Always Learning

1. Always Learning

2. CHAPTER 16 A/C System Repair

3. OBJECTIVES After studying Chapter 16, the reader will be able to: • R&R an A/C compressor. • Perform the standard bench repairs on a compressor and clutch, given the proper service manual and special tools. • R&R an A/C hose and make any necessary repairs to that hose. • R&R any A/C component, given the proper service manual. • Complete the A/C system repairs listed in the ASE Task List, Section B.

4. Barb fitting Beadlock ferrule Beadlock fitting Bubble-style crimp Compressor bench checks Compressor leak checks Ferrule Finger-style crimp Gut pack Lip-type seal Seal protector Spring-lock coupler Two-part seal KEY TERMS

5. INTRODUCTION • Much of A/C system repair consists of removing and replacing faulty components. • Most repair operations recover the refrigerant, make the actual repair, and then evacuate and recharge the system. • In a survey of its members, MACS determined that the most frequent A/C repairs involve the compressor (more than 20%), hoses, control devices, the evaporator, electrical circuits, the TXV or OT, the receiver–drier or accumulator, and the condenser (3%).

6. INTRODUCTION • COMPRESSOR DIAGNOSIS

7. TECH TIP • Many compressors use a nut to secure the clutch hub so a wrench can be easily used to rotate the compressor shaft. Many other compressors do not; a special compressor turner tool that threads into the clutch hub is available. This tool provides a method to rotate the shaft.

8. COMPRESSOR REPAIR • COMPRESSOR R&R • BALANCING THE OIL CHARGE • CLUTCH AND CLUTCH COIL R&R • DAMPER DRIVE SERVICE • COMPRESSOR SHAFT SEAL R&R • COMPRESSOR REPAIR • COMPRESSOR BENCH CHECKS • COMPRESSOR OIL LEVEL CHECKS

9. TECH TIP • If the failed compressor sent debris into the discharge line, the line and the condenser should be replaced or flushed to remove the debris or a filter should be installed to keep it from traveling downstream. Many technicians install one or two inline filters to ensure the system operates properly or to protect the new compressor. • When a compressor fails internally, it will often send metal particles into the suction line. The compressor must be replaced with a new or rebuilt unit, but the debris can enter the new compressor and cause early failure. A suction filter screen has been developed to trap the debris in the suction line.

10. TECH TIP • Replacing a failed compressor is expensive, and sometimes this can exceed the value of the vehicle or what the customer can afford. If the failure causes a misalignment or seizure of the pulley, the drive belt will fail and the engine will not run very long without it. A compressor bypass pulley is available for some vehicles that serves as an idler pulley and allows proper drive belt operation.

11. TECH TIP • Some late-model clutch assemblies have undergone changes to improve clutch holding power. Early and late versions of these units should not be combined because this can cause rubbing between the parts or clutch slippage. If one of these parts has to be replaced, all three portions should be replaced as a unit. Another point to remember on three-part assemblies is that the clearance, or air gap, between the hub and rotor pulley must be adjusted during replacement and that magnetic action pulls the coil into the rotor pulley as the clutch operates. These parts must be properly positioned as they are assembled. • If a slipping clutch is found, check to determine if the clutch surfaces were wet or dry. Wet surfaces indicate that a seal leak caused the problem. Dry surfaces indicate that excessive clearance, weak clutch coil magnetism, or excessive high-side pressure caused the problem.

12. TECH TIP • Some manufacturers recommend measuring clutch gap using a dial indicator. Set up the dial indicator with the measuring stylus against the clutch plate. Turn on the A/C to energize the clutch, or, using jumper wires, connect the coil to a battery; the amount of clutch plate travel (air gap) will be shown on the dial indicator.

13. TECH TIP • Parts should be lubricated with mineral oil as they are assembled. It is less hygroscopic and safer for you to use, and the small amount that is used will not affect an R-134a system. Mineral oil is currently available in aerosol containers, making its use easier and faster.

