GM Service Manual Online
For 1990-2009 cars only

Tools Required

    • J 39183-C R-134a Manifold Gauge Set
    • J 6742-03 Thermometer Dial

    Important: Perform the A/C system performance test only under the following conditions:

       • The vehicle is not exposed to direct sunlight.
       • The ambient temperature is within 30-35°C (86-95°F).

  1. Turn the ignition switch to LOCK.
  2. Apply the parking brake.
  3. Connect the J 39183-C manifold gauge set High side (RED) and Low side (BLU) hoses to their respective service ports on the vehicle.
  4. Start the engine and let it warm up to normal operating temperature. Let the engine run at normal idle speed.
  5. Keep all of the doors and windows and the hood open.
  6. Set the temperature control to the coldest position.
  7. Set the mode control to the IP outlet position.
  8. Set the blower intake to the recirculate position
  9. Set the blower speed to the highest position.
  10. Press the A/C switch to the ON position.
  11. Place the J 6742-03 thermometer dial probe through the IP center outlet.
  12. Run the A/C system until the outlet air temperature reaches the lowest temperature. This should take approximately 3 minutes.
  13. Monitor the thermometer and record the center outlet air temperature when it stabilizes.
  14. Monitor the gauge set and record the refrigerant pressures when they stabilize. Normal operating pressures should be within the range below. However, on-vehicle operating pressures are affected by ambient temperature and humidity variables.
  15. High Side Pressure Range
    1275-1670 kPa (185-244 psi)

    Low Side Pressure Range
    150-300 kPa (21-43 psi)

    A/C Inlet Temperature
    30-35°C (86-95°F)

  16. Turn the blower speed selector to OFF.
  17. Turn the ignition switch to LOCK.
  18. Remove the thermometer.
  19. Disconnect the manifold gauge set.

Compare the recorded High and Low side refrigerant system pressures and the outlet air temperature with the table below. If the recorded values are not within the specifications, refer to TXV A/C System Diagnosis (Insufficient Cooling) .


Object Number: 345538  Size: MF
(1)Normal High Side Pressure Range
(2)Normal Low Side Pressure Range
(3)System Pressure vs. Ambient Temperature Graph
(4)Normal Center Air Outlet Temperature Range
(5)Center Air Outlet Temperature vs. Ambient Temperature Graph

Refrigerant-134a Pressure-Temperature Relationship

°C

°F

kPa

PSI

This table indicates the pressure of the Refrigerant-134a at various temperatures.

For instance, a drum of refrigerant at room temperature of 26.6° C (80° F) will have a pressure of 595.6 kPa (86.4 PSI). If the refrigerant is heated to 51.6° C (125° F), the pressure will increase to 1278.8 kPa (185.5 PSI).

The refrigerant also can be used conversely in order to determine the temperature at which the Refrigerant-134a boils under various pressures. For example, at a pressure of 188.2 kPa (27.3 PSI), Refrigerant-134a boils at 0° C.

-23.3

-10

12.4

1.8

-20.5

-5

27.0

3.9

-17.7

0

43.2

6.3

-15.0

5

60.8

8.8

-12.2

10

80.1

11.6

-9.4

15

101.3

14.7

-6.6

20

124.3

18.0

-3.8

25

149.4

21.7

-1.1

30

176.6

25.6

0.0

32

188.2

27.3

1.6

35

206.2

29.9

4.4

40

238.0

34.5

7.2

45

272.5

39.5

10.0

55

349.4

50.7

15.5

60

392.3

56.9

18.3

65

438.2

63.6

21.1

70

487.3

70.7

23.8

75

539.7

78.3

26.6

80

595.6

86.4

29.4

85

655.1

95.0

32.2

90

718.5

104.2

35.0

95

785.6

113.9

37.7

100

856.9

124.3

40.5

105

932.3

135.2

43.3

110

1012.1

146.8

46.1

115

1096.4

159.0

48.8

120

1185.2

171.9

51.6

125

1278.8

185.5

54.4

130

1377.3

199.8

60.0

140

1589.6

230.5