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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) Diagnostics - Pressure Zone A

Air Conditioning (A/C) Diagnostics - Pressure Zone A

Step Action Yes No
DEFINITION: The high and low side pressures may be normal or slightly less than normal.
  • Air delivery concern
  • Slight refrigerant under charge
  • Refrigerant contamination
1 Were you sent here from the A/C System Performance Test? Go to Step 2  Go to Air Conditioning (A/C) System Performance Test 
2 Refer to the panel air outlet temperatures recorded during the A/C system performance test.
Does the discharge air temperature between the right and left center panel outlets vary by more than 1-2°C (2-3°F)?		 Go to Step 7  Go to Step 3 
3 Did the customer mention that the A/C system output temperatures are good at first, but then turn warm during extended drives? Go to Step 4  Go to Step 5 
4 Increase engine speed to 2,000 RPM.
During extended operation of the A/C system, does the low side pressure decrease, possibly accompanied by heavy frost on the liquid line between the expansion device and the evaporator?		 Go to Air Conditioning (A/C) Diagnostics - Pressure Zone D  Go to Step 5 
5 Refer to the pressures recorded during the A/C system performance test.
Inspect for the following conditions:
Do the listed conditions exist?		 Go to Step 7  Go to Step 6 
6 Refer to the pressures recorded during the A/C system performance test.
Inspect for the following conditions:
Do the listed conditions exist?		 Go to Step 8  Go to Air Temperature Malfunction
7 The A/C system may be undercharged.
  1. Leak test A/C system. Refer to Leak Testing .
  2. Recharge the A/C system to specifications. Refer to Refrigerant Recovery and Recharging .

Is the repair complete?		 Go to Step 14  -
8 The A/C system may be contaminated.
View the J 43600  information screen for detection of foreign gases in the A/C system. See Special Tools .
Do foreign gases exist?		 Go to Step 9  Go to Step 10 
9
  1. Evacuate the A/C system to a scavenging tank. Refer to Refrigerant Recovery and Recharging .
  2. Recharge the A/C system to specifications.
Is the repair complete?		 Go to Step 14  -
10 The A/C system may contain too much moisture or air.
  1. Evacuate and recharge the A/C system to specifications. Refer to Refrigerant Recovery and Recharging .
  2. Operate the A/C system and inspect the panel outlet air temperatures. Refer to Air Conditioning (A/C) System Performance Test .

Are the panel outlet temperatures within the specified ranges of the A/C Performance Test Table?		 Go to Step 15  Go to Step 11 
11 The A/C system may contain too much refrigerant oil.
  1. Recover the refrigerant from the A/C system. Refer to Refrigerant Recovery and Recharging .
  2. Remove the accumulator. Refer to Accumulator Replacement .
  3. Drain and measure the refrigerant oil from the accumulator.

Were more than 148 ml (5 oz) of refrigerant oil drained from the accumulator?		 Go to Step 12  Go to Step 13 
12
  1. Reinstall the accumulator. Refer to Accumulator Replacement .
  2. Flush the A/C system. Refer to Flushing .
  3. Add the specified amount of refrigerant oil to the accumulator. Refer to Refrigerant System Capacities .
  4. Recharge the A/C system. Refer to Refrigerant Recovery and Recharging .
Are the repairs complete?		 Go to Step 14  -
13
  1. Add the specified amount of refrigerant oil to the accumulator. Refer to Refrigerant System Capacities .
  2. Install the accumulator. Refer to Accumulator Replacement .
  3. Recharge the A/C system. Refer to Refrigerant Recovery and Recharging .
Are the repairs complete?		 Go to Step 14  -
14
  1. Record the low and high side pressures and the instrument panel (I/P) outlet air temperature.
  2. Compare the outlet temperatures to those listed in the A/C System Performance Chart. Refer to Air Conditioning (A/C) System Performance Test .
Are the high and low side pressures and I/P panel outlet temperatures within specifications?		 Go to Step 15  Go to Air Conditioning (A/C) System Performance Test 
15 Operate the system in order to verify the repair.
Did you find and correct the condition?		 System OK Go to Symptoms - HVAC Systems - Automatic
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