14. HOSE AND FITTING REPAIR • FITTING REPAIR • LINE REPLACEMENT • HOSE REPAIR AND MAKEUP

15. TECH TIP • An iron fitting nut tends to seize onto the aluminum, male fitting of some components. If this occurs, heat the fitting nut using a hot air gun, and carefully work the nut back and forth until it is free. To prevent this problem from occurring, some technicians put never-seize compound or mineral refrigerant oil on these threads when assembling a component. • Some technicians use a machinist No. 3 center drill bit to make a hole through the fitting’s nut. The smaller, straight portion of the bit is the right length to pass through the nut; stop drilling as you feel the drill break through the nut. Next spray penetrating oil into the hole using the spray straw, and rotate the nut to work the fitting loose.

16. TECH TIP • Several vehicle manufacturers use a quick-connect fitting that uses a plastic coupling/cage that locks over the fitting to hold it together. Depending on this coupling, a special tool or screwdriver is required to unlock the cage and separate the fitting. To assemble a quick-connect fitting, slide the two refrigerant lines together, place the plastic cage over the fitting, and close the cage.

17. TECH TIP • Special clamps are available from aftermarket sources to help cure spring-lock coupling leakage. These clamps secure the two coupling parts to eliminate the relative motion that causes the leak.

18. TECH TIP • In the past, a screw or worm gear clamp was commonly used, but these clamps are no longer recommended because they will not pass the coupling integrity performance requirements. Some screw clamps are fitted with a locator extension that places the clamp directly over the barbs.

19. TECH TIP • Another method of fixing metal line damage such as a rub-through is a splice kit that uses a sealing sleeve and ferrule. The damaged line portion can be removed, and the two ends can be joined using the splice and properly sized sealing sleeves and ferrules.

20. A/C SYSTEM COMPONENT REPLACEMENT • If faulty, a major A/C component (the accumulator, condenser, evaporator, OT, receiver–drier, or TXV) is repaired by removing and replacing it with a new one. • Except for an OT, which requires a puller and some TXVs, the R&R operations are very similar.

21. TECH TIP • An experienced technician will often inspect failed components such as evaporators to determine if a leak was caused by an inside-out or outside-in failure. Inside-out failure is caused by acids inside of the system; the accumulator or receiver–drier must be replaced and the refrigerant recycled to remove the acids. • When the compressor, evaporator, or TXV is replaced, the receiver–drier or accumulator should also be replaced. These failures were possibly caused by system contamination. This contamination will probably have loaded the desiccant capacity with moisture.

22. TECH TIP • An outside-in failure can be caused by moisture and acids generated by decaying leaves in the bottom of the evaporator case. If this type of debris is found while replacing an evaporator, it is recommended that a screen be added to the fresh-air intake to reduce chances of future problems. • It is good practice to keep the plastic caps in place on the new components until just before installation to keep as much moisture out of the system as possible. Remember, too, that removal of an accumulator, condenser, evaporator, or receiver–drier also removes a certain amount of oil from the system, and new oil should be added to the new part. The actual amount is usually specified in the service.

23. SUMMARY • Most A/C system repairs involve recovering the refrigerant, removing and replacing the faulty component, recycling the refrigerant, recharging the system, and verifying a successful repair. • Most new components must have the proper amount of the proper type of oil added to them. • A faulty compressor is normally replaced with a new or rebuilt unit. • Many compressor failures cause debris to enter the highside and sometimes the low-side hoses. • Compressor debris must be cleaned out of the high and low sides, or filters/screens can be installed to trap this material.

24. SUMMARY • All or part of a clutch assembly can be replaced, and the clutch air gap should be adjusted. • Faulty compressor shaft seals can be removed and replaced. • New O-rings should be lubricated with mineral oil, and line fittings should be tightened to the specified torque, when replacing refrigerant lines. • Care should be taken when making up a replacement hose assembly to ensure proper crimping of the ferrule. • Most A/C system components can be removed and replaced.

