GM Service Manual Online
For 1990-2009 cars only

    Important: Record the relative humidity and ambient temperature conditions at the time of the test.

  1. Park the vehicle inside or in the shade. The ambient temperature must be at least 16°C (60°F).
  2. Open the windows in order to ventilate the interior.
  3. Vent the engine exhaust.
  4. Open the hood and install the high and low side pressure gauges.
  5. Record the ambient temperature outside.
  6. Record the relative humidity. Use a psychrometer or consult the local weather bureau.
  7. Close the doors and the windows.
  8. Set the A/C control assembly to outside air mode with the blower speed set to high and the temperature to full cold. Push the A/C button in order to turn on the A/C.
  9. Open the A/C air outlet deflectors.
  10. Place a thermometer in the right center A/C outlet.
  11. Place the transaxle in PARK and start the engine.
  12. Stabilize the engine at 2000 RPM.

  13. Run the A/C system until the outlet air reaches the lowest temperature (about 3 minutes).
  14. Record the outlet air temperature and the high side and low side pressures.
  15. Turn off the engine and compare the readings with the upper limit data in the A/C Performance Table. A normally operating A/C system should not exceed the levels shown.
  16. If the readings exceed the table limits. Refer to VDOT Air Conditioning (A/C) System Diagnosis .
  17. If the reading are under the table limits. Refer to Refrigerant System Checks .

A/C Performance Table

Relative Humidity

(%)

Ambient Air Temperature

Maximum Low Side Pressure

Engine Speed

(RPM)

Maximum Right Center Air Outlet Temperature

Maximum High Side Pressure

°F

°C

PSI

kPa

°F

°C

PSI

kPa

20

70

21

37

255

2000

46

8

248

1710

80

27

37

255

47

8

303

2069

90

32

37

255

53

12

358

2468

100

38

38

262

54

12

358

2268

30

70

21

37

255

2000

48

9

264

1820

80

27

37

255

50

10

314

2165

90

32

39

269

57

14

374

2579

100

38

43

262

60

16

396

2482

40

70

21

37

255

2000

49

9

286

1972

80

27

37

255

53

12

336

2317

90

32

42

290

60

16

391

2696

100

38

49

338

66

19

435

2999

50

70

21

37

255

2000

51

11

303

2069

80

27

39

269

56

13

352

2427

90

32

46

317

63

17

413

2848

100

38

55

379

72

22

*

*

60

70

21

37

255

2000

53

12

319

2199

80

27

42

290

59

15

374

2579

90

32

49

338

66

19

429

2958

100

38

60

414

78

26

*

*

70

70

21

37

255

2000

55

13

336

2317

80

27

45

310

62

17

391

2696

90

32

53

365

70

21

446

3075

80

70

21

41

283

2000

56

13

352

2427

80

27

48

331

65

18

407

2806

90

32

57

393

73

23

*

*

90

70

21

45

310

2000

58

14

369

2544

80

27

52

359

68

20

424

2923

* A/C compressor turns OFF due to excessive High Side Pressure