GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 GMC Suburban - 2WD 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 System Performance Test

Tools Required

J 21213-A Four Jack Dual Range Temperature Tester

  1. Park the vehicle indoors or in a shaded area.
  2. Open the hood, the doors, and the windows in order to ventilate the interior.
  3. Vent the engine exhaust, if necessary.
  4. Install the high and low side pressure gauges.
  5. Route the lines over the front of the grille.
  6. Close the hood completely.
  7. Record the ambient temperature near the vehicle.
  8. Record the temperature and the relative humidity by using a psychrometer or by consulting the local weather bureau.
  9. Close the doors.
  10. Close all of the windows except for the front side windows.
  11. Set the mode control to the A/C position.
  12. Set the blower control on the HIGH position.
  13. Set the temperature control to the FULL COLD position.
  14. Open the air conditioning outlets.
  15. Install the J 21213-A into the right center air conditioning outlet.
  16. Place the transmission in park.
  17. Start the engine.
  18. Stabilize the engine speed at 1500 RPM.
  19. Start the timer.
  20. Operate the air conditioning system for 10 minutes.
  21. Record the following data:
    22. • The outlet air temperature
    • The high-side pressure
    • The low-side pressure
  22. Turn the ignition to the OFF position.
  23. Compare the readings to the table below.
  24. If you suspect a malfunction in the refrigerant system due to abnormal system pressures, inspect the system for the following conditions:
    25. 24.1. The outer surfaces of the radiator and the condenser cores are blocked by dirt, leaves, or other material.
    24.2. The areas between the condenser and radiator are clogged with dirt, leaves and other material.
    24.3. The evaporator core, the condenser core, the hoses, the tubes and other components are restricted or kinked.
    24.4. The system is leaking refrigerant.
    24.5. The air ducts have leaks or restrictions.
    24.6. The airflow rate is low due to a restriction in the evaporator core.
    24.7. The compressor clutch slips.
    24.8. The drive belt tension is improper.
    24.9. The accumulator is plugged.
    24.10. The expansion (orifice) tube is plugged.
  25. If you do not find a condition, continue with the CCOT A/C System Diagnosis. Refer to.

Relative Humidity

Ambient Air Temperature

Maximum Low Side Pressure

Engine Speed

Maximum Center Air Outlet Temperature

Maximum High Side Pressure

40%

26.7°C

(80°F)

220 kPa

(32 psi)

1500 RPM

10.6°C

(51°F)

1 572 kPa

(228 psi)

26.7°C

(90°F)

268 kPa

(39 psi)

10.6°C

59°F

1 931 kPa

(280 psi)

37.8°C

(100°F)

308 kPa

(44 psi)

18.9°C

(66°F)

2 075 kPa

301 psi

43.3°C

(110°F)

317 kPa

(46 psi)

23.9°C

(75°F)

2 255 kPa

(327 psi)

48.9°C¹

(120°F)¹

310 kPa¹

(45 psi)¹

17.2°C¹

(63°F)¹

2 530 kPa¹

(367 psi)¹

50%

21.1°C²

(70°F)²

193 kPa²

(28 psi)²

6.1°C²

(43°F)²

1 103 kPa²

(160°F)²

70%

21.1°C

(70°F)

234 kPa

(34 psi)

12.2°C

(54°F)

1 572 kPa

(228 psi)

32.2°C

(90°F)

324 kPa

(47 psi)

18.3°C

(65°F)

2 006 kPa

291 psi

80%

26.7°C

(80°F)

268 kPa

39 psi

14.4°C

58°F)

1 731 kPa

(251 psi)

¹Determine in MAX A/C with all of the windows closed.

²The compressor cycles ON and OFF.