GM Service Manual Online
For 1990-2009 cars only

Step

Action

Values

Yes

No

Schematic Reference: HVAC Schematics

DEFINITION: The A/C compressor clutch will not disengage when no A/C request has been made and a Powertrain DTC has not been set.

1

Did you review the HVAC operation and perform the necessary inspections?

--

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Automatic

2

  1. Start the engine.
  2. Place the A/C switch in the OFF position.

Does the A/C compressor operate?

--

Go to Step 3

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

3

With the scan tool, observe the A/C OFF Switch parameter in the Climate Control Panel (CCP).

Is the A/C OFF Switch parameter OFF?

--

Go to Step 4

Go to Step 12

4

With the scan tool, observe the A/C Commanded parameter in Heating and Air Conditioning data list under Inputs.

Does the scan tool display NO?

--

Go to Step 5

Go to Step 13

5

With a scan tool, observe the A/C Relay Command parameter in the Powertrain Data List 2.

Does the scan tool display OFF?

--

Go to Step 6

Go to Step 14

6

  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Turn ON the ignition.

Does the A/C compressor clutch disengage?

--

Go to Step 7

Go to Step 9

7

Measure the resistance between the switch side of the A/C compressor clutch relay terminals.

Does the resistance measurement equal the specified value?

Go to Step 8

Go to Step 11

8

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

Did you find and correct the condition?

--

Go to Step 20

Go to Step 14

9

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

Did you find and correct the condition?

--

Go to Step 20

Go to Step 10

10

Inspect for poor connections at the harness connector of the A/C compressor clutch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 20

Go to Step 16

11

Inspect for poor connections at the A/C compressor clutch relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 20

Go to Step 15

12

Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 20

Go to Step 17

13

Inspect for poor connections at the HVAC control processor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 20

Go to Step 18

14

Inspect for poor connections at the harness connector of the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 20

Go to Step 19

15

Replace the A/C compressor clutch relay. Refer to Compressor Relay Replacement in Heating, Ventilation, and Air Conditioning.

Did you complete the replacement?

--

Go to Step 20

--

16

Replace the A/C compressor clutch hub and the plate. Refer to Compressor Clutch Plate and Hub Assembly Removal and Compressor Clutch Plate/Hub Assembly Install in Heating, Ventilation, and Air Conditioning.

Did you complete the replacement?

--

Go to Step 20

--

17

Replace the HVAC control module. Refer to HVAC Control Module Replacement .

Did you complete the replacement?

--

Go to Step 20

--

18

Replace the HVAC control processor. Refer to HVAC Control Processor Replacement .

Did you complete the replacement?

--

Go to Step 20

--

19

Important: Program the PCM.

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls - 4.6L.

Did you complete the replacement?

--

Go to Step 20

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20

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2