GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2005 🢒 STS 🢒 HVAC 🢒 Heating, Ventilation and Air Conditioning 🢒 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

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 in the Preface section.

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 Too Hot in Vehicle

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.

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