1. FIGURE 12-1 Possible A/C problems include refrigerant leaks and flow restrictions, compressor and drive belt failure, and control system malfunction. (Courtesy of Toyota Motor Sales USA, Inc.)

2. FIGURE 12-2 Many technicians begin system checks by feeling the temperature of the lines with the system operating (a); an infrared thermometer makes this check faster and more accurate (b and c). Some of the lines should be hot, and some should be cold. (a courtesy of Saturn Corporation)

3. FIGURE 12-3 Service units range from simple, self-contained units (a) to J2788-approved machines with programmable controls (b). (Courtesy of Robinair, SPX Corporation)

4. FIGURE 12-4 R-12 service ports use male flare fittings with two different sizes sealed by a Schrader valve. The low-side fitting is larger (a).R-134a service ports use quick-disconnect-type fittings, and the high-side fitting is larger (b).

5. FIGURE 12-5 A dual A/C service unit that can be used on both R-12 and R-134a systems. Note that it is essentially two side-by-side units. (Courtesy of White Industries)

6. FIGURE 12-6 Different types of refrigerants should not be mixed
FIGURE 12-6 Different types of refrigerants should not be mixed. The resulting contamination can cause excessive pressures and damage the system. (Courtesy of Zexel USA Corporation)

7. FIGURE 12-7 The blue, low-side hose is connected to the low side of the system; the red, high-side hose is connected to the high side of the system; and the center hose(s) is connected to a refrigerant container, vacuum pump, or recovery unit (not shown). (Courtesy of Zexel USA Corporation)

8. FIGURE 12-8 The faces of a low-side gauge for R-12,R-22,and R-502 (a) and for R-134a (b). The outer ring shows the pressure; the inner rings are temperature–pressure relationships. (Courtesy of TIF Instruments)

9. FIGURE 12-9 The low- and high-side gauges are mounted onto the manifold so they always read the pressure in their respective hoses. The manifold hand valves control the flow to and from the center hose.

10. FIGURE Many gauges include a calibration screw, which is used to adjust the needle position to 0 (no pressure). (Courtesy of TIF Instruments)

11. FIGURE The low- and high-side manifold valves are used to control flow through the manifold. (a) is used when pressure checking a system; (b), (c), and (d) are used for various service operations.

12. FIGURE This gauge set has a hanging hook for suspending the gauge set and hose holders to keep the working ends of the hoses clean and neat when out of use. Note the electronic digital gauges. (Courtesy of TIF Instruments)

13. FIGURE The working, system end of a hose for R-12 systems should have an O-ring seal and Schrader valve depressor (a); the manifold end should have only a gasket. The working end has a slight bend (b); the manifold end is straight.

14. FIGURE 12-14 SAE-approved service hoses should have the markings shown
FIGURE SAE-approved service hoses should have the markings shown. (Reprinted with permission from SAE Document M-106, © 1992, Society of Automotive Engineers, Inc.)

15. FIGURE Each service port should have a cap to keep out dirt with a sealing O-ring to help prevent refrigerant loss. The valve core is the primary seal, and the cap and O-ring are the secondary seal. (Courtesy of Saturn Corporation)

16. FIGURE R-12 system service hose adapters include quick seal (stops backflow out of the hose when disconnected) (a), 90° (shown) and 45° (b), flexible (c), quick disconnect (d), and straight (e). Adapter (e) is designed to fit GM Positive Seal valves. The female side is made in different sizes to fit the different high-side ports. (a, b, c, and d courtesy of Robinair, SPX Corporation; e courtesy of Kent-Moore)

17. FIGURE (CONTINUED) R-12 system service hose adapters include quick seal (stops backflow out of the hose when disconnected) (a), 90° (shown) and 45° (b), flexible (c), quick disconnect (d), and straight (e). Adapter (e) is designed to fit GM Positive Seal valves. The female side is made in different sizes to fit the different high-side ports. (a, b, c, and d courtesy of Robinair, SPX Corporation; e courtesy of Kent-Moore)

18. FIGURE A cutaway view of R-134a service ports showing the internal valve. (Courtesy of Chrysler LLC)

19. FIGURE R-134a coupler types include compact quickcouplers (a), compact manual couplers (b), and standard manual couplers (c). The lock must be lifted or compressed to install or remove the coupler, and the knob on the manual types must be turned inward to open the valve. (c is courtesy of Zexel Corporation)

20. FIGURE A gauge set may be used with different refrigerants by changing the hoses. Each hose set must have unique fittings, permanently attached, for that refrigerant. (a. Courtesy of the International Mobile Air Conditioning Association [IMACA]; b. Courtesy of Mastercool)

21. FIGURE A third gauge (compressor inlet gauge) is being used to check the operation of the EPR valve located inside the suction line port. Many technicians do not use the solid bar holding the third gauge to the manifold and keep it separate. (Courtesy of Chrysler LLC)

22. FIGURE An electronic gauge set can measure low- and high-side pressures, vacuum (in microns), and temperature. It can also calculate superheating and subcooling. (Courtesy of Robinair, SPX Corporation)

23. FIGURE A service valve is normally kept in its back-seated position (a). Turning the valve stem completely inward, using a special wrench, will front-seat the valve to shut off the hose connection (b). Turning the valve a turn or two inward will mid-seat the valve (c); this opens the ser-vice port so system pressure can be read on a gauge set.

