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

WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
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 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 3  Go to Step 4 
3 Increase engine speed to 1,500 RPM.
During extended operation of the A/C system, does the low side pressure decrease?		 Go to Air Conditioning (A/C) Diagnostics - Pressure Zone D  Go to Step 4 
4 Refer to the pressures recorded during the A/C system performance test.
CAUTION: Refer to Moving Parts and Hot Surfaces Caution .

Inspect for the following conditions:
  • The high side pressure is slightly greater than the specified pressure ranges in the A/C System performance Table but still near Zone A on the A/C Pressure-Zone Classification Chart. Refer to Air Conditioning (A/C) System Performance Test .
  • The discharge line is hot.
  • The suction line is cool.

Do the listed conditions exist?		 Go to Step 7  Go to Step 5 
5 Refer to the pressures recorded during the A/C system performance test.
Inspect for the following conditions:
  • The low side pressure is slightly lower than the specified pressure ranges but still near Zone A on the A/C Pressure-Zone Classification Chart. Refer to Air Conditioning (A/C) System Performance Test .
  • The discharge line is warm-to-hot.
  • The suction line is cool-to-warm.

Do the listed conditions exist?		 Go to Step 6  Go to Air Temperature Malfunction
6 The A/C system may be undercharged.
  1. Leak test the A/C system. Refer to Leak Testing .
  2. Evacuate and recharge the A/C system to specifications. Refer to Refrigerant Recovery and Recharging .

Is the repair complete?		 Go to Step 11  -
7 The A/C system may be contaminated.
View the J 43600  ACR 2000 Air Conditioning Service Center information screen for detection of foreign gases in the A/C system. See Special Tools .
Do foreign gases exist?		 Go to Step 8  Go to Step 9 
8
  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 11  -
9 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 11  Go to Step 10 
10
  1. Record the low and high side pressures and the instrument panel (I/P) outlet air temperature.
  2. Compare the panel outlet temperatures and pressure 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 outlet temperatures within specifications?		 Go to Step 11  Go to Air Conditioning (A/C) System Performance Test 
11 Operate the system in order to verify the repair.
Did you correct the condition?		 System OK Go to Symptoms - HVAC Systems - Automatic
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