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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> Heating, Ventilation, And Air Conditioning >> Diagnostic Information and Procedures >> Air Conditioning (A/C) System Performance Test >> Test Description

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. 1:  This step determines if there is enough refrigerant in the A/C system in order to operate the system without damage.
  2. 2:  This step measures the performance of the A/C system.
  3. 3:  This step is to allow for vehicle variations as well as high ambient air temperatures.
Step Action Values Yes No
IMPORTANT:
  • The ambient air temperature must be at least 16°C (60°F).
  • Do not induce additional air flow across the front of the vehicle during the test.
  • If you were sent here from a DTC diagnostic table, clear the DTC upon completion of this test.
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 A/C system was operating, allow the A/C system to equalize (about 2 minutes).
  4. Ensure that the ignition key is in the OFF position.
  5. Install the J 43600  ACR 2000 Air Conditioning service center. See Special Tools .
  6. Record the ambient air temperature displayed on the J 43600  . See Special Tools .
  7. Record readings of the low and high side STATIC pressures.
Are both the low and high side pressures within the specified value?
  • Above 16°C (60°F) - 345 kPa (50 psi)
  • Above 24°C (75°F) - 483 kPa (70 psi)
  • Above 33°C (90°F) - 690 kPa (100 psi)
 Go to Step 2  Go to Leak Testing 
2 
    IMPORTANT: Record the relative humidity and the ambient air temperature AT THE TIME OF THE TEST.
  1. Close the vehicle doors and windows.
  2. Open the driver door window 13-15 cm (5-6 inches).
  3. Set the HVAC control to the following positions:
    • The A/C ON
    • The blower control to the highest position
    • The HVAC control assembly to discharge air through the A/C outlets
    • Recirculation Mode
    • The temperature control to the coldest position
    • All A/C outlets OPEN
  4. Install the temperature probes to the J 43600  in the left and right center A/C air outlets. See Special Tools .
  5. Apply the parking brake.
  6. Place the transaxle/transmission in one of the following positions:
    • PARK (Automatic)
    • NEUTRAL (Manual)
  7. Start the engine and allow to idle.
  8. Operate the A/C system for 5 minutes.
  9. Inspect for the following:
    • Abnormal frost areas
    • Unusual noises
    10. IMPORTANT: When using the print function of the J 43600  for this step, press the RESET button first. See Special Tools . In order to capture the correct information, wait 5 minutes after pressing the RESET button, before pressing the PRINT button.
  10. Record the following information:
    • The outlet air temperatures
    • The low-side pressure
    • The high-side pressure
  11. Compare the low and high side pressures and the output temperatures to the table below.
Does all the data recorded fall within the specified ranges of the table below?		 - Go to Step 8  Go to Step 3 
3  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 8  Go to Step 4 
4 Do the high and low side pressures fall within the specified ranges but the outlet temperatures do not? - Go to Air Conditioning (A/C) Diagnostics - Pressure Zone A  Go to Step 5 
5 Is the low side pressure higher than the specified range and the high side pressure within or lower than the specified range? - Go to Air Conditioning (A/C) Diagnostics - Pressure Zone B  Go to Step 6 
6 Are the low and high side pressures both higher than the specified ranges? - Go to Air Conditioning (A/C) Diagnostics - Pressure Zone C  Go to Step 7 
7 Is the low side pressure within or lower than the specified range and the high side pressure higher than the specified range? - Go to Air Conditioning (A/C) Diagnostics - Pressure Zone D  Go to Step 8 
8 Operate the system in order to verify the test results.
Did you find the same results?		 - System OK Go to Symptoms - HVAC Systems - Automatic
Fig 1: A/C System Pressure - Zone Classification
GM827888Courtesy of GENERAL MOTORS CORP.
Ambient Air Temperature Relative Humidity Service Port Pressure Maximum Left Center Discharge Air Temperature
Low Side High Side
13-16°C (55-65°F) 0-100% 200-283 kPa (29-41 psi) 945-1234 kPa (137-179 psi) 11°C (52°F)
19-24°C (66-75°F) Below 40% 228-310 kPa (33-45 psi) 1082-1413 kPa (157-205 psi) 14°C (57°F)
Above 40% 248-338 kPa (36-49 psi) 1131-1469 kPa (164-213 psi) 15°C (59°F)
25-29°C (76-85°F) Below 35% 276-379 kPa (40-55 psi) 1303-1696 kPa (189-246 psi) 18°C (64°F)
35-60% 276-379 kPa (40-55 psi) 1310-1709 kPa (190-248 psi) 18°C (64°F)
Above 60% 290-400 kPa (42-58 psi) 1358-1765 kPa (197-256 psi) 19°C (66°F)
30-35°C (86-95°F) Below 30% 317-434 kPa (46-63 psi) 1544-2006 kPa (224-291 psi) 22°C (72°F)
30-50% 324-441 kPa (47-64 psi) 1558-2034 kPa (226-295 psi) 22°C (72°F)
Above 50% 365-510 kPa (53-74 psi) 1675-2179 kPa (243-316 psi) 26°C (79°F)
36-41°C (96-105°F) Below 20% 400-552 kPa (58-80 psi) 1917-2503 kPa (278-363 psi) 28°C (82°F)
20-40% 393-546 kPa (57-79 psi) 1910-2496 kPa (274-357 psi) 28°C (82°F)
Above 40% 400-552 kPa (58-80 psi) 1910-2496 kPa (277-362 psi) 28°C (82°F)
42-46°C (106-115°F) Below 20% 448-621 kPa (65-90 psi) 2172-2834 kPa (315-411 psi) 31°C (88°F)
Above 20% 462-634 kPa (67-92 psi) 2220-2896 kPa (322-420 psi) 32°C (90°F)
47-49°C (116-120°F) Below 30% 531-731 kPa (77-106 psi) 2379-3116 kPa (347-452 psi) 43°C (109°F)
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