GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: HVAC Schematics

1

Did you review the Air Delivery Description and Operation and the Air Temperature Description and Operation and perform the necessary inspections?

Go to Step 2

Go to Symptoms - HVAC Systems - Manual

2

  1. Start the engine.
  2. Turn the blower switch to the OFF position.
  3. Turn the A/C switch to the OFF position.

Does the compressor clutch disengage?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

Disconnect the compressor clutch relay.

Does the compressor clutch disengage?

Go to Step 5

Go to Step 4

4

Test for a short to voltage in the compressor clutch supply voltage circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 9

5

Exchange the compressor clutch relay with a known good relay (the horn relay or the shiftlock relay).

Does the compressor clutch operate normally?

Go to Step 10

Go to Step 6

6

  1. Reconnect the compressor clutch relay.
  2. Disconnect the compressor control module connector.

Does the compressor clutch engage?

Go to Step 7

Go to Step 8

7

Test for a short to ground in the compressor clutch relay control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 11

8

Test for a short to ground in the A/C request signal circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 11

9

Replace the A/C compressor clutch. Refer to Air Conditioning Clutch Coil Replacement .

Did you complete the replacement?

Go to Step 12

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10

Replace the A/C compressor clutch relay. Refer to Compressor Relay Replacement .

Did you complete the replacement?

Go to Step 12

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11

Replace the A/C compressor control module. Refer to Air Conditioning (A/C) Compressor Control Module Replacement .

Did you complete the replacement?

Go to Step 12

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12

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3