary action. (P-3) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure Follow procedures outlined in the service manual. Ensure that the engine is cold, and wear eye protection. Contaminants can lodge in screens and valves, causing a restriction. Any time a major c­ omponent, such as a compressor and/or receiver-drier/accumulator assembly, is replaced an auxiliary filter should be installed. The following procedure will outline the steps for installing a filter in the liquid line. 1. Recover the refrigerant from the system. Follow the procedures outlined in job sheet “Recover and Recycle Refrigerant,” and replace any other component that needs service at this time, following the appropriate job sheet for each operation. a.  List amount of refrigerant recovered. b.  List amount of oil removed during recovery process.

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2. Locate the liquid refrigerant line between the condenser outlet and the metering device. Find an accessible area with a straight section of line longer than the filter’s assembly. Following the instructions accompanying the filter, determine the length of line that needs to be removed, and mark the tubing. How much line must be removed?

3. Using a tubing cutter, remove the section of line and debur using the deburring tool. 4. Lubricate the O-rings and ferrule fitting that accompany the filter kit assembly and install according to the directions in the kit. Never reuse O-rings. Outline the ­instructions. 

5. Tighten the ferrule fittings to the specified torque. List torque specifications.

6. Evacuate and recharge the system. 7. Perform system performance check to verify proper system operation and recheck the system for leaks. a.  Were any leaks detected? b.  List high-side and low-side pressure readings. c.  List duct discharge temperatures.

Instructor’s Response 

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Chapter 10

BASIC TOOLS Basic mechanic’s tool set

Case and Duct Systems

Fender cover Safety glasses Manifold and gauge set (for R-12 or R-134a, as applicable) Calibrated cup

Upon Completion and Review of this Chapter, you should be able to: ■■ ■■

Remove and replace the blower motors.

■■

Test the vacuum system.

Remove and replace the blower motor resistor or power module.

■■

Perform temperature control door adjustment.

■■

Replace the cabin air filter.

■■

Remove and replace the heater core.

■■

Remove and replace the evaporator.

■■

Troubleshoot, service, and adjust the operation of the in-vehicle mode circuits such as vent, HI-LO, MAX (cool/heat), and defrost.

■■

Perform odor control treatment of the case and duct system.

A maze of ducts, vents, motors, wiring, and vacuum hoses makes up the typical automotive air-conditioning case and duct system in today’s modern vehicle (Figure 10-1). The somewhat inaccessibility of most of its components adds to the mystique of this often neglected ­component of the air-conditioning system. While it is true that there are literally hundreds of variations, troubleshooting and s­ ervicing are not difficult if one is familiar with the system. Windshield defroster Side window demister

Side window demister Dash outlet

Dash outlet

Heater outlet floor ducts Recirculating air FIGURE 10-1  A typical case/duct system.

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Classroom Manual Chapter 10, page 309

Debris is foreign matter, such as the remains of something broken or deteriorated. HI/LO is also referred to as BI-LEVEL. An actuator is a device that transfers a vacuum or electric signal to a mechanical motion. An actuator typically performs an on/off or open/close function

Fresh Air Inlet Most of the heater and air-conditioning mode functions are performed with some outside air, except when MAX is selected. Though not generally noticeable, the quality of the air-conditioning system can be affected if the fresh air inlet screen is blocked with leaves or other debris. In time, if neglected, this debris can deteriorate and be pulled into the heater/evaporator case where it can cause serious airflow blockage through the evaporator and heater core. The fresh air inlet (Figure 10-2) is often concealed by the hood and is therefore overlooked during preventive maintenance. Cleaning this area should be a part of a periodic preventive maintenance schedule.

Component Replacement The greatest problem arises from the lack of data necessary to properly service any particular unit or system. It is necessary to have the manufacturer’s service manuals for specific step-by-step procedures. For example, consider the replacement of an HI/LO actuator motor. The “big three” automakers differ for one year model, as follows.

Chrysler 1. Remove the left and right underpanel silencer ducts. 2. Remove the floor console. 3. Remove the center floor heat adaptor duct. 4. Remove the rear seat heat forward adaptor duct. 5. Loosen the center support bracket; pry rearward to gain access to the actuator. 6. Remove the actuator retaining screws. 7. Remove the actuator (Figure 10-3). 8. Remove the electrical connections from the actuator. 9. To reinstall, reverse the order of removal.

FIGURE 10-2  Clean debris from the fresh air inlet.

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Mode door actuator

Temperature door actuator

A/C - heating unit assembly Blend air door actuator

Recirculation door actuator

FIGURE 10-3  Typical Chrysler mode door actuator location.

Defrost actuator Register actuator

Plenum

Floor actuator FIGURE 10-4  Typical Ford mode door actuator details.

Ford

1. Disconnect the vacuum hose. 2. Remove the retaining screws. 3. Remove the actuator from the linkage. 4. Remove the actuator (Figure 10-4). 5. For installation, reverse the removal procedures.

General Motors

1. Disable the air bag deployment system. 2. Remove the battery negative (2) cable and fuse. 3. Remove the instrument panel. 4. Remove the floor outlet assembly. 5. Remove the windshield defroster vacuum hoses. 6. Remove the windshield defroster air distribution assembly. 7. Remove the vacuum hose from the upper/lower mode valve actuator. 8. Remove the retaining nuts or screws. 9. Remove the actuator (Figure 10-5). 10. To install the new actuator, reverse the preceding procedure.

General Motors calls its air bag deployment system a “Supplemental Inflatable Restraint (SIR).”

399 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

A/C defrost actuator

Up-down valve actuator

Air inlet assembly

Tubing connector

Air inlet valve actuator

Vacuum tube harness

FIGURE 10-5  Typical General Motors mode door actuator details.

Classroom Manual Chapter 10, page 324

This comparison is not to suggest that Ford’s procedure is the simplest or that General Motors’ procedure is the most difficult. The procedures vary considerably for all year/model ­applications. The example, which was randomly selected, is intended to provide a general comparison of what may be expected in the day-to-day service of air-conditioning systems and to express the importance of having an appropriate service manual at hand.

Blower Motor Silicone rubber, available in tube form, is ideal for sealing mating surfaces.

Blower motor replacement is generally a little more straightforward than some of the other case/duct components (Figure 10-6). See Photo Sequence 13. This procedure, however, should be considered typical for any type vehicle. For reassembly or the installation of a new blower motor assembly, reverse P13-9 through P13-1. If the gasket, P13-7, was damaged or destroyed, replace it with a new gasket or seal the mating surfaces with a suitable caulking material.

Replacing the Power Module or Resistor

SPECIAL TOOLS Coolant recovery system, if applicable Hose clamp pliers, if applicable

WARNING: This component may be very hot. Take care before touching it with bare hands. Blower motor connection

Blower

Blower motor

Heater and A/C module Cooling hose

FIGURE 10-6  Blower motor and plenum details.

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PHOTO SEQUENCE 13 Typical Procedure for Removing a Blower Motor

P13-1  Disconnect the battery ground (2) cable.

P13-2  Disconnect or remove any wiring, brackets, or braces that hamper blower motor service.

P13-3  Disconnect the blower motor lead(s).

P13-4  Disconnect the blower motor ground (2) wire.

P13-5  Disconnect the blower motor cooling tube (if applicable).

P13-6  Remove the attaching screws.

P13-7  Remove the blower and motor assembly. The sealing gasket often acts as an adhesive. If this is the case, carefully pry the blower flange away from the case.

P13-8  Remove the shaft nut or clip, if applicable.

P13-9  Remove the blower wheel. Do not lose the space; use it on the replacement motor. Reverse the sequence to install the new motor.

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4-wire connector

2-wire connector

SERVICE TIP:

When servicing the case/duct systems, it is important that excessiveforce not be used or damage to the system will result. If the case/ duct system will not separate, the likelihood is that there is still one or more fasteners in place. Reinspect the assembly for hidden fasteners before attempting to proceed. You will save both time and aggravation in the long run if you proceed with care and caution when working on plastic components. A power module controls the operation of the blower motor in an automatic temperature control system.

SPECIAL TOOLS Coolant recovery system Refrigerant recovery system Hose clamp pliers

CAUTION:

Do not use undue force when ­connecting the heater hoses. ­Damage to the new heater core may occur if care is not taken.

ECC power module

Blower motor

Evaporator and blower assembly Cooling hose FIGURE 10-7  Typical power module.

1. Remove the brace(s) or cover(s) that may restrict access to the power module or resistor (Figure 10-7). 2. Remove the electrical connector(s). 3. Remove the retainer(s), if equipped. 4. Remove the retaining screws or nuts. 5. Remove the power module or resistor. 6. For replacement, reverse the procedure.

Replacing the Heater Core Access to the heater core is gained by following directions given in specific service manuals. This procedure is typical and assumes that the procedure for access to the heater core is available. 1. Drain the cooling system into a clean container. The coolant may be reused, reclaimed, or discarded in a manner consistent with Environmental Protection Agency (EPA) guidelines. 2. Disconnect the battery ground (–) cable. 3. Disconnect the heater hoses at the bulkhead. This is a good opportunity to inspect the heater hoses and replace any that show signs of deterioration. 4. Gain access to the heater core as outlined in the appropriate service manual. 5. Remove the retaining screws, brackets, or straps. 6. Remove the core from the case (Figure 10-8).

Heater core

Heater unit

FIGURE 10-8  Removing the heater core from the case.

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Replacing the Evaporator Core To illustrate the importance of proper service manuals for this service, it may be noted that a 1990s Ford Taurus/Mercury Sable manual instructs the technician, “Using a hot knife, cut the top of the air-conditioning evaporator housing between the raised outline.” An illustration is included in the manual to show the area to be cut (Figure 10-9). Some service manuals simply say to remove the blower motor and assembly screws before separating the case halves and removing the evaporator (Figure 10-10). The following procedure assumes that access to the evaporator has been determined. 1. Recover the refrigerant. 2. Drain the radiator if the heater hose(s) has to be removed to gain access. 3. Remove the heater hose(s), if necessary. 4. Remove any wiring harness, heat shields, brackets, covers, and braces that may restrict access to the evaporator core. 5. Remove the liquid line at the thermostatic expansion valve (TXV) or fixed orifice tube (FOT). 6. Remove the suction line at the evaporator or accumulator outlet. 7. Gain access to the evaporator core as outlined in the service manual. 8. Lift the evaporator from the vehicle. 9. Drain the oil from the evaporator into a calibrated cup. 10. For replacement, reverse the preceding procedure. First, replace the oil with the same amount and type as drained in step 9. Hacksaw

A hot knife is a tool that has a heated blade. It is used for separating objects, for example, evaporator cases. Drain coolant into a clean container so it may be reused. Replace any heater hoses found to be brittle or damaged. Discard all O-rings. They should be replaced with new O-rings on reassembly. Dispose of used oil in accordance with local ordinances.

Internal hinge line A/C evaporator housing

FIGURE 10-9  Use a hacksaw or hot knife to cut the case.

FIGURE 10-10  Split case halves to remove the evaporator.

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Removing and Replacing the Evaporator

SPECIAL TOOLS Flare nut wrench set Torque wrench

This procedure is given in four parts: 1. Aftermarket 2. Factory or Dealer Installed (Domestic) 3. Factory or Dealer Installed (Import) 4. Rear Heating/Cooling Unit Prior to servicing the evaporator, the air-conditioning system refrigerant must be removed by the recovery process. This procedure should be performed prior to step 1 outlined in either part. On completion of this service, the air-conditioning system should be properly evacuated and charged with the appropriate refrigerant as outlined in Chapters 6 and 7 of this manual.

Part 1. Aftermarket 1. Remove the liquid line from the metering device. 2. Remove the suction line from the evaporator. 3. Remove and discard O-rings, if equipped. 4. Remove the electrical lead wire(s). Also, disconnect the ground wire. 5. Remove the mounting hardware; remove the evaporator from the vehicle. 6. Check to see if there is a measurable amount of lubricant in the evaporator. NOTE: Add an equivalent amount of proper, clean, and fresh lubricant to the replacement evaporator. 7. To install the evaporator, reverse steps 1, 2, 4, and 5. Install new O-rings, if applicable. H-valve systems are not equipped with an accumulator, but instead have a receiver-drier.

Part 2. Factory or Dealer Installed (Domestic) (Figure 10-11) 1. Remove the liquid line from the metering device inlet. NOTE: If an H-valve metering device, skip to step 5. 2. Remove and discard the O-ring, if equipped. 3. Remove the suction line from the evaporator. A/C evaporator core A/C evaporator core housing (RH)

A/C evaporator core housing (LH)

O-ring

Blower motor

Cycling switch

Blower motor resistor assembly

A/C suction accumulator/drier

Orifice tube

FIGURE 10-11  Exploded view of an evaporator assembly.

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4. Remove and discard the O-ring, if equipped. NOTE: If not an H-valve system, skip steps 5 and 6 and proceed with step 7. 5. Remove the suction/liquid lines from the H-valve. 6. Remove and discard the gasket or O-rings, as applicable. 7. Remove the accumulator, if equipped, following procedures as outlined in this chapter. 8. Remove any mechanical linkages or vacuum lines from the evaporator controls. 9. Remove mounting bolts and hardware, as applicable, from the evaporator housing. 10. Separate the housing to gain access to the evaporator core. 11. Carefully lift the evaporator assembly from the vehicle. NOTE: Do not force the assembly. 12. If there is a measurable amount of lubricant in the evaporator, add an equivalent amount of proper, clean, and fresh lubricant to the replacement evaporator. 13. Install a replacement evaporator by reversing steps 1, 3, and 7–11 or 5 and 7–11, as applicable.

Use new gaskets and O-rings when required.

Part 3. Factory or Dealer Installed (Import) (Figure 10-12) 1. Remove the liquid line and suction line from the evaporator. 2. Immediately cap the fittings (evaporator and hose) to keep moisture and debris out of the system. Glove compartment

O-rings Cooling case (upper)

Wiring harness Suction hose Cooling unit

Evaporator

Expansion valve

Thermistor

Cooling case (lower)

Lower dash panel O-rings

O-ring

Suction hose

FIGURE 10-12  Typical import cooling unit.

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3. Remove and discard O-rings or gaskets, as applicable. 4. Remove any obstructions, such as dash panels or the glove box to gain access to the ­cooling unit. 5. Remove mechanical linkages, electrical wires, or vacuum lines from the cooling unit. 6. Remove mounting bolts and hardware, as applicable, from the cooling unit. 7. Lift the cooling unit assembly from the vehicle. There should be no need to force the assembly. 8. Separate the housing to gain access to the evaporator core. 9. Install a replacement evaporator core by reversing steps 1 and 4–8. NOTE: Use new O-rings or gaskets to replace those removed in step 3. 10. If there was a measurable amount of lubricant in the evaporator, add an equivalent amount of proper, clean, and fresh lubricant to the replacement evaporator.

Part 4. Rear Heating/Cooling Unit (Figure 10-13)

There are many variations on procedures to service the rear heating/cooling unit. The ­manufacturer’s service manual should be followed for any particular procedure. The following procedure is given as typical only. 1. Drain the coolant from the radiator. It may not be necessary to drain all of the coolant, however. 2. Remove the liquid line and suction line from the evaporator.

Rear heater duct

Rear A/C unit Cooling unit case Heater core

Evaporator

Cooling unit RH quarter case trim panel

Expansion valve O-rings

LH quarter trim panel

Blower HI relay Blower resistor

Blower motor O-ring

Case bottom Suction hose FIGURE 10-13  Typical rear heating/cooling unit.

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3. Immediately cap the fittings (evaporator and hose) to keep moisture and debris out of the system. 4. Remove and discard O-rings or gaskets, as applicable. 5. Remove the coolant hoses from the heater core. 6. Remove the heater grommet, if applicable. 7. Remove any obstructions, such as seats, panels, trim, or controls, to gain access to the heating/cooling unit. 8. Remove any mechanical linkages, electrical wires, or vacuum lines from the heating/ cooling unit. 9. Remove mounting bolts and hardware, as applicable, from the unit. 10. Lift the heating/cooling assembly from the vehicle. There should be no need to use force. 11. Separate the case to gain access to the evaporator and heater cores as well as to the ­metering device. NOTE: If when replacing the evaporator there is a measurable amount of lubricant, add an equivalent amount of proper, clean, and fresh lubricant to the replacement evaporator. 12. Install a replacement component by reversing steps 1, 2, and 5–11. NOTE: Use new O-rings or gaskets to replace those removed in step 4.

Odor Problems An odor emitting from the air-conditioning system ducts may be caused by a leaking heater core or hose inside the heater/evaporator case. An odor may also be caused by refrigeration oil leaking into the heater/evaporator case due to a leaking evaporator. The remedy is to repair or replace the leaking parts. A musty odor is usually due to water leaks, a clogged evaporator drain tube, or mold and mildew on the evaporator core. Mold and mildew, which are fungi, are most common in air-conditioning systems in vehicles operated in hot and humid climates. The odor, generally noted during startup, may be caused by debris in the heater/evaporator case or by microbial fungi growth on the evaporator core.

Classroom Manual Chapter 10, page 324

Odor Control Treatment

When a musty odor develops in the HVAC system, the only remedy is to eradicate the odor causing microscopic mold, bacteria, and mildew. The most common practice is to apply a liquid antimicrobial deodorizer and disinfectant product that is commercially available from both parts stores and vehicle manufacturers. For best results, follow the directions that come with the product. The following is a ­typical process for eliminating HVAC odor and applying the product to specific locations in the air duct system. This procedure could vary from one vehicle to another due to system control features. Always consult the manufacturer’s recommendations. WARNING: Always read and follow all instructions and warnings that come with disinfectant products, and only use these products in a well-ventilated area with vehicle doors and windows open and wearing eye protection. Do not use these products around flames or other sources of ignition. 1. Connect a siphon-type air-conditioning disinfectant sprayer to a 12 oz. (354.88 mL) bottle of disinfectant solution. 2. Remove the cabin air filter (if equipped) and reinstall the cover.

SPECIAL TOOLS Siphon-type air-­ conditioning disinfectant sprayer Liquid antimicrobial ­disinfectant 12 fluid ounces (354.88 mL) 407

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3. Spray approximately 4 oz. (118.29 mL) of the solution into the fresh air inlet with the blower on high speed, the mode door in the fresh air position, and the temperature ­control set to cold. 4. Next, locate the recirculated air inlet on the passenger side of the interior c­ ompartment and set the HVAC control panel to recirculation mode. Spray approximately 2 oz. (59.15 mL) of the solution into the air recirculation intake with the blower on high speed. NOTE: In some instances, it may be necessary to remove the blower motor resistor in order to direct the disinfectant sprayer toward the evaporator core. 5. Next, repeat step 3, but this time place the temperature control on full hot position. 6. Finally, turn the system and blower off and spray the remainder of the product into each of the air outlets in the system (defroster, floor vent, panel discharge, and side vents). 7. Reinstall the cabin air filter if one was removed in step 2. 8. Allow the vehicle to sit for at least 30 minutes with the windows open. Operate the system before returning it to the customer.

CAUTION:

Do not permit the coils of the blower resistor to become grounded to any metal surface. Technical service bulletins (TSB) contain updated information provided by the vehicle manufacturer regarding vehicle problems and offering solutions to problems encountered in their vehicles.

Classroom Manual Chapter 10, page 329

In some vehicles, the vacuum connection will be at the base of the carburetor.

WARNING: This procedure should only be performed on a cold vehicle to ­prevent the disinfectant from coming in contact with hot engine components. Take extreme care not to get disinfectant in eyes, on hands, or on clothing. Wash thoroughly with soap and water immediately after handling.

WARNING: If the disinfectant gets into the eyes, hold the eyelids open and flush with a steady, gentle stream of water for 15 minutes. Immediately seek ­professional medical attention.

Delayed Blower Control

An aftermarket delayed blower control may be installed in many systems to reduce the probability of a recurrence of odors caused by mold and mildew. It is installed following the instructions included with the package or as given in a manufacturer’s technical service bulletin (TSB). The delayed blower control is used to dry out the evaporator and air distribution system. After the air-conditioning compressor has been in operation for 4 or 5 minutes, the control will cause the blower motor to run after the ignition switch is placed in the OFF position. The delayed blower control will operate the blower motor at high speed for 5 minutes to clear the evaporator core of accumulated condensate, thereby reducing the recurrence of odors caused by mold and mildew.

Testing the Vacuum System The first step in troubleshooting the vacuum system is to ensure that manifold vacuum is available at the selector switch. Vacuum diagrams are generally provided in the manufacturer’s service manual to help identify color coding and connections (Figure 10-14). The following is a typical procedure to quickly check the vacuum control system for improper or erratic direction of airflow from the outlets. 1. Are other vacuum-operated devices operational? 2. Do other vacuum motors operate properly? a. If yes, there is a vacuum source. b. If no, proceed with step 3.

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FIGURE 10-14  An under hood vacuum system decal.

10 5

15 Vacuum in Hg

0

20 25

30

Vacuum gauge Adapter Tee To vacuum source

To vacuum system FIGURE 10-15  Check the vacuum source.

3. Disconnect the hose at the manifold inlet. 4. Connect a vacuum gauge, a short hose, and a vacuum tee in line with the vacuum source and system (Figure 10-15). 5. Is there now a vacuum signal? a. If yes, check for a defective check valve or hose(s). b. If no, check for blockage or restriction at the manifold fitting and correct it as required.

Vacuum Switch

The vacuum control provides a vacuum passage for selected circuits in the control system. To test for a defective vacuum control: 1. Disconnect the hose from the inoperative vacuum motor at the switch. 2. Connect a vacuum gauge to the vacant port.

SPECIAL TOOLS Vacuum pump Vacuum gauge Vacuum hose 409

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FIGURE 10-16  A typical vacuum check valve.

Check valves are used to prevent a loss of vacuum during acceleration and after engine shutdown

3. Move the switch through all of its positions. 4. Is there a vacuum at the port in either position? a. If yes, the switch is probably all right. b. If no, the switch may be defective; proceed with step 5. 5. Is there a vacuum signal at any of the other ports? a. If yes in step 5 but no in step 4, the switch is defective and should be replaced. b. If no, the problem may be a defective restrictor, check valve, hose, or reserve tank.

Check Valve

A check valve (Figure 10-16) allows flow in one direction and blocks (checks) the flow in the other direction. See Photo Sequence 14 for testing a check valve.

Reserve Tank Vacuum reserve tanks may be made of plastic or metal.

SPECIAL TOOL Heat gun

Using the same setup as for testing the check valve, insert the hose onto the vacuum reserve tank instead of the check valve. 1. Start the vacuum pump. 2. Observe the vacuum gauge. 3. Turn off the vacuum pump. If there is a vacuum and it holds for 5 minutes, the tank may be considered all right. If there is little or no vacuum or it does not hold for 5 minutes, the tank is defective. Leaks in vacuum tanks may usually be repaired by using a fiberglass-reinforced resin.

Hose

A vacuum hose is often made of synthetic rubber or nylon. Deterioration, cracking, and splitting are problems found with vacuum hoses. The best way to determine the condition of vacuum hoses is by visual inspection. If a hose shows signs of deterioration, it should be replaced.

Restrictor

A restrictor is generally a porous bronze filter whose purpose is to prevent minute particles of dust and debris from entering the vacuum system where they could restrict control circuits or cause component damage. The restrictor also slows the mode door operation to reduce the noise from mode door operation. It is not practical to clean a restrictor. If in doubt, the simplest remedy is to replace it. 410 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

PHOTO SEQUENCE 14 Typical Procedure for Testing a Check Valve

P14-1  Remove the check valve from the vehicle.

P14-2  Attach a vacuum source, such as a vacuum pump. The direction of flow should be away from the pump.

P14-3  Turn on the pump and observe the gauge. If there is a vacuum, the check valve is good. Proceed with step 4. If there is no vacuum, the check valve is defective and must be replaced.

P14-4  Turn off the pump.

P14-5  Disconnect the check valve.

P14-6  Reverse and reconnect the check valve.

P14-7  Turn on the vacuum pump and observe the gauge. If there is a vacuum, the check valve is defective and must be replaced. If there is now no vacuum but the pump held a vacuum for step 3, the check valve is good and may be returned to the vehicle.

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Temperature control cable

Retainer

Cam

Heater control assembly

Retainer

Temperature control cable FIGURE 10-17  Temperature door adjustment details.

Temperature Door Cable Adjustment

The temperature door is a door within the case/ duct system that directs air through the heater and evaporator core.

Remove access panels or components to gain access to the temperature door (Figure 10-17) and proceed as follows: 1. Loosen the cable and attach the fastener at the heater case assembly. 2. Make sure that the cable is properly installed and routed to ensure no binding and ­freedom of movement. 3. Place the temperature control lever in the full cold position and hold it in place. 4. Tighten the cable fastener that was loosened in step 1. 5. Move the temperature control lever from full cold to full hot to full cold positions. 6. Repeat step 5 several times and check for freedom of movement. 7. Recheck the position of the door. If it is loose or out of position, repeat steps 2 through 7. If it is still in position and secure, replace the access panels and covers.

Classroom Manual Chapter 10, page 312

Mode Selector Switch The mode selector switch provides an electrical or vacuum signal to the mode doors or control module assembly. The mode selector switch determines mode door position and air discharge location selected by drive (i.e., dash vent, defrost). Photo Sequence 15 illustrates a typical procedure for removal and replacement of the mode selector switch.

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PHOTO SEQUENCE 15 Removing and Replacing the Mode Selector Switch The following is a typical procedure for removing a mode selector switch. The switch is replaced by reversing the procedure given. For specific procedures, consult the appropriate manufacturer’s service manual.

P15-1  Disconnect the battery ground-cable.

P15-2  Remove the instrument panel finish appliqué.

P15-3  Remove the screws holding the control assembly to the instrument panel.

P15-4  Sufficiently pull the control assembly from the instrument panel to gain access to the rear electrical connector, control cable, and mode switch.

P15-5  Depress the latches of the electrical connector to disengage the connector from the control assembly.

P15-6  Disconnect the temperature control connector from the control assembly.

P15-7  Remove the knob from the mode selector switch.

P15-8  Remove the mode selector switch attaching screw(s) and remove the switch.

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Classroom Manual Chapter 10, page 325

Cabin Air Filter The procedure for cleaning or replacing the filter varies from vehicle to vehicle, so it is ­important to follow manufacturer’s recommended procedures. If the vehicle is equipped with an air filter (Figure 10-18), instructions may be found in the owner’s manual or on a label inside the glove box. The following is a typical procedure: 1. Remove the dash undercover. 2. Remove the glove box. 3. Remove instrument reinforcement from the instrument panel. 4. Remove the filter retaining clip. 5. Remove the air filter from the case/duct (Figure 10-19). 6. Clean and install a new filter. 7. Replace components in reverse order used to remove them.

Customer Care: Both the vehicle owner and the service technician often neglect the cabin air filter. As the technician, you need to educate the consumer on the advantages of frequent service of the cabin air filter. A properly maintained system will result in improved airflow and air quality for the passenger compartment.

Ventilation air filter

Fresh air

Purified air

Recirculation air

Blower Blower

Evaporator

FIGURE 10-18  Some systems today have a cabin air filter.

Evaporator case

Ventilation air filter

Clip

FIGURE 10-19  Remove the air filter from the evaporator case.

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Electric Mode Door Actuator Many automatic and manual climate control air-conditioning systems use electronic mode door actuators to control mode door operation. On an automatic climate control system, the actuator motors are sent commands from the climate control module or body computer. On manual air-conditioning systems, a control knob operates a potentiometer (variable ­resistor) which varies a voltage signal to the mode door motor (Figure 10-20). This is how the ­temperature knob (hot/cold) activates the electronic blend door actuator on a manual system. A control module is not used and the control voltage is supplied directly from the A/C-Heater control head assembly. The following is a typical testing procedure (refer to Figure 10-20), it is not meant to replace manufacturer service information: 1. Disconnect mode door actuator connector. 2. Turn ignition on. 3. Test for battery voltage on terminal 7. 4. Test for battery ground on terminal 8. 5. Test for continuity between terminals 3 and 4 as the potentiometer (temperature control) knob is turned. The resistance should change from low to high as the knob is turned in one direction and from high to low in the opposite direction. 6. Test for continuity between terminals 3 and 6 as the potentiometer (temperature control) knob is turned. The resistance should change from low to high as the knob is turned in one direction and from high to low in the opposite direction. 7. Test for battery voltage between terminals 7 and 8. 8. Reconnect mode door actuator connector. 9. Test for near battery voltage on terminal 4. 10. Test for voltage on terminal 3 as the potentiometer (temperature control) knob is turned. Diagnosis: ■■ If voltage or ground is missing in steps 3 and 4, check fuse and wires for shorts and opens. ■■ If continuity was not present in step 5 or 6, check wiring; if ok, replace potentiometer. If signal dropped out, replace potentiometer. If all the above readings are within range remove mode door actuator and check the door for mechanical binding or looseness or for a broken shaft or door. If door movement checks out ok, then replace the mode door actuator. AC heater control assembly

Blend door actuator

Potentiometer

M

7

Solid state 6 8

3

4

FIGURE 10-20  Typical electronic mode door actuator (motor) wiring diagram for a manual climate control system.

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Problems Encountered Block or ladder diagrams, covering several pages, are often used in manufacturers’ service manuals to troubleshoot problems with automotive air-conditioning duct systems. It is therefore recommended that the appropriate service manuals be consulted for specific troubleshooting procedures. Table 10-1 lists the problems that typically are encountered in the case/ duct system. Always follow a manufacturer’s recommended procedures and heed its cautions when troubleshooting any control system. The unintentional grounding of some circuits can cause immediate and permanent damage to delicate electronic components. The use of a testlight, powered or nonpowered, is not recommended for underdash service. The battery in a powered testlight or the added resistance on a nonpowered test lamp may be sufficient to cause failure to the delicate balance of solid-state electronic circuits. These circuits are susceptible to damage by electrostatic discharge (ED) merely by touching them. Electrostatic discharge is a result of static electricity, which “charge” a person simply by their sliding across a seat, for example. To provide an extra margin of safety, the technician should wear a grounding bracelet (Figure 10-21), an electrical conducting device that surrounds the wrist and attaches to a known ground source. This device ensures that the body will not store damaging static electricity by providing a path to ground for it to be discharged. TABLE 10-1:  TYPICAL CASE/DUCT SYSTEM PROBLEMS Vacuum System

Motor System

No vacuum-to-air conditioner master control

No power to air-conditioner mode selector

Air conditioner control leaks vacuum

High resistance connection in air conditioner control

Damaged, kinked, or pinched vacuum hose

Broken, loose, or disconnected electrical wiring

Damaged or leaking vacuum motor

Damaged or defective actuator motor

Actuator arm disconnected at door crank

Actuator linkage disconnected at door crank

Damaged or leaking vacuum reserve tank

Defective fuse, circuit breaker, or fusible link

Damaged or leaking check valve

Defective diode or component in programmer

FIGURE 10-21  Wear a grounding bracelet when working around sensitive electronic components.

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Passenger Compartment Heating Performance (Trouble Tree)

The following is an example of a typical diagnostic trouble tree for heating system performance. Always refer to specific manufacturer diagnostic information when troubleshooting system malfunctions. Step #

Diagnostic Step

YES

NO

1

Start the engine and allow it to idle for 10 minutes. Does the engine reach operating temperature?

Go to step 2.

Go to step 8.

2

a. b. c. d. e.

Go to step 6.

Go to step 3.

3

a. Install a thermometer in the center panel vent. b. Connect a clamp-on thermocouple or other contact thermometer to the heater core outlet hose. c. Select the PANEL discharge mode. d. Select the highest blower speed setting. e. Set the temperature control to maximum heat setting. f. Record the temperature at: Center panel vent _______________ Heater core outlet hose _______________ g. Compare the recorded temperatures. h. Are the two temperature readings about equal?

Go to step 4.

Go to step 5.

4

Inspect and repair the following areas for cold air leaking into the passenger compartment or duct system: ∙ Cowl ∙ Recirculation door ∙ HVAC case assembly

Go to step 9.

—

Select the FLOOR discharge mode. Set the blower to the lowest speed setting. Set the temperature control to maximum heat setting. Feel the heater core inlet and outlet hose temperature. Does the inlet hose feel hotter than the outlet hose?

Were repairs completed? 5

a. Inspect the temperature control door operation. b. Perform necessary repairs. Were repairs completed?

Go to step 9.

—

6

a. b. c. d. e. f. g. h.

Go to step 7.

Go to step 9.

7

Replace the heater core.

Go to step 9.

—

8

Repair the low engine temperature condition. Refer to the diagnostic section if the engine fails to reach operating temperature.

Go to step 9.

—

9

Operate the system to verify the repair. Was the original system complaint corrected and is the system functioning as designed?

System is operating as designed.

Go to step 1.

Turn the engine off. Backflush the heater core. Start the engine. Select the FLOOR discharge mode. Set the blower to lowest speed setting. Set the temperature control to maximum heat setting. Feel the heater core inlet and outlet hose temperature. Does the inlet hose feel hotter than the outlet hose?

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Terms to Know Actuator Debris Hot knife Power module Technical service bulletin (TSB) Temperature door

case study A customer brings a late-model vehicle into the shop with the complaint that air does not come out of the dash outlets regardless of the mode selected. Before attempting to check the under-dash air distribution system, it is noted that the vehicle is equipped with an air bag s­ ystem. The service manual cautions that the air bag system should be disarmed before performing any underdash service.

Following service manual procedures, the technician disarms the air bag. In this case, the technician disconnects and tapes the negative (2) battery terminal, removes the fuses, disconnects the wiring harness and, finally, removes the air bag module from the vehicle. By taking time to heed the service manual warnings, ­possible air bag deployment and injury are avoided.

ASE-STYLE REVIEW QUESTIONS 1. Technician A says that a slight amount of conditioned air is made available at the defroster duct outlet at all times to prevent windshield fogging. Technician B says that a positive in-vehicle ­pressure is maintained at all times to prevent exhaust gas infiltration. Who is correct? C. Both A and B A. A only B. B only D. Neither A nor B 2. Technician A says that a vacuum reserve tank helps maintain a vacuum in the system at all times only when the engine is running. Technician B says that the check valve prevents ­vacuum loss when the engine is stopped. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 3. Technician A says that a check valve prevents vacuum flow in either direction. Technician B says that a check valve permits vacuum flow in either direction. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 4. Technician A says cleaning the fresh air inlet should be part of a periodic preventative maintenance schedule.

Technician B says debris in the fresh air intake can contaminate the refrigerant. Who is correct? C. Both A and B A. Technician A only B. Technician B only D. Neither A nor B 5. An odor from the evaporator may be caused by all of the following, except: C. Oil A. Mold B. Mildew D. All of the above 6. An odor emitting from the case and duct system may be caused by all of the following, except: C. Mold and mildew A. A leaking heater core B. Refrigerant oil leak D. Refrigerant gas leak 7. It is necessary to drain the engine coolant before replacing which component? A. The vacuum diaphragm B. The blower motor C. The heater core D. All of the above 8. Technician A says mode doors may be vacuum operated. Technician B says mode doors may be electrically operated. Who is correct? A. Technician A only C. Both A and B B. Technician B only D. Neither A nor B

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9. Technician A says when a musty odor develops the odor causing mold and mildew must be eradicated. Technician B says that a liquid antimicrobial ­deodorizer and disinfectant is used to eliminate odors in duct systems. Who is correct? A. Technician A only C. Both A and B B. Technician B only D. Neither A nor B

10. Technician A says a block or ladder diagrams are used to aid in troubleshooting air-conditioning duct system faults. Technician B says the use of test lights is not recommended for under dash service. Who is correct? A. Technician A only C. Both A and B B. Technician B only D. Neither A nor B

ASE CHALLENGE QUESTIONS 1. All of the following statements about a typical air-­ conditioning system set to MAX cooling are true, except: A. The heater coolant flow control valve is open. B. The compressor clutch coil is energized. C. The blower motor is running. D. The outside/recirculate door is positioned to recirculate. 2. When should the cabin air filter be replaced if the vehicle is operated in dusty or high pollution conditions? A. Every 3 months or 3000 miles B. Once a year or every 12,000 miles C. Every 15,000 miles D. Every 30,000 miles 3. The least likely cause of an inoperative vacuum motor is: A. A split hose C. A defective vacuum switch B. A defective check D. A kinked hose valve

4. A customer complains of the passenger compartment temperature always being too hot, cold, or not changing as the temperature range is changed on the control panel. On an electronic mode door actuator (motor) system all of the following could cause this problem, except: A. Faulty actuator B. Faulty potentiometer C. Open or shorted wire D. Mode door moving too freely 5. During normal comfort control operation with the windows closed, harmful gases are not allowed to enter the vehicle because: A. The vehicle is airtight when the windows are closed B. They are removed by natural convection in the ambient airstream C. They are carried away by the force of the ram air D. Of a slight in-vehicle positive pressure

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Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

JOB SHEET

57

Name ______________________________________ Date ________________________

Case/Duct System Diagnosis Upon completion of this job sheet, you should be able to make basic checks of the vacuum system of an air-conditioning case/duct system. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Operating Systems and Related Controls Diagnosis and Repair. Task #3. Diagnose malfunctions in the vacuum, mechanical, and electrical components and controls of the heating, ventilation, and A/C (HVAC) system; determine necessary action. (P-2) Task #6. Inspect A/C-heater ducts, doors, hoses, cabin filters, and outlets; perform necessary action. (P-1) Tools and Materials Vehicle with manually controlled, factory-installed air-conditioning system Service manual Chapter 8 of Classroom Manual Selected air-conditioning system tools Vacuum pump Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure Disconnect the vacuum source hose and connect a vacuum pump to the vacuum reserve tank. It will not be necessary to run the engine for a vacuum source. Gain access to the vacuum motors of the mode doors and determine the vacuum signal applied to each for the following air delivery conditions.

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Use the abbreviations: fv for full vacuum pv for partial vacuum nv for no vacuum Air Delivery Condition

Defroster

Actuator Motor (Pot) A/C Bi-level

Air Inlet

1. MAX

________ 

________ 

________ 

________ 

2. NORM

________ 

________ 

________ 

________ 

3. Bi-level (B/L)

________ 

________ 

________ 

________ 

4. VENT

________ 

________ 

________ 

________ 

5. Heat (HTR)

________ 

________ 

________ 

________ 

6. BLEND

________ 

________ 

________ 

________ 

7. Defog

________ 

________ 

________ 

________ 

8. OFF

________ 

________ 

________ 

________ 

Instructor’s Response     

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58

JOB SHEET Name ______________________________________ Date ________________________

Air Delivery Selection Upon completion of this job sheet, you should be able to trace the air delivery in each of the six basic air delivery modes. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Operating Systems and Related Controls Diagnosis and Repair. Task #8. Check operation of automatic or semi-automatic heating, ventilation, and air-­conditioning (HVAC) control systems; determine necessary action. (P-2) Tools and Materials Service manual Blue and red pencil Procedure In each of the diagrams below, show the position of the mode doors using a red pencil. Show the airflow using a blue pencil. 1. A typical dual-zone duct system with passenger-side full hot selected and driver-side full cold selected. Both driver and passenger selected panel air.

