GM Service Manual Online
For 1990-2009 cars only
Table 1: A/C Performance Table

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. This step determines if there is enough refrigerant in the A/C system to operate it without damage.

  2. This step is to determine if the A/C compressor is operating.

  3. This step measures the performance of the A/C system.

  4. This step is to allow for vehicle variations as well as high ambient temperatures.

Step

Action

Value(s)

Yes

No

DEFINITION: The following test measures the A/C system operating efficiency by comparing:

    • The ambient air temperature
    • The ambient air humidity
    • The pressure at the high-pressure side of the refrigeration system
    • The pressure at the low-pressure side of the refrigeration system
    • The temperature of the air being discharged into the passenger compartment

1

  1. Park the vehicle inside or in the shade.
  2. Open the windows in order to ventilate the interior of the vehicle.
  3. If the engine is at operating temperature, allow the engine to cool.
  4. Ensure that the ignition key is in the OFF position.
  5. Install the J 39500-B .
  6. Record readings of the low and high side STATIC pressures.
  7. The low and high side pressure readings should be almost equal to each other once the system has come to rest.

Are both the low and high side pressures above the specified value ?

345 kPa (50 psi)

Go to Step 2

Go to Leak Testing

2

  1. Start the vehicle.
  2. Turn the A/C on.
  3. Visually inspect under the hood to see if the A/C compressor clutch is engaged

Does the compressor clutch engage ?

--

Go to Step 3

Go to HVAC Compressor Clutch Does Not Disengage

3

  1. Turn the engine OFF.
  2. Important: Record the relative humidity and the ambient temperature AT THE TIME OF THE TEST.

  3. Record the ambient temperature at the vehicle.
  4. Record the relative humidity, using one of the following methods:
  5. • Use a psychrometer
    • Consult the local weather bureau
  6. Close the vehicle doors and windows.
  7. Open the driver's door window 5-6 inches.
  8. Set the HVAC control assembly to the following positions:
  9. • The A/C on
    • The blower control to the highest position
    • The HVAC control assembly to discharge air through the I/P outlets
    • The temperature control to the coldest position
  10. Install a thermometer in the I/P left center air outlet.
  11. Install a thermometer in the I/P right center air outlet.
  12. Apply the parking brake.
  13. Place the transaxle/transmission in one of the following positions:
  14. • PARK
    • NEUTRAL
  15. Start the engine and elevate the engine RPM to 2000 and maintain.
  16. Operate the A/C system for 5 minutes.
  17. Record the following information:
  18. • The outlet air temperature
    • The low-side pressure
    • The high-side pressure
  19. Compare the low and high side pressures and the output temperature to the table below (LINK).

Does all the data recorded fall within the specified ranges of the table below?

--

Go to Step 9

Go to Step 4

4

If the pressures and temperatures recorded do not fall within the specified ranges:

  1. Continue to operate the A/C system for an additional 5 minutes.
  2. Record the pressures and temperatures again.
  3. Compare the low and high side pressures and the output temperature to the table below.

Does all the data recorded fall within the specified ranges of the table below?

--

Go to Step 9

Go to Step 5

5

Compare the recorded pressures to the A/C System Pressure - Zone Classification Chart below.

Do both the low and high side pressures fall within Zone A on the chart ?

--

Go to Cooling Insufficient - Air Conditioning (A/C) System - Pressure Zone A

Go to Step 6

6

Do the pressures fall within Zone B ?

--

Go to Cooling Insufficient - Air Conditioning (A/C) System - Pressure Zone B

Go to Step 7

7

Do the pressures fall within Zone C ?

--

Go to Cooling Insufficient - Air Conditioning (A/C) System - Pressure Zone C

Go to Step 8

8

Do the pressures fall within Zone D ?

--

Go to Cooling Insufficient - Air Conditioning (A/C) System - Pressure Zone D

Go to Step 9

9

Operate the system in order to verify the repair.

Did you correct the condition ?

--

System OK

Go to Symptoms in HVAC System - Manual

A/C System Pressure -- Zone Classification


Object Number: 466373  Size: MF

A/C Performance Table

Relative Humidity

Ambient Air Temperature

Low Side Pressure

Engine Speed

High Side Pressure

Center Air Outlet Temperature

Front

Rear

°C

°F

kPa

psi

kPa

psi

°C

°F

°C

°F

Important: Use this table in conjunction with the appropriate diagnostic tables.

20%

27

80

186-228¹

27-33¹

2000 RPM

1496-1538¹

217-223¹

10¹

50¹

11¹

51¹

32

90

200-241

29-35

1703-1744

247-253

12

53

12

53

38

100

241-283

35-41

2186-2227

317-323

14

58

16

60

30%

20

70

186-228¹

27-33¹

2000 RPM

1496-1538¹

217-223¹

10¹

50¹

11¹

51¹

27

80

221-262

32-38

1772-1813

257-263

13

56

13

56

32

90

241-238

35-41

2144-2186

311-317

15

59

16

60

38

100

290-331

42-48

2496-2537

362-368

18

64

18

64

40%

21

70

186-228¹

27-33¹

2000 RPM

1496-1538¹

217-223¹

11¹

51¹

11

51

27

80

248-290¹

36-42¹

2048-2089¹

297-303¹

15¹

59¹

15

59

32

90

276-317

40-46

2427-2468

352-358

18

65

18

65

38

100

338-379

49-55

2668-2710

387-393

22

72

22

72

50%

21

70

207-248¹

30-36¹

2000 RPM

1807-1848¹

262-268¹

13¹

55¹

13

55

27

80

269-310

39-45

2193-2234

318-324

17

63

17

63

32

90

290-331

42-48

2462-2503

357-363

21

70

21

70

38

100

352-393

51-57

2703-2744

392-398

24

76

24

76

60%

21

70

221-262¹

32-38¹

2000 RPM

1875-1917¹

272-278¹

13¹

55¹

13

55

27

80

269-310¹

39-45¹

2220-2262¹

322-328¹

16¹

60¹

16

60

32

90

297-338

43-49

2462-2503

357-363

18

64

18

64

38

100

359-400

52-58

2703-2744

392-398

22

71

23

73

70%

21

70

228-269¹

33-39¹

2000 RPM

1910-1951¹

277-283¹

11¹

51¹

11

51

27

80

276-317¹

40-46¹

2324-2365¹

337-343¹

14¹

58¹

15

59

32

90

310-352

45-51

2462-2503

357-363

18

65

19

67

38

100

359-400

52-58

2737-2779

397-403

23

74

23

74

80%

21

70

290-331¹

42-48¹

2000 RPM

1944-1986¹

282-288¹

10¹

50¹

11

51

27

80

310-352

45-51

2358-2400

342-348

13

56

14

58

32

90

338

49

2462-2503

357-363

19

67

21

69

90%

21

70

241-283¹

35-41¹

2000 RPM

1979-2020¹

287-293¹

15¹

59¹

16

60

27

80

317-359

46-52

2393-2434

347-353

16

61

17

62

¹This data reflects the performance obtained while the engine cooling fans were operating in series (low speed), rather than in parallel (high speed).