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

WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
Step Action Value 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 (LY7)  or Air Conditioning (A/C) System Performance Test (L26)  or Air Conditioning (A/C) System Performance Test (LS4) 
2 Refer to the instrument panel outlet air temperatures recorded during the A/C system performance test.
Does the discharge air temperature between the right and left center instrument 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
  1. Refer to the pressures recorded during the A/C system performance test.
    2. CAUTION: Refer to Moving Parts and Hot Surfaces Caution .
  2. Inspect for the following conditions:
Do the listed conditions exist?		 - Go to Step 7  Go to Step 6 
6
  1. Refer to the pressures recorded during the A/C system performance test.
  2. Inspect for the following conditions:
Do the listed conditions exist?		 - Go to Step 8  Go to Diagnostic Starting Point - Heating, Ventilation and Air Conditioning 
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 action complete?		 - Go to Step 13  -
8 The A/C system may be contaminated.
View the information screen on the J 43600  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 action complete?		 - Go to Step 13  -
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 instrument panel outlet air temperatures. Refer to Air Conditioning (A/C) System Performance Test (LY7)  or Air Conditioning (A/C) System Performance Test (L26)  or Air Conditioning (A/C) System Performance Test (LS4) .

Are the instrument panel outlet air temperatures within the specified ranges of the A/C Performance Test Table?		 - Go to Step 14  Go to Step 11 
11 The A/C system may contain too much refrigerant oil.
IMPORTANT: Review the vehicle's A/C repair history.

If the vehicle history shows multiple A/C repairs and is suspected of improper PAG oil balancing in the previous repairs, perform the following procedure:
  1. Drain all of the PAG oil drain bottle on the ACR 2000.
  2. Flush the A/C system. Refer to Flushing .

Was more than the total system capacity of refrigerant oil recovered from the ACR 2000 oil drain bottle?		 150 ml (5 oz.) Go to Step 12  Go to Step 13 
12
  1. Add the specified amount of refrigerant oil. Refer to Refrigerant System Capacities .
  2. Recharge the A/C system. Refer to Refrigerant Recovery and Recharging .
Are the actions complete?		 - Go to Step 13  -
13
  1. Record the low and high side pressures and the instrument panel outlet air temperature.
  2. Compare the instrument panel outlet air temperatures to those listed in the A/C System Performance Chart. Refer to Air Conditioning (A/C) System Performance Test (LY7)  or Air Conditioning (A/C) System Performance Test (L26)  or Air Conditioning (A/C) System Performance Test (LS4) .
Are the high and low side pressures and the instrument panel outlet air temperatures within specifications?		 - Go to Step 14  -
14 Operate the system in order to verify the repair.
Did you find and correct the condition?		 - System OK Go to Symptoms - HVAC Systems - Manual or Symptoms - HVAC Systems - Automatic
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