GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 GMC C Sierra - 2WD 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 HVAC Compressor Clutch Does Not Disengage

Test Description

The number below refers to the step number on the diagnostic table.

  1. These actions will disable the HVAC control module output to powertrain control module (PCM) or engine control module (ECM).

Step

Action

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

DEFINITION: The A/C compressor clutch will not disengage when an A/C request has not been made and a Powertrain DTC has not been set.

1

Did you perform the HVAC Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Manual

2

  1. Start the engine.
  2. Place the mode switch in the PANEL position.
  3. Place the A/C request switch in the OFF position.

Does the A/C compressor clutch engage?

Go to Step 3

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

3
  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the supply voltage circuit of the A/C compressor clutch with a test lamp that is connected to ground.

Does the test lamp illuminate?

Go to Step 4

Go to Step 8

4

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

Did you find and correct the condition?

Go to Step 13

Go to Step 5

5
  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the control circuit and the ignition 3 voltage circuit of the A/C compressor clutch relay.

Does the test lamp illuminate?

Go to Step 6

Go to Step 7

6

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 13

Go to Step 9

7

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

Did you find and correct the condition?

Go to Step 13

Go to Step 10

8

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

Did you find and correct the condition?

Go to Step 13

Go to Step 11

9

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

Did you find and correct the condition?

Go to Step 13

Go to Step 12

10

Replace the A/C compressor clutch relay.

Did you complete the replacement?

Go to Step 13

--

11

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

Did you complete the replacement?

Go to Step 13

--

12

Important: Program the PCM/ECM.

Replace the PCM/ECM. Refer to the appropriate procedure:

    •  Powertrain Control Module Replacement in Engine Controls - 4.3L
    •  Powertrain Control Module Replacement in Engine Controls - 4.8L, 5.3L, 6.0L
    •  Engine Control Module Replacement in Engine Controls - 6.6L (LB7)
    •  Engine Control Module Replacement in Engine Controls - 6.6L (LLY)
    •  Powertrain Control Module Replacement in Engine Controls - 8.1L

Did you complete the replacement?

Go to Step 13

--

13

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3