Driver windshield air

Driver floor air

Heater core

Evaporator core

Blower and motor

Driver panel air Fresh air

Passenger panel air Passenger windshield air

Passenger floor air

Recirculate air

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2. A typical dual-zone duct system with passenger-side full cold selected and driver-side warm selected. Passenger selected panel air and driver selected floor air. Driver windshield air

Driver floor air

Heater core

Evaporator core

Blower and motor

Driver panel air Fresh air

Passenger panel air Passenger windshield air

Passenger floor air

Recirculate air

3. Airflow when DEFROST is selected from both passenger and driver outlets and full heat is selected by both driver and passenger. Driver windshield air

Driver floor air

Heater core

Evaporator core

Blower and motor

Driver panel air Fresh air

Passenger panel air Passenger windshield air

Passenger floor air

Recirculate air

4. Both driver and passenger select MAX cooling with panel air. Driver windshield air

Driver floor air

Heater core

Evaporator core

Blower and motor

Driver panel air Fresh air

Passenger panel air Passenger windshield air

Passenger floor air

Recirculate air

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5. Airflow in the cooling mode when BI-LEVEL is selected. Both driver and passenger select bi-level cooling with panel air discharge, but the driver wants full cold while the passenger wants warm air. Driver windshield air

Driver floor air

Heater core

Evaporator core

Blower and motor

Driver panel air Fresh air

Passenger panel air Passenger windshield air

Passenger floor air

Recirculate air

Instructor’s Response     

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Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

JOB SHEET

59

Name ______________________________________ Date ________________________

Replace Case and Duct System Components Upon completion of this job sheet, you should be able to remove and replace case and duct system components. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Operating Systems and Related Controls Diagnosis and Repair. Task #6. Inspect A/C-heater ducts, doors, hoses, cabin filters, and outlets; perform necessary action. (P-1) Tools and Materials Vehicle with air-conditioning system in need of case/duct service Service manual Appropriate tools Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure 1. Determine what component part or assembly is in need of replacement. Describe your procedure and how you arrived at your decision. Procedure    Component   

CAUTION:

If equipped with air bag(s), follow ­specific manufacturer’s service procedures for replacing defective components.

2. Look up the manufacturer’s procedures in the appropriate service manual. Service manual (title) __________________________ Year __________________________ Section _________________ Page __________________ Component _________________ 3. Following the recommended procedures, remove necessary components to gain access to and remove the defective part. Procedure   

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4. Obtain the replacement part. Compare it with the part removed. Are they the same or is the new part improved? Conclusion    5. Install the new part. Procedure    6. If possible, check the new component for proper operation. Procedure    7. Replace all components removed in step 3 to gain access. Procedure    8. Write a brief summary of any problems encountered with this repair.     Instructor’s Response     

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JOB SHEET

60

Name ______________________________________ Date ________________________

Adjust a Door Cable Upon completion of this job sheet, you should be able to adjust a case/duct system door cable. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Operating Systems and Related Controls Diagnosis and Repair. Task #5. Inspect and test A/C-heater control cables, motors, and linkages; perform necessary action. (P-3) Tools and Materials Vehicle with air-conditioning system Service manual Hand tools, as required Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure 1. Following procedures outlined in the service manual, gain access to the control cable. Procedure    2. Adjust the cable. Procedure    3. Check cable operation. Readjust, if necessary. Procedure   

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4. In reverse order, replace components removed in step 1. Procedure    5. What specific problems, if any, were encountered during this procedure?     Instructor’s Response     

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JOB SHEET

61

Name ______________________________________ Date ________________________

HVAC Odor Control Treatment Upon completion of this job sheet, you should be able to eradicate the odor-causing ­microscopic mold, bacteria, and mildew that may develop in an HVAC system. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: ­Refrigeration System Component Diagnosis and Repair. Task #10. Inspect evaporator housing water drain; perform necessary action. (P-1) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Siphon-type air-conditioning disinfectant sprayer Liquid antimicrobial disinfectant, 12 fluid ounces (354.88 mL) Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure For the best results, follow the directions that come with the product. The following is a typical process for eliminating HVAC odor and applying the product to specific locations in the air duct system. This procedure may vary from one vehicle to another due to system control features. Always consult the manufacturer’s recommendations. Ensure that the engine is cold, and wear OSHA-approved eye protection. 1. Connect a siphon-type air-conditioning disinfectant sprayer to a 12 oz. (354.88 mL) bottle of disinfectant solution. 2. Inspect the evaporator housing water drain; perform the necessary actions if it is determined to be restricted. Was a restriction found?   3. Spray approximately 4 oz. (118.29 mL) of the solution into the fresh air inlet with the blower on high speed, the mode door in the fresh air position, and the temperature control set to cold.

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4. Next, locate the recirculated air inlet on the passenger side of the interior compartment and set the HVAC control panel to recirculation mode. Spray approximately 2 oz. (59.15 mL) of the solution into the air recirculation intake with the blower on high speed. 5. Next, repeat step 3, but this time place the temperature control on full hot position. 6. Finally, turn the system and blower off and spray the remainder of the product into each of the air outlets in the system (defroster, floor vent, panel discharge, and side vents). Did you have enough product to complete this procedure? 7. Allow the vehicle to sit for at least 30 minutes with the windows open. Operate the system before returning it to the customer. Did the odor control treatment remove the objectionable smell?     Instructor’s Response     

432 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

JOB SHEET

62

Name ______________________________________ Date ________________________

Temperature Control Diagnosis Upon completion of this job sheet, you should be able to diagnose temperature control problems in the heater/ventilation system and determine the necessary action. NATEF Correlation NATEF MAST Correlation: HEATING AND AIR CONDITIONING: Heating, Ventilation, and Engine Cooling Systems Diagnosis and Repair. Task #3. Diagnose temperature control problems in the heater/ventilation system; determine PCM to interrupt system operation; determine necessary action. (P-2) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Thermometer Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure The temperature control regulates the temperature of the air inside the vehicle. The blue region is for cooler temperatures and the red areas are for warmer temperatures. Blended air is achieved by mixing the amount of cooled (blue area) air with warmed (red area) air. The following are typical diagnostic procedures for temperature control operation; for ­specific information, refer to the vehicle manufacturer’s diagnostic information. 1. First, verify that the engine coolant has reached operating temperature and that the air-conditioning system is functioning correctly. 2. Check the heater core inlet and outlet temperature of the heater hoses. Both hoses should be hot. 3. Verify that the fresh air intake is not obstructed with debris and that the cabin air filter is clean, if the cabin is equipped with one. 4. Place the temperature control selector in the full hot position and select the panel vent mode. Place the thermometer in the center panel vent. The outlet temperature should be approximately 608F (15.58C) above ambient air temperature. a.  Ambient air temperature  b.  Outlet temperature 

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5. Place the temperature control in the full cold position and select panel vent mode. The thermometer should still be in the center panel vent. The outlet temperature should be approximately 408F (4.48C) below ambient air temperature. a.  Ambient air temperature  b.  Outlet temperature  6. If the outlet temperature failed either steps 4 or 5, check the temperature control mode door actuator operation. a. If the temperature control mode door is cable actuated, go to Job Sheet 55, Adjust a Door Cable. 7. If the system passed both steps 4 and 5, the system is functioning correctly. Always refer to the manufacturer’s information, when available, to determine the proper ­system functioning parameters. Instructor’s Response 

434 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

JOB SHEET

63

Name ______________________________________ Date ________________________

Electronic Actuator Control Diagnosis Upon completion of this job sheet, you should be able to diagnose failures in the electrical controls of heating, ventilation, and A/C (HVAC) systems and to determine the necessary action. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Operating Systems and Related Controls Diagnosis and Repair. Task #3. Diagnose malfunctions in the vacuum, mechanical, and electrical components and controls of the heating, ventilation, and A/C (HVAC) system; determine necessary action. (P-2) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Digital multimeter Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure With the various designs of electronic HVAC control heads and actuators in use today, it is necessary to refer to the manufacturer’s specific diagnosis and troubleshooting information. Proceed with extreme care when diagnosing and servicing the underdash electrical systems. One improper test point could cause serious damage to one of the onboard computers. The following is meant to be a general procedure for inspecting the electronic actuator and control head operation for an electronically controlled temperature control door. The ­temperature control regulates the temperature of the air inside of the vehicle. The blue region is for cooler temperatures, and the red areas are for warmer temperatures. Blended air is achieved by mixing the amount of cool (blue area) air with warmed (red area) air. The following are typical diagnostic procedures for temperature control operation; for specific information, refer to the vehicle manufacturer’s diagnostic information. Extreme caution must be exercised while working on underdash components. Failure to do so could inadvertently trigger the inflatable restraint system. 1. First, verify that the engine coolant has reached operating temperature and that the air-conditioning system is functioning correctly. 2. Check the heater core inlet and the outlet temperature of the heater hoses. Both hoses should be hot. 435 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

3. Verify that the fresh air intake is not obstructed with debris and that the cabin air filter is clean, if the cabin is equipped with one. Control head

Blend door actuator

Cold

Hot

M

7

Solid state 6 8

3

4

4. Place the temperature control selector in the full hot position and select the panel vent mode. Place the thermometer in the center panel vent. The outlet temperature should be approximately 608F (15.58C) above ambient air temperature. a.  Ambient air temperature  b.  Outlet temperature  5. Place the temperature control in the full cold position and select panel vent mode. The thermometer should still be in the center panel vent. The outlet temperature should be approximately 408F (4.48C) below ambient air temperature. a.  Ambient air temperature  b.  Outlet temperature  6. If the outlet temperature failed either steps 4 or 5, check the temperature control mode door actuator operation. a.  First, verify that 12 volts are available at the actuator power supply wire. b.  Next, verify that the actuator ground wire is intact and functioning properly. c. Then, obtain specific diagnostic information for the system and check both input and output signals. d. Most systems allow for testing of the actuator through the scan tool or climate ­control panel. Actuators that are duty cycled are more accurately diagnosed through this method. 7. If the system passed both steps 4 and 5, the system is functioning correctly. Always refer to the manufacturer’s information, when available, to determine the proper ­system functioning parameters. Instructor’s Response 

436 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

JOB SHEET

64

Name ______________________________________ Date ________________________

Remove and Replace the Heater Core Upon completion of this job sheet, you should be able to remove and reinstall the heater core assembly. NATEF Correlation NATEF AST Correlation: HEATING AND AIR CONDITIONING: Heating, Ventilation, and Engine Cooling Systems Diagnosis and Repair. NATEF MAST Correlation: HEATING AND AIR CONDITIONING: Heating, Ventilation, and Engine Cooling Systems Diagnosis and Repair. Task #4. Determine procedure to remove, inspect, and reinstall heater core. (P-2) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure Access to the heater core is gained by following the procedures outlined in the appropriate service manual. The following procedure is typical and assumes that the procedure for access to the heater core is available. Ensure that the engine is cold, and wear OSHAapproved eye protection. 1. Drain the cooling system into a clean container. The coolant may be reused, reclaimed, or discarded in a manner consistent with Environmental Protection Agency (EPA) guidelines. How much coolant and what type was removed? 2. Disconnect the battery ground (2) cable. A “Keep Alive” device may need to be used so volatile memory is not lost in modules. 3. Disconnect the heater hoses at the bulkhead. This is a good opportunity to inspect the heater hoses and replace any that show signs of deterioration. Do any hoses require replacement?

CAUTION:

Do not use undue force when ­connecting the heater hoses. ­Damage to the new heater core may occur if care is not taken.

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4. Gain access to the heater core as outlined in the appropriate service manual. How long does the labor time list this entire service procedure should take (Flat Rate)? 5. Remove the retaining screws, brackets, or straps. 6. Remove the core from the case. Can you see the cause of the failure? 7. Install the new heater core. 8. Reverse disassembly procedures. 9. Refill the cooling system. How much coolant was required? What type of coolant was required?

10. Did you complete the job in the “Flat Rate” time specified in the labor time guide?

Instructor’s Response 

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JOB SHEET

65

Name ______________________________________ Date ________________________

Remove and Replace the Evaporator Upon completion of this job sheet, you should be able to remove and reinstall an evaporator assembly. NATEF Correlation NATEF AST Correlation: HEATING AND AIR CONDITIONING: Refrigeration System Component Diagnosis and Repair. NATEF MAST Correlation: HEATING AND AIR CONDITIONING: Refrigeration System Component Diagnosis and Repair. Task #12. Determine procedure to remove and reinstall evaporator; determine required oil quantity. (P-2) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure Access to the evaporator assembly is gained by following the procedures outlined in the appropriate service manual. The following procedure is typical and assumes that the procedure for access to the evaporator is available. Ensure that the engine is cold, and wear OSHA-approved eye protection. 1. Recover the refrigerant. How much refrigerant was removed? Was any refrigerant oil removed, if so how much?

CAUTION:

2. If the heater hose(s) and heater core must be removed to gain access, drain the cooling system into a clean container. The coolant may be reused, reclaimed, or discarded in a manner consistent with Environmental Protection Agency (EPA) guidelines. Was it necessary to drain the cooling system?

Do not use undue force when ­connecting the heater hoses. ­Damage to the heater core may occur if care is not taken.

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3. Disconnect the battery ground (2) cable. A “Keep Alive” device may need to be used so volatile memory is not lost in control modules. 4. Disconnect the heater hoses at the bulkhead, if necessary. This is a good opportunity to inspect the heater hoses and replace any that show signs of deterioration. Was this step necessary? Do any hoses require replacement?

5. Remove any wiring harness, heat shields, brackets, covers, and braces that may restrict access to the evaporator core. 6. Remove the liquid line at the thermostatic expansion valve (TXV) or fixed orifice tube (FOT). 7. Remove the suction line at the evaporator or accumulator outlet. 8. Gain access to the evaporator core as outlined in the service manual. 9. Lift the evaporator from the vehicle. 10. Drain the oil from the evaporator into a calibrated cup. How much if any was removed? 11. For replacement, reverse the preceding procedure. First, replace the oil with the same amount and type as drained in step 9, if greater than the amount specified by the manufacturer. How much oil was added to the system? Why?  12. What was the labor time listed for this complete procedure in the labor time guide?

Instructor’s Response 

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JOB SHEET

66

Name ______________________________________ Date ________________________

Remove and Replace a Blower Motor Upon completion of this job sheet, you should be able to remove and replace a blower motor. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Operating Systems and Related Controls Diagnosis and Repair. Task #1. Inspect and test A/C-heater blower, motors, resistors, switches, relays, wiring, and protection devices; perform necessary action. (P-1) Tools and Materials Late-model vehicle Shop manual Safety glasses or goggles Hand tools, as required Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure Follow the procedures outlined in the manufacturer’s shop manual. These procedures are given as a typical guideline for the task. 1. While wearing safety glasses or goggles, carefully remove the battery ground cable. If this is required, a “Keep Alive” memory saving device may need to be used. Was it used? 2. Disconnect the BCM or PCM (if applicable) following procedures given in the service manual. Was this necessary? 3. Remove any components, such as coolant reservoir, that may prevent blower motor removal. Was it necessary to remove additional components?

4. Remove electrical connector(s) and ground wire(s), if applicable. What connection needed to be removed?

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5. Remove all retaining screws and fasteners. 6. If necessary, use a sharp utility knife to cut through any gasket material that may restrict the removal of the blower motor assembly. 7. Lift the blower and motor from the case/duct. 8. Remove the retaining nut or clip from the motor shaft and remove the blower, if applicable. 9. Slide the blower onto the new motor shaft and secure it with a nut or clip. Was it necessary to reuse the old blower motor turbine (squirrel cage)? 10. Reverse the removal procedure and replace the blower and motor. Replace any gasket material cut in step 6 with black weatherstrip adhesive. Do not use RTV. What did you use to seal the unit? 11. Make electrical connections, reversing the order of steps 1, 2, and 4. 12. Replace any components removed in step 3. 13. Test blower motor operation and check for noises. Is it operating as designed and is it noise free?

14. What is the labor time listed for this service procedure in the labor time guide?

Instructor’s Response 

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JOB SHEET

67

Name ______________________________________ Date ________________________

Inspect and Replace Cabin Air Filter Upon completion of this job sheet, you should be able locate, inspect, and replace the cabin air filter. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Operating Systems and Related Controls Diagnosis and Repair. Task #6. Inspect and test A/C-heater ducts, doors, hoses, cabin filters, and outlets; perform necessary action. (P-1) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Cabin air filter Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure The procedure for cleaning or replacement of the cabin air filter varies from ­manufacturer to manufacturer. Location of the access panel also varies among vehicle models, so it is important to follow manufacturers’ recommended procedures. Typical replacement intervals for the cabin air filter are every 15,000 miles. The following is a typical procedure for replacement of a cabin air filter element with an access panel located in the passenger compartment. 1. Remove the dash undercover (kick panel). 2. Remove the glove box assembly. 3. Remove the access panel for the cabin air filter located on the duct case. 4. Remove the filter retaining clip. 5. Remove the cabin air filter from the case/duct.

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6. Clean or install a new filter element. 7. Replace components in the reverse order used to remove them. NOTE: Access to some cabin air filters is in the engine compartment under the cowl cover. Always refer to vehicle service information. Instructor’s Response 

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Chapter 11

BASIC TOOLS Basic mechanic’s tool set

Diagnosis and Service of System Controls

Fender cover Digital multimeter Jumper leads Fused jumper leads

Upon Completion and Review of this Chapter, you should be able to: ■■

■■

■■

■■

Discuss the methods used to diagnose fuse and circuit breaker defects.

■■

Recognize and identify the components of the climate control system.

■■

Understand and practice the methods used to diagnose compressor clutch malfunctions.

■■

Identify and troubleshoot the different types of pressureand temperature-actuated controls.

■■

Understand the function of and be able to troubleshoot the components of an automatic temperature control system. Identify and test sensors and actuators on an automatic climate control system. Activate the self-diagnostic test mode on an automatic climate control system. Use a scan tool to diagnose an automatic climate control system and verify the operation of the CAN bus line.

The control system of an automotive air-conditioning system, at first, may seem to be very complex. And, indeed, it is a complex system of many single wires. Compare the control ­system schematic to a road map. As one looks at a road map and notes the many highways and byways, it also looks complex. There is, however, only one route that is of interest at any one time. All the other routes are unimportant for any particular journey. For the most part, the same is true when diagnosing any control system or subsystem; although the “map” may seem very complex, most of it will prove to be of no interest. The schematic in Figure 11-1 is a composite of several car line schematics and, while it may be representative of several make or model automobiles, it should not be considered ­typical for any specific make or model. For specific information, manufacturers’ shop and service manuals must be consulted. Refer to the schematics of this text as you are led through a systematic approach to diagnosis, troubleshooting, and repair procedures for today’s modern automotive air-­conditioning systems.

Customer Care: Climate control systems today are very complicated and not for the do-it-yourselfer. There are many similarities among all the systems, but the ­terminology may differ from manufacturer to manufacturer, and the specific values for sensor diagnosis may differ. In order to be successful in diagnosing automatic climate control systems, you must have access to a high-quality information ­system, such as manufacturer service information or systems like ALLDATA or Mitchell on Demand.

An electrical schematic often requires several pages in a service manual.

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A fusible link is a type off use made of a special wire that melts in order to open a circuit when current draw is excessive.

B+

Hot in run

IP fuse panel Junction block

HVAC 20A

Mode selector

Open refers to a break in an electrical circuit. Overload is any electrical load in excess of the design criteria.

Classroom Manual Chapter 11, page 340

A voltmeter is an instrument used to measure voltage of an electrical circuit. An ohmmeter is an instrument used to measure (in ohms) the resistance of a circuit or component. Take care not to short fuses or circuit breakers to ground when testing them. Hot is a term used to describe the positive (1) side of an energized electrical system. Shorts refer to intentional or unintentional grounding or crossing of an electrical circuit.

Blower switch

LO M1 M2 HI

Blower motor

Blower motor relay

Evaporator pressure control switch

A/C clutch

FIGURE 11-1  A typical automotive air-conditioning electrical system schematic.

Fuses and Circuit Breakers Note that there are several fuses, a circuit breaker, and a fusible link in the schematic. The purpose of these devices is to provide optimum protection to all of the circuits at all times. A fuse or fusible link is generally used in circuits that are hot all the time; that is, circuits that are not interrupted when the ignition switch is open. This provides a positive nonrestorable interruption of power should an overload occur when the vehicle is unattended. A circuit breaker, on the other hand, is generally used only in circuits that are interrupted when the ignition switch is open (off ). There are several methods that may be used to check a fuse or circuit breaker: in-­ vehicle testing with a voltmeter or nonpowered test lamp and out-of-vehicle testing with an ­ohmmeter or powered test lamp. To test a fuse or circuit breaker in the vehicle, use a voltmeter or test lamp as follows: 1. Connect one lead of the test lamp or voltmeter to body ground (2). 2. Touch the other lead to the positive (hot) side of the fuse or circuit breaker in the fuse block or holder (Figure 11-2). If the lamp does not light or if voltage is not indicated, power is not available and the problem is elsewhere. If the lamp lights or if voltage is indicated, power is available. Proceed with step 3. 3. Touch the lead to the other side of the fuse or circuit breaker (Figure 11-3). If the lamp does not light or if voltage is not indicated, the fuse is blown or the circuit breaker is defective. Proceed with step 4. If the lamp lights or voltage is indicated, the problem is elsewhere and further testing is necessary. 4. Test protected components for shorts or overloads, then replace the fuse or circuit breaker.

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FIGURE 11-2  Touch the lead to the hot side of the fuse block or holder.

FIGURE 11-3  Touch the lead to the other side of the fuse.

SPECIAL TOOLS Nonpowered test lamp Voltmeter Make sure that the test lamp is not burned out.

To test a fuse or circuit breaker that has been removed from the vehicle, follow this procedure: 1. Set the omm to the ohmmeter scale, touch the leads together, and zero the meter or make sure that the test lamp battery is good. 2. Touch the two leads of the ohmmeter or test lamp to either side of the fuse or circuit breaker (Figure 11-4). If the ohmmeter indicates a low resistance or if the test lamp lights, the fuse or circuit breaker is good. If there is no resistance indicated on the ohmmeter or if the test lamp does not light, the fuse is blown or the circuit breaker is defective.

SPECIAL TOOLS Powered test lamp Ohmmeter

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FIGURE 11-4  Touch the two leads to either side of the fuse.

Classroom Manual Chapter 11, page 344

Thermostat The thermostat (Figure 11-5) cycles the air-conditioning compressor electromagnetic clutch on and off as determined by a preset temperature. There are two types of thermostat: fixed and variable. Testing either type of thermostat is a relatively simple matter if it has been removed from the vehicle. Proceed as follows.

Variable-Type Thermostat

SPECIAL TOOLS Powered test lamp Ohmmeter

The variable-type thermostat is generally found on aftermarket air-conditioning systems. 1. Connect an ohmmeter or powered test lamp to the two terminals of the thermostat ­(Figure 11-6). 2. While observing the ohmmeter or test lamp, rotate the thermostat from fully clockwise (cw) to fully counterclockwise (ccw). If a low resistance is noted or if the test lamp lights, the thermostat is probably all right. If no resistance is noted or if the test lamp does not light, the thermostat is defective. 3. Repeat step 2 several times to ensure stable and consistent results.

FIGURE 11-5  A typical thermostat.

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FIGURE 11-6  Connect an ohm meter to the two terminals of a thermostat.

Fixed-Type Thermostat

A fixed-type thermostat that has no provisions for temperature adjustment is generally found on factory-installed air-conditioning systems. Two beakers of water are required: one cooled with ice (328F or 08C), and the other heated to about 1208F (498C). The thermostat is tested as follows: 1. Connect the ohmmeter or test lamp in the same manner as in the adjustable thermostat test. 2. Is low resistance noted or is the lamp lit? Generally, at ambient temperature, the ­thermostat will be closed. If the answer is yes, proceed with step 3. If the answer is no, proceed with step 5. 3. Immerse the capillary tube end or remote bulb into the ice bath (Figure 11-7). 4. Did the resistance increase or the lamp go out? A reduction in temperature below the set point should open the thermostat contacts. If the answer is yes, proceed with step 5. If the answer is no, the contacts are stuck closed and the thermostat is defective. 5. Immerse the capillary tube in the hot bath. 6. Did the resistance decrease (Figure 11-8) or the lamp light? If the answer is yes, the thermostat is probably all right. If the answer is no, the thermostat is probably defective with contracts stuck open.

SPECIAL TOOLS Powered test lamp Ohmmeter

Systems with a fixed thermostat usually maintain the desired in-car temperature by tempering cooled and heated air in the plenum section of the duct system.

CAUTION:

Technicians need to wear a static discharge wrist strap when servicing ­electrical devices containing solidstate components such as control modules. Static ­electric discharge may damage ­sensitive circuits. FIGURE 11-7  Immerse the cap tube into an ice bath.

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FIGURE 11-8  Did the resistance decrease?

Clutch pulley

Snapring

Field coil

Pulley bearing

Clutch hub Hub key

Dust shield

Snapring

Shims

Locknut

FIGURE 11-9  Details of a typical electromagnetic clutch.

Electromagnetic Clutch The electromagnetic clutch (Figure 11-9) starts compressor action when wanted and stops it when it is not wanted. The clutch either works or it does not work. It may be noisy when it works, which is a sign that it needs attention before it fails. If it does not work, the problem may be that it is burned, slipping, will not engage, or will not disengage.

The Compressor Clutch Does Not Work

If the compressor clutch is the only component that does not work or if it works intermittently, the problem may be the clutch. It is more likely, however, that it is in the clutch electrical circuit (Figure 11-10). Testing the Clutch Circuit. The following procedure should be considered a typical procedure only. For specific procedures, follow the manufacturer’s instructions outlined in the appropriate service manual for safely testing an electrical circuit. 1. Touch the test lamp leads to the battery terminals to check the integrity of the fuse and bulb (Figure 11-11). 2. Disconnect the clutch coil from the wiring harness.

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Hot in run

A/C fuse 10A

Hot at all times

UBEC

Ign fuse 10A

Compressor clutch relay

A/C controller

A/C clutch

5v A/C pressure transducer FIGURE 11-10  A typical clutch electrical circuit.

FIGURE 11-11  Touch the fused test lamp leads to the vehicle battery to test for integrity.

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3. Turn the ignition switch to ON and place the air-conditioning system controls in any COOL position. 4. Connect a fused test lamp from ground to the positive (1) terminal of the disconnected wiring harness. a. If the test lamp does not light, the fuse, clutch relay, or wiring may be defective. Troubleshooting procedures are similar to those outlined for the blower motor ­circuit. Repair or replace components as necessary. NOTE: The problem could be in the power train control module (PCM). Consult the manufacturer’s service manual for troubleshooting procedures. Photo Sequence 16 ­illustrates a typical procedure for testing PCM wiring and circuits. b. If the test lamp lights, proceed with step 5. 5. Turn the control back and forth from minimum (MIN) to maximum (MAX) cooling several times while observing the test lamp. a. If the test lamp flickers or goes out, the PCM may be defective. Further testing of the PCM is indicated. b. If the test lamp remains on, proceed with step 6. 6. Remove the clutch and clutch coil and bench test the individual parts as follows: a. Visually inspect the clutch rotor and armature assembly. b. If the rotor or armature is heavily scored, as in Figure 11-12, or shows signs of ­overheating, replace the assembly. 7. Bench test the clutch coil. a. Connect a jumper wire from the clutch coil frame (Figure 11-13A) or ground wire (Figure 11-13B) to the battery ground (2) cable. b. Connect a fused test lamp from the battery positive (1) terminal to the clutch coil lead wire. c. If the test lamp does not light, the clutch coil is defective (open) and must be replaced. d. If the test lamp lights, the clutch coil is not defective. NOTE: If the clutch coil is shorted, the test lamp will also light. If suspected of being shorted, hold the resistance test as outlined in Job Sheet 49. e. Reinspect the ground wire, rotor, and armature to determine the problem. f. Correct as necessary.

FIGURE 11-12  Inspect the clutch rotor and armature surfaces.

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PHOTO SEQUENCE 16 Procedure for Testing PCM-Controlled Air Conditioners

P16-1  Locate the power train control module (PCM) and gain access to its wiring harness. Disconnect the PCM.

P16-2  Check for a poor connection at the PCM.

P16-3  Inspect the wiring harness for damage.

P16-4  Connect a digital voltmeter to the relay driver circuit at the PCM harness connector.

P16-5  Turn the ignition switch to ON. Do not start the engine.

P16-6  Observe the voltmeter while moving connectors and wiring harness relating to the relay.

P16-7  Note any change in voltage while moving the relay driver wiring harness. Change indicates a wiring harness fault.

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Lead wire

Lead wire Ground wire

Or

Frame

Frame A Clutch coil assembly

B Clutch coil assembly Lead wire

Frame C Clutch coil assembly FIGURE 11-13  Clutch coil electrical connection: (A) grounded through the frame, (B) grounded through the ground wire, and (C) grounded through the connector.

Noisy

The thickness of a snapring is just as important as its diameter.

Problem 1. Slipping belt 2. Misaligned belt 3. Clutch slipping 4. Rotor/pulley snapring missing 5. Rotor/pulley snapring improperly installed 6. Rotor-to-armature air gap too small 7. Improper field coil snapring 8. Field coil snapring installed improperly 9. Damaged bearing

Remedy Tighten belt Align belt See “Clutch Will Not Engage” Replace snapring Properly install new snapring Properly adjust air gap Install proper snapring Reinstall snapring Replace clutch assembly

Burned Clutch

A burned clutch is often noted by charred paint, blued steel, melted bearing seals, broken springs, or a charred field coil. To prevent a recurrence, all of the problems leading to a 454 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

burned clutch should be addressed before replacing it. These problems and the recommended remedies are: Problem 1. Compressor shaft seal leak 2. Compressor thru bolt leak 3. Oil leak: engine, power steering, transmission 4. Missing rotor/pulley snapring 5. Improperly installed rotor/pulley snapring 6. Improper field coil snapring 7. Improperly installed field coil snapring 8. Mismatched components

Clutch Will Not Engage

Problem 1. Excessive air gap 2. Poor electrical connection(s) 3. Undersized wiring 4. Damaged wiring 5. Defective clutch relay 6. Electrical component failure 7. Shorted field coil 8. Open field coil

Clutch Will Not Disengage

Problem 1. Improper air gap 2. Rotor/pulley snapring not installed 3. Rotor/pulley snapring improperly installed 4. Electrical problem

Remedy Replace shaft seal Repair as required Repair or replace as required Make sure that snapring is installed Make sure that snapring is properly installed Make sure that snapring is proper Make sure that field coil snapring is installed properly Replace with matched components

Remedy Adjust air gap Repair as required Use minimum 18-gauge wire Repair as required Replace relay Replace defective component Replace field coil Replace field coil

Remedy Adjust air gap Install snapring Reinstall snapring Correct problem as required

Pressure Switches and Controls There are many types of pressure switch controls used in the automotive air-conditioning system. These are the low-pressure cutoff switch, high-pressure cutoff switch, compressor discharge pressure switch, and pressure cycling switch. Replacement is rather simple. Remove the old pressure switch and install a new one. A word of caution, however. If it is not known if the switch is equipped with a Schrader-type service port, the refrigerant must first be removed from the system. At atmospheric pressure, a low- or high-pressure switch should be normally closed (nc). If there is a low-pressure switch, a vacuum pump may be used to see at what low pressure (if any) it opens. Similarly, a nitrogen source may be substituted for the vacuum pump to test the operation of a high-pressure switch. A test lamp is used to determine if and when the pressure switch opens or closes.

Many component malfunctions are due to a defective ground connection.

Classroom Manual Chapter 11, page 347

When replacing a pressure switch, make certain that the new replacement is the same pressure range as the old defective one.

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TEMPERATURE GAUGE INACCURATE OR INOPERATIVE Disconnect the temperature gauge sender wire. Connect the system tester to the sender wire and a good ground. Turn the ignition ON.

Gauge responds to tester accurately.

Gauge does not respond or reading is inaccurate.

Gauge indicates well beyond “HOT” end of scale.

Replace sender.

Disconnect gauge leads at engine harness connector. Connect gauge wires to system tester.

Remove gauge. Check for loose nuts and poor ground.

Gauge responds to tester accurately.

Gauge does not respond to tester.

Check wiring between the sender connector and the engine harness. Repair as required.

Remove the gauge. Check for loose or open connections at gauge and instrument cluster connector.

Connections OK.

Loose or open connections.

Replace gauge.

Repair connections. Reinstall gauge.

Connections and ground are OK. Replace gauge. Loose nuts or ground connection. Reinstall gauge. Tighten nuts or repair the ground connection. Reinstall gauge.

FIGURE 11-14  A diagnostic chart for a typical temperature gauge/sending unit test.

Classroom Manual Chapter 11, page 350

Classroom Manual Chapter 11, page 352

Coolant Temperature Warning Switches There are two types of coolant temperature warning systems: warning lamps and gauge ­systems. Testing the warning lamp system is rather straightforward. If the lamp(s) is/are good and the wiring is sound, an inoperative system is generally due to a defective sending unit. It is a relatively simple matter to substitute a new sending unit if a defective unit is suspected. The gauge system requires the use of a tester, however. A diagnostic chart of a typical temperature gauge/sending unit test is shown in Figure 11-14.

Vacuum Switches and Controls Vacuum-controlled actuators, often called motors, are used to position the A/C-defog valve, up-mode valve, down-mode valve, and the inside air valve (Figure 11-15).

Sensor Testing with a Scan Tool

Most scan tools will display the voltage values or switch position of many sensors. Access to this information differs, depending on the scan tool used. For example, when using the Tech2 (Figure 11-16), if the tool display reads BODY COMP MENU, select STATE DISPLAY. The display will change to BODY COMP STATE. By selecting SENSORS, the value of selected 456 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

To engine manifold

Vacuum reservoir Outside air shut-off door

Blower motor

Heater control head Temperature door

Defrost

(cable operated)

Dash outlets

Mode door

Demister

Heater core Heat door FIGURE 11-15  A typical vacuum control schematic.

FIGURE 11-16  The Tech2 scan tool used by General Motors and Isuzu.

sensors can be viewed. If the technician is interested in a switch position, select INPUTS/ OUTPUTS, and the display will indicate the various positions of various switches used as inputs to the computer.

Breakout State A breakout box (Figure 11-17) is a device that, when connected between the module and the wiring harness, allows the technician to “see” the exact information the computer is receiving and sending. The breakout box taps directly into the sensor or actuator circuit, providing the technician with the exact voltage signal being sent or received. A breakout box connected into the system allows a digital multimeter (DMM) to be used to measure the voltage signals and resistance values of the circuit (Figure 11-18). The diagnostic manual provided with the breakout box

A breakout box is a tool that is connected to the vehicle wiring harness and is used for pinpoint testing circuits with a voltmeter or ohmmeter.

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FIGURE 11-17  A breakout provides test points for voltmeter and ohmmeter connections.

FIGURE 11-18  Using the breakout box to test a circuit.

should be used as a guide through a series of test procedures. Comparing the test results with specifications will lead to the problem area.

Automatic (Electronic) Temperature Controls The two basic automatic temperature control (ATC) systems are those that use their own microprocessor (climate control module) and those that incorporate the controls of the system into the BCM. Always refer to published manufacturer diagnostic information and technical service bulletins (TSBs) before attempting any repair. As with any other electrical system diagnosis and repair procedure, you will need to refer to circuit schematics and specifications for the vehicle you are diagnosing. Even ATC systems of the same manufacturer will have different service and diagnostic procedures based on the specific model and year of the vehicles. It cannot be overemphasized that specific make, model, and year vehicle service information is required to accurately 458 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

diagnose and troubleshoot ATC systems. That being said, there are similarities among systems and the fundamental sensor operation and diagnosis are the same. With the complexity and interconnectedness of today’s computer and network-controlled systems, you must always be thinking about the interrelatedness of various vehicle systems and subsystems. Prior to attempting to diagnose any ATC system complaint, first verify that there are no power train codes (P0XXX or P1XXX) or network codes (U0XXX) present. A P0115—Engine Coolant Temperature Circuit Malfunction—may not allow the compressor clutch to be engaged.

Programmer

The programmer is generally identified by the electrical and vacuum lines attached to it. It primarily contains a small circuit board that controls a small reversible DC motor that adjusts the air mix valve to blend cold and warm air. It also contains four vacuum ­solenoids that control the various vacuum mode actuators. The programmer also p ­ rovides data for blower speed selection and operation to provide selected in-vehicle temperature conditions. Typically, to remove the programmer (Figure 11-19), gain adequate access by removing the right-side sound barrier and glove box. Then: 1. Remove the brackets and covers to gain access to the programmer. 2. Remove the threaded rod from the programmer. 3. Remove the vacuum connector retaining nut. 4. Remove the vacuum and electrical connectors from the programmer. 5. Remove the programmer from the vehicle. 6. To replace, reverse the preceding procedure.

Blower Control

For any given ECC signal, the blower control module has a predetermined blower motor voltage value. A signal from the BCM to the programmer causes a variable voltage signal to be sent to the power module. Variable Resistor Test.  (Figure 11-20) The control assembly variable resistor, also referred to as a sliding resistor or blower speed control, can be tested in or out of the vehicle by the following procedure: 1. Disconnect the electrical connector to the variable resistor. 2. Connect an ohmmeter’s test leads across the terminals. 3. Set the comfort control lever to the 65 selection and note the resistance. The resistance in this position should be less than 390 ohms (390 Ω). 4. Slowly move the comfort control lever toward the right while observing the ohmmeter. When the ohmmeter indicates 930 H, the lever should be near the 75 setting. Temperature blend lever

Link

Programmer

Classroom Manual Chapter 11, page 358

Solenoids are electromagnetic devices controlled remotely by electrically energizing or de-energizing a coil.

SERVICE TIP:

If you suspect an intermittent electrical problem with the climate control module, grasp the wiring harness near the module connection and shake it. Next, lightly tap the module assembly to see if the problem is affected by the vibrations. This will aid in locating troublesome intermittent internal connections or board failures. The variable resistor assembly is also referred to as a sliding resistor.

Recirculation air inlet assembly FIGURE 11-19  A typical programmer.

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Sliding resistor Ohmmeter

The compressor clutch is used to turn the compressor on and off. A diode may be thought of as an electrical check valve; it provides current flow in one direction and blocks current flow in the opposite direction.

FIGURE 11-20  Testing the control assembly slide resistor with a DMM on the Ω setting. The resistor values should be within specifications and the transition should be smooth as the level is moved.

NOTE: The ohmmeter should have indicated a smooth increase in resistance. 5. Move the lever to the 85 setting. The resistance value should increase smoothly to at least 1,500 Ω. If the resistance values are not within these specifications or the increase in resistance is not smooth, the control assembly must be replaced.

Clutch Control

Spikes are unwanted momentary highvoltage electrical surges.

The compressor clutch is controlled by the PCM from inputs to the PCM, such as engine coolant temperature as well as rpm, and to the body computer module (BCM), such as outside temperature, in-car temperature, sun load temperature, and air-conditioning system high-and low-side temperatures/pressures. The clutch diode (Figure 11-21) is found connected across the electromagnetic clutch coil in many systems. Its purpose is to prevent unwanted electrical spikes that could damage delicate minicomputer electrical systems and subsystems as the clutch is engaged and disengaged.

Diode 12 V From clutch control

Clutch coil Ground

FIGURE 11-21  A clutch diode prevents electrical spikes.