24. FIGURE The low-side service port is normally located between the evaporator outlet and the compressor inlet. The high-side service port is between the compressor outlet and the evaporator inlet.

25. FIGURE The valve depressor opens the Schrader valve as the service hose is connected to the fitting.

26. FIGURE To reduce leakage when connecting a hose to an R-12 service port, push the hose firmly against the fitting and then finger-tighten the fitting nut.

27. FIGURE 12-26 An R-12 service port cap can be stored on the manifold’s hose holder.

28. FIGURE When the gauges are connected, they should both show the same pressure, which is dependent on the temperature. When the system is turned on the pressures will change, depending on evaporator temperature (low side) and ambient temperature (high side). Pressures will equalize again after the system is shut off.

29. FIGURE 12-28 An A/C system checklist
FIGURE An A/C system checklist. (Courtesy of the International Mobile Air Conditioning Association [IMACA])

30. FIGURE During normal operation, most systems will have a low-side pressure around 20 to 30 psi and a high-side pressure that is dependent on ambient temperature. Service information should be checked to determine the pressure for a specific system.

31. FIGURE Proper high-side pressure can only be determined from the temperature of ambient air entering the condenser. A dial pocket thermometer (a), an infrared, non-contact thermometer (b), or a digital thermometer (c) can be used. (b. courtesy of Raytek Corporation)

32. FIGURE Clutch cycle time is determined by adding the time that the clutch runs to the time that it is stopped.

33. FIGURE The FlexTemp is an IR thermometer with a flexible probe that can be used to take temperature readings in areas that are difficult to reach. (Courtesy of Neutronics, Inc.)

34. FIGURE A sight glass can be used to determine the condition of the refrigerant passing through the liquid line. (Courtesy of Chrysler LLC)

35. FIGURE Relative humidity is determined by measuring dry and wet bulb temperatures. Dry bulb temperature is measured using a plain thermometer (a); wet bulb temperature is measured with a damp sock over the thermometer (b). (Courtesy of Fluke; reproduced with permission)

36. FIGURE Relative humidity is the point where dry and wet bulb temperatures intersect on a psychrometric chart. In this example, a 17°C wet bulb and a 24°C dry bulb indicate 50% RH. (Courtesy of Fluke; reproduced with permission)

37. FIGURE This meter combines a quick and easy method of measuring humidity along with a non-contact infrared thermometer. (Courtesy of Santech Industries)

38. FIGURE 12-37 An electronic sight glass connected to a system
FIGURE An electronic sight glass connected to a system. Bubble indicator lights light up and a beep sounds to indicate liquid or gas passing through the liquid line. (Courtesy of TIF Instruments)

39. FIGURE This troubleshooting chart relates possible system problems to abnormal gauge pressures. (Courtesy of Zexel USA Corporation)

40. FIGURE 12-39 The low- and high-side pressures for a TXV system at 80°F
FIGURE The low- and high-side pressures for a TXV system at 80°F. Note that they will vary about 10 to 15 psi on the low side and about 50 psi on the high side. High-side pressures are also dependent on ambient temperature.

41. FIGURE 12-40 Vent temperatures will vary with ambient temperature and relative humidity.

42. FIGURE 12-41 The low-side pressures of various systems (a)
FIGURE The low-side pressures of various systems (a).If a third gauge is used on a properly operating STV system, it will show a pressure drop across the STV (b).An STV that is stuck closed (c), and an STV that is stuck open (d).

43. FIGURE 12-42 Typical gauge readings for a normal system (a) and faulty systems (b, c, and d).

44. FIGURE The top orifice tube is nearly plugged with a black material; the lower one has some small metal flakes on the screen that probably came from the compressor.

45. FIGURE The high- and low-side service ports can be at different locations. Restricted components will cause different high- or low-side pressures depending on the location of the service port or restriction. For example, a plugged condenser will cause high high-side pressure with service port A or low high-side pressure with service port B.

46. FIGURE Part of this evaporator face is plugged by an oily mud and leaf debris. This reduces heat transfer and air flow.

47. FIGURE In a fully to slightly undercharged OT system, the bottom of the accumulator is as cold as the line just downstream from the OT. A warmer accumulator indicates an undercharge.