25. REVIEW QUESTIONS • When installing a new or rebuilt compressor, it is a good practice to read the ______________ ______________ to determine the ______________ and ______________ of oil to put into the replacement compressor. • Always check the ______________ ______________ whenever a clutch is installed, and ______________ it to the proper clearance if necessary. • When a clutch slips, it will ______________ in a short period of time and probably ______________ the bearing. • A lip-type compressor shaft seal must have a shaft surface that is ______________ and not ______________ . • As you install a shaft seal cartridge, you should ______________ ______________ that the driving flats of the seal engage the ______________ on the ______________ . • It is a good practice to test a used replacement compressor to determine there are no ______________ or ______________ leaks and the shaft ______________ smoothly with no excessive ______________ .

26. REVIEW QUESTIONS • A replacement O-ring must have the correct ______________ and ______________ and be made from the proper ______________ of ______________ . • When an A/C fitting is replaced, it must be tightened to the correct ______________ of ______________ . • Leaks at a spring-lock coupling can often be stopped by using a(n) ______________ ______________ . • A replacement fitting for an R-134a hose should be of the ______________ style and crimped using a(n) ______________ style of crimp. • When a new component such as an accumulator or evaporator is replaced, the proper amount of ______________ should be ______________ to that component. • When replacing an older-style TXV, be sure to ______________ the thermal bulb to the evaporator tailpipe and wrap it ______________ tape.

27. CHAPTER QUIZ 1. Normal compressor repairs include replacement of the ______________ . • shaft seal • clutch coil • reed valves • All of these

28. CHAPTER QUIZ 2. Technician A says that when the compressor is replaced, the oil levels should be checked. Technician B says that the oil from the old compressor can be reused. Who is correct? • A only • B only • Both A and B • Neither A nor B

29. CHAPTER QUIZ 3. Technician A says that as the clutch drive hub is replaced, the air gap should be checked at three different places. Technician B says that the air gap is not important as long as the clutch ohms are correct. Who is correct? • A only • B only • Both A and B • Neither A nor B

30. CHAPTER QUIZ 4. Technician A says that it is important to position snap rings correctly when replacing clutch parts on a compressor. Technician B says that the whole clutch assembly should be replaced if the pulley bearing fails. Who is correct? • A only • B only • Both A and B • Neither A nor B

31. CHAPTER QUIZ 5. The clutch must be removed and replaced to ______________ . • get access to the compressor shaft seal • remove and replace the compressor • Both A and B • Neither A nor B

32. CHAPTER QUIZ 6. Technician A says that shaft seal parts should be well lubricated as they are installed. Technician B says that special tools are often required when removing or replacing seal parts. Who is correct? • A only • B only • Both A and B • Neither A nor B

33. CHAPTER QUIZ 7. Oil level in an A/C compressor can be checked at any time. • True • False

34. CHAPTER QUIZ 8. When a compressor is replaced, it is a good practice to also replace the ______________ . • TXV • OT • Both A and B • receiver–drier or accumulator

35. CHAPTER QUIZ 9. Technician A says that you must install the compressor and charge the system to check for seal leaks. Technician B says that if you apply pressure to a compressor discharge port, pressure will show up immediately at the suction port. Who is correct? • A only • B only • Both A and B • Neither A nor B

36. CHAPTER QUIZ 10. Technician A says that most leaks at line fittings can be stopped by tightening the fitting nut a little tighter. Technician B says that line fitting O-rings should be properly positioned and lubricated with a drop of refrigerant oil as they are installed. Who is correct? • A only • B only • Both A and B • Neither A nor B

37. CHAPTER QUIZ 11. A new hose can be made up in the shop by installing the correct ends onto the right size, type, and length of hose. • True • False

38. CHAPTER QUIZ 12. Technician A says that new refrigerant oil should be added to new components such as accumulators or condensers as they are installed. Technician B says that two wrenches should be used when tightening most line fittings. Who is correct? • A only • B only • Both A and B • Neither A nor B