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Climate Control System Sensors Many climate control sensors are similar in design and function to sensors used in other systems, such as engine management and emissions control systems. The service technician needs to have a good understanding of basic electricity and electronics first. The Today’s Technician Automotive Electricity and Electronics textbook is a good place to start. Today’s systems require the use of enhanced diagnostic scan tools and manufacturer service information to accurately diagnose both sensor and software used in climate control systems. Always refer to published diagnostic information and TSBs before attempting any repair. The following is an overview of sensor operation and diagnosis for common automatic climate control systems.

Evaporator Temperature Sensor

The evaporator temperature sensor, also called a fin sensor (Figure 11-22), is an NTC thermistor that monitors the temperature of the evaporator core. The sensor probe is inserted between the evaporator fins to sense changes in core temperature. The sensor modifies a voltage reference signal (Figure 11-23) with a change in evaporator temperature and this signal is sent to the climate control module or BCM/PCM. This sensor may be either a two-wire or a three-wire sensor depending on the make and model of the vehicle. The two-wire design uses a 5 V reference wire and a signal return wire to the control module. The three-wire design has a 5 V reference wire, a signal return wire, and a ground wire all connected to the control module. The evaporator temperature sensor is used by the control module to turn the compressor clutch ON and OFF. When evaporator temperature typically drops below 338F (18C), a command is sent over the data bus to the PCM to interrupt compressor clutch engagement to prevent condensed water from freezing on the evaporator fins and restricting airflow. To prevent rapid compressor cycling, the control module does not request the compressor back on until the evaporator temperature rises to a temperature above the turn-off temperature, generally 378F (38C) to 458F (78C). By comparing the readings from a DMM, scan tool, and thermometer the sensor can be diagnosed for accurate operation.

As a thermistor’s temperature increases, its resistance decreases.

Classroom Manual Chapter 11, page 370

Evaporator housing

Thermistor in place FIGURE 11-22  An evaporator temperature sensor (thermistor).

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HVAC controller 5V IC

Fin probe-type evaporator temperature sensors

Evaporator housing

Pickup in place

FIGURE 11-23  The evaporator temperature sensor is an NTC thermistor.

Following is an example of a typical chart for evaporator sensor values at various temperature ranges. Temperature

Classroom Manual Chapter 11, page 366

Voltage

Resistance in kΩ

508F (108C)

1.90

9.95

458F ( 7.28C)

2.06

11.38

408F ( 4.48C)

2.23

13.05

358F (1.68C)

2.40

15.00

308F (21.18C)

2.58

17.29

258F (23.98C)

2.76

19.99

208F (26.78C)

2.94

13.19

158F (27.28C)

2.98

23.90

Sun Load Sensor

The sun load sensor is located on the top of the dash panel where the sun rays will hit the sensor in the same manner they would hit the front passengers. The sun load sensor is a

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Body control module (BCM) 5V IC

Photodiode Sunload sensor

FIGURE 11-24  The sun load sensor is a photodiode that is mounted on the top surface of the instrument panel.

photodiode that modifies a voltage signal by varying sensor resistance with a change in sunlight levels (intensity), not temperature (Figure 11-24). The sun load sensor is not serviceable or adjustable and must be replaced as an assembly if defective. The first step in the diagnostic process is to verify that the sensor is unobstructed: ■■ Check that there are no window stickers on the windshield directly above the sensor. ■■ Check that there are no items such as parking passes on top of the dashboard in front of sensor. ■■ Check that the defroster grille and sun load sensor are properly installed. ■■ Check the position of the wiper blades and arms. When a customer complains of poor system performance on sunny days, especially in the early afternoon, the position of the sun load sensor should be checked. The sun load sensor operation is typically checked using a scan tool and DMM. Refer to vehicle-specific service information and electrical diagrams for diagnostic information. Faults in the sun load sensor circuit will set a diagnostic trouble code. WARNING: On vehicles equipped with air bags, disable the air bag system before attempting to diagnose or work on the steering column, instrument panel, and dash assemblies. Failure to follow manufacturer’s service warning may result in personal injury or death. Sun load sensor quick test: 1. Park the vehicle outside on a sunny day. 2. Turn the ignition to the ON position, but do not start the vehicle yet. 3. Connect the scan tool to the vehicle data link connector (DLC). 463 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

5 4 3 Volts 2 1

0.233 0.465 0.698 930 1.163 1,396 1,628 (200, (400, (600, (800, (1,000, (1,200, (1,400, 794) 1,587) 2,381) 3,174) 3,968) 4,762) 5,555) Sunload kW (kcal/h)m2 FIGURE 11-25  The sun load sensor is photodiode sensor: As the sun intensity increases, the signal line voltage will decrease.

4. Select “Sensor Data Stream” from the menu. 5. Observe the sun load sensor input value (Figure 11-25). 6. Start the engine and allow it to idle. Turn the air-conditioning system on and select FULL AUTO mode. Set the temperature to approximately 708F (218C) on the ATC system. Allow the vehicle to run and the system to stabilize for 10 minutes. 7. Cover the sensor with a dark piece of paper or cloth while observing data values on the scan tool. Cover and uncover the sensor several times, waiting 30–60 seconds between each interval to give the system time to react. The sensor data values should respond quickly to changes in light levels. If the sensor values do not change, further diagnosis will be required. Consult specific vehicle service information for detailed diagnostic steps. If data steam values are not available with the scan tool you are using, perform the preceding test and pay attention to blower motor speed and center duct output temperature. Both the air volume and temperature should change during the test. Classroom Manual Chapter 11, page 371

Infrared Temperature Sensor

The infrared temperature sensor detects and measures thermal radiation emitted by the front seat passenger area and converts this data into a pulse width modulated output signal that is sent to the ATC module. The ATC system software logic uses the input information to adjust airflow temperature and flow rate to compensate for solar heat gain or evaporator heat loss in order to maintain the comfort level selected by the passenger(s). Sensor operation is checked using a diagnostic scan tool. Refer to vehicle-specific service information and electrical diagrams for diagnostic information. The ATC module continuously monitors the infrared temperature sensor circuit and will set diagnostic trouble codes for any circuit or sensor malfunction. Infrared temperature sensor quick test: 1. Turn the ignition to the ON position, but do not start the vehicle yet. 2. Connect the scan tool to the vehicle DLC. 3. Select “Sensor Data Stream” from the menu. 4. Observe the infrared temperature sensor input value.

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5. Start the engine and allow it to idle. Turn the air-conditioning system on and select FULL AUTO mode. Set the temperature to approximately 708F (218C) on the ATC system. Allow the vehicle to run and the system to stabilize for 10 minutes. 6. Get two small buckets and two small towels. Fill one bucket with hot water and place a towel in it. Fill the other bucket with cold water and ice and place the other towel in this bucket. 7. Squeeze out the cold towel so as not to drip water on the interior of the car, and allow it to hang directly in front of the sensor while observing data values on the scan tool. Next squeeze out the hot towel so as not to drip water on the interior of the car, and allow it to hang directly in front of sensor while observing data values on the scan tool. Repeat this process from cold to hot several times, waiting 30–60 seconds between each interval to give the system time to react. The sensor data values should respond quickly to changes in heat levels. If the sensor values do not change, further diagnosis will be required. Consult specific vehicle service information for detailed diagnostic steps. If data steam values are not available with the scan tool you are using, perform the preceding test and pay attention to blower motor speed and center duct output temperature. Both the air volume and temperature should change during the test.

Coolant Temperature Sensor

The engine coolant temperature sensor is an NTC thermistor and is mounted in an engine coolant passage. Like other sensors, it is supplied a 5 V reference voltage that is modified by the resistance of the sensor (Figure 11-26). This modified voltage is sent via the signal line to the PCM/ECM and shared on the data bus line. The sensor resistance can range from 100,000 ohms to a few hundred ohms depending on coolant temperature. An increase

Classroom Manual Chapter 11, page 371

PCM 12V 5V Coolant temperature sensor Voltage sensing circuit

(4.5V) Resistance

Voltage (0.3V)

Cold

Hot

FIGURE 11-26  The engine coolant temperature sensor is an NTC thermistor.

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in temperature will cause a decrease in sensor resistance. If a high-temperature condition is detected, the PCM/ECM will deactivate the air-conditioning compressor clutch relay. When the engine returns to normal temperature, the control module will reengage the compressor clutch. The ATC system also uses coolant temperature information as part of its cold engine lockout strategy and will not allow the blower motor to operate until warm coolant is available for heating the air via the heater core. Coolant temperature sensor quick test: 1. Turn the ignition to the ON position, but do not start the vehicle yet. 2. Connect the scan tool to the vehicle DLC. 3. Select “Sensor Data Stream” from the menu. 4. Observe the coolant temperature value. 5. Using a noncontact infrared thermometer, measure the temperature at or near the ­coolant temperature sensor. If the data stream value and the measured temperature are the same, proceed to the next step. If the values are not the same, further diagnosis will be required. 6. Start the engine and allow it to idle. 7. For the next 10 minutes monitor the actual sensor temperature and scan tool data value for engine coolant temperature. If they are similar, the system is operating normally. If the values are not the same, further diagnosis will be required. Consult specific vehicle service information for detailed diagnostic steps. Classroom Manual Chapter 11, page 367

Ambient Temperature Sensor

To test the ambient temperature sensor (ATS), first remove it from its socket and then measure its resistance using an ohmmeter. At an ambient temperature between 708F and 808F (218C and 278C), the sensor resistance should be between 225 and 235 H. If the resistance is not within this range, the ambient sensor is defective and must be replaced. NOTE: Because ohmmeter battery current flow through the sensor and body heat will affect the readings, do not hold the sensor in your hand or leave the ohmmeter connected for longer than 5 seconds (Figure 11-27).

DVOM

Ambient temperature sensor

60

70 80 90

Thermometer FIGURE 11-27  Test the ambient temperature sensor at room temperature. Avoid touching the sensor during testing. Also, do NOT connect the ohmmeter for longer than 5 seconds.

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In-Car Temperature Sensor

The in-car temperature sensor, a thermistor, is located inside an aspirator. To provide an accurate temperature reading, a small sample of air is drawn through the aspirator across the in-car temperature sensor. The resistive value of the in-car temperature sensor is sent to the BCM and is used by the ECC for calculations to maintain the preselected in-vehicle temperature conditions. The following procedure may be used to test the in-car temperature sensor: 1. Disconnect its electrical connector. Do not disconnect the aspirator tubes or remove the temperature sensor from the panel. 2. Place a test thermometer into the air inlet grill near the sensor. 3. Set the blower motor speed control to MED. 4. Depress then pull out the NM-A/C button. This will turn off the compressor and close the water valve. 5. Operate the blower while quickly measuring the resistance of the sensor. NOTE: Do not leave the ohmmeter connected to the sensor terminals for longer than 5 seconds or inaccurate readings will result. Ohmmeter battery current flow through the sensor, a thermistor, and body heat will affect resistance. Resistance of the in-car temperature sensor should be 1,100–1,800 H at an ambient temperature between 708F and 808F (218C and 278C). The sensor must be replaced if the resistance is not within these specifications.

Aspirator

The aspirator is an assembly device that houses the in-car temperature sensor (Figure 11-28). A quick method for testing the aspirator assembly to verify that it is providing enough ­airflow to the in-car temperature sensor is to set the controls for HI blower speed while in the heat mode of operation. Place a piece of paper, large enough to cover the aspirator air inlet, over

Classroom Manual Chapter 11, page 369

An aspirator is a device that uses a negative pressure (suction) to move air. To aspirate is to draw by suction.

Instrument panel In-car sensor

Aspirator tube

In-car air

Aspirator

Out

In Main airstream

FIGURE 11-28  A typical in-car temperature sensor and aspirator.

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Cover air inlet

FIGURE 11-29  When performing the aspirator paper test, the vacuum should hold the paper against the grille.

the inlet (Figure 11-29). The suction of the aspirator should be great enough to hold the paper against the inlet grille. If it is not, refer to the aspirator system diagnostic chart in Figure 11-30. Classroom Manual Chapter 11, page 363

Pressure Transducer

The pressure transducer is mounted on the high-pressure discharge line from the refrigerant compressor and shuts off the compressor if discharge pressure is either too high or too low. Some systems also use the signal to control condenser cooling fan operation. The pressure transducer is a three-wire sensor consisting of a 5-volt reference, ground, and output signal wire (Figure 11-31). The pressure transducer varies voltage on the signal wire in relation to refrigerant system high-side pressure. An increase in pressure will cause an increase in signal voltage. The operating range for the sensor is 0.10 volt for zero (0) psig and 4.90 volts for 450 psig (3,103 kPa). The normal operating range for the sensor is 1.0 V 5 75 psig (517 kPa) to 4.4 V 5 400 psig (2,758 kPa). When diagnosing no compressor action you will need to verify the proper operation of the pressure transducer using a scan tool and manifold and gauge set. With the vehicle running and the HVAC system turned on, compare the pressure gauge readings to the pressure displayed on the scan tool data screen to verify proper operation. If the scan tool does not displace the same pressure as that displaced on the gauge diagnosis of the sensor, wiring and processor operation will be required. A quick method for diagnosing sensor wiring and the processor’s ability to interpret data is to attempt to set both a high-and a low-voltage signal code. To set a high-voltage code disconnect the sensor harness, and on the harness side of the connector, using a fused jumper lead, connect the 5 V reference wire to the signal wire. If the processor is working correctly a high-voltage (pressure) code will be set. Next, try to set the opposite code for a low-voltage (pressure) condition. Again, disconnect the sensor harness and on the harness side of the connector, using a fused jumper lead, connect the ground wire to the signal wire. If the processor is working correctly a low-voltage (pressure) code will be set.

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See the “Component Removal and Testing” section for the aspirator. Is aspiration enough to pass the “paper” test? Yes Aspiration OK

No Are the hoses connected to the aspirator loose or disconnected?

Repair as required

Yes

No Suction to in-car sensor Air drive to heater-A/C

Repair as required

Yes

Are the air drive and suction hoses interchanged on aspirator? No Is air discharged from the aspirator?

No

Repair as required

No

Yes

Check for kinks in air drive hose or blockage in hose or aspirator

Repair

Yes Disconnect the in-car sensor hose from the aspirator. Check for blockage by blowing into hose. Is hose restricted?

Is air discharge nipple of heater-A/C unit clogged?

Yes

No Is in-car sensor properly plugged into the instrument panel?

No

Repair as required

Is in-car sensor hose blocked? No

Are there any holes in the air drive or in-car sensor hoses?

Yes

Repair as required

No Are there any leaks in the instrument panel air inlet chamber?

Yes

Repair as required

Repair

Unplug in-car sensor. Does sensor hose still block airflow? No Blockage in air panel inlet chamber or grille

No

Yes

Yes Repair

Replace aspirator FIGURE 11-30  Aspirator diagnostic test chart.

Powertrain control module (PCM) 5V 5V

IC

A/C pressure transducer FIGURE 11-31  The refrigerant system pressure transducer varies voltage on the signal wire in relation to refrigerant system high-side pressure and sends this information to the control module.

469

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Powertrain control module (PCM) 5V 5V

IC

1.5V AAA

FIGURE 11-32  The pressure transducer signal line may be test using a 1.5 V battery. Connect a jumper wire from the ∙ battery terminal on the 1.5 V AAA battery to the PCM signal sensing line, and use another jumper lead to connect the negative terminal to the PDM ground to send fixed information to the control module.

SERVICE TIP:

If you suspect an intermittent electrical problem with the climate control system, such as a short or open connection, grasp the wiring harness and shake it, especially near connections and splices, both in the engine compartment and behind the dash panel if access allows. This will aid in locating troublesome intermittent connections.

Classroom Manual Chapter 11, page 365

In the event that you do not have access to a scan tool, you can use a 1.5 V AAA battery to fool the computer into thinking it is receiving a valid pressure transducer voltage signal. With the vehicle running and the HVAC system turned on, disconnect the pressure transducer harness connector. Using two jumper leads connect the positive terminal of the 1.5 V battery to the signal wire and connect the ground terminal of the battery to the connector ground wire (Figure 11-32). If the air-conditioning compressor engages, the pressure transducer is faulty; only allow the refrigerant system to operate for less than a minute during this test to avoid the potential for system overpressurization.

Temperature and Mode Door Control

Heater Flow Control Valve

The heater flow control valve is opened or closed by a signal from the BCM to provide in-vehicle temperature control. If the valve is found to be defective, it must be replaced. Photo Sequence 17 illustrates a typical procedure for replacing a heater flow control valve.

Actuators

An actuator is a device that transforms a vacuum or electrical signal to a mechanical motion. It is the component that performs the actual work commanded by the computer. An actuator may be an electric or vacuum motor, relay, switch, or solenoid that typically performs an on/off, open/close, or push/pull operation. Testing Actuators.  Most systems allow for testing of the actuator through the scan tool or FCC panel while in the correct mode. Actuators that are duty cycled by the computer are more accurately diagnosed through this method. As in the earlier example of r­ etrieving trouble codes from the Chrysler system using the DRB-II scan tool, select ACTUATOR TESTS. This will allow activation of selected actuators to test their operation.

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PHOTO SEQUENCE 17 Typical Procedure for Replacing a Heater Flow Control Valve

P17-1  Drain the coolant from the system and recycle it.

P17-2  Loosen and remove the inlet hose clamp at the heater core. Slip the heater hoses off their fittings.

P17-3  Loosen and remove the retaining bolt for the bracket of the heater control valve.

P17-4  Remove all other heating control valve retaining bolts and any parts that may interfere with the removal of the control valve.

P17-5  Remove the control valve and inspect the hoses connected to it.

P17-6  Clean the coolant pipes and hoses. Make sure all damaged parts are replaced. Then replace the heater control valve.

P17-7  Install and tighten all heater control valve and valve bracket retaining nuts and bolts.

P17-8  Install new clamps and connect the heater hoses to the heater core.

P17-9  Fill the cooling system with fresh coolant to the correct level. Bleed the system, if necessary.

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PHOTO SEQUENCE 17

(CONTINUED)

P17-10  Pressure test the system and check for leaks. Run the engine and allow it to reach normal operating temperature. Then shut it off and retest for leaks.

A servomotor is an electrical motor that is used to control a mechanical device, such as a coolant control valve.

Servomotors

A servomotor is a vacuum or electric motor that is used to control the position of the mode and blend air doors in an automotive heating and air-conditioning case/duct system. Servomotor Test.  The servomotor must be removed from the vehicle for testing. Follow the procedures outlined in the service manual for removing the motor. While operating the motor, check for smooth operation and observe the testlight. If the motor briefly jams, the testlight illumination level will increase. If the testlight flickers while the motor is operating, the motor is not moving in a smooth fashion. The motor must be able to move to the full cw and full ccw position. If the cause of a problem cannot be corrected, the servomotor will have to be replaced.

Diagnosing SATC and EATC Systems

EATC stands for electronic automatic temperature control.

Semiautomatic or automatic control of the interior (cabin) temperature is made p ­ ossible through the use of electronic components such as microprocessors, thermistors, and ­p otentiometers that control vacuum and electric actuators. A failure in any of these ­components will result in inaccurate or no temperature control. Today’s technician must possess a basic knowledge and understanding of the operating principles of both the semiautomatic temperature control (SATC) and electronic automatic temperature control (EATC) systems and must be proficient at diagnosing and servicing these systems. These troubleshooting procedures include that portion of the system that controls its operation. Procedures to troubleshoot the other components of the system are found elsewhere in this manual.

SATC System Diagnosis

An SATC system controls both the operating mode and blower fan speed of the air-­ conditioning system. Faults within the evaporator and heater systems will have an adverse effect on the operation and control of the SATC system. To properly troubleshoot and service an SATC system, a schematic and specifications for the vehicle being diagnosed are essential. Motors and compressor clutch circuits of the SATC system are tested in the same manner as manual temperature control (MTC) systems. The air delivery control of SATC systems differs among manufacturers and requires specific diagnostic procedures. Most such systems have specific tests to troubleshoot each

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Two-terminal connector

Jumper wire

FIGURE 11-33  Jumper wire connections to set the blend door to the minimum position.

particular system, and reference should always be made to each model’s service manual. A typical example of one system and its procedures follows. Chrysler SATC Troubleshooting.  To perform some of the service manual tests on ­Chrysler’s pre-CAN bus network SATC system, it may be necessary to place the blend air door in one of three different positions. When locking the blend door in the full and minimum positions, set the controls for LOW blower speed and BI-LEVEL mode. Follow these procedures for setting the door position: 1. Set the blend door in the full reheat position by disconnecting the in-car sensor and ­turning the system ON. 2. Obtain the minimum reheat position by connecting a jumper wire between the red ­terminal wire from the variable resistor and ground (Figure 11-33) and then turning the system ON. DO NOT connect the jumper wire to the sensor side of the red terminal. 3. a. Set the blend door in the middle position by first disconnecting the negative battery cable and removing the ground screw on the passenger side cowl. b. Next, connect a jumper wire from the blower ground wire (black wire with tracer) to a good ground. c. Then reconnect the battery negative cable. d. Finally, move the temperature control lever until the blend door moves to the middle position. e. Then disconnect the jumper wire. Refer to the test point diagram in Figure 11-34 for the particular vehicle being serviced. Use a voltmeter to measure the voltage between points A and B and points J and I while the system is placed in any mode other than OFF. The voltage values at these test points should be 11 volts or more. Before performing the continuity tests (Figure 11-35 and Figure 11-36), disconnect the in-car sensor and the power feed connector. Follow the continuity test procedures to determine any system defects.

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A minimum supply of 11 volts should be available between points

Ambient sensor

Control head assembly sliding resistor

In-car sensor

J to I when system is in any mode except “OFF.”

H

K

G

E

F

D

C

J

Electronic servo motor

I

B+

FIGURE 11-34  Chrysler semiautomatic temperature control system electrical test points.

SATC CONTINUITY TEST PROCEDURE Check continuity between test points B and F. Is resistance less than 1,500 Ω or will the self-powered testlight glow?

Yes

No Remove ambient sensor socket from unit. (With sensor in socket jumper across sensor leads.) Is resistance 0 Ω or will self-powered testlight glow between test points B and F?

No

Remove the ambient sensor from its socket. Is resistance between test points B and F less than 5 KΩ or will selfpowered testlight glow? Is resistance between test points G and F 0 Ω or will self-powered testlight glow?

Yes

Yes Short to ground in circuit C22 No Test ambient sensor Yes Open in circuit H4 No

Test in-car sensor, refer to “Component Removal and Testing” section

Does not pass test

Replace

Open in circuit C22

In-car sensor OK Test ambient sensor Ambient sensor OK Perform continuity test II

Does not pass test

Replace Caution: A self-powered testlight must be used to test circuit. Do not apply external 12-volt source to test circuits.

FIGURE 11-35  SATC continuity test procedure (part 1).

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SATC CONTINUITY TEST PROCEDURE Refer to “Component Service Procedures” section for information on servomotor and control head assembly sliding resistor. Disconnect SATC electrical harness between sliding resistor and servomotor. Refer to wiring schematic for SATC. Check continuity between test points A to I, K to C, D to E, F to G, H to J, and J to B.

Open circuit

Repair harness

Continuity OK Check for short between points I to J, J to K, D to C, and E to F.

Short circuit

Repair harness

No short circuits Test components. Refer to “Component Service Procedures” section. FIGURE 11-36  SATC continuity test procedure (part 2).

EATC System Diagnosis Proper diagnostics of EATC systems depends on system design. There are two basic system designs: those that use their own microprocessor and those that incorporate the controls of the system into the BCM. Since the first introduction of CAN networked systems in the early 2000s, system operation has varied depending on vehicle model and year. Some systems allow the retrieval of DTCs and other data using a scan tool. Other systems do not support scan tool diagnostics and still rely on self-diagnostics through the climate control head as in the past. Still others support both scan tool diagnostics and self-diagnostics via the control head. Scan tool diagnostics operate in the same manner for climate control systems as it does for engine and emissions-related diagnostics. Scan tools give the technician the ability to look at the sensor and actuator date and, in many cases, bidirectional control is possible. Bidirectional control allows the scan tool to function as the control module, allowing the technician to command actuators ON and OFF, such as the compressor clutch relay and mode door motor position. Trouble codes for climate control systems may be in the form of typical power train-related codes (i.e., PXXXX), body-related codes (i.e., BXXXX), and sometimes are network-related fault codes (i.e., UXXXX). It is important never to ignore any diagnostic trouble code when systematically troubleshooting a failure with a climate control system or subsystem. Please refer to the end of Chapter 11 in the Classroom Manual for a list of codes relevant to the climate control system; the list is comprehensive but is in no way meant to substitute for manufacturer’s service and diagnostic information. You should explain to a customer that systems today are interrelated and a fault in one system often causes performance issues in another system.

Classroom Manual Chapter 11, page 380

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The following discussion focuses on the self-diagnostic routines on a dual climate control system used on Jeep to illustrate the diagnostic capabilities of these systems. The automatic zone control (AZC) system performs self-diagnostic routines as part of normal system operation similar to the diagnostic routines used in OBD II power train systems. During normal operation, the control module continuously monitors various system parameters. In the event a fault is detected, both a current and a history code will be stored. If the fault is intermittent, the current code will be erased after several successful drive cycles, but the history code will remain. The fault code may be retrieved by using a scan tool or entering the self-diagnostic mode through the front display panel of the control head. The control panel has three different self-diagnostic routines. They are the fault code test, the input circuit test, and the actuator test. Like older automatic and semiautomatic climate control systems, self-diagnostics is entered by performing a sequence of steps within a specific period using the control head buttons or knobs. To enter self-diagnostics, turn the ignition key to the RUN position with engine OFF. Depress and HOLD both the A/C and the RECIRC buttons and rotate the left temperature control knob cw one detent (Figure 11-37). During this phase of the test, all ­segments of the control panel should illuminate for as long as you hold the buttons. If the segments on the control panel fail to illuminate, replace the control head assembly. Once control panel illumination has been verified, release the A/C and the RECIRC ­buttons. The control panel will clear and then display any fault codes stored. A zero on the display screen indicates that no codes are stored. If fault codes are available, they will be ­presented in ascending number order. Each code will be displayed for 1 second. When all codes have been displayed, the code display cycle will be repeated until the left temperature control knob is rotated cw one detent or the ignition switch is turned to OFF. In order to erase fault codes, hold down the A/C and the RECIRC buttons for 3 seconds while the system is in the fault code display mode. Fault code clearing is verified when two bars appear on the display. It should be noted that only history codes can be cleared. The fault must be found and repaired before current codes are removed. After the fault code mode has been completed, the self-diagnostic select test mode phase may be entered. To select a test rotate the left temperature control knob until the desired test appears on the display screen. It will be necessary to refer to the manufacturer’s service information to determine the correct test number for the fault being diagnosed. Once you

To enter diagnostics mode

A/C

74

74

Hi

Lo Lo AUTO Hi

OFF AUTO

Left temperature control knob FIGURE 11-37  The automatic zone control head buttons and knobs are used to enter the selfdiagnostic mode.

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have scrolled to the correct test number and it appears on the display, press the A/C button to activate the test. As an example, “21” will test the current mode position. It should also be noted that on many automatic climate control systems today a relearn procedure is required if the control assembly, mode door actuators, or sensors are replaced. Also if the vehicle battery has been disconnected or completely discharged for an extended period, a relearn test may have to be conducted before the climate control system will function. With some makes and models, a scan tool is required to activate this relearn process. Always consult specific vehicle and manufacturer service information as well as TSBs before attempting a repair to familiarize yourself with the system.

Separate Microprocessor-Controlled Systems

Most EATC systems that use a separate microprocessor for diagnosis have the microprocessor contained in the control assembly (Figure 11-38). Also, most of these early systems provide a means of self-diagnostics and have a method of retrieving trouble codes. Typical examples of such systems follow. Nissan ATC Diagnostics.  The ATC systems used on Nissan/Infinity are similar in operation and function to that of the domestic manufacturers. The following discussion is based on the self-diagnostic system of an Infinity M35/45 but is representative of many Nissan platforms and serves as an example of diagnostic systems used on Asian import vehicles. The self-diagnostic system diagnoses HVAC system sensors, actuator motors, blower motor, and any electrical component associated with the climate control system. The self-diagnostic mode for this system is entered by first turning the key to the ON position and starting the engine. The OFF button on the A/C control panel must be pressed and held for at least 5 seconds. The OFF button must be pressed within 10 seconds of the engine starting. The self-diagnostic test will be cancelled if the AUTO button is pressed or the ignition is cycled to the OFF position. Moving from one test to the next is accomplished by pressing the temperature control buttons on the driver’s side (Figure 11-39). By pressing the UP temperature button you will advance forward in the self-diagnostic steps, and by pressing the DOWN temperature button you will back up one step. The following are the five basic steps of the self-diagnostic tests: 1. All of the LEDs and display segments are illuminated. If any of the segments or LEDs are not illuminated, the component is defective and the control head must be replaced.

Faceplate with keypad switches

Edgeboard connector Microprocessor FIGURE 11-38  Most EATC systems use a separate microprocessor located in the control assembly.

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Start engine

Within 10 seconds after starting engine, press

OFF

switch for at least

5 seconds FRESH VENT “OFF” Step 1 - LEDs and segments are checked

Ignition switch: OFF AUTO

switch: ON

Step 2 - Input signals from each sensor are checked

Ignition switch: OFF

Step 3 - Mode door motor position switch is checked

Ignition switch: OFF

AUTO

AUTO

switch: ON

switch: ON Self-diagnostic function is canceled

Step 4 - Actuators are checked

Ignition switch: OFF AUTO

Step 5 - Temperature detected by each sensor is checked

AUXILIARY MECHANISM Temperature setting trimmer

switch: ON

Ignition switch: OFF AUTO

switch: ON

Ignition switch: OFF AUTO

switch: ON

FIGURE 11-39  The five-step self-diagnostic process for Nissan/Infinity automatic temperature control systems.

2. Press the UP temperature control arrow to move to step 2. The input signals from each sensor are checked by the control module. If no faults are detected with the input sensors, the control head will display “20.” If an input sensor fault is detected a code for that sensor will be displayed. 478 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Code Number

Malfunctioning Sensor and Door Motor

21

Ambient Temperature Sensor

22

In-Car Temperature Sensor

24

Intake Sensor

25

Sun Load Sensor

26

Air Mix Door Motor PBR (Driver Side)

27

Air Mix Door Motor PBR (Passenger Side)

3. Press the UP temperature control arrow to move to step 3. The mode and intake door motor position switch(es) will be checked. If no faults are detected with the mode door or intake door motor position switch(es), the control head will display “30.” If a mode door or intake door motor position switch fault is detected, a code for the defective switch will be displayed ranging from 31 to 39. Code Number

Malfunctioning Mode Door Position Switch

31

VENT (driver’s side)

32

DEFROST (driver’s side)

33

VENT (passenger side)

34

DEFROST (passenger side)

35

VENT (open)

36

VENT (shut)

37

FRESH AIR

38

20% FRESH AIR

39

RECIRCULATION

4. Press the UP temperature control arrow to move to step 4. The actuators will be checked. The operation of each mode door motor is checked. The A/C control panel displays “41” and the control module positions the mode door in the vent position, then the intake door in the recirculation (REC) position, and the air mix door is moved to the full cold position. Press the DEF (defrost) button to move to the next mode in step 4 and “42” will be displayed on the control panel. There are six modes in step 4 and each mode is represented by a number on the A/C control panel. These numbers range from 41 to 46. The DEF button is used to select the next mode. In each mode, the A/C controller commands a specific door position, blower motor voltage, and compressor clutch operation. Door operation may be checked by the air discharge from the various ducts. Code Number

41

42

43

44

45

46

Mode Door Position

Vent

Bi-Level 1

Bi-Level 2

Floor

Defrost/Floor

Defrost

Upper Ventilator Door Position

Open

Closed

Closed

Closed

Closed

Closed

Intake Door Position

Recirculated

Recirculated

20% Fresh

Fresh

Fresh

Fresh

Air Mix Door Position

Full Cold

Full Cold

Full Hot

Full Hot

Full Hot

Full Hot

Blower Motor Duty Ratio

37%

91%

65%

65%

65%

91%

Compressor

ON

ON

OFF

OFF

ON

ON

Electronic Control Valve Duty Ratio

100%

100%

0%

0%

50%

100%

5. Press the UP temperature control arrow to move to step 5. Temperature detection by each sensor is checked. After this mode is entered, “51” is displayed in the A/C panel display. If the DEF button is pressed, the temperature sensed by the ambient air sensor is displayed on the control panel display. Press the DEF button again and the temperature sensed by the in-car sensor is displayed on the control panel display. Press the DEF button a third time and the temperature sensed by the intake sensor is displayed on the control panel display (Figure 11-40). When the temperature displayed varies significantly from the actual temperature, the sensor and connections should be tested with an ohmmeter and a voltmeter. 479 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Display

5

Display

Display Temperature detected by ambient sensor

Display Temperature detected by intake sensor

Temperature detected by in-vehicle sensor

FIGURE 11-40  Step 5 of the five-step self-diagnostic process for Nissan/Infinity automatic temperature control systems displays the temperature detected by each sensor.

Press the intake switch and CAN communication error between each unit is checked. If no faults with the CAN network are detected the control head will display “52.” After step 5 has completed, the blower speed button may be pressed to enter the auxiliary mode. After this mode is entered, “61” is displayed in the A/C panel display. Next, the temperature on the display may be adjusted so it is the same as the in-car temperature felt by the driver. After the auxiliary mode is entered, press the up or down temperature control buttons until the A/C control head displays the same temperature as that inside the vehicle. The temperature can be tailored 668F (638C) between the temperature displayed and that felt by the customer. Chrysler EATC Troubleshooting.  Before entering self-diagnostics, start the vehicle and allow it to reach normal operating temperature. Ensure that all exterior lights are off and press the PANEL button. If the display illuminates, the self-diagnostic mode can be entered. If, however, the display does not illuminate, check the fuses and circuits to the control assembly. If the fuses and circuits are good, replace the ATC computer. If the display illuminates, the self-diagnostic mode may be entered by pressing the BI-LEVEL, FLOOR, and DEFROST buttons simultaneously (Figure 11-41). If no trouble codes are present, the self-test program will be completed within 90 seconds and display a “75.” During the process of running the self-diagnostic tests, make four observations that the computer is not able to make by itself: 1. When the test is first initiated, all of the display symbols and indicators should illuminate. 2. The blower motor should operate at its highest speed. 3. Air should flow through the panel outlets. 4. The air temperature should become hot, then cycle to cold. The diagnostic flowchart may be used to determine the correct test to perform if any of these functions fail (Figure 11-42). The proper procedures for an observed failure are found in the table in Figure 11-43. Failure code

.13 75

AC

BI-level

TEMP

FAN

Off

Panel

BiLevel

Floor

Depress to start test cycle FIGURE 11-41  Use the buttons to enter diagnostics.

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Start engine. Allow time to warm up. Turn off running lights if on. Select panel mode operation by momentarily pushing the panel button. Does the ATC computer display light up?

No

Yes

Momentarily push floor and bi-level buttons together to start the self-diagnostics test.

Are the fuses and wiring OK? Refer to group 8T No

Yes Replace the ATC computer

Repair the wiring or replace the fuse

The control will flash on and off

1. The blower will stop and the computer will flash a failure code number from 1 to 15

Precomputer aided diagnostics

13

A. Do all of the display symbols and indicators illuminate (as pictured above)? B. Does the blower motor operate at its highest speed? (if not, see symptom B in figure 10.43) C. Is the air directed from the panel outlets? (if not, see symptom B in figure 10.43) D. Does the outlet air temperature become hot and then cycle to cold? (if not, see symptom D in figure 10.43)

The computer will do one of two things.

Record this number and push the panel button to resume test

2. Display

88 This means the test is over. If no failure code and answers to questions A, B, C, and D were yes, then the system is OK. Refer to computer-aided diagnostics if the display indicated any failure codes

FIGURE 11-42  A typical Chrysler diagnostic flowchart for an ATC system in which a technician must answer four questions.

If a fault is detected in the system, a trouble code will be flashed on the display panel. To resume the test, record the trouble code then press the PANEL button. Refer to the service manual to diagnose the trouble codes received. Ford EATC Troubleshooting.  To correctly diagnose Ford’s EATC system, the exact system description as well as the exact procedures for trouble code retrieval are required. This is because Ford uses different versions of EATC systems that have different diagnostic capabilities. The following is only a typical example of performing the self-test: 1. Turn the ignition switch to the RUN position. 2. Place the temperature selector to the “90” setting and select the OFF mode. 3. Wait 40 seconds while observing the display panel. If the VFD display begins to flash, there is a malfunction in the blend actuator circuit, the actuator, or the control assembly. If the LED light begins to flash, this indicates there is a malfunction in one of the other actuator circuits, the actuators, or the control assembly. 4. If no flashing of displays occurs, place the temperature selection to “60” and select the DEF mode.

481

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DIAGNOSTIC CHART NO

PROBABLE CAUSE

PROCEDURE

A

1. Control

B

1. Wiring problem 2. Power vacuum module

a. Replace control module CAUTION: Take care when working around the the blower motor fan. The power/vacuum heat sink is hot (12 volts). DO NO T operate the module for a period longer than 10 minutes with the unit removed from the housing. b. Ensure that the connections are good at the blower motor and power/vacuum module. c. If diagnostic test results in a code 8 or 12, refer to the fault code page in the service manual. If no codes are present, check the blower motor fuse. d. Disconnect the blower motor and check for voltage. A reading of 3 to 12 volts for 1 to 8 bar segments on the display is correct. If correct, replace motor. e. If voltage is not correct, measure the voltage-tovehicle ground. Voltage should read 12 volts with the ignition ON. If OK, replace the power/vacuum module.

C

1. Vacuum leakage 2. Power vacuum leakage

a. Service if any codes are found. b. Check all connections. c. Disconnect vacuum control and connect it to a manual control to test each port. To test the check valve, select Panel Mode, disconnect the engine vacuum, and see if mode changes quickly. d. Try a new power/vacuum module.

D

1. Refrigeration system

a. Complete diagnostic test. Refer to the Fault Code page in the Shop Manual if code appears. b. If a temperature difference of 40˚F (22.2˚C) or more is noted during the test, the blend-air door is engaged in the servomotor actuator. A lower temperature indicates a blend-air door operation problem c. Check heater system 85˚F setting is full heat; 65˚F is full cool. d. Check air-conditioning system.

2. Heater system 3. Blend-air door

FIGURE 11-43  If the technician’s answer was NO to any of the self-diagnosis test questions of Figure 11-42, this diagnostic chart may be used to isolate the fault.

5. Wait 40 seconds while observing the VFD and LED displays. If there are no malfunctions in the actuator drive or feedback circuits, the displays will not flash. 6. Regardless of whether or not flashing displays were indicated, continue with self-­ diagnostics. Press the OFF and DEFROST buttons at the same time. 7. Within 2 seconds, press the AUTO button. Once the self-diagnostics is entered, if an “88” is displayed, there are no trouble codes present. If there are any trouble codes retrieved, they will be displayed in sequence until the COOLER button is pressed. Always exit self-test mode by pressing the COOLER button before turning the ignition switch to the OFF position. Refer to the trouble code chart in Figure 11-44. When service repairs have been performed on the system, rerun the self-test to confirm that all faults have been corrected. 482 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

CODE

SYMPTOM

POSSIBLE CAUSE

1

Blend actuator is out of position. VFD flashes.

Open circuit in one or more actuator leads Actuator output arm jammed Actuator inoperative Control assembly inoperative

2

Mode actuator is out of position. LED flashes.