48. FIGURE When measuring the Delta T across the evaporator, one electronic thermometer is attached to the inlet and another to the outlet. The temperature difference is the Delta T. The jumper wire at the clutch cycling switch keeps the compressor operating. (Courtesy of Chrysler LLC)

49. FIGURE This chart indicates the amount of refrigerant that should be added to this particular system, depending on the Delta T. With any system, a Delta T of 3 to 10°F indicates a full charge of refrigerant. (Courtesy of Chrysler LLC)

50. FIGURE Subcooling is determined from the high-side pressure and an accurate measurement of the condenser outlet. (Courtesy of Chrysler LLC)

51. FIGURE The point of intersection between the temperature and pressure indicates the relative charge level on this chart. Above the solid line is an undercharge; below the dashed line is an overcharge. (Courtesy of Chrysler LLC)

52. FIGURE The thermal bulb of the TXV should be clamped tightly to the evaporator tailpipe and insulated with a foam sleeve (a) or wrapped with insulating tape, a thick, pliable tape (b). (b courtesy of Four Seasons)

53. FIGURE Chilling the thermal bulb with ice water (a) or CO2 should cause the valve to close and the low-side pressure to drop. Warming the bulb with your hand (b) should cause the valve to open and the low-side pressure to increase. (Courtesy of Chrysler LLC)

54. FIGURE This A/C diagnostic tool uses low- and high-side pressure, ambient temperature, relative humidity, and A/C component temperature readings from various locations to input into the PDA. The PDA guides the technician through the test procedure, analyzes the data, and then determines if the system is operating properly or, if not, what is wrong. (Courtesy of Neutronics, Inc.)

55. FIGURE These four leak detection methods have various amounts of success depending on the leak rate.

56. FIGURE Removing the tip protector from the electronic leak detector probe allows the filter or sensor to be replaced. (Courtesy of INFICON)

57. FIGURE 12-56 This electronic leak detector uses infrared sensing
FIGURE This electronic leak detector uses infrared sensing. A leak is indicated by a variable-intensity audible/sound signal and a flashing LED. (Courtesy of INFICON)

58. FIGURE Infrared energy is sent through a filter that removes all the energy that is not in the range of refrigerants. Any refrigerant passing through the sampling cell will remove more of the energy and cause the leak detector to respond. (Courtesy of INFICON)

59. FIGURE An ultrasonic leak detector converts the sound of a gas leaking through a small opening into a sound that we can hear using a set of headphones. It also displays the leak rate on a scale. (Courtesy of Robinair, SPX Corporation)

60. FIGURE 12-59 A fluorescent tracer leak detection kit
FIGURE A fluorescent tracer leak detection kit. Tracer solutions are charged into the system; a color stain visible under an ultraviolet light indicates the leak area. (Courtesy of Bright Solutions)

61. FIGURE 12-60 Bubble leak detector. This is like a liquid soap mixture.

62. FIGURE A flame leak detector (no longer recommended) heats the copper reaction plate to red-hot. The flame color will change if a CFC touches this plate.

63. FIGURE A leak in the high side of a system shows up best right after the system is shut off, before the pressure drops off. (Courtesy of Zexel USA Corporation)

64. FIGURE The leak detector probe should be kept under the line or component, within 1/4 inch, and when checking a hose, moved along at a rate of 2 inches per second (a). Move the probe around each line fitting and service port (b and c). (b and c are courtesy of Toyota Motor Sales USA, Inc.)

65. FIGURE These special tools are used to remove and replace Schrader valves (a); this tool allows Schrader valve replacement on charged systems (b). An assortment of valve cores (c).

66. FIGURE Some electronic leak detectors have a sensitivity adjustment that is usually adjusted to give a slow noise or light response. (Courtesy of TIF Instruments)

67. FIGURE The most probable leak areas are indicated by arrows, but leaks can occur anywhere along a hose and at the compressor (a). The oily, dirty coating (arrow) on this hose indicates a probable leak (b). (a courtesy of Zexel USA Corporation)

68. FIGURE Refrigerant leaks cause bubbles to form when liquid leak detector is spread over the area. This pinpoints the leak location. (Courtesy of Saturn Corporation)

69. FIGURE Tracer solutions can be injected into a system that is shut off using a hand-powered injector (a) or added into an operating system by using a dye injector (b) or Tracer-Stick capsule (c). (Courtesy of Tracer Products, a division of Spectronics Corporation)

70. FIGURE (CONTINUED) Tracer solutions can be injected into a system that is shut off using a hand-powered injector (a) or added into an operating system by using a dye injector (b) or Tracer-Stick capsule (c). (Courtesy of Tracer Products, a division of Spectronics Corporation)

71. FIGURE A refrigerant leak shows up as a yellow-green glow under ultraviolet light (a).A leak shows up easier if yellow fluorescent enhancer glasses are worn (b).(a courtesy of Robinair, SPX Corporation; b courtesy of Bright Solutions)

72. FIGURE 12-70 Line connections must be tightened to the correct torque
FIGURE Line connections must be tightened to the correct torque. A crow’s-foot adapter is being used on the torque wrench as a backup wrench keeps the other half of the fitting stationary. (Courtesy of Nissan Motor Corporation in USA)

73. FIGURE The Flex-View unit allows a technician to inspect the evaporator through a 1/2-in.hole. (Courtesy of Robinair, SPX Corporation)