Same as 1

3

Pan/Def actuator is out of position. LED flashes.

Same as 1

4

Fresh air/recirculator actuator is out of position. LED flashes.

Same as 1

1, 5

Blend actuator output shorted. VFD flashes.

2, 6

Mode actuator is shorted. LED flashes.

Same as 1, 5

3, 7

Pan/Def actuator output shorted, LED flashes.

Actuator output is shorted to supply voltage Actuator inoperative Control assembly inoperative

4, 8

Fresh air/recirculator actuator output is shorted. LED flashes.

Same as 3, 7

9

Output A or B shorted to ground, or to supply voltage, or together Actuator inoperative Control assembly inoperative

No failures found; see supplemental diagnosis.

10, 11

A/C clutch never ON.

Circuit 321 open BSC inoperative Control assembly inoperative

10, 11

A/C clutch always ON.

Circuit 321 shorted to ground BSC inoperative Control assembly inoperative

12

System stuck in full-heat. In-car temperature must be stable above 60°F for this test to be valid.

Circuit 788, 470, 767, or 790 is open. Ambient or in-car sensor inoperative

13

System stays in full A/C.

Remove control assembly connectors. Measure resistance between pin 10 of connector #1 and pin 2 of connector #2. If the resistance is less than 3 KΩ, check wiring and in-car and ambient sensors. If resistance is greater than 3 KΩ, replace the control assembly.

14

Blower always at Max speed.

Turn OFF ignition. Remove connector #2 . Remove terminal #5. Replace connector, tape terminal and turn ON ignition. If blower still is at Max speed, check circuit 184 and the BSC. If the blower stops, control assembly inoperative.

15

Blower never runs.

Circuit 184 shorted to power supply BSC inoperative Control assembly inoperative

FIGURE 11-44  Trouble code chart for Ford EATC system.

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GM ETCC Troubleshooting.  General Motors (GM) uses several different versions of the microprocessor-controlled electronic touch climate control (ETCC) system. Depending on the GM division and system design, the door controls can be either by vacuum or by electric servomotor. Methods of entering diagnostics also vary between divisions and models. For this reason, the correct service manual for the system being serviced is needed to perform correct diagnostic procedures. Knowledge of one ETCC system type is no guarantee that you will be able to service other ETCC systems without the use of the proper service manual. Many GM EATC systems can be checked for proper operation by using a functional chart (Figure 11-45). In addition, troubleshooting charts that correspond with fault code or symptoms (Figure 11-46) are a great help.

ELECTRONIC CLIMATE CONTROL (ECC) FUNCTIONAL TEST Air-conditioning system diagnostics should begin with a functional test. This test should be performed in the order listed in the chart below. If the answer to any test question is NO, proceed to the specific trouble tree for further testing. Do not omit any steps in the test. Check the fuses and stop hazard operation to verify the stop/hazard fuse. Warm the engine up before performing the functional test, and check LED's above each button as the test is performed. TEST 1 2 3

4 5 6 7 8

SYSTEM CHECKS

CONTROL SETTING

TROUBLE TREE

Do the MPG and control head display? Do COOLER and WARMER push buttons operate? Set TEMP to 60˚F (42.2˚C) a. Does blower operate? b. Is there low blower speed? c. Is there high blower speed? d. Is air flow from A/C outlets? e. Does compressor engage? 1. engage? 2. disengage? f. Is A/C outlet air cold? 1. Is there only heat? 2. Is cooling adequate? g. Does recirc door fully open? (allow 1–2 minutes) Set temperature to 90˚F (67.2˚C) a. Is heat adequate? Set temperature to 85˚F (67.2˚C) a. Is air warm or hot? Does front defroster operate? Does rear defroster operate? Does rear defroster turn OFF?

All

1

All

1

LO-AUTO-HI LO HI ECON-LO-AUTO-HI

2A 2B 2C 3

LO-AUTO-HI OFF-ECON LO-AUTO-HI

4 5 6

AUTO-HI

7 8

AUTO

9

LO-AUTO FRT DEF RR DEF RR DEF OFF

10 11 12 13

FIGURE 11-45  General Motors’ Electronic Automatic Temperature Control (EATC) function test.

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Ensure that the headlights and twilight sentinel are turned “OFF.” Start the engine and check for any blown fuses. Check hazard fuse by operating the hazard switch. Connect test lamp from programmer pin “L” to ground

No light

Repair open harness or grounded B+ line 50

No light

Jumper programmer pin “N” to ground. Check display

Light Probe programmer pin “M” with test light to ground Light Probe programmer pin “4” with test light to ground

Not OK No light

Repair wire 140 for an open or ground condition

Replace programmer Check wire 990 for open

Light Probe programmer pin “J” with test light to ground

OK

No light

Repair wire 974 for an open or ground condition

Display

Repair wire 990 for an open condition

Replace the power module

Light Probe programmer pin “12” with test light to ground No display Check and repair open terminal 12 connection Replace control head FIGURE 11-46  A typical General Motors’ Electronic Automatic Temperature Control (EATC) troubleshooting flowchart.

BCM-Controlled EATC Systems

Because the BCM-controlled EATC system incorporates many different microprocessors within its system, diagnostics can be very complex (Figure 11-47). Faults that seem to be unrelated to the EATC system may cause the system to malfunction. Since it was first introduced in 1986, BCM-controlled EATC systems have become increasingly popular on many GM vehicles. Each model year brings forth revisions and improvements in the system that also require different diagnostic procedures. In addition, system logic, as used by the different GM divisions, has changed through the years. It is not possible to generally describe the diagnostic procedures required to service the many systems now in use. For this reason, one must have the correct service manual for the system being diagnosed. There are several different methods used to retrieve trouble codes,

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Ignition Feed

Fuse block Body computer module (BCM) Interior lights dimming

Climate control panel (CCP)

L

5V

Ignition input

U

+16 V

5V

V.F. Dim

Data input/ output

Solid state

R

P

N

T +5 V LED indicator Clock

Electronic climate control (ECC) control head sector

S

V

C14

Battery + B2

C2 Ignition input

C1

5V Data input/ output

+1.2 V

Solid state voltage regulator

5V

Body computer module (BCM)

+12 V

+12 V

Blower speed variable voltage output

Fuseable link

re 15 V

D13

C2

Solid state C13

C2

Blower feedback B9

A9

C1

2

BC

B Blowe r speed input

Fuseable link

C1 Batter y input

Blower motor driver circuit

Electronic climate control (ECC) power module

A C2 C Body computer module (BCM)

A

C2

B M Blower motor

FIGURE 11-47  The BCM-controlled ATC system has several modules that use multiplexing to share information.

and it is important to follow the correct procedure. In all systems, PCM codes are displayed first, followed by BCM codes. Codes associated with the EATC system can be in either set of codes, as well as network codes (e.g., PXXXX, BXXXX, and UXXXX). Once the codes have been retrieved, refer to the correct diagnostic chart. This test will pinpoint the fault in a logical manner. After all repairs to the system are complete, follow the service manual procedure for erasing codes and for resetting the system. Rerun the diagnostic test to confirm that the system is operating properly.

Trouble Codes Most BCMs are capable of displaying the fault codes that were stored in memory. The procedure used to retrieve the codes varies greatly, and reference must be made to the appropriate service manual for the correct procedure. 486 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

BCM TROUBLE CODES CODE

NOTES

F10 F11 F12 F13 F30 F31 F32 F40 F43 F46 F47 F48 F49 F51

1 1–2 1–3 1 1 1 1–4 1 1 2 2–5 2–5 1 1 Notes:

PROBLEM Outside temperature sensor circuit A/C high-side temperature sensor circuit A/C low-side temperature sensor circuit In-car temperature sensor circuit CCP to BCM data circuit FDC to BCM data circuit Air mix door problem Heated windshield problem Low refrigerant problem Low refrigerant pressure High temperature clutch disengage BCM prom error

1 2 3 4 5

Classroom Manual Chapter 11, page 376

Does not turn on any light Turns on SERVICE A/C light Disengages A/C clutch Turns on cooling fans Switches from AUTO to ECON

FIGURE 11-48  Body control module (BCM) diagnostic trouble codes lead the technician to the problem.

Only some systems retain the code when the ignition is turned off and do not require test driving the vehicle to duplicate the fault. Once the fault is detected by the computer, the code must be retrieved before the ignition switch is turned off. The trouble code, however, does not necessarily indicate the faulty component. It only indicates that circuit of the system that is not operating properly (Figure 11-48). For example, the code displayed may be F11, indicating an air-conditioning system high-side temperature sensor problem. This does not mean, however, that the sensor is defective. It means that the fault is in that circuit, which includes the wiring, connections, and BCM as well as the sensor. To locate the problem, follow the diagnostic procedure in the service manual for the code received (Figure 11-49). There are two types of code that can be displayed: intermittent code and hard fault code.

Hard and Intermittent Codes

Some BCMs store trouble codes in their memory until they are erased by the technician or until a predetermined number of engine starts have occurred. Usually, the first set of fault codes to be displayed represent all of the fault codes that are stored in memory, including both hard and intermittent codes. The second set of fault codes to be displayed are only hard codes. The codes that are displayed in the first set but not displayed in the second set are intermittent codes. Most diagnostic charts cannot be used to locate intermittent faults. This is because the testing at various points of the chart requires that the fault be present to locate the problem. Intermittent problems are often caused by poor electrical connections. Diagnosis, then, should start with a good visual inspection of the connectors, especially those involved with the trouble code. 487 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

IGNITION “ON” - ENTER DIAGNOSTICS DISPLAY BCM DATA PARAMETERS P.2.7.

–15 TO –10

210 OR MORE

1. DISCONNECT THE SENSOR CONNECTOR. 2. JUMPER THE HARNESS TERMINALS TOGETHER. 3. NOTE THE PARAMETER VALUES.

1. DISCONNECT THE SENSOR CONNECTOR. 2. NOTE THE PARAMETER VALUES.

209 OR LESS

210 OR MORE

1. REMOVE JUMPER FROM BETWEEN TERMINALS. 2. JUMPER CIRCUIT 732 TO A KNOWN GROUND. 3. NOTE THE PARAMETER VALUES.

–15 TO –10

–9 TO 209

MALFUNCTION NOT PRESENT AT THIS TIME (See notes on intermittents in the appropriate manufacturer's service manual.)

–9 OR MORE

REPLACE SENSOR

1. CHECK CIRCUIT 732 FOR A SHORT TO GROUND.

IF NOT SHORTED, REPLACE BCM.

CHECK FOR FAULTY SENSOR CONNECTOR OR FAULTY SENSOR.

209 OR LESS

210 OR MORE

REPAIR OPEN IN CIRCUIT 736.

1. REMOVE JUMPER TO GROUND. 2. BACKPROBE BCM CONNECTOR B4 WITH A JUMPER TO GROUND. 3. NOTE PARAMETER VALUE. 209 OR LESS

210 TO 215

CHECK FOR FAULTY BCM CONNECTOR OR FAULTY BCM. REPAIR OPEN IN CIRCUIT 732.

FIGURE 11-49  A typical diagnostic chart used to locate the cause of General Motors’ trouble code using Tech 2 scan tool.

Visual Inspection.  One of the most important checks to be made before diagnosing a BCMcontrolled system is a complete visual inspection. The inspection can ­identify faults that could otherwise waste time in unnecessary diagnostics. Inspect the following: 1. Sensors and actuators for physical damage 2. Electrical connections to actuators, control modules, and sensors 3. All ground connections 4. Wiring for signs of broken or pinched wires or burned or chaffed spots indicating contact with sharp edges or hot exhaust manifolds 5. Vacuum hoses for breaks, cuts, disconnects, or pinches NOTE: Check wires and hoses that are hidden under other components. 488 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Entering BCM Diagnostics There are, perhaps, as many methods of entering BCM diagnostics as there are vehicle makes and models. One thing that most have in common, however, is that a scan tool must be plugged into the diagnostic connector for the system to be tested. Always refer to the correct service manual for the vehicle being serviced, and use only the methods identified for retrieving trouble codes. Once the trouble codes are retrieved, consult the appropriate diagnostic chart for instructions on isolating the fault. It is also important to check the codes in the order required by the manufacturer.

Chrysler’s DRB-III

The following procedure for using the DRB-III scanner is meant as a general guide only. It is intended to complement, not to replace, the service manual. Improper methods of trouble code retrieval may result in damage to the computer. Early Chrysler systems use several modules that share information with the body controller through a multiplex system (Figure 11-50). Connecting the DRB-III into the diagnostic connector will access information concerning the operation of most vehicle

SERVICE TIP:

Before attempting to diagnose today’s climate control systems, first retrieve any stored diagnostic codes. If an intermittent soft code is retrieved, road testing the vehicle may be required in order to duplicate the complaint and accessing codes before the ignition is cycled off.

Base body controller Overhead console Bus –

Bus +

Time Temp Fuel Econ Info Reset 1:37 PM Sat April 29

DLC

Lamp outage module

Engine node

Single module engine controller (S.M.E.C.) FIGURE 11-50  Multiplex system used to interface several different modules.

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Bus diagnostic connector (underdash or in dash fuse panel) FIGURE 11-51  Diagnostic connector location.

systems. A typical procedure for entering body controller diagnostics using the DRB-III scanner is as follows: 1. Locate the diagnostic connection using the component locator (Figure 11-51). 2. Insert the correct program cartridge into the DRB-III scanner. 3. Connect the DRB-III to the vehicle by plugging its connector into the vehicle’s diagnostic connector. 4. Turn the ignition switch to the RUN position. After the power-up sequence is completed, the copyright date and diagnostic program version should be displayed. 5. The display will change to a selection menu. The entire menu is not displayed; press the down arrow until the desired selection is found. In this example, press the down arrow twice. 6. Select 4 (SELECT SYSTEM) to enter the diagnostic test program. The display will change to a menu for selecting the system to be tested. Use of the down arrow reveals additional choices. Push the down arrow until the BODY option is shown. 7. Enter body system diagnostics by selecting 3 (BODY). The display will change to indicate that the BUS test is being performed (Figure 11-52). If the message is different from that shown in the figure, there is a problem in the CCD bus that must be corrected. No further testing is possible until this problem is corrected. 8. After a few seconds, the display will change and ask for input concerning the body style of the vehicle. Use the down arrow and scroll through the choices available. 9. Enter the number indicating the body style being diagnosed. 10. The display will then ask that a module be selected. Select BODY COMPUTER.

Bus test in progress Bus operational FIGURE 11-52  This message must appear before proceeding with the diagnostics.

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11. The display will indicate the name of the module selected, along with the version number of the module. Then, after a few seconds, the display will indicate BODY COMP MENU. 12. Use the down arrow key to scroll the menu selection, if needed. Press 2 (READ FAULTS). The DRB-III will either display that no faults were detected or provide the fault codes. The first screen will indicate the number of fault codes found, the code for the first fault, and a description of the code. Scroll down the entire list of codes retrieved.

Retrieving Cadillac BCM Trouble Codes These procedures may vary among models, years, and the type of instrument cluster installed. Refer to the appropriate manufacturer’s service manual for the vehicle being tested. Pre-CAN bus network Cadillac systems allow access to trouble codes and other system operation information through the ECC panel. The BCM and the electronic control module (ECM) share information with each other so both system codes are retrieved through the ECC. The following procedure may typically be followed to enter diagnostics: 1. Place the ignition switch in the RUN position. 2. Depress the OFF and WARMER buttons on the ECC panel simultaneously (Figure 11-53). Hold the buttons until all display segments are illuminated.

Press to enter diagnostics

Outside temp

Off

Econ

Auto

Cooler

Warmer

Lo

Hi

Press to clear ECM codes

Press to exit diagnostics Snapshot: Econ and Cooler

Increment: Hi

Snapshot review: Econ and Warmer

Decrement: Lo

FIGURE 11-53  The buttons on the electronic climate control panel allow the technician to access information from the computer when it is in the diagnostic mode.

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Cadillac uses the onboard ECC panel to display trouble codes, whereas other General Motors (GM) vehicles use a Tech II scan tool. Beginning in 1996, the Tech II scan tool was used to retrieve codes on certain models. That same year, Cadillac switched to the use of the Tech II scan tool to retrieve class 2 data. When diagnosing GM systems, make sure to follow the procedures specifically designated by GM for the vehicle being tested. Diagnosis should not be attempted if all segments of the display do not ­illuminate. A problem may be misdiagnosed as the result of receiving an incorrect code. For ­example, if two segments of a display fail to illuminate, a code 24 could look like code 21 (Figure 11-54). When the segment check is completed, the computer will display any trouble codes in its memory. An “8.8.8” will be displayed for about 1 second, then an “..E” will appear. This signals the beginning of engine controller trouble codes. The display will show all engine controller trouble codes beginning with the lowest number and progressing through the higher numbers. All codes associated with the engine controller will be prefixed with an “E.” If there are no codes, however, “..E” will not be displayed. Once all “E” codes are displayed, the computer will display BCM codes. The BCM codes are prefixed by an “F”. An “F” will precede the first set of codes displayed. The first set will be all codes stored in memory for the last 100 engine starts. An “.F.F” will appear to signal the separation of the first pass and the second. The second set of trouble codes will be all hard codes. When all codes are displayed, “.7.0” will be displayed, indicating that the system is ready for the next diagnostic feature to be selected. To erase the BCM trouble codes, press the OFF and LOW buttons simultaneously until “F.O.O” appears. Release the buttons and “.7.0” will reappear. Turn off the ignition switch and wait at least 10 seconds before reentering the diagnostic mode. When in the diagnostic mode, exit the system without erasing the trouble codes by pressing AUTO on the ECC panel, and the temperature will reappear in the display.

Segment burned out

Becomes

FIGURE 11-54  Burned-out segments give a false code.

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case study A customer complains that an abnormal noise is ­coming from under the hood of her car. The service writer asks the customer the usual questions: “When did the noise start? When does it make the noise? How often is the noise noticeable?” The customer answers the questions and notes that the noise seems to be growing louder. She first noticed the noise a few days ago. After noting the mileage, the service writer checks the computer for the service record. According to the records, no major work has been performed on the car. Also, it seems to have been serviced regularly and is well maintained. On starting the car for a test drive, the noise is immediately noted. The service writer raises the

Terms to Know hood and, using a mechanic’s stethoscope, is able to ­pinpoint the noise at the air-conditioner compressor. “It couldn’t be the compressor,” the customer says. “I just had that repaired a week ago.” The ­customer then explains that the repairs were made by an independent dealer in another city while the customer was out of town. An inspection of the compressor clutch by the technician reveals that the wrong field coil snapring was installed. The snapring, which was too thin, allowed the field coil to barely touch the rotor, ­creating a noise. Fortunately for the customer, no major ­damage was done to the clutch, and a proper snapring ­corrected the problem.

Aspirator Breakout box Electronic automatic temperature control (EATC) Fusible link Ohmmeter Open Overload Servomotor Shorts Solenoids Spikes Voltmeter

ASE-STYLE REVIEW QUESTIONS 1. Technician A says an sun load sensor may be tested by placing a dark piece of cloth over sensor while observing data values on a scan tool. Technician B says an infrared temperature sensor may be tested by alternately placing a cold damp towel and a hot damp towel in front of the sensor while observing data values on a scan tool. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 2. On an automatic temperature control system that will not hold the temperature set at the control panel, what should the technician do first? A. Replace the temperature mode door actuator. B. Replace the climate control panel. C. Check and replace the in-car temperature sensor if faulty. D. Refer to the appropriate manufacturers service information. 3. On a vehicle equipped with and automatic temperature control system the blower motor will not function when the vehicle is first started and heat is selected. Which of the following is the most likely cause? A. The blower motor has higher than specified resistance. B. The ambient air temperature is faulty. C. The system is functioning normally. D. The in-car temperature sensor is faulty.

4. Technician A says that a trouble code may be displayed on some master control heads. Technician B says that there are provisions for ­connecting an external scan tool on some systems. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 5. Technician A says that a thermostat is used for temperature control in some systems. Technician B says that a low-pressure control is used for temperature control in some systems. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 6. A rattling noise is heard when the engine is running and the air conditioning is off. Technician A says this noise may be caused by too narrow gap between the compressor’s armature and rotor. Technician B says a quick accurate test is to see if the clutch is the source is to switch on the air conditioning to see if the noise stops. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

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7. Technician A says an in-car temperature sensor may be tested by measuring its resistance at 708F (218C) and 808F (278C). Technician B says an ambient ­temperature sensor may be tested by measuring its amperage at 708F (218C) and 808F (278C). Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 8. All of the following air-conditioning system sensors are varying resistive sensors except: A. Sun Load Sensor B. Evaporator Temperature Sensor C. Infrared Temperature Sensor D. Ambient Temperature Sensor

9. Pressure switches are being discussed: Technician A says that a test lamp should never be used to test the operation of a pressure switch. Technician B says that at atmospheric pressure a low – pressure switch should be normally closed. Who is correct? A. A only B. B only C. Both A and B D. Neither A nor B

ASE CHALLENGE QUESTIONS 1. The following statements regarding a visual inspection for intermittent faults are all true, except: A. Inspect electrical connections to actuators, control ­modules, and sensors. B. Inspect wiring for signs of broken or pinched wires. C. Inspect for catastrophic component failure. D. Inspect all ground connections. 2. The following statements regarding the relationships between the cooling system and air-conditioning ­system are all true, except: A. An overheating engine will affect air-conditioning system performance. B. Ambient air first passes through the radiator, then the condenser. C. The same blower motor is used for the heater and air conditioner. D. An air-conditioning system places an additional load on the cooling system. 3. Electrical testing is being discussed: Technician A says that an analog ohmmeter should not be used to test an electronic circuit. Technician B says that a digital ohmmeter may be used to test any electrical or electronic circuit. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

Diode 12 V From Clutch control

Clutch coil Ground

4. The diode shown in the illustration above is used to: A. Increase voltage in the clutch coil circuit B. Reduce voltage in the clutch coil circuit C. Block the flow of current in the electrical system D. Prevent voltage spikes in the electrical system 5. Which of the following is not a tool used by the airconditioning system technician? A. Scan tool C. DRB-III scanner B. Breakout box D. OBD-5 scanner

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JOB SHEET

68

Name ______________________________________ Date ________________________

Diagnose Temperature Control Problems in the Heater/Ventilation System Upon completion of this job sheet, you should be able to diagnose temperature control problems in the heater/ventilation system and determine the necessary action; diagnose blower system problems in the heater/ventilation system and determine the necessary action; and inspect, test, adjust, or replace climate control temperature and sun load sensors. NATEF Correlation NATEF MAST Correlation: HEATING AND AIR CONDITIONING: Heating, Ventilation, and Engine Cooling Systems Diagnosis and Repair. Task #3. Diagnose temperature control problems in the heater/ventilation system; determine PCM to interrupt system operation; determine necessary action. (P-2) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Tables 11-1 through 11-5 that follow in this job sheet Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure Follow procedures outlined in the Shop Manual. Give a brief description of your procedure following each step. Ensure that the engine is cold, and wear eye protection. The ­following procedures are meant to be a guide for diagnosing an automatic temperature control s­ ystem. For specific information on the vehicle you are working on, always refer to specific manufacturer’s service information contained in the vehicle’s service manual or other data system. 1. Referring to Table 11-1, check system for proper airflow and determine necessary action. Improper airflow ■■ ■■ ■■ ■■

No airflow No fresh air from vents No cool air from vents No warm air from vents

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2. Referring to Table 11-2, check the system for unusual noise and determine necessary action. Unusual noise while HVAC system is in operation ■■ Chattering sounds ■■ Squealing sounds ■■ Grinding sounds

3. Referring to Table 10-3, check the system for poor, intermittent, or no cooling and determine necessary action. Inadequate or no cooling ■■ Little to no airflow from ducts ■■ Air not cool ■■ Air not warm Intermittent or no cooling ■■ A/C system cycles rapidly ■■ Cycles on high-pressure protector

4. Referring to Table 10-4, check the system for poor, intermittent, or no cooling and determine necessary action. Inadequate or no cooling ■■ Little to no airflow from ducts ■■ Air not cool with A/C selected ■■ Air not warm Intermittent or no cooling ■■ A/C system cycles rapidly ■■ Cycles on high-pressure protector

5. Referring to Table 10-5, check the system for no cooling and determine necessary action. No cooling ■■ Compressor will not engage ■■ Compressor always engaged ■■ High blower speed only ■■ No blower ■■ Improper air delivery ■■ Insufficient heating ■■ Insufficient cooling

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Instructor’s Response 

TABLE 11-1 Diagnose the cause of temperature control problems in the heater/ventilation system; d ­ etermine needed repairs. Diagnose temperature control system problems; determine needed repairs. Diagnose blower system problems; determine needed repairs. Inspect, test, adjust, or replace climate control temperature and sun load sensors. Problem Area

Symptoms

Possible Causes

IMPROPER AIRFLOW

No airtflow

1. Detective master control 2. No: a. Vacuum, if pneumatic b. Power, if electric 3. Defective: a. Motor, if electric b. “Vacuum Pot,” if pneumatic c. Cable, if manual

No fresh air from vents

1. Defective master control; electric, pneumatic, or manual 2. Detective: a. Wiring, if electric b. Hose, ir pneumatic c. Cable, if manual 3. Defective actuator: a. Motor, if electric b. “Vacuum Pot,” if pneumatic c. Retainer, if cable

No cool air from vents

1. Defective master control; electric, pneumatic, or manual 2. Defective: a. Wiring, if e lectric b. Hose, if pneumatic c. Cable, if manual 3. Defective actuator: a. Motor, if electric b. “Vacuum Pot,” if pneumatic c. Retainer, if cable 4. Defective or inoperative air conditioner 5. Detective (open) heater coolant flow control valve 6. Duct disconnected or missing

No warm air from vents

1. Defective master control; electric, pneumatic, or manual 2. Defective: a. Wiring, if e lectric b. Hose. if pneumatic c. Cable, if manual 3. Defective actuator: a. Motor, if electric b. “Vacuum Pot,” it pneumatic c. Retainer, if cable 4. Defective (closed) heater coolant flow control valve 5. Heater (hoses) disconnected 6. Duct disconnected or missing

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TABLE 11-2 Diagnose the cause of unusual operating noises of the A/C system; determine needed repairs. Problem Area

Symptoms

Possible Causes

NOISE

Chattering sound

1. 2. 3. 4. 5.

Squealing sounds

1. 2. 3. 4. 5.

Loose or glazed belt(s) Worn belt(s) and or pulley(s) Defective AIC clutch or idler pulley bearing(s) Defective blower motor Defective A/C compressor

Grinding sounds

1. 2. 3. 4.

Defective A/C clutch Defective AIC compressor Defective bearing(s) in clutch or idler Defective coolant (water) pump

Defective blower motor Blower loose on motor shaft Blower rubbing insulation on mode door gasket Debris in duct Low compressor: a. Lubricant b. Refrigerant 6. Loose bracket or other part(s)

TABLE 11-3 Diagnose the cause of failure in the electrical control system of heating, ventilating, and A/C systems, determine needed repairs. Inspect, test, repair, replace, and adjust load sensitive A/C compressor cutoff systems. Inspect, test, repair, and replace engine cooling/condenser fan motors, relays/modules, switches, sensors, wiring, and protection devices. Problem Area

Symptoms

Possible Causes

INADEQUATE OR NO COOLING

Little to no airflow from ducts

1. 2. 3. 4. 5.

Blown fuse or defective circuit breaker Defective blower speed control or resistor Defective master control Defective relay Defective wiring

Air not cool

1. 2. 3. 4. 5.

Defective clutch coil or ground connection Defective low-or high-pressure control Defective temperature control Defective relay Defective sensor

Air not warm

1. 2. 3. 4. 5.

Defective master control Defective temperature control Defective electric coolant flow control valve Defective relay Defective sensor

A/C system cycles rapidly

1. Defective low-pressure control 2. Defective high-pressure control 3. Thermostat adjustment

Cycles on high-pressure protector

1. Defective or inoperative cooling fan or motor 2. Defective high-pressure control 3. Engine overheating

INTERMITTENT OR NO COOLING

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TABLE 11-4 Inspect, test, repair, and replace A/C compressor clutch components or assembly. Inspect, lest, repair, replace, and adjust A/C-related engine control systems. Inspect, test, adjust, repair, and rep lace electric actuator motors, relays/ modules, sensors, wiring, and protection devices. Diagnose compressor clutch control system; determine needed repairs. Inspect, test, repair, and rep lace electric and vacuum molars, solenoids, and switches. Problem Area

Symptoms

Possible Causes

INADEQUATE OR NO COOLING

Little to no airflow from ducts

1. 2. 3. 4. 5.

Air not cool with A/C selected

INTERMITTENT OR NO COOLING

1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Blown fuse or defective circuit breaker Defective blower speed control or resistor Defective masler control Defective relay Defective wiring Defective clutch coil Poor electncal connection Defective low-pressure control Defective high-pressure control Defective temperature control Defective master control Defective relay Defective sensor Defective module Shorted clutch diode

Air not warm

1. 2. 3. 4. 5. 6.

Defective master control Defective temperature control Defective electric coolant flow control valve Defective relay Defective sensor Defective module

A/C system cycles rapidly

1. 2. 3. 4. 5. 6.

Defective low-pressure control Defective high-pressure control Thermostat adjustment Defective module Defective relay Loose or defective wiring

Cycles on high pressure protector

1. Defective or inoperative cooling fan motor 2. Defective high-pressure control 3. Engine overheating

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TABLE 11-5 Inspect, test, and replace automatic temperature control (ATC) control panel. Inspect, test, adjust, or replace ATC microprocessor (climate control computer/programmer). Check and adjust calibration of ATC system. Problem Area

Symptoms

Possible Causes

NO COOLING

Compressor will not engage

1. 2. 3. 4. 5. 6. 7.

A/C clutch relay Low-side temperature sensor Defective low-pressure switch Open clutch coil Power steering pressure switch (if equipped) Defective wiring Defective BCM

Compressor always engaged

1. 2. 3. 4.

Defective clutch Defective clutch relay Shorted control signal circuit Mechanical binding

High blower speed only

1. 2. 3. 4.

Open feedback circuit Defective programmer Open signal circuit Defective BCM

No blower

1. 2. 3. 4. 5. 6. 7.

Blown fuse or circuit breaker Defective blower motor Loose or disconnected motor ground Improper signal to programmer due to open or short Power modules feed open Defective programmer Defective BCM

Improper air delivery

1. 2. 3. 4.

Loss of vacuum source Leak in vacuum circuit Defective programmer Defective BCM

Insufficient heating

1. 2. 3. 4. 5.

Air mix valve Defective (closed) coolant flow control valve Air mix valve linkage Programmer amn adjustment Programmer

Insufficient cooling

1. 2. 3. 4. 5.

Insufficient airtlow Refrigeration problems Air mix valve linkage Programmer arm adjustment Programmer

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JOB SHEET

69

Name ______________________________________ Date ________________________

Using a Scan Tool to Access HVAC System Upon completion of this job sheet, you should be able to connect and use a scan tool to access and record HVAC information and diagnostic trouble codes (DTCs). NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: General: A/C System Diagnosis and Repair. Task #9. Using a scan tool, observe and record related HVAC data and trouble codes. (P-3) Tools and Materials Late-model vehicle equipped with a BCM Service manual or information system Safety glasses or goggles Scan tool Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure

1. Locate the data link connector. Where is the connector located?  2. Connect the scan tool to the DLC and turn the ignition switch to the RUN position. 3. Initialize the scan tool. 4. Select Displace DTC stored. Are there any current power train, body control, or ­network DTCs stored? a.  List PXXXX code stored  b.  List BXXXX code stored  c.  List UXXXX code stored  5. Select History codes. Are there any history power train, body control, or network DTCs stored? a.  List PXXXX code stored  b.  List BXXXX code stored  c.  List UXXXX code stored  6. Next, enter the body control module (BCM) functions. Select the HVAC system.

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7. What information is displayed about the HVAC or BCM data stream?  8. How is this information useful in monitoring the HVAC system?  9. For the circuit with the fault code associated with it, look at all sensors and input/ output values. Are any of the values out of specifications? If so, which sensors or ­actuators? 

10. Follow the diagnostic chart for the fault code. What are your conclusions? 

Instructor’s Response 

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JOB SHEET

70

Name ______________________________________ Date ________________________

Testing an Ambient Air Temperature Sensor Upon completion of this job sheet, you should be able to check the operation of an ambient temperature sensor. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Operating Systems and Related Controls Diagnosis and Repair. Task #3. Diagnose malfunctions in the vacuum, mechanical, and electrical components and controls of the heating, ventilation, and A/C (HVAC) system; determine necessary action. (P-2) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Digital multimeter (DMM) Thermometer Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size ____________________________ Procedure Always follow the procedures outlined in the service manual for the specific make, model, and year vehicle being tested. 1. Describe the location of the ambient temperature sensor (ATS).  2. What color are the wires connected to the sensor?  3. Record the resistance specifications for a normal ATS for the vehicle being tested based on current ambient air temperature within 1 foot of the sensor. 

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4. Disconnect the harness connector from the sensor. 5. Measure the resistance value of the sensor and the ambient air temperature within 1 foot of sensor. a.  Sensor resistance _______________ Ω b.  Ambient air temperature _______________ 8F 6. Conclusion: Is the sensor within specification range? 

Instructor’s Response 

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JOB SHEET

71

Name ______________________________________ Date ________________________

Automatic Temperature Control Diagnostics Upon completion of this job sheet, you should be able to test the electronic automatic ­temperature control system using a scan tool or self-diagnostic mode of the climate control panel and determine needed repairs. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Operating Systems and Related Controls Diagnosis and Repair. Task #3. Diagnose malfunctions in the vacuum, mechanical, and electrical components and controls of the heating, ventilation, and A/C (HVAC) system; determine necessary action. (P-2) Task #8. Check operation of automatic or semi-automatic heating, ventilation, and air-­ conditioning (HVAC) control systems; determine necessary action. (P-2) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Scan tool Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure Always follow the procedures outlined in the service manual for the specific make, model, and year vehicle being tested. 1. Describe the location of the ambient temperature sensor (ATS).

2. Activate the self-diagnostic mode or connect and activate a scan tool. What ­indications are provided to confirm that system self-diagnosis has been activated?

3. Perform a display panel segment test and record results. 

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4. Retrieve DTCs and record.  5. Are the fault codes current or history codes?  6. Perform all diagnostic tests the system is capable of running. What test is the system capable of performing? 

7. Were any system faults detected? Yes or No If yes, use the service information to trace and diagnose the cause of the fault and record your findings. 

8. Complete the repair and run the self-diagnosis test again. Was the repair completed successfully? Yes or No If no, consult your instructor for guidance. 9. Follow the procedure for erasing fault codes stored. Instructor’s Response 

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JOB SHEET

72

Name ______________________________________ Date ________________________

Testing an In-Car Temperature Sensor Upon completion of this job sheet, you should be able to check the operation of an in-car temperature sensor. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Operating Systems and Related Controls Diagnosis and Repair. Task #3. Diagnose malfunctions in the vacuum, mechanical, and electrical components and controls of the heating, ventilation, and A/C (HVAC) system; determine necessary action. (P-2) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Digital multimeter (DMM) Thermometer Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure Always follow the procedures outlined in the service manual for the specific make, model, and year vehicle being tested. 1. Describe the location of the in-car temperature sensor (ICTS).

2. What color are the wires connected to the sensor?  3. Record the resistance specifications for a normal ICTS for the vehicle being tested based on current ambient air temperature within one foot of sensor. 

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4. Disconnect the harness connector from the sensor. 5. Measure the resistance value of the sensor and the ambient air temperature within one foot of sensor. a.  Sensor resistance _______________ Ω b.  In-car temperature _______________ 8F 6. Conclusion: Is sensor within specification range? 

Instructor’s Response 

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JOB SHEET

73

Name ______________________________________ Date ________________________

Testing an Evaporator Temperature Sensor Upon completion of this job sheet, you should be able to check the operation of a two wire evaporator temperature sensor. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Operating Systems and Related Controls Diagnosis and Repair. Task #3. Diagnose malfunctions in the vacuum, mechanical, and electrical components and controls of the heating, ventilation, and A/C (HVAC) system; determine necessary action. (P-2) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Digital multimeter (DMM) Thermometer Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size ____________________________ Procedure Always follow the procedures outlined in the service manual for the specific make, model, and year vehicle being tested. 1. Describe the location of the Evaporator Temperature Sensor (ETS).

2. What color are the two wires connected to the sensor?  3. Record the resistance specifications for a normal evaporator temperature sensor for the vehicle being tested based on the current temperature of the evaporator core?  4. Disconnect the harness connector from the sensor.

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5. Measure the resistance value of the sensor and the air temperature within one foot of sensor. a.  Sensor resistance _______________ Ω b.  Evaporator Temperature at or near sensor _______________ 8F 6. Conclusion: Is sensor within specification range?  Instructor’s Response 

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JOB SHEET

74

Name ______________________________________ Date ________________________

Testing a Sun Load Sensor Upon completion of this job sheet, you should be able to check the operation of a sun load sensor by performing a quick test. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Operating Systems and Related Controls Diagnosis and Repair. Task #3. Diagnose malfunctions in the vacuum, mechanical, and electrical components and controls of the heating, ventilation, and A/C (HVAC) system; determine necessary action. (P-2) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required Diagnostic scan tool Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size ____________________________ Procedure Always follow the procedures outlined in the service manual for the specific make, model, and year vehicle being tested. During the sun load sensor quick test ventilation system air volume (blower speed) and temperature should both change. 1. Describe the location of the Sun Load Sensor (SLS).

2. What color are the two wires connected to the sensor?  3. Park the vehicle outside on a sunny day. 4. Turn the ignition to the ON position, but do not start the vehicle yet. 5. Connect the scan tool to the vehicle data link connector (DLC). 6. Select “Sensor Data Stream” from the menu. 7. Observe the sun load sensor input values. a.  Record data _______________________ 511 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

8. Start the engine and allow it to idle. Turn the air-conditioning system on and select FULL AUTO mode. 9. Set the temperature to approximately 708F (218C) on the ATC system. Allow the ­vehicle to run and the system to stabilize for 10 minutes. 10. Cover the sensor with a dark piece of paper or cloth while observing data values on the scan tool. a.  Record data before covering sensor ____________________ b.  Record data after covering sensor _____________________ 11. Cover and uncover the sensor several times, waiting 30–60 seconds between each interval to give the system time to react. The sensor data values should respond quickly to changes in light levels. Did it?  12. If the sensor values do not change, further diagnosis will be required. Consult specific vehicle service information for detailed diagnostic steps. 13. Conclusion: Is sensor within specification range? 

Instructor’s Response 

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JOB SHEET

75

Name ______________________________________ Date ________________________

Testing an Infrared Temperature Sensor Upon completion of this job sheet, you should be able to check the operation of a infrared temperature sensor by performing a quick test. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Operating Systems and Related Controls Diagnosis and Repair. Task #3. Diagnose malfunctions in the vacuum, mechanical, and electrical components and controls of the heating, ventilation, and A/C (HVAC) system; determine necessary action. (P-2) Tools and Materials Late-model vehicle Service manual or information system Safety glasses or goggles Hand tools, as required 2 hand towels Small bucket of ice water Small bucket of hot water Diagnostic scan tool Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure Always follow the procedures outlined in the service manual for the specific make, model, and year vehicle being tested. During the infrared temperature sensor quick test ventilation system air volume (blower speed) and temperature should both change. 1. Describe the location of the Infrared Temperature Sensor.

2. What color are the wires connected to the sensor?  3. Turn the ignition to the ON position, but do not start the vehicle yet. 4. Connect the scan tool to the vehicle data link connector (DLC). 5. Select “Sensor Data Stream” from the menu.

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6. Observe the infrared temperature sensor input values. a.  Record data ________________________________________ 7. Start the engine and allow it to idle. Turn the air-conditioning system on and select FULL AUTO mode. 8. Set the temperature to approximately 708F (218C) on the ATC system. Allow the ­vehicle to run and the system to stabilize for 10 minutes. 9. Get two small buckets and two small towels. Fill one bucket with hot water and place a towel in it. Fill the other bucket with cold water and ice and place the other towel in this bucket. 10. Squeeze out the cold towel so as not to drip water on the interior of the car, and allow it to hang directly in front of the sensor while observing data values on the scan tool. a.  Record data values for the infrared temperature sensor  Instructor’s Response 

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Chapter 12

BASIC TOOLS Basic mechanic’s tool set

Retrofit (R-12) [CFC-12] to R-134a [HFC-134a]

Manifold and gauge set Service hose set Thermometer Shop light(s) Fender cover Blanket Vacuum pump Can tap

Upon Completion and Review of this Chapter, you should be able to: ■■

■■

■■

■■

Recognize the difference between pure and impure refrigerant by interpreting gauge pressures relating to ambient temperature. Determine the purity of refrigerant in an air-conditioning system or container. Explain the necessity of using recovery-only equipment for contaminated refrigerant. Describe the method of affixing an access saddle valve onto an air-conditioning system.

■■

Determine when a system is void of refrigerant and air. Leak test the air-conditioning system.

■■

Recover R-12 refrigerant from a system.

■■

Diagnose and repair system components.

■■

Evacuate a system prior to charging.

■■

Flush the refrigerant system.

■■

Charge a system with R-134a refrigerant.

Introduction General information is given in this chapter regarding the proper and safe practices and ­procedures for retrofitting an automotive air-conditioning system. It is most important, h ­ owever, to follow the manufacturer’s instructions when servicing any particular make and model vehicle. This chapter includes, under the appropriate heading, procedures for the ­following: purity test, access valve installation, recovery of contaminated refrigerant, and retrofit.

Purity Test A refrigerant identifier (Figure 12-1) quickly and safely identifies the purity and type of ­refrigerant in a vehicle air-conditioning system or tank. The display will indicate the purity of the refrigerant being tested as a percentage of R-134a, R-12, and the percentage of air ­(noncondensable gas); in addition, it will indicate the presence of hydrocarbons (HC) in the sample being tested. Some analyzers will also detect the presence of R-22. A system is ­considered contaminated if it contains more than 2 percent of a “foreign” substance. Use of a refrigerant identifier, often called a purity tester, should be the first step in servicing an automotive air-conditioning system. That way, one does not have to be concerned about customer dissatisfaction or damage to the vehicle that could occur if the wrong refrigerant is used. Further, testing refrigerant protects refrigerant supplies and recovery/recycling equipment. At today’s prices, preventing just one tank of refrigerant from contamination can save several hundred dollars plus the high cost of disposing of the contaminated refrigerant. Always follow the manufacturer’s instructions for using any type of test equipment. The following procedure for using the Sentinel identifier is typical: 1. Turn on the MAIN POWER switch; the unit automatically clears the last refrigerant sample and is made ready for a new sample.

Classroom Manual Chapter 12, page 392

A purity test should be held any time there is a concern about the quality of the refrigerant in the system.

SPECIAL TOOLS Low-side (compound) gauge with gauge/hose adapter and service hose Thermometer

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FIGURE 12-1  Refrigerant identifier.

2. When READY appears on the display, connect a service hose from the tester to the vehicle air-conditioning system or tank of refrigerant being tested. 3. The tester automatically pulls in a sample and begins processing it; TESTING shows on the display. 4. Within about 1 minute, the display will show R-12, R-134a, or UNKNOWN. If UNKNOWN is displayed, the refrigerant is a mixture or is some other type of refrigerant. In either case, it should not be added to previously recovered refrigerant. Also, it should not be recycled or reused. 5. Turn off the MAIN POWER switch and disconnect the service hose. If no other method of refrigerant identification is available and there is any doubt as to the condition of the refrigerant in an air-conditioning system, the following purity test may be used. It should be noted, however, that for a pressure-temperature test to be valid, there must be some liquid refrigerant in the system. If the refrigerant has leaked to the point that only vapor remains, the pressure will be below that specified at any given temperature. Proceed as follows: 1. Park the vehicle or place the tank inside the shop in an area that is free of drafts and where the ambient temperature is not expected to go below 708F (218C). 2. Raise the hood. 3. Determine the type of refrigerant that should be in the system or tank: R-12 or R-134a. 4. Attach a 0–150 psig (0–1,000 kPa) gauge of known accuracy, appropriate for the ­refrigerant type (Figure 12-2). 5. Place a thermometer of known accuracy (Figure 12-3) in the immediate area of the vehicle or tank to measure the ambient temperature. 6. First thing the following morning: a. Note and record the pressure reading shown on the gauge. b. Note and record the temperature reading shown on the thermometer. 516 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

FIGURE 12-2  Attach an appropriate test gauge.

B

A

FIGURE 12-3  Typical (A) dial thermometer and (B) infrared temperature sensor.

7. Compare the gauge reading with the appropriate table: a. (Figure 12-4): (A) English; (B) metric for R-12. b. (Figure 12-5): (A) English; (B) metric for R-134a. Temperature Pressure Fahrenheit PSIG kPa 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85

A

80 82 83 84 86 87 88 90 92 94 96 98 99 100 101 102

551 565 572 579 593 600 607 621 634 648 662 676 683 690 696 703

Temperature Fahrenheit 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101

Pressure PSIG kPa 103 105 107 108 110 111 113 115 116 118 120 122 124 125 127 129

Temperature Pressure Celsius PSIG kPa

710 724 738 745 758 765 779 793 800 814 827 841 855 862 876 889

21.1 21.7 22.2 22.8 23.3 23.9 24.4 25.0 25.6 26.1 26.7 27.2 27.8 28.3 28.9 29.4

551 565 572 579 593 600 607 621 634 648 662 676 683 690 696 703

80 82 83 84 86 87 88 90 92 94 96 98 99 100 101 102

Temperature Celsius 30.0 30.5 31.1 31.7 32.2 32.8 33.3 33.9 34.4 35.0 35.6 36.1 36.7 37.2 37.8 38.3

Pressure PSIG kPa 710 724 738 745 758 765 779 793 800 814 827 841 855 862 876 889

103 105 107 108 110 111 113 115 116 118 120 122 124 125 127 129

B FIGURE 12-4  Temperature/pressure chart for R-12: (A) English and (B) metric.

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Temperature Pressure Fahrenheit PSIG kPa 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85

76 77 79 80 82 83 85 86 88 90 91 93 95 96 98 100

524 531 545 551 565 572 586 593 607 621 627 641 655 662 676 690

Temperature Fahrenheit 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101

Pressure PSIG kPa 102 103 105 107 109 111 113 115 117 118 120 122 125 127 129 131

A

Temperature Pressure Celsius PSIG kPa

703 710 724 738 752 765 779 793 807 814 827 841 862 876 889 903

21.1 21.7 22.2 22.8 23.3 23.9 24.4 25.0 25.6 26.1 26.7 27.2 27.8 28.3 28.9 29.4

524 531 545 551 565 572 586 593 607 621 627 641 655 662 676 690

Temperature Celsius

76 77 79 80 82 83 85 86 88 90 91 93 95 96 98 100

30.0 30.5 31.1 31.7 32.2 32.8 33.3 33.9 34.4 35.0 35.6 36.1 36.7 37.2 37.8 38.3

Pressure PSIG kPa 703 710 724 738 752 765 779 793 807 814 827 841 862 876 889 903

102 103 105 107 109 111 113 115 117 118 120 122 125 127 129 131

B FIGURE 12-5  Temperature/pressure chart for R-134a: (A) English and (B) metric.

Classroom Manual Chapter 12, page 407

A saddle valve is a two-part accessory valve that may be clamped around the metal part of a system hose to provide access to the air-conditioning system for service or the installation of additional pressure switches.

Access Valves A saddle clamp access valve may be installed if space does not permit converting the R-12 access valve into the R-134a valve configuration. Follow this procedure for the typical ­installation of the saddle valve. 1. Make certain that the system is free of refrigerant. Recover all of the refrigerant as outlined in this chapter if retrofitting the system. 2. Select the proper location for the valve. a. Will there be clearance for the hose access adapter? b. Will there be adequate clearance to close the hood and replace protective covers? c. Will access to other critical components be restricted or blocked? d. Is the tubing straight, clean, and sound? 3. Select the proper valve for the application. a. For low- or high-side use (the-low side valve is larger). b. The size of the tube the valve is to be installed on. 4. Position both halves of the saddle valve on the tube (Figure 12-6).

FIGURE 12-6  Position both halves of the valve on the tube.

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5. Place the screws (usually socket head) and tighten them evenly. Do not overtighten them; 20–30 in.-lb. (2–3 N·m) is usually recommended. 6. Insert the piercing pin in the head of the access port fitting (Figure 12-7). 7. Tighten the pin until the head touches the top of the access port (Figure 12-8). 8. Remove the piercing pin and replace it with the valve core (Figure 12-9).

CAUTION:

Make sure that the O-ring is in position.

To ensure compatibility, use only the O-ring included with the saddle valve kit.

CAUTION:

FIGURE 12-7  Insert the piercing pin.

FIGURE 12-8  Tighten the pin.

A method other than that outlined in steps 5, 6, and 7 might be recommended. Follow the recommendations provided by the manufacturer of the saddle valve when they differ from those given here.

SPECIAL TOOLS In.-lb. torque wrench with socket (to match saddle valve screws)

FIGURE 12-9  Replace the pin with the valve core.

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FIGURE 12-10  Tighten the valve core.

9. Securely tighten the valve core (Figure 12-10). 10. Install the cap (or pressure switch) on the installed fitting. There are chemicals available that will lower the ice bath temperature to as low as 2158F (2268C). The Schrader valve in the service fitting is often referred to as a valve core.

SERVICE TIP:

Recover Only—An Alternate Method This method of recovery is presented for information only. It should only be accomplished by, or under the direct supervision of, an experienced technician. The most important consideration is that the recovery cylinder will not have been filled to more than 80 percent of capacity (Figure 12-11) when the temperature is increased to ambient. Refer to the illustration (Figure 12-12) and follow these instructions: 1. Place an identified recovery cylinder into a tub of ice on the floor beside the vehicle. 2. Add water and ice cream salt. This will lower the temperature to about 08F (217.78C). 3. Connect a service hose from the high-side fitting of the system to the gas valve of the recovery cylinder. 4. Open all valves. 5. Cover the recovery cylinder and tub with a blanket to insulate them from the ambient air. 6. Place the shop light(s) or other heat source near the accumulator or receiver. 7. Allow 1 to 2 hours for recovery. The actual time that is required will depend on the ambient temperature and the amount of refrigerant to be recovered.

The recovery cylinder should be below the level of the airconditioning system. 100% 75% SPECIAL TOOLS Recovery system Tub (for ice bath)

R-12

150% 25%

FIGURE 12-11  Recovery cylinders must not be filled more than 80 percent of capacity.

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75°F ambient temperature

Recovery cylinder

Ice cream salt

Gauge manifold

Thermostatic expansion valve Receiverdrier

0°F

Evaporator 75°F

Ice 75°F Condenser Compressor

System temperature should be close to the ambient temperature FIGURE 12-12  Setup for recovering refrigerant using a cold bath tank.

Retrofit Specific procedures to retrofit any particular make or model vehicle are provided by the respective vehicle manufacturers. Several aftermarket manufacturers also offer retrofit kits for more generic applications. For example, one such manufacturer claims that three kits are all that are required to retrofit all car lines. According to early information released by ­automotive manufacturers, however, the procedure, methods, and materials vary considerably from car line to car line. For example, some require draining mineral oil, while others do not; some require flushing the system, others do not. Also, some require replacing components, such as the accumulator or receiver-drier or the condenser, and others do not. In mid-June 1993, the Society of Automotive Engineers (SAE) issued its standard J1661 “Procedure for Retrofitting R-12 Mobile Air-Conditioning Systems to R-134a.” The following service procedure, which is considered typical, is based on SAE’s J1661. Before attempting this procedure, be sure to review Chapter 12 of the Classroom ­Manual. This contains some very important information that must be understood to successfully ­retrofit a vehicle air-conditioning system.

Procedure The following step-by-step procedures are to be considered typical for retrofitting any v­ ehicle from refrigerant R-12 to refrigerant R-134a. For specific procedures, however, follow the ­manufacturer’s instructions.

Connect the Manifold and Gauge Set

Follow this procedure when connecting the R-12 manifold and gauge set into the system for service.

Prepare the System

Classroom Manual Chapter 12, page 395

CAUTION:

Do not attempt to use any other type refrigerants. Use only R-134a to retrofit an automobile airconditioning system.

1. Place fender covers on the car to avoid damage to the finish. 2. Remove the protective caps from the service valves. Some caps are made of light metal and can be removed by hand; others may require a wrench or pliers. 521 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

CAUTION:

Before beginning the retrofit procedure, perform a purity test to determine the type and quality of the refrigerant in the air-conditioning system.

A depressing pin is a pin located in the end of a service hose to press (open) a Schrader-type valve.

WARNING: Remove the caps slowly to ensure that refrigerant does not leak past the service valve.

Connect the Manifold Service Hoses WARNING: The service hoses must be equipped with a Schrader valve depressing pin (Figure 12-13). 1. Make sure that the manifold hand shutoff valves (Figure 12-14) are closed. 2. Make sure that the hose shutoff valves (Figure 12-15) are closed. 3. Finger-tighten the low-side manifold hose to the suction side of the system.

Most hand valves are closed by turning in the clockwise (cw) direction.

FIGURE 12-13  R-12 service hoses equipped with Schrader valve depresser pin.

FIGURE 12-14  Make sure that manifold hand shutoff valves are closed.

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FIGURE 12-15  Make sure that the service hose shutoff valves are closed.

Flexible adapter

45° adapter

90° adapter

Straight adapter

FIGURE 12-16  Special high-side hose adapters.

4. Finger-tighten the high-side manifold hose to the discharge side of the system. 5. If retrofitting an older vehicle or heavy-duty, off-road equipment air-conditioning system having shutoff type service valves (see Figure 12-21), use a service valve wrench to rotate the stem two turns clockwise (cw). 6. Connect the service hose to the R-12 recovery system.

Refrigerant Recovery Until the early 1990s, service technicians vented refrigerant into the atmosphere. Refrigerant was inexpensive, and the cost of recovery would probably have been greater than the cost of the refrigerant. The Clean Air Act (CAA) Amendments of 1990 changed that practice. The CAA enacted by the Environmental Protection Agency (EPA) required that, after July 1, 1992, no refrigerants may be intentionally vented.

SERVICE TIP:

The R-12 high-side fitting on most late-model car lines requires that a special adapter be connected to the hose (Figure 12-16) before being connected to the fitting.

SPECIAL TOOL Recovery system Unintentional venting in the performance of repairs is permitted under the CAA.

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CAUTION:

Certain system ­malfunctions, such as a defective ­compressor, may make this step impossible.

WARNING: Adequate ventilation must be maintained during this procedure. Do not discharge refrigerant near an open flame, as a hazardous toxic gas may be formed.

Prepare the System

1. Start the engine and adjust its speed to 1,250–1,500 rpm. 2. Set all air-conditioning controls to the MAX cold position with the blower on HI speed. 3. Operate for 10–15 minutes to stabilize the system.

Recover Refrigerant SPECIAL TOOLS Recovery cylinder Recovery system

CAUTION:

If an extension cord is used, make certain that it has an electrical rating sufficient to carry the rated load of the recovery system.

1. Return the engine speed to normal idle to prevent dieseling. 2. Turn off all air-conditioning controls. 3. Shut off the engine. 4. If not integrated in the recovery system, use a service hose and connect the recovery system to an approved recovery cylinder. 5. Open all hose shutoff valves. 6. Open both low- and high-side manifold hand valves. 7. Open the recovery cylinder shutoff valves, as applicable. 8. Connect the recovery system into an approved electrical outlet and turn on the main power switch. 9. Turn on the recovery system compressor switch. 10. Operate the vacuum pump until a vacuum pressure is indicated (Figure 12-17). 11. If the recovery system is not equipped with an automatic shutoff, turn off the compressor switch after achieving a vacuum (step 10).

FIGURE 12-17  Operate the pump until a vacuum is noted.

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12. Be sure that the vacuum holds for a minimum of 5 minutes. a. If the vacuum does not hold, repeat the procedures starting with step 9 and continue until the system holds a stable vacuum for a minimum of 2 minutes. b. If the vacuum holds, proceed with step 13. 13. Close all valves: at the recovery cylinder, recovery system, service hoses, manifold, and compressor. 14. Disconnect all hoses previously connected.

WARNING: Some recovery systems have automatic shutoff valves. Be certain they are operating properly before disconnecting the hoses to avoid refrigerant loss that could result in personal injury.

Repair or Replace Components

1. Determine what repairs, if any, are required. 2. If an oil change is required, proceed with step 3; if not, proceed with step 4. 3. Remove the necessary components to drain the oil from the component (Figure 12-18). 4. Flush the individual components while they are out of the vehicle. A typical setup for this procedure is shown in Figure 12-19. 5. Replace components such as the accumulator, receiver-drier, and/or condenser, if required. It may be necessary to replace the receiver-drier or accumulator-drier if the desiccant is not compatible with R-134a refrigerant. 6. Add or replace electrical fail-safe components, such as the refrigerant containment and high-pressure switch, if required. 7. Perform any other modifications and/or procedures required by the specific vehicle manufacturer. 8. Replace/reinstall all components serviced in steps 3 and 7. 9. If not accomplished by the requirements of steps 5, 6, or 7, repair any problems determined in step 1.

Flushing is generally not recommended unless the component has first been removed from the vehicle.

CAUTION:

It is recommended that the receiverdrier or accumulatordrier be replaced anytime the airconditioning system is opened for major repairs.

FIGURE 12-18  Drain oil from an accumulator.

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Low-pressure gauge

High-pressure gauge Adapter

Shutoff valve

Adapter

Shutoff valve Manifold gauge set

Refrigerant cylinder Shutoff valve

Condenser/ evaporator Vacuum pump

Shutoff valve

Recovery tank Recovery unit

Scale FIGURE 12-19  Typical setup for flushing a component.

Flush the System?

Only PAG or POE lubricant should be used in an R-134a refrigerant system.

CAUTION:

If the system was flushed, charge oil directly into the compressor to ­provide lubrication at startup.

Flushing the air-conditioning system is not generally recommended. Because of the screens and strainers in the system, little if any debris will be removed. Also, most liquids (moisture and lubricant) in the low areas in the system—such as in the bottom of the evaporator, muffler, receiver, or accumulator—are not removed by flushing. If flushing is to be performed, the flushing agent should be refrigerant—the same type used in the system. In the case of R-12, this is an expensive procedure. Also, system c­ omponents should be removed for individual flushing after excess lubricant has been drained from them. Refrigerants used for flushing must be recovered. There are a number of systems and techniques available for flushing an air-conditioning system. Some flush systems are attachments for the recovery/recycle machine and other systems are self-contained units. Some use refrigerant as a flushing agent and others use various fluids, even methylhydrate or naphtha (flammable fluids). Nitrogen is often used as a propellant for the cleaning fluid. Some suggest adding a filter to the liquid line after flushing to catch any remaining debris before the metering device. It is important to follow the manufacturer’s recommended procedures for the particular flushing system being used. It is also important not to neglect system lubrication after ­f lushing, regardless of the method or system used. Any lubricant flushed out of the system must be replaced with clean, fresh lubricant of the proper type for the refrigerant being used.

Prepare the System for R-134a

1. Charge the system with the proper type and quantity of lubricant as recommended by the vehicle manufacturer for R-134a refrigerant. 2. Change service ports from R-12 to R-134a access type (Figure 12-20). 3. Check for leaks. 4. Affix decals to identify refrigerant type for future service (Figure 12-21).

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Cap seal (Red and blue)

Cap seal (O-ring)

Pin extension

Conversion fitting

Conversion fitting square cut seal

Contact point of pin extension and Schrader valve

Schrader valve

FIGURE 12-20  Use adapter fittings to change R-12 service ports to R-134a service ports, and apply thread locking compound when installing.

NOTICE: RETROFITTED TO R-134a RETROFIT PROCEDURE PERFORMED TO SAE J1661 USE ONLY R-134a REFRIGERANT AND SYNTHETIC 1 2 OIL TYPE: PN: OR EQUIVALENT, OR A/C SYSTEM WILL BE DAMAGED 3 ESTER

REFRIGERANT CHARGE/AMOUNT: 4 LUBRICANT AMOUNT: PAG RETROFITTER NAME: ADDRESS: 9 CITY:

6

8

STATE:

DATE:

10

ZIP:

5

7 11

1 Type: Manufacturer of oil (Saturn, GM, Union Carbide, etc.).

6 Retrofitter name: Name of facility that performed the retrofit.

2 PN: Part number assigned by manufacturer.

7 Date: Date retrofit is performed.

3 Refrigerant charge / amount: Quantity of charge installed.

8 Address: Address of facility that performed the retrofit. 9 City: City in which the facility is located.

4 Lubricant amount: Quantity of oil installed (indicate ounces, cc, ml).

10 State: State in which the facility is located.

5 Kind of oil installed (check either PAG or ESTER).

11 Zip: Zip code of the facility.

FIGURE 12-21  A typical retrofit label.

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SYSTEM VACUUM

TEMPERATURE

kPa (ABS)

°F

°C

101.33

212

100

27.75

7.35

104

40

28.67

4.23

86

30

29.32

2.03

64

18

29.62

1.01

45

7

29.74

0.61

32

0

29.82

0.34

6

–14

29.91

0.03

–24

–31

in. Hg 0.00

FIGURE 12-22  Boiling point of water (H2 O) in a vacuum at sea level atmospheric pressure.

Evacuating the System SERVICE TIP: Retrofit conversion service fittings for R-134a refrigerant are available in several styles. Conversion fittings with extension pins offer improved performance by opening the existing Schrader valve more fully (see Figure 12-20). Be sure to use threadlock adhesive on service fittings to hold them in place. Some retrofit conversion service fittings require the removal of the existing R-12 Schrader valve or damage to the new fitting could occur.

Whenever it is serviced, an automotive air-conditioning system should be evacuated to the extent that the refrigerant has been removed. There are some who claim that moisture cannot be removed from an automotive air-conditioning system with a “standard” vacuum pump. SAE standard J1661, however, requires that a vacuum pump be capable of achieving a vacuum level of 29.2 in. Hg (2.7 kPa absolute) adjusted to altitude. The boiling point of water (H2O) at this level is 698F (20.68C) at sea level atmospheric pressure (Figure 12-22). That means that moisture cannot be removed from an air-conditioning system when the ambient temperature is below, say, 708F (21.18C). If a vacuum pump is to be used to remove moisture from an automotive air-conditioning system, a quality two-stage, high-vacuum pump is recommended for adequate performance over a long period of time. Even the best vacuum pump, however, requires regular maintenance to ensure optimum performance. Frequent oil changes are perhaps the single most important factor in a preventive maintenance (PM) program. A vacuum pump cannot handle moisture without some of it condensing in the lubricant. If this moisture is not removed by changing the oil, it can attack metal components within the pump. This will result in lockups or loss of pumping efficiency and capacity. For the average service shop, oil changes should be a normal part of the daily equipment maintenance program. It would be well, however, to change the oil after an extended pump down, especially after pumping down a system known to be wet. Specific instructions included with a vacuum pump should be followed for changing the oil.

Speed at Which a System Is Dehydrated

Several factors influence the “pumping speed” of a high-vacuum pump and thus the time required to remove all moisture from a refrigerant system. Some of the most important f­ actors include: ■■ Size of the system, in cubic feet ■■ Amount of moisture to be removed ■■ Ambient temperature ■■ Internal restrictions within the system (Schrader valves and metering device) ■■ External restrictions (between the system and vacuum pump) ■■ Size of the pump ■■ Condition of the pump (clean, fresh oil)

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PHOTO SEQUENCE 18 Removing and Replacing a Schrader Valve Core in a Service Valve The following procedure may be considered typical for replacing a Schrader valve core in an R-134a air-­conditioning system service valve. This procedure, with minor variations, may also be used to replace a Schrader valve core in ­ rocedures included by the equipment an R-12 air-conditioning system service valve as well. Always follow specific p manufacturer when they differ from those given in this text.

P18-1  Install the high-side service valve access fitting.

P18-2  Install the low-side service valve access fitting.

P18-3  With the recovery machine connected, open the appropriate gasor liquid valve (follow specific instructions for machine being used).

P18-4  Turn on the main power.

P18-5  Open the low-and high-side valve.

P18-6  Allow the recovery equipment to operate until both gauges indicate 0 psig (0 kPa) or less.

The elimination of restrictions in an air-conditioning system is not generally possible. The size of valves, manifold, and metering device cannot be altered during evacuation. The service lines, however, can be enlarged as well as shortened, and the Schrader valve cores can be removed during the evacuation process. Photo Sequence 18 illustrates the procedure for removing Schrader valve cores for evacuation and charging procedures.

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PHOTO SEQUENCE 18

(continued)

P18-7  Remove the service valve access fitting from the leaking Schrader valve core.

P18-8  Using a valve core tool, remove the leaking Schrader valve core.

P18-9  Install a new valve core using the valve core tool.

P18-10  Open the low-side hand valve.

P18-11  Start the vacuum pump.

P18-12  After 5 minutes, open the high side hand valve and proceed with procedures as outlined in Photo Sequence 7.

How Vacuum Is Measured

A micron is a unit of linear measurement equal to 125,400 of an inch.

In the automotive air-conditioning industry, vacuum is generally measured with a standard Bourdon tube compound gauge. This type of gauge is suitable for standard vacuum reading, say 29 in. Hg. It cannot be used, however, to read millimeters or microns. For this reason, it is not suitable for use with high-vacuum pumps. Electronic thermistor vacuum gauges (Figure 12-23) are available for use with highvacuum pumps. They can accurately read a vacuum as low as 1 micron by using a sensing tube mounted at some point in the vacuum service line. The readout can be an ­analog meter scale, digital display, or a light-emitting diode (LED) sequential display. One a­ dvantage of a thermistor vacuum gauge is that it is sensitive to water vapor and other condensables and

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Thermistor Vacuum Gauge

FIGURE 12-23  A thermistor vacuum gauge.

can give a good indication of the actual vacuum level within a system. A thermistor vacuum gauge, though not essential, is a worthwhile companion instrument for high-vacuum dehydration of an automotive air-conditioning system. The location of the vacuum gauge will affect its reading in relation to the actual vacuum in the system. The closer the gauge is to the vacuum source, the lower the reading. When taking a final reading of the vacuum created in an air-conditioning system, one should isolate the vacuum pump with a vacuum valve and allow the pressure in the system to equalize. If the pressure does not equalize, it is an indication of a leak. If it does equalize but only at a higher pressure, it is an indication that moisture remains in the system. If this is the case, more pumping time is required. The following service procedure for evacuating the system may be used for the independent vacuum pump (Figure 12-24) or the dedicated charging station (Figure 12-25). The vacuum pump may be used for either R-12 or R-134a refrigerant systems. The ­charging station that is pictured contains a vacuum pump, manifold and gauge set, and calibrated charging cylinder and is for R-12 only. It is compatible with all R-12 recovery and recycling systems. Robinair (and others) also produces a similar dedicated charging station for R-134a refrigerant that is compatible with all R-134a recovery and recycle systems.

FIGURE 12-24  A typical vacuum pump.

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FIGURE 12-25  A typical charging station.

Prepare the System Follow the vacuum pump manufacturer’s operating instructions if they differ from those given in this manual.

If, after 5 minutes, there is not a reasonable vacuum noted, a leak is indicated.

CAUTION:

Make sure that the port cap is removed from the exhaust port to avoid damage to the vacuum pump.

NOTE: Before performing any service procedure, ensure that both the low-side (compound) and high-side (pressure) gauges are zero calibrated. 1. Make sure that the high- and low-side manifold hand valves are in the closed position. 2. Make sure that the service hose shutoff valves are closed. 3. Remove the protective caps and covers from all service access fittings. 4. Connect the R-134a manifold and gauge set to the system in the same manner as was previously outlined for the R-12 manifold and gauge set. 5. Place the high- and low-side compressor service valves, if equipped, in the cracked position. 6. Remove the protective caps from the inlet and exhaust of the vacuum pump. 7. Connect the center manifold hose to the inlet of the vacuum pump. 8. Open all service hose shutoff valves. 9. Start the vacuum pump. 10. Open the low-side manifold hand valve. 11. Observe the low-side (compound) gauge needle. The needle should indicate a slight vacuum. 12. After 5 minutes, the compound gauge should indicate 20 in. Hg (33.8 kPa absolute) or less (Figure 12-26). 13. The high-side (pressure) gauge needle should be slightly below the zero index of the gauge. 14. If the high-side gauge does not drop below zero (Figure 12-27), unless restricted by a stop, a system blockage is indicated. a. If the system is blocked, discontinue the evacuation. Repair or remove the obstruction. b. If the system is clear, continue the evacuation with step 15. 15. Open the high-side manifold hand valve. 16. Operate the pump for 15 minutes and observe the gauges. The system should be at a vacuum of 24–26 in. Hg (20.3–13.5 kPa absolute) minimum if there is no leak. 17. If the system is not down to 24–26 in. Hg (20.3–13.5 kPa absolute), close the low-side hand valve and observe the compound gauge. a. If the compound gauge needle rises, indicating a loss of vacuum, there is a leak that must be repaired before the evacuation is continued. b. If no leak is evident, continue with the pump down.

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FIGURE 12-26  The compound gauge (low) should indicate 20 in. Hg (33.8 kPa absolute) or below.

FIGURE 12-27  The high-side gauge should drop below zero.

18. Pump for a minimum of 30 minutes, as required by SAE J1661. A longer pump down is much better, if time permits. For maximum performance, a triple pump down is ­recommended by many. 19. After pump down, close the high- and low-side manifold hand valves. 20. Shut off the vacuum pump. 21. Close all valves (service hose, vacuum pump, and compressor, if equipped). 22. Disconnect the manifold hoses. 23. Replace any protective caps previously removed.

Charging an R-134a Air-Conditioning System It may be noted that R-134a is an ozone-friendly refrigerant and, as such, poses no known threat to the environment. Nonetheless, the EPA requires that this refrigerant also be ­recovered. This law became effective in the middle of November 1995.

Procedure

1. Place the vehicle in a draft-free work area. This is an aid in detecting small leaks. 2. Close all valves (service valves, if equipped, manifold gauge, service hose shutoff valves, and refrigerant cylinder or charging station shutoff valve).

A product is considered ozone friendly if it does not pose a hazard or danger to the ozone layer. The system should now be under a deep vacuum. 533

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SPECIAL TOOL Electronic thermometer A dual-probe electronic thermometer is ideal for measuring superheat.

3. Connect the manifold and gauge set to the system following procedures previously outlined. 4. Connect the service hose to the refrigerant source. If a charging station is used, it is very important that the instructions provided by the manufacturer of the equipment are followed. 5. Open the service hose shutoff valves. 6. Open the system service valves, if equipped. 7. Observe the gauges. a. Confirm that the system is in a vacuum. If it is, proceed with step 8. b. If it is not, follow the procedure outlined for evacuating the system before proceeding. 8. Dispense one “pound” can (Figure 12-28) of R-134a refrigerant into the system. a. Invert the can for liquid dispensing (Figure 12-29). b. Open the high-side manifold hand valve.

CAUTION:

Do not open the manifold and gauge set hand valves until instructed to do so. Early opening could contaminate the ­system with moisture-laden air.

FIGURE 12-28  Dispense one can of refrigerant into the system.

FIGURE 12-29  Invert the can for liquid dispensing.

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FIGURE 12-30  Attach the electronic thermometer probes to the inlet and outlet of the evaporator.

c. Empty the contents of the can into the system. d. Close the manifold high-side valve. e. Rotate the clutch armature several revolutions by hand to ensure that no liquid refrigerant is in the compressor. 9. Attach the electronic thermometer probes (Figure 12-30) to the inlet and outlet of the evaporator. Be sure that the end of the probe makes good contact with the metal tubes of the evaporator. 10. Open all windows. 11. Place a jumper wire across the terminals of the temperature or pressure control, usually found on the accumulator. 12. Start the engine. 13. Set all air-conditioner controls to HI. 14. Allow the engine to reach normal operating temperature. 15. Note and record the temperature of the two thermometers. Calculate the difference in temperature between the inlet and outlet tubes of the evaporator. 16. Wait a few minutes and record the temperatures again to confirm the readings. 17. Note and record the ambient temperature. Compare it with the chart in Figure 12-31, as applicable. 18. Follow the temperature differential chart (step 15) to determine how much refrigerant must be added to the system to ensure a proper charge. 19. Continue charging, as required. Tap a “pound” can of R-134a. With the can upright, open the manifold low-side valve. Dispense the contents of the can into the system. Close the low-side manifold valve. Repeat this step, as required. 20. Turn off the air conditioner. 21. Stop the engine. 22. Remove the jumper wire from the temperature/pressure switch (see step 11). 23. Close all valves (manifold, hose shutoff, and service, if equipped). 24. Recover refrigerant from the service hoses. 25. Disconnect all hoses from the system. 26. Replace all protective covers and caps.

The jumper ­prevents compressor shortcycling during ­charging procedures.

CAUTION:

As a general rule, the capacity of a retrofit system for refrigerant R-134a capacity is about 90 percent of the ­original capacity for R-12 refrigerant.

Remember to replace the connector to the switch.

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60

AMBIENT TEMPERATURE (°F) 70 80 90 100 110

Evaporator Inlet to Outlet Temperature Difference

A

−8 −7 −6 −5 +13 +21 +40

16

−8 −7 −6 −5 +13 +25 +45

−8 −7 −6 −5 +13 +29 +50

−8 −7 −6 −5 +17 +33 +55

−8 −7 −6 −5 +20 +37 +60

−8 −7 −6 −5 +25 +42 +65

AMBIENT TEMPERATURE (°C) 21 27 32 38 43

Evaporator Inlet to Outlet Temperature Difference

B

−5 −4 −3 −3 +7 +10 +22

−5 −4 −3 −3 +7 +14 +25

−5 −4 −3 −2 +7 +16 +28

−5 −4 −3 −1 +9 +18 +31

−5 −4 −3 0 +11 +21 +33

−5 −4 −3 0 +14 +23 +36

AMOUNT OF R-134a TO ADD (OUNCES) 0 2 4 6 8 12 14 AMOUNT OF R-134a TO ADD (mL) 0 59 118 177 237 335 414

FIGURE 12-31  Evaporator Delta T chart for inlet and outlet temperature.

Customer Care: When performing under-hood service such as refrigerant ­retrofit, make a visual inspection of the engine cooling system. Advise the customer of any problems noticed that may lead to early failure of the cooling or heating system. These problems may include leaks, rotted or cracked radiator or heater hoses, or frayed or worn belt(s). In bringing these problems to the customer’s ­attention, the customer is made aware of pending problems. Nothing is more ­frustrating than having a breakdown due to other failures just after having extensive (and expensive) repairs. When customers are made aware of potential problems, they will generally approve repairs. While some may put off repairs, most will be thankful that your inspection may have prevented an expensive and inconvenient breakdown in the future. In any event, the customer has been made aware of pending problems that are not covered by the current repair warranty. If the customer chooses not to have the repairs made, make a proper notation on the shop order form so it may be a matter of record.

Conclusion Some final points: ■■ At the end of a successful retrofit, affix the proper label in a conspicuous place under the hood. The label (Figure 12-32) should at least contain the following information: 1. Date of retrofit. 2. Company or technician name and address. 3. Type and amount of refrigerant (R-134a) in pounds (lb.), ounces (oz.), or milliliters (mL). 4. Type and amount of lubricant (PAG or POE) in ounces (oz.) or milliliters (mL). 536 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

NOTICE: RETROFITTED TO R-134a RETROFIT PROCEDURE PERFORMED TO SAE J1661 USE ONLY R-134a REFRIGERANT AND SYNTHETIC 1 2 OIL TYPE: PN: OR EQUIVALENT, OR A/C SYSTEM WILL BE DAMAGED REFRIGERANT CHARGE/AMOUNT: 4 LUBRICANT AMOUNT: PAG RETROFITTER NAME: ADDRESS: 9 CITY:

6

8

STATE:

3 ESTER DATE:

10

ZIP:

5

7 11

1 Type: Manufacturer of oil (Saturn, GM, Union Carbide, etc.).

6 Retrofitter name: Name of facility that performed the retrofit.

2 PN: Part number assigned by manufacturer.

7 Date: Date retrofit is performed.

3 Refrigerant charge / amount: Quantity of charge installed.

8 Address: Address of facility that performed the retrofit. 9 City: City in which the facility is located.

4 Lubricant amount: Quantity of oil installed (indicate ounces, cc, ml).

10 State: State in which the facility is located.

5 Kind of oil installed (check either PAG or ESTER).

11 Zip: Zip code of the facility.

FIGURE 12-32  A retrofit label.

■■

■■

Do not remove the R-134a fitting adapters from the R-12 fittings. Once installed, they become a permanent part of the air-conditioning system. Do not overcharge the air-conditioning system with refrigerant. The typical R-134a charge of refrigerant is about 90 percent of the original R-12 refrigerant charge. Refer to the chart in Figure 12-33 for the 90 percent rule.

R-12 OUNCES MILLILITERS 48 1420 44 1302 40 1183 36 1065 32 947 30 887 28 828 26 769 24 710 22 651 20 592 18 532 16 473 14 414

R-134a OUNCES MILLILITERS 43.2 1278 39.6 1171 36.0 1065 32.4 958 28.8 852 27.0 799 25.2 745 23.4 692 21.6 639 19.8 586 18.0 532 16.2 479 14.4 426 12.6 373

FIGURE 12-33  The 90 percent rule for R-134a versus R-12 refrigerant change.

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case study

Terms to Know Depressing pin Ozone friendly Saddle valve

A customer complained about an inoperative air-­ conditioning system. Questioning the customer revealed that the system had not worked since the end of last summer. “It was going to get cool in a few weeks and I would not need the air conditioner. I decided to put it off until spring.” A visual inspection of the system by the ­technician did not reveal any oil spots or ruptured hoses indicating a leak. When the manifold set was connected, the gauges revealed system pressure was equal on both gauges. Further, the temperaturepressure chart indicated that the system pressure was within acceptable limits for R-12 refrigerant for the ambient temperature. The technician noticed that the lead wire to the clutch coil had been disconnected. Assuming that it had been intentionally disconnected, the technician reconnected it. Further questioning of the customer,

however, revealed no knowledge of a disconnected wire. Shortly after starting the engine and turning the air conditioner on, cool air was noted coming from the driver-side vent. The manifold gauges indicated proper pressures. A thermometer inserted in the passengerside vent also indicated proper temperature. Further discussion with the customer revealed that the problem apparently had begun while on vacation. The belts had been replaced and the mechanic must have pulled the wire loose during the repairs. The customer did not realize the problem for several days after the repairs since the climate was mild and the air conditioner was not turned on. The customer had not considered that the problem may have occurred during repairs. The customer suffered through the close of one summer and the start of another simply because of a mechanic’s error and putting off repairs.

ASE-STYLE REVIEW QUESTIONS 1. Technician A says that a shutoff-type service valve has a front-seated position. Technician B says that a Schrader-type service valve has a front-seated position. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 2. After stabilizing the air-conditioning system, the engine speed is returned to normal. Technician A says this is to reduce airflow across the condenser. Technician B says this is to increase the cooling ­capacity of the evaporator. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 3. All of the following may need to be performed as part of a retrofit procedure from R-12 to R-134a refrigerant, except: A. Drain old oil from system components. B. Replace all air conditioning system hoses with ­barrier hoses.

C. Replace the receiver dryer or accumulator. D. Replace or add electrical fail safe components. 4. All of the following statements about system evacuation are true, except: A. All systems should be evacuated for a minimum of 30 minutes. B. If vacuum does not reach 24 to 26 in. Hg (20.3 to 23.5 kPa absolute), evacuate for a longer time. C. Vacuum should reach at least 24 to 26 in. Hg (20.3 to 23.5 kPa absolute) in the first 15 minutes. D. The longer the evacuation period, the better the moisture removal. 5. The recommended minimum efficiency of a vacuum pump at sea level atmospheric pressure is being discussed: Technician A says that atmospheric pressure has no effect on efficiency. Technician B says that the greater the vacuum achieved, the better the efficiency. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

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6. Technician A says that POE is compatible with R-134a. Technician B says that PAG oil is compatible with R-134a. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B 7. All of the following statements are true, except: A. Flushing the air-conditioning system is not ­recommended when retrofitting. B. R-134a retrofit capacity is about 90 percent of the original R-12 capacity. C. A refrigerant identifier will identify flammable refrigerants. D. A refrigerant identifier will identify R-134a at any purity. 8. After retrofitting a vehicles air conditioning system from R-12 to R-134a a retrofit label should be affixed under the hood containing the following information, except: A. Technicians name and address B. Type and amount of refrigerant installed C. Date of retrofit D. Type and amount of lubricant installed

9. Technician A says that the new refrigerant installed must be identified on the retrofit label. Technician B says that the shop that performed the A/C system retrofit must be identified on the retrofit label. Who is correct? A. Technician A only C. Both A and B B. Technician B only D. Neither A nor B 10. If the compressor cycles while charging: Technician A says to place a jumper across the temperature switch. Technician B says to place a jumper across the lowpressure switch. Who is correct? A. A only C. Both A and B B. B only D. Neither A nor B

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ASE CHALLENGE QUESTIONS 1. A refrigerant identifier will do all of the following except: A. Display the percentage of air (non-condensable gas) B. Display the percentage of R-134a or R-12 C. Display the presence of hydrocarbons (HC) if detected D. Display the percentage of water vapor (H2O) 2. Which of the following refrigerants may be vented? A. R-12 C. Both A and B B. R-134a D. Neither A nor B 3. All of the following are removed from an air-­ conditioning system during evacuation, except: A. Air C. Refrigerant B. Moisture D. Lubricant 4. When retrofitting, the proper R-134a charge of ­refrigerant is about _______________ of the original R-12 refrigerant charge. A. 95 percent C. 85 percent B. 90 percent D. 80 percent 5. The equipment shown in the illustration (right) may be used to: A. Evacuate and charge an air-conditioning system B. Recover refrigerant from an air-conditioning system C. Recycle refrigerant that has been recovered from an air-conditioning system D. All of the above

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JOB SHEET

76

Name ______________________________________ Date ________________________

Determining Refrigerant Purity in a Mobile AirConditioning System by Verbal Communication Upon completion of this job sheet, you should be able to use good judgment regarding refrigerant purity. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Refrigerant Recovery, Recycling, and Handling. Task #2. Identify and recover A/C system refrigerant. (P-1) Tools and Materials Vehicle with air-conditioning system charged with refrigerant Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure

1. Question the customer: a.  Has the vehicle air conditioner been serviced recently?  b.  When was it serviced?  c.  By whom?  d.  What type service was performed?  e.  What type refrigerant, if any, was used?  f.  What problems are you experiencing?  Responses by the customer to the above questions help determine if the system should now be serviced. If there are any safety concerns, such as flammable refrigerant, DO NOT service the air-conditioning system. Give a brief summary of your interpretation of the customer’s responses and tell why you: 2. a.  Decided to service the air-conditioning system:

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b.  Decided not to service the air-conditioning system:

Instructor’s Response 

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JOB SHEET

77

Name ______________________________________ Date ________________________

Determining Refrigerant Purity in a Mobile Air-Conditioning System by Testing Upon completion of this job sheet, you should be able to use a refrigerant tester to test for refrigerant purity. NATEF Correlation NATEF AST and MAST Correlation: HEATING AND AIR CONDITIONING: Refrigerant Recovery, Recycling, and Handling. Task #2. Identify and recover A/C system refrigerant. (P-1) Tools and Materials Vehicle with air-conditioning system charged with refrigerant Refrigerant purity tester Instruction manual Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure

1. Determine, following Job Sheet 69, if you wish to proceed with refrigerant testing. Briefly explain:

2. Following procedures included with the purity tester, connect the tester to the airconditioning system to draw a sample of refrigerant. Describe your procedure:

3. Was there an audible signal? _______________ What would an audible signal indicate?

4. What is indicated on the readout? _______________ What does this reading mean?

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5. Based on the results of this test, what procedure will you use to recover the refrigerant?

Instructor’s Response 

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JOB SHEET

78

Name ______________________________________ Date ________________________

Identifying Retrofit Components Upon completion of this job sheet, you should be able to identify those components that must be replaced during retrofit procedures. Tools and Materials Vehicle with R-12 air-conditioning system to be retrofitted for R-134a Service manual Factory-approved retrofit kit Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure Write a short report about component replacement during retrofit from R-12 to R-134a procedures. Explain why or why not the following components should be replaced: 1. Receiver or accumulator:

2. Hose or hoses:

3. Evaporator:

4. Condenser:

5. Pressure control switch:

6. Control thermostat:

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7. Compressor:

8. Condenser fan and motor:

9. Evaporator blower and motor:

10. Other:

Instructor’s Response 

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JOB SHEET

79

Name ______________________________________ Date ________________________

R-12 to R-134a Retrofit Upon completion of this job sheet, you should be able to retrofit an R-12 air-conditioning system to an R-134a air-conditioning system. Tools and Materials Vehicle with R-12 air-conditioning system to be retrofitted for R-134a Factory-approved retrofit kit R-12 refrigerant recovery equipment R-134a refrigerant charging equipment Hand tools, as required Describe the vehicle being worked on. Year _____________________ Make _____________________ Model _____________________ VIN ____________________________ Engine type and size _____________________________ Procedure After each step, write a brief summary of your procedure: 1. Remove the R-12 refrigerant by recovering it for future use. NOTE: DO NOT vent refrigerant to the atmosphere.

2. Remove and replace any defective air-conditioning system components.

3. Remove as much of the mineral oil as possible.

4. Add or replace components as required in the retrofit procedures.

5. Add or replace lubricant as required in the retrofit procedures.

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6. Install R-134a service valve fittings and label.

7. Evacuate the air-conditioning system.

8. Leak test the air-conditioning system.

9. Charge the air-conditioning system with R-134a refrigerant.

10. Performance test the air-conditioning system.

11. What problems, if any, were encountered?

Instructor’s Response 

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APPENDIX A

ASE PRACTICE EXAMINATION

Final Exam Automotive Heating and Air Conditioning A7 1. What component part of the air-conditioning system causes the refrigerant to change from a liquid to a vapor?

A. Evaporator B. Compressor C. Condenser D. Metering device

7. The voltmeter reading in the illustration below is 0. The most probable cause of this problem is that the:

A. B. C. D.

Windings are shorted Windings are open Relay is not energized Motor is seized

2. How does the air-conditioning system remove excess humidity from the air entering the passenger ­compartment?

A. B. C. D.

Voltmeter

Moisture collects on the duct walls. Moisture condenses on the condenser. Moisture condenses on the evaporator. Moisture is separated by the blower motor.

3. During a system performance test of the air-­conditioning system operation both the high-side and low-side ­pressure readings are about the same and the ­compressor clutch is engaged. Which of the following is the most likely cause?

A. B. C. D.

Blower motor relay

A restriction in the low pressure line A faulty compressor valve plate Moisture contamination of the system A restricted expansion valve

4. Before discarding a disposable refrigerant tank, which of the following procedures should be performed?

A. Make sure the tank valve is closed to prevent ­venting to the atmosphere. B. Flush the tank with refrigerant flushing agent. C. Recover any remaining refrigerant left in the tank. D. Open the valve to eliminate the pressure.

5. Technician A says that a retrofit label must identify the type and amount of refrigerant oil. Technician B says that a retrofit label must identify the amount of new refrigerant installed. Who is correct?

A. A only B. B only

C. Both A and B D. Neither A nor B

6. All of the following may cause a compressor clutch to slip, except:

A. B. C. D.

Overcharge of refrigerant Loose drive belt Improper air gap Low voltage

Blower motor Blower motor relay

Ammeter

Blower motor

20 A fuse

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APPENDIX A

ASE PRACTICE EXAMINATION

8. The motor does not operate when connected as shown in the illustration above. The fuse is good, and 15 A is displayed on the ammeter. The most likely cause of this problem is that the:

A. B. C. D.

Windings are shorted Windings are open Brushes are defective No power is going to the motor

9. High-voltage “spikes” are eliminated when the clutch is engaged and disengaged with the use of a:

A. Thermistor B. Resistor

C. Transistor D. Diode

10. A vehicle is brought in for service with the customer complaint that a foul odor is present when the air-­ conditioning system is on. Technician A says that the cause may be ice forming on the evaporator core. Technician B says that the cause may be mold and ­bacteria growing on the evaporator core. Who is correct?

A. A only B. B only

C. Both A and B D. Neither A nor B

11. The refrigerant leaving the condenser is a ________.

A. B. C. D.

Cold, low-pressure vapor Hot, high-pressure vapor Cold, low-pressure liquid Hot, high-pressure liquid

12. A manifold and gauge set may be used for all of the ­following except:

A. B. C. D.

Charging the system with refrigerant Evacuating the refrigerant system Checking system contamination Checking system pressures

13. The loss of a vacuum signal at the control will most likely cause the system to “fail safe” to the ________ mode.

A. Heat B. Defrost

C. Either A or B D. Neither A nor B

14. A “blend” refrigerant means that:

A. It contains more than one component in its composition. B. It may be mixed (blended with) another refrigerant. C. Both A and B D. Neither A nor B

15. The screen in the fixed orifice tube is found to be clogged. The recommended repair is to determine and correct the problem that caused the clogging and to:

A. B. C. D.

Clean the screen. Replace the screen. Replace the fixed orifice tube. Replace the fixed orifice tube and liquid line.

16. The pressure of the refrigerant in the condenser ________ as it gives up its heat to the ambient air.

A. B. C. D.

Is increased Remains about the same Is reduced Any of the above, depending on its temperature

17. The clutch air gap may be measured using a:

A. Dime B. Wire-type feeler gauge C. Stainless steel scale D. Nonmagnetic feeler gauge

18. While charging a refrigerant system, if liquid ­refrigerant is added to the low side of the system of a running air conditioner, the following component could be ­damaged.

A. B. C. D.

The evaporator assembly The condenser assembly The compressor assembly The expansion valve assembly

19. All of the following statements about a system with a variable displacement compressor are true, except:

A. There is no electromagnetic clutch. B. The cycling clutch is not used for temperature control. C. The swash plate angle determines the compressor displacement. D. When capacity demand is high, the swash plate is at its greatest angle.

20. Most vehicle manufacturers use which of the following refrigerant oil in their systems?

A. Mineral oil B. PAG oil

C. Ester oil D. PCV oil

21. All of the following are popular methods of leak ­detection, except:

A. Halogen B. Halide

C. Dye D. Vacuum

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APPENDIX A

ASE PRACTICE EXAMINATION

22. When the refrigerant container is inverted, as shown in the illustration below:

A. The air-conditioning system must be charged through the high side with the compressor off. B. The air-conditioning system must be charged through the high side with the compressor running. C. The air-conditioning system must be charged through the low side with the compressor off. D. The air-conditioning system must be charged through the low side with the compressor running.

Technician B says that the air-conditioning system may have a leak and the rise in pressure is caused by the ­introduction of ambient air. Who is correct?

C. Both A and B D. Neither A nor B

A. A only B. B only

26. On a refrigerant system equipped with an expansion valve the low-side pressure is 45 psi and the high-side pressure is 160 psi. The engine speed is 1800 rpm and the ambient air temperature is 88°F. What is the most likely cause of these pressure readings?

A. B. C. D.

System is operating correctly. Evaporator core is restricted. Receiver-dryer is restricted. Expansion valve is stuck in the open position.

27. The following statements are true about a check valve, except:

A. B. C. D.

Airflow is blocked in one direction only. Vacuum flow is blocked in one direction only. Air or vacuum is permitted to flow in one direction. A check valve is omnidirectional when used in a vacuum system.

28. What is callout E in the illustration below?

A. Wiring harness B. Cooling tube

Blower motor connection

23. Low voltage at the clutch coil may cause:

A. The clutch to slip B. A noisy clutch

C. Ground wire D. None of the above

C. Both A and B D. Neither A nor B

24. All except which of the following statements about a vacuum pump are true? A vacuum pump may be used to remove:

A. B. C. D.

Blower

Moisture from an air-conditioning system Air from an air-conditioning system Trace refrigerant from an air-conditioning system Debris from an air-conditioning system

25. The low-side gauge on a manifold and gauge set indicates a vacuum below 29 in. Hg while the vacuum pump is running. Five minutes after the pump is turned off, the gauge indicates 25 in. Hg. Technician A says that the vacuum pump was not run long enough to remove residual refrigerant from the lubricant, and the rise in pressure is caused by refrigerant outgassing.

Blower motor

Heater and A/C module E

29. All of the following may result in inadequate airflow, except:

A. B. C. D.

Duct or hose torn or disconnected Mode door binding inoperative or disconnected Defective or disconnected coolant flow control Outlet blocked or restricted

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APPENDIX A

ASE PRACTICE EXAMINATION

30. The most probable cause of windshield fogging is the:

A. Heater coolant flow control valve is leaking. B. Heater coolant flow control valve is out of adjustment. C. Heater core is restricted. D. Heater core is leaking.

31. The high-side gauge needle is below 0 as shown in the illustration below. This is an indication that the:

A. Gauge is hooked up to an air-conditioning system that is under a vacuum. B. Gauge is out of calibration and should be adjusted to zero before being used. C. Both A and B D. Neither A nor B

34. The receiver-drier or accumulator should be replaced during all of the following services, except when replacing:

A. B. C. D.

A defective service valve core A compressor A condenser An evaporator

35. All of the following information is required on a retrofit label except:

A. B. C. D.

Date of retrofit Company or technician certificate number Type and amount of refrigerant Type and amount of lubricant

36. A thermistor’s resistance is in proportion to:

A. B. C. D.

Its temperature The pressure applied to it The ambient light intensity The voltage applied to it

37. All of the following must be replaced when opened by an electrical overload, except:

A. B. C. D.

Fusible link Panel-mounted fuse In-line fuse Circuit breaker

38. What instrument can be used to test a fuse or circuit breaker?

32. During a system performance test of the air-conditioning system operation the technician notices that the low-side gauge is reading a vacuum. Which of the following is the most likely cause?

A. B. C. D.

An overcharged refrigerant system A flooded evaporator core Air contamination of the system A restricted expansion valve

33. To pass a purity test, the refrigerant being tested must be at least ________ pure.

A. 99 percent B. 98 percent

C. 97 percent D. 96 percent

A. Ohmmeter B. Voltmeter C. Both A and B D. Neither A nor B

39. The master control is turned to maximum cooling. The blower motor does not run. A jumper wire is ­connected to the blower motor case and to body metal. There is a slight spark when connected, and the motor runs. Technician A says that the problem is in the electrical control circuit. Technician B says that the problem is in the electrical ground circuit. Who is correct?

A. A only B. B only

C. Both A and B D. Neither A nor B

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APPENDIX A

ASE PRACTICE EXAMINATION

40. The blower motor in the schematic in the illustration below has ________ speeds.

A. Two B. Three B+

C. Four D. Variable

A. B. C. D.

Hot in run

IP Fuse Panel HVAC 20A

Junction block

Mode selector

LO M1

Evaporator pressure control switch

HI

Blower motor relay

Blower motor

A/C clutch

41. If the crankshaft pulley turns clockwise (cw), all of the following statements about the illustration below are true, except:

A. B. C. D.

The compressor turns clockwise (cw). The power steering pulley turns clockwise (cw). The water pump turns clockwise (cw). The alternator pulley turns clockwise (cw). PS TI

WP AP

AC CP LEGEND: AC - A/C Compressor Pulley AP - Alternator Pulley CP - Crankshaft Pulley

System is overcharged with refrigerant. System is undercharged with refrigerant. The rear expansion valve is stuck open. The front blend door is not in the correct position.

43. After driving for 20 miles the vehicle heater continues to blow cool air and the engine temperature is in the normal range. Which of the following is the most likely cause?

M2

Blower switch

42. A vehicle is equipped with dual front and rear evaporators. The rear outlet duct temperature is correct but the front duct temperature is too warm. Which of the following is the most likely cause?

A. B. C. D.

A worn water pump impeller. Thermostat is stuck in the closed position. The heater core is restricted. The radiator is restricted.

44. The least likely cause of engine overheating is a defective:

A. Temperature sending unit B. Thermostat C. Radiator cap D. Water pump

45. Extended-life antifreeze has a useful life of up to ________ miles/kilometers.

A. 50,000/80,450 B. 100,000/160,900 C. 150,000/241,350 D. 200,000/321,800

46. The environmental and health problems associated with the venting of refrigerants are being discussed. Technician A says that some refrigerants vented near an open flame may produce a toxic vapor. Technician B says that one may be subject to heavy penalties for unlawfully venting refrigerant. Who is correct?

A. B. C. D.

A only B only Both A and B Neither A nor B

47. What is the minimum number of manifold and gauge sets required to comply with federal regulations and to ensure PS - Power Steering Pulley against refrigerant contamination? TI - Tensioner/Idler Pulley A. Two C. Four WP - Water Pump Pulley

B. Three

D. Five

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APPENDIX A

48. During a system performance test of the air-conditioning system, both the high-side and low-side pressure ­readings are in the normal operating range pressures but poor cooling is achieved. Which of the following is the most likely cause?

A. B. C. D.

The compressor is faulty. Airflow through the evaporator is restricted. The receiver-dryer is saturated. Airflow through the condenser is restricted.

ASE PRACTICE EXAMINATION

50. All of the following supply valuable service and technical information for the automotive air-conditioning service technician, except:

A. MACS B. IATN C. Mitchell/All Data D. AAA

49. The information given on the label depicted in the below illustration is the vehicle’s:

A. B. C. D.

Serial and model number Refrigerant and lubricant data Emissions control data Identification number

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APPENDIX B

To convert these

to these,

METRIC CONVERSIONS

multiply by:

TEMPERATURE

To convert these

to these,

multiply by:

WEIGHT

Centigrade Degrees

Fahrenheit Degrees

1.8 then + 32

Grams

Ounces

0.03527

Fahrenheit Degrees

Centigrade Degrees

0.556 after − 32

Ounces

Grams

28.34953

Kilograms

Pounds

2.20462

Pounds

Kilograms

0.45359

LENGTH Millimeters

Inches

0.03937

Inches

Millimeters

25.4

WORK

Meters

Feet

3.28084

Centimeter Kilograms

Inch-Pounds

0.8676

Feet

Meters

0.3048

Inch-Pounds

Centimeter-Kilograms

1.15262

Kilometers

Miles

0.62137

Meter Kilograms

Foot-Pounds

7.23301

Miles

Kilometers

1.60935

Foot-Pounds

Meter Kilograms

1.3558

Kilograms/Square Centimeter

Pounds/Square Inch

14.22334

Pounds/Square Inch

Kilograms/Square Centimeter

0.07031

PRESSURE

AREA Square Centimeters

Square Inches

0.155

Square Inches

Square Centimeters

6.45159

VOLUME Cubic Centimeters

Cubic Inches

0.06103

Bar

Pounds/Square Inch

14.504

Cubic Inches

Cubic Centimeters

16.38703

Pounds/Square Inch

Bar

0.0689

Cubic Centimeters

Liters

0.001

Pounds/Square Inch

Kilopascals

6.895

Liters

Cubic Centimeters

1,000

Kilopascals

Pounds/Square Inch

0.145

Liters

Cubic Inches

61.025

Cubic Inches

Liters

0.01639

Liters

Quarts

1.05672

Quarts

Liters

0.94633

Liters

Pints

2.11344

Pints

Liters

0.47317

Liters

Ounces

33.81497

Ounces

Liters

0.02957

Millileters

Ounces

0.3381497

Ounces

Millileters

29.57

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APPENDIX C

AIR-CONDITIONING SPECIAL TOOL SUPPLIERS

Bright Solutions, Inc. Troy, MI

OTC Division SPX Corporation Owatonna, MN

Carrier Corporation Syracuse, NY

Owens Research, Inc./Tubes ’N Hoses Dallas, TX

Clardy Manufacturing Corporation Fort Worth, TX

P & F Technologies Ltd. Mississauga, ONT, Canada

Classic Tool Design, Inc. New Windsor, NY

Ritchie Engineering Company Inc. Garrett, IN

Component Assemblies, Inc. Bryan, OH

Robinair Division SPX Corporation Montpelier, OH

Corrosion Consultants, Inc. Roseville, MI

RTI Technologies, Inc. York, PA

CPS Products, Inc. Hialeah, FL

The S. A. Day Manufacturing Company, Inc. Buffalo, NY

Envirotech Systems, Inc. Niles, MI

Snap-On Tools Corporation Kenosha, WI

FJC, Inc. Davidson, NC

Superior Manufacturing Company Morrow, GA

Floro Tech, Inc. Pitman, NJ

Technical Chemicals Company Dallas, TX

Four Seasons Division of Standard Motor Products, Inc. Lewisville, TX 75057

Thermolab, Inc. Farmersville, TX

Interdynamics, Inc. Brooklyn, NY

TIF Instruments, Inc. Miami, FL

K. D. Binnie Engineering Pty. Ltd. Kirrawee, NSW, Australia

Tracer Products Division Spectronics Corporation Westbury, NY

KD Tools Lancaster, PA

Uniweld Products Ft. Lauderdale, FL

Kent Moore Division SPX Corporation Warren, MI

Uview Ultraviolet Mississauga, ONT, Canada

Lincor Distributors N. Hollywood, CA

Varian Vacuum Technologies Lexington, MA

MAC Tools Washington Courthouse, OH

Viper/T-Tech Division Century Manufacturing Company Minneapolis, MN

Mastercool, Inc. Rockaway, NJ Neutronics, Inc. Exton, PA

Yokagawa Corporation of America Newnan, GA

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APPENDIX D

WHERE TO SEND CONTAMINATED REFRIGERANT

For a complete and up-to-date list on companies that will accept contaminated refrigerant from your shop, check the EPA-Certified Refrigerant Reclaimers. This list is updated as additional refrigerant reclaimers are approved. Reclaimers appearing on this list are approved to reprocess used refrigerant to at least the purity level specified in Appendix A to 40 CFR part 82, subpart F (based on

ARI Standard 700, “Specifications for Fluorocarbon and Other Refrigerants”). Reclamation of used refrigerant by an EPA-certified reclaimer is required in order to sell used refrigerant not originating from and intended for use with motor vehicle air conditioners. The website is: www.epa.gov/ozone/title6/608/­ reclamation/reclist.html.

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GLOSSARY GLOSARIO Note: Terms are highlighted in color, followed by Spanish translation in bold. Absolute  Perfect in quality or nature, complete. Usually

Ambient sensor  A thermistor used in automatic

Absoluto  Perfecto en su calidad o naturaleza, completo.

Sensor amblente  Termistor utilizado en unidades de

Access valve  See Service port and Service valve.

Ambient temperature  The temperature of the surrounding

used in refrigeration context when referring to temperature or pressure.

Suele usarse en contextos de refrigeración cuando se refiera a la temperatura o la presión.

Valvula de acceso  Ver Service port [Orificio de servicio] y

Service value [Válvula de servicio].

Accumulator  A tank located in the tailpipe to receive the

refrigerant that leaves the evaporator. This device is constructed to ensure that no liquid refrigerant enters the compressor.

temperature control units to sense ambient temperature. Also see Thermistor. regulación automática de temperatura para sentir la temperatura ambiente. Ver también Thermistor [Termistor]. air.

Temperatura del ambiente  La temperatura del aire

alrededor.

Amperage  A term used to describe the number of electrons

moving past a fixed point in a conductor in one second. Current is measured in units called amperes or amps.

Acumulador  Tanque ubicado en el tubo de escape para

Amperaje  A termino para describir el número de electrones

Acme  A type of fitting thread. The service hose

Approved power source  A power source that is consistent

Acme  Un tipo de rosca de guarnición. Las conexiones

Fuente aprobada de potencia  Fuente de potencia que

Actuator  A device that transfers a vacuum or electric signal

Armature  The part of the clutch that mounts onto the

recibir el refrigerante que sale del evaporador. Dicho dispositivo está diseñado de modo que asegure que el refrigerante líquido no entre en el compresor.

connections to the R-134a manifold set have ½-16 acme threads. del tubo de servio al conjunto de la manívela de R-134a tienen las roscas acme de 16.

to a mechanical motion. An actuator typically performs an on/off or open/close function.

Accionador  Dispositivo que transfiere una serial de

vacio o una señal eléctrica a un movimiento mecánico. Típicamente un accionador lleva a cabo la función de modulación de impulsos o la de abrir y cerrar.

Adapter  A device or fitting that permits different size parts

or components to be fastened or connected to each other.

Adaptador  Dispositivo o ajuste que permite la sujección o

conexión entre sí de piezas de tamaños diferentes.

Aftermarket  A term generally given to a device or accessory

that is added to a vehicle by the dealer after original manufacture, such as an air-conditioning system.

Postmercado  Término dado generalmente a un dispositivo

o accesorio que el distribuidor de automóviles agrega al automóvil después de la fabricación original, como por ejemplo un sistema de acondi-cionamiento de aire.

Air gap  The space between two components such as the

rotor and armature of a clutch.

Espacio de aire  El espacio entre dos componentes, como

por ejemplo el rotor y la armadura de un embrague.

que se mueven más allá de un punto fijo en un conductor en un segundo. El Corriente se mide en unidades se llama amperios o amperes. with the requirements of the equipment so far as voltage, frequency, and ampacity are concerned.

cumple con los requisitos del equipo referente a la tensión, frecuencia, y ampacidad.

crankshaft and engages with the rotor when energized.

Armadura  La parte del embrague que se fija al cigüeñal y se

engrans al exitarse el rotor.

Asbestos  A silicate of calcium (Ca) and magnesium (Mg)

mineral that does not burn or conduct heat. It has been determined that asbestos exposure is hazardous to health and must be avoided.

Asbesto  Mineral de silicato de calcio (Ca) y magnesio (Mg)

que no se quema ni conduce el calor. Se ha establecido que la exposición al asbesto es nociva y debe evitarse.

Aspirator  A device that uses a negative (suction) pressure

to move air.

Aspirador  Un dispositivo que usa una presión negativa (la

succión) para mover el aire.

Atmospheric pressure  Air pressure at a given altitude. At

sea level, atmospheric pressure is 14.696 psia (101.329 kPa absolute).

Presión atmosférica  La presión del aire a una dada altitud.

Al nivel del mar, la presión atmosférica es de 14,696 psia (101.329 kPa absoluto).

AUTO  Abbreviation for automatic.

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AUTO  Abreviatura del automático. Back seat (service valve)  Turning the valve stem to the left

(ccw) as far as possible back seats the valve. The valve outlet to the system is open and the service port is closed. Asentar a la izquierda (válvula de servicio)  El girar el vástago de la válvula al punto más a la izqiuerda posible asienta a la izquierda la válvula. La salida de la válvula al sistema está abierta y el orificio de servicio está cerrado. Barb fitting  A fitting that slips inside a hose and is held in place with a gear-type clamp. Ridges (barbs) on the fitting prevent the hose from slipping off. Accesorio arponado  Ajuste que se inserta dentro de una manguera y que se sujeta en su lugar con una abrazadera de tipo engranaje. Proyecciones (puas) en el ajuste impiden que se deslice la manguera. Barrier hose  A hose having an impervious lining to prevent refrigerant leakage through its wall. Air-conditioning systems in vehicles have had barrier hoses since 1988. Manguera de barrera  Una manguera que tiene un forro impervio que previene el goteo del refrigerante a través de su muro. Los sistemas de aire acondicionado en los vehículos han incluido las mangueras de barrera desde el 1988. BCM  An abbreviation for blower control module. BCM  Abreviatura de módulo regulador del soplador. Belt  See V-belt and Serpentine belt. Correa  Ver V-belt [Correa en V], y Serpentine belt [Correa serpentina]. Belt tension  Tightness of a belt or belts, usually measured in foot-pounds (ft.-lb.) or Newton-meters (N·m). Tensión de la correa  Tensión de una correa o correas, medida nor-malmente en libras-pies (ft.-lb.) o metros-Newton (N·m). Blower  See Squirrel-cage blower. Soplador  Ver Squirrel-cage blower [Soplador con jaula de ardilla]. Blower motor  See Motor. Motor de soplador  Ver Motor. Blower relay  An electrical device used to control the function or speed of a blower motor. Rele del soplador  Dispositivo eléctrico utilizado para regular la fun-ción o velocidad de un motor de soplador. Boiling point  The temperature at which a liquid changes to a vapor. Punto de ebullición  Temperatura a la que un líquido se convierte en vapor. Break a vacuum  The next step after evacuating a system. The vacuum should be broken with refrigerant or other suitable dry gas, not ambient air or oxygen. Romper un vacío  El paso que inmediatamente sigue la evacuación de un sistema. El vacío debe de romperse con refrigerante u otro gas seco apropiado, y no con aire ambiente u oxígeno.

Breakout box  A tool in which the probes of a digital volt-

ohmmeter (DVOM) may be inserted to access various sensors and actuators through pin connectors to the computer. Accesorio detector  Una herramienta en la cual las sondas de un ohmímetro digital (DVOM) pueden insertarse para ganar la entrada a varios sensores e actuadores de la computadora por medio de las conexiones a las espigas de contacto. Bypass  An alternate passage that may be used instead of the main passage. Desviación  Pasaje alternativo que puede utilizarse en vez del pasaje principal. Bypass hose  A hose that is generally small and is used as an alternate passage to bypass a component or device. Manguera desviadora  Manguera que generalmente es pequeña y se utiliza como pasaje alternativo para desviar un componente o dispositivo. CAA  Clear Air Act. CAA  Ley para Aire Limpio. Calibration  To check, adjust, or determine the accuracy of an instrument used for measuring, for example, temperature or pressure. Calibración  Revisar, ajustar o determinar la precisión de un instrumento que se usa para medir, por ejemplo, la temperatura o la presión. Can tap  A device used to pierce, dispense, and seal small cans of refrigerant. Macho de roscar para latas  Dispositivo utilizado para perforar, dis-tribuir y sellar pequeñas latas de refrigerante. Can tap valve  A valve found on a can tap that is used to control the flow of refrigerant. Válvula de macho de roscar para latas  Válvula que se encuentra en un macho de roscar para latas utilizada para regular el flujo de refrigerante. Cap  A protective cover. Also used as an abbreviation for capillary (tube) or capacitor. Tapadera  Cubierta protectiva. Utilizada tambien como abreviatura del tubo capilar o capacitador. Cap tube  A tube with a calibrated inside diameter and length used to control the flow of refrigerant. In automotive airconditioning systems, the tube connecting the remote bulb to the expansion valve or to the thermostat is called the capillary tube. Tubo capilar  Tubo de diámetro interior y longitud calibrados; se utiliza para regular el flujo de refrigerante. En sistemas automotrices para el acondicionamiento de aire el tubo que conecta la bombilla a distancia con la válvula de expansión o con el termostato se llama el tubo capilar. Carbon monoxide (CO)  A major air pollutant that is potentially lethal if inhaled, even in small amounts. An odorless gas composed of carbon (C) and hydrogen (H) formed by the incomplete combustion of any fuel containing carbon.

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Monóxido de carbono (CO)  Un contaminante de aire principal

que puede ser letal si se inhala, aún en pequeñas cantidades. Un gas sin olor compuesto de carbono (C) e hidrógeno (H) formado por la combustión incompleta de cualquier combustible que contiene el carbono. Carbon seal face  A seal face made of a carbon composition rather than from another material such as steel or ceramic. Frente de carbono de la junta hermética  Frente de la junta

hermética fabricada de un compuesto de carbono en vez de otro material, como por ejemplo el acero o material cerámico.

Caution  A notice to warn of potential personal injury

situations and conditions.

Precaución  Aviso para advertir situaciones y condiciones que

podrían causar heridas personales.

CCW Counterclockwise. CCW  Sentido inverso al de las agujas del reloj. Celsius  A metric temperature scale using zero as the freezing

point of water. The boiling point of water is 1008C (2128F).

Celsio  Escala de temperatura métrica en la que el cero se

utiliza como el punto de congelación de agua. El punto de ebullición de agua es 1008C (2128F).

Ceramic seal face  A seal face made of a ceramic material

instead of steel or carbon.

Frente cerámica de la junta hermética  Frente de la junta

hermética fabricada de un material cerámico en vez del acero o carbono.

Certified  Having a certificate. A certificate is awarded

or issued to those who have demonstrated appropriate competence through testing or practical experience.

Certificado  El poseer un certificado. Se les otorga o emite un

certificado a los que han demostrado una cierta capacidad por medio de exámenes y/o experiencia practica.

CFC-12  See Refrigerant-12. CFC-12  Ver [Refrigerante-12]. Charge  A specific amount of refrigerant or oil by volume or

weight.

Carga  Cantidad específica de refrigerante o de aceite por

volúmen o peso.

Check valve  A device located in the liquid line or inlet to the

drier. The valve prevents liquid refrigerant from flowing the opposite way when the unit is shut off.

Válvula de retención  Dispositivo ubicado en la línea de

líquido o en la entrada al secador. Al cerrarse la unidad, la válvula impide que el refrigerante líquido fluya en el sentido contrario.

Circuit breaker  A circuit protection device that will create

an open in the circuit if the current passing through it exceeds the amperage rating number. But will automatically reset and close once the current overload drops below the rated value.

Disyuntor  El aparato de protección del circuito que creará

un circuito abierto en el circuito si la corriente que pasa a través de él sobrepasa el número de calificación de amperaje. Pero automáticamente restablece y cierre una vez que la sobrecarga de corriente cae por debajo del valor nominal. Clean Air Act (CAA)  A Title IV amendment signed into law in 1990 that established national policy relative to the reduction and elimination of ozone-depleting substances. Ley para Aire Limpio (CAA)  Enmienda Titulo IV firmado y aprobado en 1990 que estableció la política nacional relacionada con la reducción y eliminación de sustancias que agotan el ozono. Clockwise  A term referring to a clockwise (cw), or left-toright rotation or motion. Sentido de las agujas del reloj  Término que se refiere a un movimiento en el sentido correcto de las agujas del reloj (cw por sus siglas en ingles), es decir, rotación o movimiento desde la izquierda hacia la derecha. Clutch  An electromechanical device mounted on the airconditioning compressor used to start and stop compressor action, thereby controlling refrigerant circulating through the system. Embrague  Dispositivo electromecánico montado en el compresor del acondicionador de aire y utilizado para arrancar y detener la acción del compresor, regulando así la circulación del refrigerante a través del sistema. Clutch coil  The electrical part of a clutch assembly. When electrical power is applied to the clutch coil, the clutch is engaged to start and stop compressor action. Bobina del embrague  La parte eléctrica del conjunto del embrague. Cuando se aplica una potencia eléctrica a la bobina del embrague, éste se engrana para arrancar y detener la acción del compresor. Clutch pulley  A term often used for “clutch rotor”; that portion of the clutch in which the belt rides. Polea del embrague  Un término que se suele usa para el “rotor del embrague.” Esa porción del embrague en la cual viaja la correa. Compound gauge  A gauge that registers both pressure and vacuum (above and below atmospheric pressure); used on the low side of the systems. Manómetro compuesto  Calibrador que registra tanto la presión como el vacio (a un nivel superior e inferior a la presión atmosférica); utilizado en el lado de baja presión de los sistemas. Compression fitting  A type of fitting used to connect two or more tubes of the same or different diameter together to form a leakproof joint. Ajuste de compresión  Tipo de ajuste utilizado para sujetar dos

o más tubos del mismo tamaño o de un tamaño diferente para formar una junta hermética contra fugas.

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Compression nut  A nut-like device used to seat the

compression ring into the compression fitting to ensure a leakproof joint.

Tuerca de compresión  Dispositivo parecido a una tuerca

utilizado para asentar el anillo de compresión dentro del ajuste de compresión para asegurar una junta hermética contra fugas.

Compression ring  A ring-like part of a compression fitting

used for a seal between the tube and fitting.

Aro de compresión  Pieza parecida a un anillo del ajuste de

compresión utilizada como una junta hermética entre el tubo y el ajuste.

Compressor shaft seal  An assembly consisting of springs,

snaprings, O-rings, shaft seal, seal sets, and gasket. The shaft to be turned without a loss of refrigerant or oil.

Junta hermética del arbol del compresor  Conjunto que

consiste de muelles, anillos de muelles, juntas tóricas, una junta hermética del arbol, conjuntos de juntas herméticas, y una guarnición. La junta hermética del arbol está montada en el cigüerñal del compresor y permite que el arhol se gire sin una pérdida de refrigerante o aceite.

Customer  The vehicle owner or a person who orders or pays

for goods or services. Cliente  El dueño de un vehículo o una persona que pide y/o paga para las mercancías y servicios. CW  Abbreviation for clockwise. Also cw. CW  Abreviatura del sentido de las agujas del reloj. Tambien cw. Cycle clutch time (total)  Time from the moment the clutch engages until it disengages, then reengages. Total time is equal to on time plus off time for one cycle. Duración del ciclo del embrague (total)  Espacio de tiempo medido desde el momento en que se engraña el embrague hasta que se desengrañe y se engrañe de nuevo. El tiempo total es equivalente al trabajo efectivo más el trabajo no efectivo por un ciclo. Cycling-clutch pressure switch  A pressure-actuated electrical switch used to cycle the compressor at a predetermined pressure. Automata manométrico del embrague con funcionamiento cíclico  Interruptor eléctrico accionado a presión utilizado

Cracked position  A mid-seated or open position.

para ciclar el compresor a una presión predeterminada. Cycling-clutch system  An air-conditioning system in which the air temperature is controlled by starting and stopping the compressor with a thermostat or pressure control. Sistema de embrague con funcionamiento cíclico  Sistema de acondicionamiento de aire en el cual la temperatura del aire se regula al arrancarse y detenerse el compresor con un termostato o regulador de presión. Cycling time  A term often used for “cycling-clutch time.” The total time from when the clutch engages until it disengages and again engages; equal to one on time plus one off time for one cycle. Funcionamiento cíclico  Un término que se usa para “tiempo de cliclaje del embrague.” El total del tiempo desde que se engancha el embrague hasta que se desengancha y engancha de nuevo; iguala a un tiempo prendido más un tiempo apagado por un ciclo. Debris  Foreign matter such as the remains of something broken or deteriorated. Escombro  Materia extranjera tal como los restos de algo roto o deteriorado. Decal  A label that is designed to stick fast when transferred. A decal affixed under the hood of a vehicle is used to identify the type of refrigerant used in a system. Calcomania  Etiqueta diseñada para pegarse fuertemente al ser trans-ferido. Una calcomania pegada debajo de la capota se utiliza para identificar el tipo de refrigerante utilizado en un sistema. Department of Transportation  The U.S. Department of Transportation is a federal agency charged with regulation and control of the shipment of all hazardous materials.

Posición parcialmente asentada  Posición abierta o media

Departamento de Transportes  El Departamento de

Constant tension hose clamp  A hose clamp, often referred to

as a “spring clamp,” so designed that it is under constant tension.

Grapa de manguera de tensión constante  Una grapa de

manguera, que suele referirse como “grapa de resorte,” diseñada en tal manera para estar bajo una tensión constante.

Contaminated  A term generally used when referring to a

refrigerant cylinder or a system that is known to contain foreign substances such as other incompatible or hazardous refrigerants.

Contaminado  Témino generalmente utilizado al referirse a un

cilindro para refrigerante o a un sistema que es reconocido contener sustan-cias extrañas, como por ejemplo otros refrigerantes incompatibles o peligrosos.

Contaminated refrigerant  Any refrigerant that is not at least

98 percent pure. Refrigerant may be considered to be contaminated if it contains excess air or another type of refrigerant.

Refrigerante contaminado  Cualquier refrigerante que no

es al menos el 98 por ciento puro. El refrigerante puede considerarse contaminado si contiene un exceso del aire o cualquier otro tipo de refrigerante.

Counterclockwise (ccw)  A direction, right to left, opposite to

that of a clock.

Sentido contrario al de las agujas del reloj  Dirección de la

derecha hacia la izquierda contraria a la correcta de las agujas del reloj.

asentada.

Transportes de los Estados Unidos de America es una

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agencia federal que tiene a su cargo la regulación y control del transporte de todos los materiales peligrosos. Dependability  Reliability; trustworthiness. Caracter responsible  Digno de confianza; integridad. Depressing pin  A pin located in the end of a service hose to

press (open) a Schrader-type valve.

Pasador depresor  Pasador ubicado en el extremo de una

manguera de servicio para forzar que se abra una válvula de tipo Schrader.

Diagnosis  The procedure followed to locate the cause of a

malfunction.

Diagnosis  Procedimiento que se sigue para localizar la causa

de una disfunción.

Disarm  To turn off; to disable a device or circuit. Desarmar  Apagar, incapacitar un dispositivo o un circuito. Disinfectant  A cleansing agent that destroys bacteria and

other microorganisms.

Desinfectante  Un agente de limpieza que destruye la bacteria

u otros microorganismos.

Dissipate  To reduce, weaken, or use up; to become thin or

weak.

Disipar  Reducir, debilitar o agotar; aclarar o ser débil. Drive pulley  The pulley that transmits the input force to other

pulleys or devices.

Polea motriz  La polea que transmite la fuerza de entra a las

otras poleas o dispositivos.

Dry nitrogen  The element nitrogen (N) that has been

processed to ensure that it is free of moisture.

Electronic charging meter  A term often used for “electronic

scale,” a device used to accurately dispense or monitor the amount of refrigerant being charged into an airconditioning system.

Medidor electrónico de carga  Un término que se suele usar

para una “escala electrónica,” un dispositivo que se usa para repartir y/o regular la cantidad del refrigerante que se usa para cargar un sistema de acondicionado de aire.

English fastener  Any type of fastener with English size

designations, numbers, decimals, or fractions of an inch.

Asegurador inglés  Cualquier tipo de asegurador provisto

de indicaciones, números, decimales, o fraciones de una pulgada del sistema inglés.

Environmental Protection Agency (EPA)  An agency of the

U.S. government that is charged with the responsibility of protecting the environment and enforcing the Clean Air Act (CAA) of 1990.

Agencia para la Protección del Medio Ambiente (EPA) Agencia

del gobierno estadounidense que tiene a su cargo la responsabilidad de proteger el medio ambiente y ejecutar la Ley para Aire Limpio (CAA por sus siglas en inglés) de 1990.

EPA  Environmental Protection Agency. EPA  Agencia para la Protección del Medio Ambiente. Etch  An intentional or unintentional erosion of a metal

surface generally caused by an acid.

Atacar con ácido  Desgaste previsto o imprevisto de una

superficie metálico, ocasionado generalmente por un ácido.

Etching  See Etch. Ataque con acido  Ver Etch [Atacar con ácido].

Nitrógeno seco  El elemento nitrógeno (N) que ha sido

Evacuate  To create a vacuum within a system to remove all

Dual Two

Evacuar  El dejar un vacío dentro de un sistema para remover

procesado para asegurar que esté libre de humedad.

Doble Dos. Dual system  Two systems; usually refers to two evaporators

in an air-conditioning system, one in the front and one in the rear of the vehicle, driven off a single compressor and condenser system.

Sistema doble  Dos sistemas; se refiere normalmente a dos

evaporadores en un sistema de acondicionamiento de aire; uno en la parte delantera y el otro en la parte trasera del vehículo; los dos son accionados por un solo sistema compresor condensador.

Duct  A tube or passage used to provide a means to transfer

air or liquid from one point or place to another.

Conducto  Tubo o pasaje utilizado para proveer un medio para

trans-ferir aire o líquido desde un punto o lugar a otro.

EATC  Electronic automatic temperature control. EATC  Regulador automático y electrónico de temperatura. ECC  Electronic climate control. ECC  Regulador electrónico de clima.

traces of air and moisture.

comple-tamente todo aire y humedad.

Evacuation  See Evacuate. Evacuacion  Ver Evacuate [Evacuar]. Evaporator core  The tube and fin assembly located inside the

evaporator housing. The refrigerant fluid picks up heat in the evaporator core when it changes into a vapor.

Núcleo del evaporador  El conjunto de tubo y aletas ubicado

dentro del alojamiento del evaporador. El refrigerante acumula calor en el núcleo del evaporador cuando se convierte en vapor.

Expansion tank  An auxiliary tank that is usually connected

to the inlet tank or a radiator and that provides additional storage space for heated coolant. Often called a coolant recovery tank.

Tanque de expansión  Tanque auxiliar que normalmente se

conecta al tanque de entrada o a un radiador y que provee almacenaje adicional del enfriante calentado. Llamado con frecuencia tanque para la recuperación del enfriante.

External  On the outside.

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Externo  A exterior.

Fluorescent tracer dye  A dye solution introduced into the

el exterior de una pieza, como por ejemplo un árbol. Facilities  Something created and equipped to serve a particular function, such as a specialty garage used to service motor vehicles. Instalación  Ago creado y equipado para servir en una función particular, tal como un taller especializado que mantiene los vehículos motorizados. Fan relay  A relay for the cooling or auxiliary fan motors. Relé del ventilador  Relé para los motores de enfriamiento y/o los auxiliares. Federal Clean Air Act  See Clean Air Act. Ley Federal para Aire Limpio  Ver Clean Air Act [Ley para Aire Limpio]. Fill neck  The part of the radiator on which the pressure cap is attached. Most radiators, however, are filled via the recovery tank. Cuello de relleno  La parte del radiador a la que se fija la tapadera de presión. Sin embargo, la mayoría de radiadores se llena por medio del tanque de recuperación. Filter  A device used with the drier or as a separate unit to remove foreign material from the refrigerant. Filtro  Dispositivo utilizado con el secador o como unidad separada para extraer material extraño del refrigerante. Filter drier  A device that has a filter to remove foreign material from the refrigerant and a desiccant to remove moisture from the refrigerant. Secador del filtro  Dispositivo provisto de un filtro para remover el material extraño del refrigerante y un desecante para remover la humedad del refrigerante. Flammable refrigerant  Any refrigerant that contains a flammable material and is not approved for use. Any refrigerant, however, may be considered flammable under certain abnormal operating conditions. Refrigerante inflamable  Cualquier refrigerante que contiene una materia inflamable y que no es aprobado su uso. Cualquier refrigerante, no obstante, puede considerarse inflamable bajo ciertas condiciones de operación abnormales. Flange  A projecting rim, collar, or edge on an object used to keep the object in place or to secure it to another object. Brida  Cerco, collar, o extremo proyectante ubicado sobre un objeto uti-lizado para mantener un objeto en su lugar o para fijarlo a otro objeto. Flare  A flange or cone-shaped end applied to a piece of tubing to provide a means of fastening to a fitting.

air-conditioning system for leak-testing procedures. An ultraviolet (UV) lamp is used to detect the site of the leak. Colorante fluorescente trazadora  Una solución de tinta que se introduce en un sistema de aire acondicionado con el fin de comprobar los procedimientos contra fugas. Una lámpara ultravioleta (UV) se usa para detectar el sitio de la fuga. Forced air  Air that is moved mechanically such as by a fan or blower. Aire forzado  Aire que se mueve mecánicamente, como por ejemplo por un ventilador o soplador. Fringe benefits  The extra benefits apart from a salary that an employee may expect, such as vacation, sick leave, insurance, or employee discounts. Beneficios extras  Los beneficios extras además del sueldo que un empleado puede esperar recibir, incluyendo las vacaciones, tiempo libre para enfermedad, la aseguranza o los discuentos de empleados. Front seat  Closing of the line, leaving the compressor open to the service port fitting. This allows service to the compressor without purging the entire system. Never operate the system with the valves front seated. Asentar a la derecha  El cerrar la línea, dejando abierto el compresor al ajuste del orificio de servicio, lo cual permite prestar servicio al compresor sin purgar todo el sistema. Nunca haga funcionar el sistema con las válvulas asentadas a la derecha. Functional test  See Performance Test. Prueba funcional  Ver Performance Test [Prueba de rendimiento]. Fungi  Plural of “fungus,” an organism, such as mold, that grows in the damp atmosphere inside an evaporator plenum, often producing an undesirable odor. Hongos  Plural de “hongo” un organismo tal como el hongo, que crece en la atmósfera húmeda de un pleno evaporador, produciendo muchas veces un olor no agradable. Fusible link  A type of fuse made of a special wire that melts to open a circuit when current draw is excessive. Cartucho de fusible  Tipo de fusible fabricado de un alambre especial que se funde para abrir un circuito cuando ocurre una sobrecarga del circuito. Fuses  A replaceable circuit protection device that will melt if the current passing through it exceeds the rating number of the fuse creating an open in the circuit. Fusible  Un dispositivo de protección del circuito reemplazable que se funde si la corriente que pasa a través de él sobrepasa el número de clasificación, creando un circuito abierto en el circuito del fusible.

Abocinado  Brida o extremo en forma cónica aplicado a una

Gasket  A thin layer of material or composition that is placed

External snapring  A snapring found on the outside of a part

such as a shaft.

Anillo de muelle exterior  Anillo de muelle que se encuentra en

pieza de tubería para proveer un medio de asegurarse a un ajuste.

between two machined surfaces to provide a leakproof seal between them.

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Guarnición  Capa delgada de material o compuesto que se

coloca entre dos superficies maquinadas para proveer una junta hermética para evitar fugas entre ellas.

Gauge  A tool of a known calibration used to measure

components. For example, a feeler gauge is used to measure the air gap between a clutch rotor and armature.

Calibrador  Herramienta de una calibración conocida

utilizada para la medición de componentes. Por ejemplo, un calibrador de espesores se utiliza para medir el espacio de aire entre el rotor del embrague y la armadura.

Graduated container  A measure such as a beaker or measuring

cup that has a graduated scale for the measurement of a liquid.

Recipiente graduado  Una medida, como por ejemplo un

cubilete o una taza de medir, provista de una escala graduada para la medición de un líquido.

Gross weight  The weight of a substance or matter that

includes the weight of its container.

Peso bruto  Peso de una sustancia o materia que incluye el

peso de su recipiente.

Ground  A general term given to the negative (2) side of an

electrical system.

Tierra  Término general para indicar el lado negativo (2) de

un sistema eléctrico.

Grounded  An intentional or unintentional connection of a

wire, positive (1) or negative (2), to the ground. A short circuit is said to be grounded.

Puesto a tierra  Una conexión prevista o imprevista de un

alambre, positiva (1) o negativa (2), a la tierra. Se dice que un cortocircuito es puesto a tierra.

Hazard  A possible source of danger that may cause damage to

a structure or equipment or that may cause personal injury.

Peligro  Un causante posible de un peligro que puede dañar

una estructura o un equipo o puede causar daño personal.

HCFC  Hydrochlorofluorocarbon refrigerant. HCFC  Refrigerante de hidroclorofluorocarbono. HFC-134a  A hydrofluorocarbon refrigerant gas used as a

refrigerant. The refrigerant of choice to replace R-12 in automotive air-conditioning systems. Often referred to as R-134a, this refrigerant is not harmful to the ozone.

HFC-134a  Un refrigerante de gas hidrofluorocarbono que

se usa como refrigerante. Es el refrigerante preferido para remplazar el CFC-12 en los sistemas de aire acondicionador automotrices. Suele referirse como el R134-a, este refrigerante no es dañino al medio ambiente.

Header tanks  The top and bottom tanks (downflow) or side

tanks (crossflow) of a radiator. The tanks in which coolant is accumulated or received.

Tanques para alimentación por gravedad  Los tanques

superiores e inferiores (flujo descendente) o los tanques laterales (flujo transversal) de un radiador. Tanques en los cuales el enfriador se acumula o se recibe.

Heater  That part of the climate control comfort system

consisting of the heater core, hoses, coolant flow control valve, and related controls used to provide air to the vehicle interior. Calentador  Esa parte del sistema de confort de aclimatizaje que con-siste del núcleo de calefacción, las mangueras, la válvula de flujo del fluido refrigerante, y los controles parecidos que sirven para suminis-trar aire al interior de un vehículo. Heater core  A radiator-like heat exchanger located in the case/duct system through which coolant flows to provide heat to the vehicle interior. Núcleo del calentador  Intercambiador de calor parecido a un radiador y ubicado en el sistema de caja/conducto a través del cual fluye el enfriador para proveer calor al interior del vehículo. Heat exchanger  An apparatus in which heat is transferred from one medium to another on the principle that heat moves to an object with less heat. Intercambiador de calor  Aparato en el que se transfiere el calor de un medio a otro, lo cual se basa en el principio que el calor se atrae a un objeto que tiene menos calor. HI  The designation for high as in blower speed or system mode. HI  Indicación para indicar marcha rápida, como por ejemplo la veloci-dad de un soplador o el modo de un sistema. High-side gauge  The right-side gauge on the manifold used to read refrigerant pressure in the high side of the system. Calibrador del lado de alta presión  El calibrador del lado derecho del múltiple utilizado para medir la presión del refrigerante en el lado de alta presión del sistema. High-side hand valve  The high-side valve on the manifold set used to control flow between the high side and service ports. Válvula de mano del lado de alta presión  Válvula del lado de alta presión que se encuentra en el conjunto del múltiple, utilizada para regular el flujo entre el lado de alta presión y los orificios de servicio. High-side service valve  A device located on the discharge side of the compressor; this valve permits the service technician to check the high-side pressures and perform other necessary operations. Válvula de servicio del lado de alta presión  Dispositivo ubicado en el lado de descarga del compresor; dicha válvula permite que el mecánico verifique las presiones en lado de alta presión y lleve a cabo otras funciones necesarias. High-side switch  See Pressure switch. Autómata manométrico del lado de alta presión  Ver Pressure switch Autómata manométrico. High-torque clutch  A heavy-duty clutch assembly used on

some vehicles known to operate with higher-than-average head pressure.

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Embrague de alto par de torsión  Conjunto de embrague para

servicio pesado utilizado en algunos vehiculos que funcionan con una altura piezométrica más alta que la normal. Hot  A term given the positive (1) side of an energized electrical system. Also refers to an object that is heated. Cargado/caliente  Término utilizado para referirse al lado positivo (1) de un sistema eléctrico excitado. Se refiere tambien a un objeto que es calentado. Hot knife  A knife-like tool that has a heated blade. Used for separating objects, for example, evaporator cases. Cuchillo en caliente  Herramienta parecida a un cuchillo provista de una hoja calentada. Utilizada para separar objetos; p.e. las cajas de evaporadores. Housekeeping  A system of keeping the shop floors clean, lighting adequate, tools in good repair and operating order, and storing materials properly. Aseo  Un sistema de mantener limpios los pisos del taller, la alumbración adecuada, las herramientas reparadas y funcionando, y el almacenaje adecuada de los materiales. Hub  The central part of a wheel-like device such as a clutch armature. Cubo  Parte central de un dispositivo parecido a una rueda, como por ejemplo la armadura del embrague. Hygiene  A system of rules and principles intended to promote and preserve health. Higiene  Sistema de normas y principios cuyo propósito es promover y preservar la salud. Hygroscopic  Readily absorbing and retaining moisture. Higroscópico  Lo que absorbe y retiene facilmente la humedad. Idler  A pulley device that keeps the belt whip out of the drive belt of an automotive air conditioner. The idler is used as a means of tightening the belt. Polea loca  Polea que mantiene la vibración de la correa fuera de la cor-rea de transmisión de un acondicionador de aire automotriz. Se utiliza la polea loca para proveerle tensión a la correa. Idle speed  The speed (rpm) at which the engine runs while at rest (idle). Marcha mínima  Velocidad (rpm) a la que no hay ninguna carga en el motor (marcha mínima). Idler pulley  A pulley used to tension or torque the belt(s). Polea tensora  Polea utilizada para proveer tensión o par de torsión a la(s) correa(s). In-car temperature sensor  A thermistor used in automatic temperature control units for sensing the in-car temperature. Also see Thermistor. Sensor de temperatura del interior del vehículo Termistor utilizado en unidades de regulación automática de temperatura para sentir la temperatura del interior del vehículo. Ver también Thermistor [Termistor].

Indexing tab  A mark or protrusion on mating components to

ensure that they will be assembled in their proper position.

Fijación indicadora  Una marca o una parte sobresaliente de

los com-ponentes parejadas para asegurar que se asamblean en su posición correcta.

Insert fitting  A fitting that is designed to fit inside, such as a

barb fitting that fits inside a hose.

Ajuste inserto  Ajuste diseñado para insertarse dentro de un

objeto, como por ejemplo un ajuste arponado que se inserta dentro de una manguera.

Internal snapring  A snapring used to hold a component or

part inside a cavity or case.

Anillo de muelle interno  Anillo de muelle utilizado para sujetar

un componente o una pieza dentro de una cavidad o caja.

Jumper  A wire used to temporarily bypass a device or

component for the purpose of testing.

Barreta  Alambre utilizado para desviar un dispositivo o

componente de manera temporal para llevar a cabo una prueba.

Kilogram  A unit of measure in the metric system. One

kilogram is equal to 2.2010–2.615 pounds in the English system.

Kilogramo  Unidad de medida en el sistema métrico. Un

kilogramo equivale a 2205 libras en el sistema inglés.

KiloPascal  A unit of measure in the metric system. One

kiloPascal (kPa) is equal to 0.145 pound per square inch (psi) in the English system.

Kilopascal  Unidad de medida en el sistema métrico. Un

kilopascal (kPa) equivale a 0,145 libra por pulgada cuadrada en el sistema inglés.

kPa KiloPascal. kPa Kilopascal. Liquid  A state of matter; a column of fluid without solids or

gas pockets.

Líquido  Estado de materia; columna de fluido sin sólidos ni

bolsillos de gas.

Low-refrigerant switch  A switch that senses low pressure due

to a loss of refrigerant and stops compressor action. Some alert the operator and set a trouble code.

Interruptor para advertir un nivel bajo de refrigerante  Interruptor que siente una presión baja debido

a una perdida de refrigerante y que detiene la acción del compresor. Algunos interruptores advierten al operador y/o fijan un código indicador de fallas.

Low-side gauge  The left-side gauge on the manifold used to

read refrigerant pressure in the low side of the system.

Calibrador de lado de baja presión  El calibrador en el lado

izquierdo del múltiple utilizado para medir la presión del refrigerante del lado de baja presión del sistema.

Low-side hand valve  The manifold valve used to control flow

between the low side and service ports of the manifold.

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Válvula de mano del lado de baja presión  Válvula de

distribución utilizada para regular el flujo entre el lado de baja presión y los orificios de servicio del colector. Low-side service valve  A device located on the suction side of the compressor that allows the service technician to check low-side pressures and perform other necessary service operations. Válvula de servicio del lado de baja presión Dispositivo ubicado en el lado de succión del compresor; dicha válvula permite que el mecánico verifique las presiones del lado de baja presión y lleve a cabo otras funciones necesarias de servicio. Manifold  A device equipped with a hand shutoff valve. Gauges are connected to the manifold for use in system testing and servicing. Múltiple  Dispositivo provisto de una válvula de cierre accionada a mano. Calibradores se conectan al múltiple para ser utilizados para llevar a cabo pruebas del sistema y para servicio. Manifold and gauge set  A manifold complete with gauges and charging hoses. Conjunto del múltiple y calibrador  Múltiple provisto de calibradores y mangueras de carga. Manifold hand valve  Valves used to open and close passages through the manifold set. Válvula de distribución accionada a mano  Válvulas utilizadas para abrir y cerrar conductos a través del conjunto del múltiple. Manufacturer  A person or company whose business is to produce a product or components for a product. Fabricante  Persona o empresa cuyo propósito es fabricar un producto o componentes para un producto. Manufacturer’s procedures  Specific step-by-step instructions provided by the manufacturer for the assembly, disassembly, installation, replacement, or repair of a particular product manufactured by them. Procedimientos del fabricante  Instrucciones específicas a seguir paso por paso; dichas instrucciones son suministradas por el fabricante para montar, desmontar, instalar, remplazar, y/o reparar un producto específico fabricado por él. MAX  A mode, maximum, for heating or cooling. Selecting MAX generally overrides all other conditions that may have been programmed. MAX (Máximo)  Modo máximo para calentamiento o enfriamiento. El seleccionar MAX generalmente anula todas las otras condiciones que pueden haber sido programadas. Metric fastener  Any type fastener with metric size designations, numbers, or millimeters. Asegurador métrico  Cualquier asegurador provisto de

indicaciones, números, o milímetros.

Mid-positioned  The position of a stem-type service valve

where all fluid passages are interconnected. Also referred to as “cracked.”

Ubicación-central  Posición de una válvula de servicio de tipo

vástago donde todos los pasajes que conducen fluidos se interconectan. Lla-mado también “parcialmente asentada”.

Mildew  A form of fungus formed under damp conditions. Hongo  Un tipo de hongo que se desarrolla en las condiciones

húmedas.

Mold  A fungus that causes disintegration of organic matter. Hongo  Un hongo que causa la disintegración de la materia

orgánica.

Motor  An electrical device that produces a continuous

turning motion. A motor is used to propel a fan blade or a blower wheel.

Motor  Dispositivo eléctrico que produce un movimiento

giratorio continuo. Se utiliza un motor para impeler las aletas del ventilador o la rueda del soplador.

Mounting  See Flange. Brida de montaje  Ver Flange [Brida]. Mounting boss  See Flange. Protuberancia de montaje  Ver Flange [Brida]. MSDS  Material safety data sheet. MSDS  Hojas de información sobre la seguridad de un material. Mushroomed  A condition caused by pounding of a punch or

a chisel, producing a mushroom-shaped end that should be ground off to ensure maximum safety.

Hinchado  Condición ocasionada por el golpeo de un punzón

o cincel, lo cual hace que el extremo vuelva en forma de un hongo y que debe ser afilado para asegurar máxima seguridad.

Net weight  The weight of a product only; container and

packaging not included.

Peso neto  Peso de solo el producto mismo; no incluye el

recipiente y encajonamiento.

Neutral  On neither side; the position of gears when force is

not being transmitted.

Neutro  Que no está en ningún lado; posición de los

engranajes cuando no se transmite la potencia.

Noncycling clutch  An electromechanical compressor clutch

that does not cycle on and off as a means of temperature control; it is used to turn the system on when cooling is desired and off when cooling is not desired.

Embrague sin funcionamiento cíclico Embrague

electromecánico del compresor que no se enciende y se apaga como medio de regular la temperatura; se utiliza para arrancar el sistema cuando se desea enfriamiento y para detener el sistema cuando no se desea enfriamiento.

Observe  To see and note; to perceive; to notice. Observar  Ver y anotar; percibir; fijarse en algo.

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OEM  Original equipment manufacturer. OEM  Fabricante original del equipo. Off-road  A term often used for an “off-the-road” vehicle. Fuera de carretera  Un término que se usa para referirse a un

vehículo “fuera de la carretera.” Off-the-road  Generally refers to vehicles that are not licensed for road use, such as harvesters, bulldozers, and so on. Fuera de carretera  Generalmente se refiere a vehículos que no son permitidos operar en la carretera, como por ejemplo cosechadoras, rasadoras, etcétera. Ohmmeter  An electrical instrument used to measure the resistance in ohms of a circuit or component. Ohmiometro  Instrumento eléctrico utilizado para medir la resistencia en ohmios de un circuito o componente. Open  Not closed. An open switch, for example, breaks an electrical circuit. Abierto  No cerrado. Un interruptor abierto corta un circuito eléctrico, por ejemplo. Open circuit  A term used to indicate that current flow is stopped. By opening the circuit, the path for electron flow is broken. Circuito abierto  Un término usado para indicar que el flujo de corriente se detiene. Abriendo el circuito, la ruta para el flujo del electrón está rota. Orifice  A small hole. A calibrated opening in a tube or pipe to regulate the flow of a fluid or liquid. Orificio  Agujero pequeño. Apertura calibrada en un tubo o cañeria para regular el flujo de un fluido o de un líquido. O-ring  A synthetic rubber or plastic gasket with a round- or square-shaped cross-section. Junta tórica  Guarnición sintética de caucho o de plástico provista de una sección transversal en forma redonda o cuadrada. OSHA  Occupational Safety and Health Administration. OSHA  Direccion para la Seguridad y Salud Industrial. Outside temperature sensor  See Ambient sensor. Sensor de la temperatura ambiente  Ver Ambient sensor [Sensor ambiente]. Overcharge  Indicates that too much refrigerant or refrigeration oil is added to the system. Sobrecarga  Indica que una cantidad excesiva de refrigerante o aceite de refrigeración ha sido agregada al sistema. Overload  Anything in excess of the design criteria. An overload will generally cause the protective device such as a fuse or pressure relief to open. Sobrecarga  Cualquier cosa en exceso del criterio de diseño. General-mente una sobrecarga causará que se abra el dispositivo de protección, como por ejemplo un fusible o alivio de presión. Ozone friendly  Any product that does not pose a hazard or danger to the ozone.

Sustancia no dañina al ozono  Cualquier producto que no es

peligroso o amenaza al ozono.

Park  Generally refers to a component or mechanism that is at

rest.

Reposo  Generalmente se refiere a un componente o

mecanismo que no está funcionando.

PCM  Power control module. PCM  Módulo regulador del transmisor de potencia. Performance test  Readings of the temperature and pressure

under controlled conditions to determine if an airconditioning system is operating at full efficiency.

Prueba de rendimiento  Lecturas de la temperatura y presión

bajo condiciones controladas para determinar si un sistema de acondicionamiento de aire funciona a un rendimiento completo.

Piercing pin  The part of a saddle valve that is used to pierce a

hole in the tubing.

Pasador perforador  Parte de la válvula de silleta utilizada para

perforar un agujero en la tubería.

Pin type  A single or multiple electrical connector that is

round or pin shaped and fits inside a matching connector.

Conectador de tipo pasador  Conectador eléctrico único o

múltiple en forma redonda o en forma de pasador que se inserta dentro de un conectador emparajado.

Poly belt  See Serpentine belt. Correa poli  Ver Serpentine belt [Correa serpentina]. Polyol ester (ESTER)  A synthetic oil-like lubricant that is

occasionally recommended for use in an R-134a system. This lubricant is compatible with both R-134a and R-12.

Poliolester  Lubrificante sintético parecido a aceite que se

recomienda de vez en cuando para usar en un sistema HFC134a. Dicho lubrificante es compatible tanto con HFC-134a como CFC-12.

Positive pressure  Any pressure above atmospheric. Presión positiva  Cualquier presión sobre la de la atmosférica. Pound  A weight measure, 16 oz. A term often used when

referring to a small can of refrigerant, although the can does not necessarily contain 15 oz.

Libra  Medida de peso, 16 onzas. Término utilizado con

frecuencia al referirse a una lata pequeña de refrigerante, aunque es posible que la lata contenga menos de 16 onzas.

Pound cans  This is a generic term used when referring to

small disposable cans of refrigerant that contain less than 16 oz. of refrigerant.

Latas de una libra  Éste es un término general que se usa para

referirse a las latas pequeñas desechables que contienen menos de 16 onzas del refrigerante.

“Pound” of refrigerant  A term used by some technicians when

referring to a small can of refrigerant that actually contains less than 16 oz.

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Libra de refrigerante  Término utilizado por algunos

mecánicos al referirse a una lata pequeña de refrigerante que en realidad contiene menos de 16 onzas.

Power module  Controls the operation of the blower motor in

an automatic temperature control system.

Transmisor de potencia  Regula el funcionamiento del motor

del soplador en un sistema de control automático de temperatura.

Prueba de pureza  Prueba estática que puede llevarse a cabo

para com-parar la presión del refrigerante con un gráfico de temperatura apro-priado para determinar la pureza del mismo.

Radiation  The transfer of heat without heating the medium

through which it is transmitted.

Radiación  La transferencia de calor sin calentar el medio por

el cual se transmite.

Predetermined  A set of fixed values or parameters that have

Ram air  Air that is forced through the radiator and condenser

Predeterminado  Valores fijos o parámetros que han sido

Aire  Admitido en sentido de la marcha. Aire forzado a través

Pressure  The application of a continuous force by one body

Rebuilt  To build after having been disassembled, inspected,

been programmed or otherwise fixed into an operating system.

programados o de otra manera fijados en un sistema de funcionamiento.

onto another body. Force per unit area or force divided by area usually expressed in pounds per square inch (psi) or kilopascal (kPa).

Presión  La aplicación de una fuerza contínua de un cuerpo

contra otro cuerpo. La fuerza por unidad de un área o la fuerza dividida por el área suele expresarse en libras por pulgada cuadrada (psi) o kilopascal (kPa).

Pressure gauge  A calibrated instrument for measuring

pressure.

Manometro  Instrumento calibrado para medir la presión. Pressure switch  An electrical switch that is activated by a

predetermined low or high pressure. A high-pressure switch is generally used for system protection; a low-pressure switch may be used for temperature control or system protection.

Autómata manométrico  Interruptor eléctrico accionado por

una baja o alta presíon predeterminada. Generalmente se utiliza un autómata manométrico de alta presión para la protección del sistema; puede utilizarse uno de baja presión para la regulación de temperatura o protección del sistema.

Propane  A flammable gas used as a propellant for the halide

leak detector.

Propano  Gas inflamable utilizado como propulsor para el

detector de fugas de halogenuro.

Psig  Pounds per square inch gauge. Psig  Calibrador de libras por pulgada cuadrada.

coils by the movement of the vehicle or the action of the fan.

de las bobinas del radiador y del condensador por medio del movimiento del vehículo o la acción del ventilador.

and worn and after damaged parts and components are replaced.

Reconstruído  Fabricar después de haber sido desmontado y

revisado, y luego remplazar las piezas desgastadas y averiadas.

Receiver-drier  A tank-like vessel having a desiccant and used

for the storage of refrigerant.

Receptor-secador  Recipiente parecido a un tanque

provisto de un desecante y utilizado para el almacenaje de refrigerante.

RECIR  An abbreviation for the recirculate mode, as with air. RECIR  Abreviatura del modo recirculatorio, como por

ejemplo con aire.

Recovery system  A term often used to refer to the circuit

inside the recovery unit used to recycle or transfer refrigerant from the air-conditioning system to the recovery cylinder.

Sistema de recuperación  Término utilizado con frecuencia

para referirse al circuito dentro de la unidad de recuperación interior utilizado para reciclar y/o transferir el refrigerante del sistema de acondi-cionamiento de aire al cilindro de recuperación.

Recovery tank  An auxiliary tank, usually connected to the

inlet tank of a radiator, which provides additional storage space for heated coolant.

Tanque de recuperación  Tanque auxiliar que normalmente se

conecta al tanque de entrada de un radiador, lo cual provee almacenaje adi-cional para el enfriante calentado.

Purge  To remove moisture and air from a system or a

Refrigerant  A chemical compound, such as R-134a, used

Purgar  Remover humedad y/o aire de un sistema o un

Refrigerante  Un compuesto químico, tal como el R-134a, que

component by flushing with a dry gas such as nitrogen (N) to remove all refrigerant from the system. componente al descargarlo con un gas seco, como por ejemplo el nitrogeno (N), para remover todo el refrigerante del sistema.

Purity test  A static test that may be performed to compare

the suspect refrigerant pressure with an appropriate temperature chart to determine its purity.

in an air-conditioning system to achieve the desired refrigerating effect.

se usa en un sistema de aire acondicionado para realizar un efecto refrigerante deseado.

Refrigerant-12  The refrigerant used in automotive air

conditioners, as well as other air-conditioning and refrigeration systems. The chemical name of Refrigerant-12 is dichlorodifluoromethane. The chemical symbol is CC12 F2 . 569

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Refrigerante 12  Refrigerante utilizado tanto en

acondicionadores de aire automotrices como en otros sistemas de acondicionamiento de aire y refrigeración. Ele nombre químico del Refrigerante-12 es diclorodifluorometano, y el símbolo químico es CC12 F2 .

Relay  An electrical switch device that is activated by a low-

current source and controls a high-current device.

Relé  Interruptor eléctrico que es accionado por una fuente de

corriente baja y regula un dispositivo de corriente alta.

Reserve tank  A storage vessel for excess fluid. See Recovery

tank, Receiver-drier, and Accumulator.

Tanque de reserva  Recipiente de almacenaje para un exceso

de fluido. Ver Recovery tank [Tanque de recuperación], Receiverdrier [Receptor-secador], y Accumulator [Acumulador].

Resistance  Opposition to current flow. Resistencia  Oposición al flujo de corriente. Resistor  A voltage-dropping device that is usually wire wound

and that provides a means of controlling fan speeds.

Resistor  Dispositivo de caída de tensión que normalmente

es devanado con alambre y provee un medio de regular la velocidad del ventilador.

Respirator  A mask or face shield worn in a hazardous

environment to provide clean fresh air and oxygen.

Mascarilla  Máscara o protector de cara que se lleva puesto en

un ambi-ente peligroso para proveer aire limpio y puro y/o oxígeno.

Responsibility  Being reliable and trustworthy. Responsabilidad  Ser confiable y fidedigno. Restricted  Having limitations. Keeping within limits,

confines, or boundaries.

Restringido  Que tiene limitaciones. Mantenerse dentro de

límites, confines, o fronteras.

Restrictor  An insert fitting or device used to control the flow of

refrigerant or refrigeration oil.

Limitador  Pieza inserta o dispositivo utilizado para regular el

flujo de refrigerante o aceite de refrigeración.

Rotor  The rotating or freewheeling portion of a clutch; the

belt slides on the rotor.

Rotor  Parte giratoria o con marcha a rueda libre de un

embrague; la correa se desliza sobre el rotor.

RPM  Revolutions per minute; also rpm or r/min. RPM  Revoluciones por minuto; tambien rpm o r/min. Running design change  A design change made during a

current model/year production.

Cambio al diseño corriente  Un cambio al diseño hecho

durante la fabricación del modelo/año actual.

RV  Recreational vehicle. RV  Vehículo para el recreo.

Saddle valve  A two-part accessory valve that may be clamped

around the metal part of a system hose to provide access to the air-conditioning system for service. Válvula de silleta  Válvula accesoria de dos partes que puede fijarse con una abrazadera a la parte metálica de una manguera del sistema para proveer acceso al sistema de acondicionamiento de aire para llevar a cabo servicio. SAE  Society of Automotive Engineers. SAE  Sociedad de Ingenieros Automotrices.

Safety  Freedom from danger or injury; the state of being safe. Seguridad  Libre de peligro o daño, calidad o estado de seguro. Scan tool  A portable computer that may be connected to the

vehicle’s diagnostic connector to read data from the vehicle’s onboard computer.

Dispositivo explorador  Una computadora portátil que se

puede conectar al conector diagnóstico del vehículo para leer los datos de la computadora abordo del vehículo.

Schrader valve  A spring-loaded valve similar to a tire valve. The

Schrader valve is located inside the service valve fitting and is used on some control devices to hold refrigerant in the system. Special adapters must be used with the gauge hose to allow access to the system.

Válvula Schrader  Válvula con cierre automático parecida al

vástago del neumático. La válvula Schrader está ubicada dentro del ajuste de la válvula de servicio y se utiliza en algunos dispositivos de regulación para guardar refrigerante dentro del sistema. Deben utilizarse adaptadores especiales con una manguera calibrador para permitir acceso al sistema.

Seal  Generally refers to a compressor shaft oil seal; matching

shaft-mounted seal face and front head-mounted seal seat to prevent refrigerant and oil from escaping. May also refer to any gasket or O-ring used between two mating surfaces for the same purpose.

Junta hermética  Generalmente se refiere a la junta hermética

del árbol del compresor; la frente de junta hermética montada en el árbol y el asiento de junta hermética montado en el cabezal delantero empare-jados para evitar la fuga de refrigerante y/o de aceite. Puede referirse también a cualquier guarnición o junta tórica utilizada entre dos superficies emparejadas para el mismo propósito.

Seal seat  The part of a compressor shaft seal assembly that is

stationary and matches the rotating part, known as the seal face or shaft seal.

Asiento de la junta hermética  Parte del conjunto de la junta

hermética del árbol del compresor que es inmóvil y que se empareja a la parte rotativa; conocido como la frente de junta hermética o la junta hermética del árbol.

Serpentine belt  A flat or V-groove belt that winds through all

of the engine accessories to drive them off the crankshaft pulley.

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Correa serpentina  Correa plana o con ranuras en V que

atraviesa todos los accesorios del motor para forzarlos fuera de la polea del cigüeñal.

Service port  A fitting found on the service valves and some

control devices; the manifold set hoses are connected to this fitting.

Orificio de servicio  Ajuste ubicado en las válvulas de servicio

y en algunos dispositivos de regulación; las mangueras del conjunto del colector se conectan a este ajuste.

Service procedure  A suggested routine for the step-by-step

act of troubleshooting, diagnosing, and repairs.

Procedimiento de servicio  Rutina sugerida para la acción a seguir

paso a paso para detectar fallas, diagnosticar, y/o reparar.

Service valve  See High-side (Low-side) service valve. Válvula de servicio  Ver High-side (Low-side) service valve

[Válvula de servicio del lado de alta presión (baja presión)].

Servomotor  An electrical motor that is used to control a

mechanical device, such as a heater coolant flow control valve.

Motor servo  Un motor eléctrico que se usa para controlar un

disposi-tivo mecánico, tal como una válvula de control de flujo del fluido refrigerante del calentador.

Shaft  A long cylindrical-shaped rod that rotates to transmit

power, such as a compressor crankshaft.

Eje  Una biela cilíndrica larga que gira para transferir la

potencia, tal como un cigüeñal del compresor.

Shaft key  A soft metal key that secures a member on a shaft

to prevent it from slipping.

Chaveta del árbol  Chaveta de metal blando que fija una pieza

a un árbol para evitar su deslizamiento.

Shaft seal  See Compressor shaft seal. Junta hermética del árbol  Ver Compressor shaft seal [Junta

hermética del árbol del compresor].

Short  Of brief duration, for example, short cycling. Also

refers to an intentional or unintentional grounding of an electrical circuit.

Breve/corto  De una duración breve; p.e., funcionamiento

cíclico breve. Se refiere también a un puesto a tierra previsto o imprevisto de un circuito eléctrico.

Shutoff valve  A valve that provides positive shutoff of a fluid

or vapor passage.

Válvula de cierre  Válvula que provee el cierre positivo del

pasaje de un fluido o un vapor.

Sliding resistor  A resistor having the provision of varying its

resistance depending on the position of a sliding member. Aso may be referred to as a “rheostat” or “pot.”

Resistor deslizante  Un resistor que tiene la provisión de

variar su resistencia según la posición de una parte deslizante. Tambien puede referirse como un reóstato o un potenciómetro/reductor.

SNAP  An acronym for “Significant New Alternatives Policy.” SNAP  Una sigla del término “Póliza de Alternativas Nuevas

Significantes.”

Snapring  A metal ring used to secure and retain a component

to another component.

Anillo de muelle  Anillo metálico utilizado para fijar y sujetar

un com-ponente a otro.

Snapshot  A feature of OBD II that shows, on various

scanners, the conditions that the vehicle was operating under when a particular trouble code was set. For example, the vehicle was at 1258F , ambient temperature was 558F, throttle position was part throttle at 1.45 volts, rpm was 1450, brake was off, transmission was in third gear with torque converter unlocked, air-conditioning system was off, and so on.

Instantáneo  Una característica del OBD II que muestra, en

varios detectores, las condiciones bajo las cuales operaba el vehículo cuando se registró un código de fallo. Por ejemplo, el vehículo regis-traba 1258F , la temperatura del ambiente era el 558F, la posición del regulador estaba en una posición parcial de 1.45 voltios, el rpm era 1450, el freno estaba desenganchada, la transmisión estaba en la ter-cera velocidad con el convertidor del par desenclavado, el sistema de acondicionador de aire estaba apagado, y etcétera.

Society of Automotive Engineers  A professional organization

of the automotive industry. Founded in 1905 as the Society of Automobile Engineers, the SAE is dedicated to providing technical information and standards to the automotive industry.

Sociedad de Ingenieros automotrices  Organización profesional

de la industria automotriz. Establecido en 1905 como la Sociedad de Ingenieros de Automoviles (SAE por sus siglas en ingles), dicha sociedad se dedica a proveerle información técnica y normas a la indústria automotriz.

Socket  The concave part of a joint that receives a concave

member. A term generally used for “socket wrench,” referring to a female 6-, 8-, or 12-point wrench so designed to fit over a nut or bolt head.

Casquillo  La parte cóncava de una junta que recibe una parte

cóncava. El término “socket” generalmente se usa para indicar una “llave de tubo” y se refiere a la parte hembra de una llave de tamaño de 6, 8, o 12 puntos diseñada para quedar en una tuerca o una cabeza de un perno.

Solenoid  See Solenoid valve. Solenoide  Ver Solenoid valve [Válvula de solenoide]. Solenoid valve  An electromagnetic valve controlled remotely

by electrically energizing and de-energizing a coil.

Válvula de solenoide  Válvula electromagnética regulada a

distancia por una bobina electronicamente.

Solid state  Referring to electronics consisting of semiconductor

devices and other related nonmechanical components.

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Estado sólido  Se refiere a componentes electrónicos

que consisten en dispositivos semiconductores y otros componentes relacionados no mecánicos.

Spade-type connector  A single or multiple electrical

connector that has flat spade-like mating provisions.

Conectador de tipo azadón  Conectador único o múltiple

provisto de dispositivos planos de tipo azadón para emparejarse.

Specifications  Design characteristics of a component or

assembly noted by the manufacturer. Specifications for a vehicle include fluid capacities, weights, and other pertinent maintenance information.

Especificaciones  Características de diseño de un componente

o con-junto indicadas por el fabricante. Las especificaciones para un vehículo incluyen capacidades del fluido, peso y otra información pertinente para el mantenimiento del vehículo.

Spike  In our application, an electrical spike. An unwanted

momentary high-energy electrical surge.

Impulso afilado  En nuestro campo, un impulso afilado

eléctrico. Una elevación repentina eléctrica de alta energia no deseada.

Spring lock  Part of a spring lock fitting. A special fitting used

to form a leakproof joint.

Obturador de resorte  Parte de una fijación de obturador de

resorte. Una fijación especial que sirve para formar una junta a prueba de fugas.

Spring lock fitting  A special fitting using a spring to lock the

mating parts together, forming a leakproof joint.

Ajuste de cierre automático  Ajuste especial utilizando un

resorte para cerrar piezas emparejadas para formar así una junta hermética contra fugas.

Squirrel-cage blower  A blower wheel designed to provide a

large volume of air with a minimum of noise. The blower is more compact than the fan and air can be directed more efficiently.

Soplador con jaula de ardilla  Rueda de soplador diseñada para

proveer un gran caudal de aire con un mínimo de ruido. El soplador es más compacto que el ventilador y el aire puede dirigirse con un mayor rendimiento.

Stabilize  To make steady. Estabilizar  Quedarse detenida una cosa. Standing vacuum test  A leak test performed on an air-

conditioning system by pulling a vacuum and then determining, by observation, if the vacuum holds for a predetermined period of time to ensure that there are no leaks.

Prueba de vacío fijo  Una prueba de fugas que se efectúa en

el sistema de aire acondicionado por medio de establecer un vacío y luego determinar, por observación, si se mantiene el vacío por un periodo prescrito de tiempo para asegurar que no hay fugas.

Stratify  Arrange or form into layers. To fully blend.

Estratificar  Arreglar o formar en capas. Mezclar

completamente. Subsystem  A system within a system. Subsistema  Sistema dentro de un sistema. Sun load  Heat intensity or light intensity produced by the sun. Carga del sol  Intensidad calorífica y/o de la luz generada por el sol. Sun-load sensor  A device that senses heat or light intensity that is placed on the dashboard to determine the amount of sun entering the vehicle. Sensor de carga de sol  Un dispositivo que detecta la intensidad del calor o de luz que hay en la tabla de instrumentos para determinar la cantidad de luz del sol entrando al vehículo. Superheat switch  An electrical switch activated by an abnormal temperature-pressure condition (a superheated vapor); used for system protection. Interruptor de vapor sobrecalentado  Interruptor eléctrico accionado por una condición anormal de presión y temperatura (vapor sobrecalentado); utilizado para la protección del sistema. System  All of the components and lines that make up an airconditioning system. Sistema  Todos los componentes y líneas que componen un sistema de acondicionamiento de aire. Tank  See Header tanks and Expansion tank. Tanque  Ver Header tanks [Tanques para alimentación por gravedad] y Expansion tank [Tanque de expansión]. Tare weight  The weight of the packaging material. See Net weight and Gross weight. Taraje  Peso del material de encajonamiento. Ver Net weight [Peso neto] y Gross weight [Peso bruto]. Technical service bulletin (TSB)  Periodic information provided by the vehicle manufacturer regarding any problems and offering solutions to problems encountered in their vehicles. Boletín de servicio técnico (TSB)  La información periódica proveído por el fabricante del vehículo concernante cualquier problema que se encuentra en sus vehículos y proporcionando las soluciones. Technician  One concerned and involved in the design, service, or repair in a specific area, such as an automotive service technician or, more specifically, automotive airconditioning service technician. Técnico  Uno que se concierna y se involucra en el diseño, el servicio, o la reparación en un área específico, o más específicamente, un técnico de servicio de aire acondicionado automotivo. Temperature door  A door within the case/duct stem to direct air through the heater and evaporator core. Puerta de temperatura  Puerta ubicada dentro del vástago de caja/conducto para conducir el aire a través del nucleo del calentador y/o del evaporador.

572 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Temperature switch  A switch actuated by a change in

temperature at a predetermined point. Interruptor de temperatura  Interruptor accionado por un cambio de temperatura a un punto predeterminado. Tensioner  A device used to impart tension, such as an automatic belt tensioner. Tensionador  Un dispositivo que se usa para mantener la tensión, tal como un tensionador de correa automático. Tension gauge  A tool for measuring the tension of a belt. Manómetro para tensión  Herramienta para medir la tensión de una correa. Thermistor  A temperature-sensing resistor that has the ability to change values with changing temperature. Termistor  Resistor sensible a temperatura que tiene la capacidad de cambiar valores al ocurrir un cambio de temperatura. Torque  A turning force, for example, the force required to seal a connection; measured in (English) foot-pounds (ft.-lb.) or inch-pounds (in.-lb.); (metric) Newton-meters (N·m). Par de torsión  Fuerza de torcimiento; por ejemplo, la fuerza requerida para sellar una conexión; medido en libras-pies (ft.-lb.) (inglesas) o en libras pulgadas (in.-lb.); metrosNewton (N·m [metricos]). Triple evacuation  A process of evacuation that involves three pump downs and two system purges with an inert gas such as dry nitrogen (N). Evacuación triple  Proceso de evacuación que involucra tres envíos con bomba y dos purgas del sistema con un gas inerte, como por ejemplo el nitrógeno seco (N). Troubleshoot  The act of diagnosing the cause of various system malfunctions. Detección de fallas  Procedimiento o arte de diagnosticar la causa de varias fallas del sistema. TXV  Thermostatic expansion valve. TXV  Válvula de expansión termostática. Ultraviolet (UV)  The part of the electromagnetic spectrum emitted by the sun that lies between visible violet light and X-rays. Ultravioleta  Parte del espectro electromagnético generado por el sol que se encuentra entre la luz violeta visible y los rayos X. Ultraviolet dye  A fluid that may be injected into the air-conditioning system for leak-testing purposes. An ultraviolet (UV) lamp is used to locate the leak. Tinta ultravioleta  Un fluido que se puede inyectar en un sistema de aire acondicionado para comprobar contra las fugas. Una lámpara ultravioleta se usa para localizar la fuga. Vacuum gauge  A gauge used to measure below atmospheric pressure. Vacuómetro  Calibrador utilizado para medir a una presión inferior a la de la atmósfera.

Vacuum motor  A device designed to provide mechanical

control by the use of a vacuum. Motor de vacío  Dispositivo diseñado para proveer regulación mecánica mediante un vacío. Vacuum pump  A mechanical device used to evacuate the refrigeration system to rid it of excess moisture and air. Bomba de vacío  Dispositivo mecánico utilizado para evacuar el sistema de refrigeración para purgarlo de un exceso de humedad y aire. Vacuum signal  The presence of a vacuum. Señal de vacío  Presencia de un vacío. V-belt  A rubber-like continuous loop placed between the engine crankshaft pulley and accessories to transfer rotary motion of the crankshaft to the accessories. Correa en V  Bucle continuo parecido a caucho ubicado entre la polea del cigüeñal del motor y los accesorios para transferir el movimiento giratorio de aquel a estos. Ventilation  The act of supplying fresh air to an enclosed space such as the inside of an automobile. Ventilación  Proceso de suministrar el aire fresco a un espacio cerrado, como por ejemplo al interior de un automóvil. V-groove belt  See V-belt. Correa con ranuras en V  Ver V-belt [Correa en V]. VIN  An acronym for “vehicle identification number.” VIN  Una sigla para “numero de identificación del vehículo.” Voltage  It is the electrical pressure that causes electrons to move through the circuit. Voltaje  Es la presión eléctrica que causa los electrones para moverse a través del circuito. Voltage drop  A resistance in the circuit that reduces the electrical pressure available after the resistance. The designed resistance in the circuit is the load component, such as a blower motor, and would drop or use all the available voltage. Unwanted voltage drops in a circuit could be unwanted resistance in circuit conductors, connections. Caída del Voltaje  Una resistencia en el circuito que reduce la presión eléctrica disponible después de la resistencia. La resistencia diseñada en el circuito es el componente de carga, tales como un abanico eléctrico, y podría bajar o utilizar todo el voltaje disponible. La caída de voltaje no deseada en un circuito podría ser una resistencia no deseada en conductores del circuito, conexiones. Voltmeter  A device used to measure volt(s). Voltímetro  Dispositivo utilizado para la medición de voltios. Wiring harness  A group of wires wrapped in a shroud for the distribution of power from one point to another point. Cableado preformado  Grupo de alambres envuelto por una gualdera para distribuir potencia de un punto a otro.

573 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

INDEX A Abrasion in belt, 116 Access valves, 518–520 Accumulator, 202–203, 244 Acme connections, 160 A/C switch, testing, 90–91 Actuator, 398, 470 electronic mode door, 415–416 Adapter, 523 Adhesives, 5–7 Aftermarket, 404 Air bags, disarming, 463. See also Supplemental inflatable restraint (SIR) Air-conditioning control head, 302 Air-conditioning special tool suppliers, 556 Air-conditioning system clutch test, 336–339 defective components, 299–302 electrically-driven, 371–376 evacuating, 249–252 failures, causes of, 302, 343–345 functional testing, 302 inspecting, 293–295 performance testing, 168–171, 238–241, 311–312 (See also Charging of system) pressure switch test, 204–205, 310, 455–456 replacing, 196 system charge test, 254–260, 309–310 (See also Charging of system) Air ducts, 293 Air filter, 414 Ambient air, 316 Ambient temperature, 101, 315, 536 Ambient temperature sensor, 466 Ammeter function, 78–79 Amperage flow, 78, 79 Antifreeze, 8–9, 129–130 draining and refilling, 131–132 extended-life, 130 flushing system of, 130, 353, 526–528 loss of, 136 low-tox, 130 preventive maintenance, 129–130 recovery and recycle system, 57, 130 Asbestos, 5 ASE practice examination, 549–554

Aspirator, 467–468, 469 ATC (automatic temperature control) system. See also EATC (electronic automatic temperature control) systems actuators, 398, 470 ambient temperature sensor, 466 aspirator, 467–468, 469 blower control, 408, 459–460 clutch control, 460 clutch diode, 338, 339 control panel, 491 evaporator thermistor, 481 heater flow control valve, 470, 471–472 programmer, 459 sensors, 461–470 testers (scan tool), 59–60, 459–457 Auto-ranging meter, 75

B Barb fitting, 190 Barrier hoses, 161 Battery charge, 84 Battery, disconnecting/reconnecting, 183 Battery ground cable, 4 BCM (blower control module), 459 cadillac trouble codes, retrieval of, 491–492 EATC system controlled by, 485–486 entering diagnostics, 489 trouble codes, 486–487 Beadlock hose assembly, 193–194 Belt failure troubleshooting, 114–119 abrasion in, 116 EPDM wear, 116 improper installation of, 116–119 pilling, 116–119 Belts, 110–119, 136, 340, 536 serpentine, 110–112 V-belt, 110 Belt tension, 110–114 Belt tension gauge, 110, 295 Benefits, fringe, 47 Bimetallic cycling design, 81 Blower control, 408, 459–460 Blower motor, 400, 401 Blower motor circuit typical domestic schematic, 76 typical import schematic, 75 575

Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Blower motor circuit, troubleshooting, 84–86 A/C switch, 90–91 blower motor, 87–89 blower motor speed resistor, 89 blower motor switch, 89–90 fuses and blower motor relay, 86–87 Boiling point of water, 528 Box-sockets, 27 Breakout box, 457 Bright Solutions, Inc., 556 Bulk refrigerant, 263 Bypass hose, 123

C Cabin air filter, 414 Can tap, 48, 50–51 Can tap valve, 261–262 Cap tube, 449 Carbon monoxide (CO), 5 Carbon seal face, 371 Carrier corporation, 556 Case and duct systems, 397 blower motor replacement, 400, 401 cabin air filter, 414 check valve test, 410, 411 component replacement, 398–400 delayed blower control, 408 electronic mode door actuator, 415–416 evaporator core replacement, 403 evaporator replacement, 404–407 heater core replacement, 402 mode selector switch, 412–413 odor problems, 407–408 power module replacement, 400 temperature door cable adjustment, 412 troubleshooting, 416–417 typical problems, 416–417 vacuum system test, 408–409 Caustics, 5–7 CCOT (Cycling Clutch Orifice Tube), 198, 306–307 CFC-12 charging meters, 263 connecting manifold and gauge set, 164–165 definition of, 158 fittings, 528 gauge set, 157 identifying, 55–56 90 percent rule, 537

pressure-temperature chart, 266–267 recovery equipment for, 55–56 service hose, 161 system with hand valves, 166–168 system with Schrader-type valves, 166 Charge, 246 Charging meters, 263 Charging of system, 254–256. See also Overcharging from bulk source, 263–265 recovery/recycling equipment, 259–260 system charge test, 309–310 typical procedure for, 257–258 Charging of system HFC-134a system, 533–536 Charging station, 531, 532 Check valve, 410, 411 Chisels, 33 Chrysler A590 compressor, 354 actuator replacement, 398–399 C171 compressor, 354 DRB-III, 489–491 EATC troubleshooting, 480–481 SATC troubleshooting, 473–475 Circuit breaker, 79, 81, 82 Circuit breakers, 446–448 Circuit protection device, 79–83 Clamping diode, 335 Clamps, 123–126, 128–129 Clardy Manufacturing Corporation, 556 Classic Tool Design, Inc., 556 Clean Air Act (CAA), 187, 523 Clutch circuit, testing, 314 control of, 460 cycling, 184 diode, 338, 339 electromagnetic, 450–455 fan, 120 Nippondenso, 357–358 noncycling, 184 testing, 336–339 Clutch coil bench test, 339 problems and remedies, 452 Cold, 7 Component Assemblies, Inc., 556 Component servicing accumulator, 202–203

576 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

compressor, 185 condenser, 203 cycling clutch system, 184 diagnostic techniques, 184 English and metric fasteners, 181–182 equipment for, 185 FOT (fixed orifice tube), 198–202 hoses and fittings, 188 noncycling clutch system, 184 preparation for, 186 pressure switch, 204–205, 455–456 receiver-drier, 203–204, 244 refrigerants, 523–526 safety considerations for, 182–183 service procedures, 186 tools for, 185 TXV replacement, 196–197 Compound gauge, 157, 530 Compressor, 185 Chrysler A590 compressor, 354 Chrysler C171 compressor, 354 clutch amperage draw and resistance test, 340 cycling time, 312 defective, 299–300 Diesel Kiki, 60 drive belt, 112, 340 electrically-driven air-conditioning, 371–376 electronic inverter, removal and service, 372–376 identification of, 340–345 inline filter, 353 leak testing, 243 Nippondenso, 354 oil level, 367–368 Panasonic (Matsushita), 361–364 Panasonic vane-type, 361 removing and replacing, 347–349 Sanden (Sankyo), 364–366 servicing, 364 (See also Specific manufacturers) shaft oil seal, 364–367 types of, 336 York, 166 Compressor clutch, 335 Compressor tools, 60 Condenser a defective, 300 leak testing, 245 servicing, 203 Connections, 521–523

Constant tension hose clamp, 125 Contaminated refrigerant, 236–237 Contamination detection, 241–243 Control panel, 491 Control system, 445–446. See also ATC (automatic temperature control) system blower motor, 400 coolant temperature warning switches, 456 electromagnetic clutch, 450–455 fuses and circuit breakers, 446–448 pressure switch, 204–205, 310, 455–456 schematic of, 445 testing, 170–171 vacuum control, 456–457 vacuum switches, 409–410, 456–457 Control valve, 127–128 Coolant heat storage tank, 135 Coolant pump, 105–106 Coolant pump-mounted fan, 120 Coolant temperature sensors, 461, 465–466. See also Specific sensors Coolant temperature warning switches, 456 Cooling system. See also Antifreeze draining and refilling, 131 fans, 119–123 flushing, 130–134 heater system, 126–129 hoses and clamps, 123–126 leak testing with pressure tester, 101–103 pressure caps, 106–107 pulleys, 110 pump, 105–106 radiators, 103–105 recovery tank, 126 thermostats, 108–109 treatment, 130 troubleshooting, 135–136 Corrosion Consultants, Inc., 556 Coupler fittings, 163 CPS Products, Inc., 556 Cycling Clutch Orifice Tube (CCOT), 198, 306–307 Cycling switch, 455 Cycling time, 312

D Debris, 398 Delayed blower control, 408 Delta T chart, 536

577 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Depressing pin, 522 Diagnosis. See also Electrical diagnosis and testing; Trouble codes air conditioning, 184, 293 aspirator, 469 compressor noise, 340–343 defective components, overview of, 299–302 failures, causes of, 302, 343–345 Ford FOT system, 314–317 functional testing, 302 high-and low-side pressures, 295 orifice tube system, 307 refrigerant CCOT, 306–307 refrigerant FOT, 305–306 SATC, 472–475 of system controls, 445–446 temperature gauge/sending unit, 456 thermostatic expansion valve, 303 variable displacement compressor, 312–313 Diesel Kiki compressor, 60 Digital multimeter (DMM), 74–75 Diode, 335–339 Disarm, 186 Discharge line, 302 Dissipate, 103 Drive plate, 299 Drive pulley, 110 Dry nitrogen, 253 Ducts, air, 293, 397–398 Dye, adding to system, 246–247

E EATC (electronic automatic temperature control) systems BCM-controlled systems, 485–486 definition of, 472 diagnosing, 475–486 separate microprocessor-controlled systems, 477–484 ECC (electronic climate control) functional test, 484 EG-based antifreeze, 8–9 Electrical diagnosis and testing, 74 Electrically-driven air-conditioning compressor, 371–376 Electrical system schematic, 445–446 Electrical troubleshooting. See also troubleshooting ammeter function, 78–79 digital multimeter, 74–75 electrical diagnosis, 74 ohmmeter function, 77–78 open circuit, 73

voltage drop, 73, 74, 77 voltmeter function, 75–77 Electric cooling system service, hybrid, 134–135 Electrochemical activity, 105 Electromagnetic clutch, 450–455 Electronic inverter compressor, removal and service, 372–376 Electronic mode door actuator, 415–416 Electronic scale, 58–59, 263 Employee-employer relationship, 46 Employee obligations, 47 Engine overcooling/overheating, 135–136 English fasteners, 181 Environmental Protection Agency (EPA), 372 Envirotech Systems, Inc., 556 Etching, 371 Ethylene glycol (EG), 8 Ethylene propylene diene M-class rubber (EPDM), 115 belt wear, 116 Evacuate, 250 Evacuation of system, 250, 528–533 triple evacuation method, 250 typical procedure for, 257–258 Evaporator, 221 defective, 299 Delta T chart, 536 drain tube, 171 inlet and outlet tubes, checking, 309, 317 removing and replacing, 404–407 temperature, checking, 169–170 Evaporator core, 299, 403 Evaporator temperature sensor, 461–462 Evaporator thermistor, 481 Eye protection, 23, 50–52, 182

F Facilities, 46 Failures, causes of, 302, 343–345 Fall, bracing against backward, 22 Fan clutch, 120 Fan relay, 121 Fans coolant pump-mounted, 120 electric, 120–123 flexible, 120 testing and troubleshooting, 119–123 Fasteners, 181–182

578 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Federal Clean Air Act, 187, 523 FFOT (Ford Fixed Orifice Tube), 314–317 Fibrous materials (asbestos), 5 Fill neck, 101 Filter, air, 414 Fin sensor, 461 Fire prevention, 20–22 Fittings, 163, 188, 190–192, 528 Fixed orifice tube (FOT), 198. See also Orifice tube, FOT Fixed orifice tube/cycling clutch (FOTCC), 198 Fixed-type thermostat, 449–450 FJC, Inc., 556 Flammable flushing agents, 526 Flange, 344 Flare fitting, 189 Flexible fan, 120 Floro Tech, Inc., 556 Fluorescent leak detector, 52–54 Flushing of system, 130, 353, 526–528 Flux, 9 Ford actuator replacement, 398–399 EATC troubleshooting, 481–483 FX6 compressor, 354 FX15 compressor, 354 Ford Fixed Orifice Tube (FFOT) compressor performance, poor, 317 diagnosis, system, 314–317 FOT (fixed orifice tube), 198. See also Orifice tube, FOT FOTCC (fixed orifice tube/cycling clutch), 198 Four Seasons, 556 Frearson screwdriver, 33 Fresh air inlet, 398 Fringe benefits, 47 Fumes, 9 Functional test, 302 Fuses, 85–87, 446–448 Fusible link, 79, 446

G Gasket, 197 Gas (halide) leak detector, 245 Gas, noncondensable, 265–267 Gauge calibration, 159 Gauge system, 456 General Motors actuator replacement, 399–400 CCOT diagnosis, 306–307

EATC troubleshooting, 484–485 ETTC troubleshooting, 484–485 Glues, 5–7 Gross weight, 264 Ground, 85

H Halide (gas) leak detector, 245 Halogen (electronic) leak detector, 53, 247–248 Hammers, 27, 30, 52 Hand tools, 26–35, 52. See also specific tools Harrison compressors, 204 Hazards, 4 H-block thermostatic expansion valve, 303 Head pressure performance charts, 170 Health and safety program, 16–19 Heat, 7 Heater core, 126–127, 402 Heater flow control valve, 470, 471–472 Heater system, 126–129 Heat exchanger, 126 Heating system performance trouble tree, 417 Heavy acceleration, problem during, 184 HFC-134a charging system, 533–536 connecting manifold and gauge set, 163–164 definition of, 158 gauge set, 157 identifying, 55–56, 515–516 90 percent rule, 537 pressure-temperature chart, 266–267 recovery equipment for, 56 retrofitting to use, 515 service hose, 161 system adaptation for, 521–522 High-side adapter, 166 gauge, 159, 532 hand valve, 165, 262 hose adapters, 523 service hose, 162 switch, 348 High-side system, inspection for even temperature, 169–170 High-voltage service plug, 13 Hose, 161–163. See also Barrier hose inspection of, 123, 128–129 leak testing, 245 servicing, 188–190

579 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Hose, heater, 123 Hose, radiator, 123, 536 Hose, service, 161–163 connections to manifold, 56, 160–161, 521–522 high-side adapters, 523 shut-off valves, 162 Hose, vacuum, 184, 410 Hot, 446 Hot knife, 403 Housekeeping, 13 fire prevention, 20–22 hand tool use, 27–28 walking and working surfaces, 22 Hub, 357–358 H-valve TXV, 197 Hybrid electric cooling system service, 134–135 Hybrid electric vehicle (HEV) system, 10–13 high-voltage service plug, 13 insulated glove integrity test, 11–13 Hydrocarbon (HC), 55 Hygiene, personal, 46

I Identifying, 515–516 Idler pulley, 110 Idle speed, 306 In-car temperature sensor, 467 Indexing tab, tensioner, 114 Information resources, 60–61 Infrared temperature sensor, 464–465 Inlet, fresh air, 398 Inline filter, 353 Insert fitting, 190 Insufficient cooling, 306–307 Insulated glove integrity test, 11–13 Interdynamics, Inc., 556 Internal snapring, 362

J Jumper, 535

K K. D. Binnie Engineering Pty. Ltd., 556 KD Tools, 556 Kent Moore Division, 556 Kilogram, 263 KiloPascals, 64 KiloPascals absolute, 64 KPa, 64, 65, 159, 169

L Lamp, warning, 456 Leak detector, 52–54, 245, 247–248 Leak testing, 243–245 accumulator, 243 compressor, 244 halide (gas) for, 245 halogen (electronic) detector, 53, 247–248 with pressure tester, 101, 103 solution for, 245–246 tracer dye, 246–247 typical procedure for, 249, 250, 257–258 Lincor Distributors, 556 Liquid crystal display, 74 Liquid line, 302 Liquid line filter, 353 Logo, 345 Low-side gauge, 157–159 hand valve, 165, 262 service hose, 166 Low-side system, inspection for even temperature, 169–170 Lubricant, 345–347

M Machine guarding, 20 MACS (Mobile Air Conditioning Society), 61 MAC Tools, 556 Manifold, 49, 160–164 Manifold and gauge set, 48–50, 157–159. See also Hose, service; Manifold hand valves charging system with, 263–265 connecting, 163–168 gauge calibration, 159 HFC-134a system, 164 high-side gauge, 159, 532 low-side gauge, 49, 157–159 performance testing and, 168–171 R-12 system with hand valves, 166–168 R-12 system with Schrader-type valves, 166 Manifold hand valves, 262, 524 Mastercool, Inc., 556 Material Safety Data Sheet (MSDS), 8, 130 Matsushita compressor, 361 Metering devices, 245 Metric conversions, 555 Metric fasteners, 181–182 Metric system, 63–65 Micron, 530

580 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Mode selector switch, 412–413 Moisture, 187, 528 Mounting boss (flange), 344 Mounting bosses, 344

N Neutronics, Inc., 556 Nippondenso compressors, 354 (Chrysler) Models A590 and C171, 354 (Ford) Models FX6 and FX15, 354 oil, checking/adding, 354 removing and replacing, 355–356 seal replacement, 354 servicing, 354, 357–360 Nissan ATC diagnostics, 477–480 Nitrogen for evacuation, 250 for flushing, 187 leak detector, 52–54 No cooling, 136 Noncondensable gas, 265–267

O Occupational Safety and Health Administration (OSHA), 5, 15–16 Odor problems, 407–408 Off-road vehicle, 346 Ohmmeter, 446 Ohmmeter function, 77–78 Ohm’s law, 74 Oil, 192 changing, 528 disposal of, 403 mixing types of, 167 overcharging of, 361 Open, 446 Opportunities, 46 Orifice tube, CCOT, 198 clutch test, 308 General Motors diagnosis, 307–308 Orifice tube, FOT defective, 300–301 diagnosing, 307–308 Ford system, diagnosis of, 314–317 removing and replacing accessible, 198–200 nonaccessible, 201–202 O-ring, 188, 364, 519 O-ring servicing, 195

OTC Division, 556 Overcharging, 255, 348, 373, 537 Overcooling, 135 Overheating, 136 Overload, 79, 446 Owens Research, Inc./Tubes ’N Hoses, 556 Oxygen-deficient atmosphere, 7 Ozone friendly, 533

P Paints, 5–7 Panasonic (Matsushita), Compressor, 361 clutch assembly, servicing, 361–362 oil checking/adjusting, 354 reassembly, 363 shaft seal, servicing, 362–363 Panasonic vane-type, compressor, 361 Parts, stocking, 186 Performance testing, 168–171, 238–241, 311–312 Personal safety, 4–13 P & F Technologies Ltd., 556 PG-based antifreeze, 9 Phillips screwdriver, 32 Piercing pin, 519 Pilling, 116–119 Pin type connector, 347 Plastic blade fuses, 80 Pliers, 27, 31–32, 52. See also Snapring pliers Polyalkaline glycol (PAG), 243, 526 Polyol ester (POE), 526 Pound cans, 51, 254, 261–263 “Pound” of refrigerant, 254 Power module, 400 Power tool safety, 20–22 Powertrain control module (PCM), 453 Pressure caps, 103, 106–107 cycling switch, 455 gauge, 49, 157 low-and high-side, 157–159 switch, 204–205, 310 switch test, 455–456 transducer, 468–470 Pressure controls, leak testing, 245 Pressure-temperature chart, 266–267 Programmer, 459 Propylene glycol (PG), 8, 130 Psig, 158, 169 Pullers, 33–35 581

Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Pulley bearing, 358–359 Pulley, idler/clutch, 110 Punches, 33, 52 Purge, 187 Purity test, 515–518

Q Quick test clutch, 306 sun load sensor, 462–464

R Radiation, 7 Radiator, 103–105 Radiator pressure caps, 106–107 Ram air, 103 Ratchets, safety considerations, 25 Receiver-drier, 203–204, 244 Recovery equipment, 56, 259–260 Reco-very system, 56–57, 187–188 antifreeze, 57, 130 charging, 254–260 equipment use, 259 recovering, 191–192 recover only method, 520–521 refrigerant removal process, 523–526 removing air from refrigerant, 250 Recovery tank, 126 Recycling antifreeze, 57, 130 refrigerant, 56–57 Reed and Prince screwdriver, 32 Refrigerant, 7–8. See also “Pound” of refrigerant adding for leak testing, 246 can tap, 50–51 can tap valve, 261 disposal of, 56 identifier, 55–56, 236, 515, 516 leak testing, 243–245 lines, 302 90 percent rule, 537 purity test for, 515–518 recovery and recycle system, 56–57 safe handling of, 254 testing for noncondensable gas, 265–267 Refrigerant containers. See also Refrigerant cylinders pound cans, 51, 254, 261–263 Refrigerant cylinders, 254, 520

Relative humidity, performance charts, 170 Relay, 121 Removing and replacing accumulator, 202–203 compressor, 347–349 condenser, 203 evaporator, 404–407 fixed orifice tube (FOT), 198–202 mode selector switch, 412–413 receiver-drier, 203–204 schrader valve core in a service valve, 529–530 thermostatic expansion valve (TXV), 196–197 Repair order, 63–64 Reserve tanks, 410 Resistors, 400, 459 Respirators, 5 Restrictor, 410 Retrofit conversion fittings, 528 label, 527 procedure, 521–523 refrigerants, 515 Retrofitting systems using, 515 Ritchie Engineering Company Inc., 556 Robinair Division, 556 Rotor, 369–371 Rpm, 524 RTI Technologies, Inc., 556 Running design change, 341

S S. A. Day Manufacturing Company, Inc., 556 Saddle valve, 518 Safety. See also Health and safety program; Safety hazards fall, bracing against backward, 22 fire prevention, 20–22 housekeeping, 20–22 personal, 4–9 power tool rules, 20–22 refrigerant, handling of, 254 service procedures, 182–183 shop, 13–19 tool tips for, 23 unsafe tools, 24 walking and working surfaces, 22 Safety hazards asbestos, 5 carbon monoxide, 5

582 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

fumes from welding, burning, soldering, 9 heat and cold, 7 oxygen-deficient atmosphere, 7 radiation, 7 refrigerants, 7–8 solvents, caustics, paints, glues, adhesives, 5–7 Sanden (Sankyo) compressor, 364 SATC, 472–475 Scale, electronic, 58–59 Scan tool, 459–457 Schematics control system, 445–446 typical domestic system, 76 typical import system, 75 Schrader valve, 166, 520 removing and replacing core, 529–530 Screwdrivers, 25–26, 32–33, 52 Seal evaporator, 299 seat, 363, 365 Sealant contamination detection, 241–243 Semi-automatic temperature control (SATC) system, 472–475 Sensors, 461–470 scan tool, testing with, 59–60, 459–457 Serpentine belt, 110–112 Service hose, 162–163, 167 Service manuals, 61–63 Service procedures, 182 Service tools, 48–52 Service valves, leak testing, 244 Service valve wrench, 167 Servicing. See also Compressor; System servicing and testing components, 181–205 procedures, 61–63 procedures, 182–183, 186 Shop rules and regulations, 45–47 Servomotors, 472 Shaft key, 354, 355, 370 Shaft oil seal, 364 Shaft seal, 340, 354, 355–356, 367 Shop safety, 13–19 health and safety program, 16–19 technician training for, 19 Shorts, 446 Shroud, 104 Shut-off valves, 246, 522, 524 Sludge control, Panasonic compressor, 361

Snap-On Tools Corporation, 556 Snapring, 357, 454 Snapring pliers, 204, 354, 358, 361, 362 Soap solution, 245–246 Society of Automotive Engineers (SAE), 190, 521 Socket wrenches, 28–31, 52 Solenoids, 459 Solvents, 5–7 Spade type connector, 347 Special purpose tools, 31, 52–54 Specifications, 62 Spikes, 460 Spring lock fitting, 194, 195 Standing vacuum test, 250 Stratify, 253 Suction line, 302 Sun load sensor, 462–464 Superheat, 204–205, 534 Superheat switch, 346 Superior Manufacturing Company, 556 Supervision, 46 Supplemental inflatable restraint (SIR), 399 System charge test, 309–310 System servicing and testing, 235 blockage, checking for, 261 dye or trace solution, adding, 246–247

T TDC (top dead center), 366 Technical Chemicals Company, 556 Technical service bulletin, 408 Technicians, 4 Technician training, shop safety, 19 Temperature door (cable control), 412 Temperature gauge/sending unit, 456 Tensioner, belt, 110, 114 Tension gauge, 295 Thermal protector, Panasonic compressor, 361 Thermolab, Inc., 556 Thermometer, 52 electronic, 53, 57–58, 534, 535 infrared, 133, 300 laser-sighted, digital readout, infrared, 300 Thermostat, 108–110, 448–449 fixed-type, 449–450 removal of, 108–109 testing, 109–110, 170 variable-type, 448

583 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Thermostatic expansion valve (TXV) defective, 302 diagnosing, 303–304 servicing H-valve TXV, 197 servicing standard TXV, 196–197 TIF Instruments, Inc, 556 Tools. See also specific tools compressor, 60 hand, 26–35, 52 quality standards for, 24 safe use of, 23–35 service, 48–52 special purpose, 31, 52–55 Tool suppliers, 556 Torque, 194 Toyota Hybrid, 135 Toyota Hybrid DTC P1151, 135 Tracer dye leak testing, 246–247 Tracer products division, 556 Triple evacuation method, 250 Trouble codes, 486–487 Cadillac trouble codes, retrieval of, 491–492 Ford EATC system, 483 Troubleshooting. See also Blower motor circuit troubleshooting; Diagnosis; troubleshooting belt failure, 114–119 case and duct systems, 416–417 drive and accessory belts, 113 EATC, 480–483 fans, 119–123 heater and cooling system, 135–136 low flow, 243 SATC, 473–475 vacuum system, 408–409

U Ultraviolet lamp, use of, 246–247 Ultraviolet (UV) light, 7 Undercharging, 254, 348 Uniweld Products, 556

Utility hose, 163 Uview Ultraviolet, 556

V Vacuum check valves, 410, 411 gauge, 531 hose, 184, 410 loss of, 184 measured, 530–531 pump, 52, 54–55, 185, 531 signal, 412 switches, 409–410, 456–457 system, testing, 408–409 test, standing, 250 Variable displacement orifice tube (VDOT), 198 Variable resistor test, 459–460 Variable-type thermostat, 448 Varian Vacuum Technologies, 556 V-belt, 110 VDOT (Variable displacement orifice tube), 198 Vehicle Identification Number (VIN), 61 Ventilation, 5, 9, 524 V-groove, 110, 364 Viper/T-Tech Division, 556 Voltage drop, 73, 74, 77 Voltmeter, 446 Voltmeter function, 75–77

W Wages and benefits, 46–47 Walking surfaces, 22 Wetting, 9 Working surfaces, 22 Wrenches, 23, 26–31, 185

Y Yokagawa Corporation of America, 556 York compressors, 167

584 Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.