GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 GMC C Sierra - 2WD 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 HVAC Compressor Clutch Does Not Engage

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. The A/C compressor relay output is disabled if engine coolant temperature is above 121°C (250°F). The engine coolant indicator will illuminate at this temperature.

    2.

  2. These actions will enable the A/C compressor to operate.

    3.

  3. This test ensures that there is sufficient refrigerant in the A/C system. The specific values come from the A/C System Performance Test in Heating, Ventilation and Air Conditioning.

    4.

  4. If the HVAC control module does not respond to requests, the module is inoperative.

    5.

  5. This action ensures that the powertrain control module (PCM) is getting an A/C request from the HVAC control module.

    6.

  6. If the A/C request LED does not illuminate the HVAC control module is not grounding the A/C request signal circuit.

    7.

  7. Since the A/C system pressure has been verified in Step 4 this step will verify the integrity of the A/C request signal circuits, if the A/C Request Signal parameter is Yes then there is a concern with the A/C high pressure switch.

    8.

  8. Since the A/C system pressure has been verified in Step 4 this step will verify the integrity of the A/C low pressure signal circuit and the ground circuit of the A/C low pressure switch, if the A/C Compressor Cycling Switch parameter is Normal then there is a concern with the A/C low pressure switch.

    9.

  9. If the test lamp remains illuminated the A/C compressor clutch relay control circuit is shorted to ground.

    10.

  10. If the fused jumper opens during this step the A/C compressor clutch supply voltage circuit is short to ground.

    11.

  11. Ensure that both A/C request signal circuits of the A/C high pressure switch are tested for listed conditions.

Step

Action

Yes

No

Schematic Reference : HVAC Schematics

DEFINITION: The A/C compressor clutch will not engage when an A/C request has 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 - Automatic

2

  1. Start the engine.
  2. Observe the coolant temperature indicator.

Is the engine coolant temperature indicator illuminated?

Go to Engine Coolant Temperature Indicator Always On in Engine Cooling

Go to Step 3

3

    Important: For A/C compressor operation, the ambient air temperature must be above 3°C (38°F).

  1. Start the engine.
  2. Place the blower motor switch in the maximum speed position.
  3. Place the A/C switch in the ON position.
  4. Place the air temperature control switch in the coldest position.

Does the A/C compressor operate?

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

Go to Step 4

4
  1. Park the vehicle inside or out of direct sunlight.
  2. Open the window in order to ventilate the interior of the vehicle.
  3. If the A/C system was operating, wait for approximately 2 minutes.
  4. Turn OFF the ignition.
  5. Install J 43600 .
  6. Record the ambient temperature at the vehicle.
  7. Record the low side and the high side STATIC pressures.
  8. Compare the pressure values with the specifications for the ambient air temperature. Refer to Air Conditioning (A/C) System Performance Test in Heating, Ventilation and Air Conditioning.

Are the pressure values within the specifications for the ambient air temperature, and within 103 kPa (15 psi) of each other?

Go to Step 5

Go to Leak Testing in Heating, Ventilation and Air Conditioning

5

Is the HVAC control module inoperative?

Go to Step 20

Go to Step 6

6
  1. Start the engine.
  2. With a scan tool, observe the A/C Request Signal parameter in the powertrain data list.
  3. Place the A/C request switch in the ON position.

Does the scan tool indicate that the A/C Request Signal parameter is Yes?

Go to Step 9

Go to Step 7

7

Does the A/C request indicator illuminate?

Go to Step 8

Go to Step 31

8
  1. Turn OFF the ignition.
  2. Disconnect the A/C high pressure switch.
  3. Connect a 3-ampere fused jumper between the A/C request circuits at the A/C high pressure switch connector.
  4. Start the engine.
  5. With a scan tool, observe the A/C Request Signal parameter.
  6. Place the A/C request switch in the ON position.

Does the scan tool indicate that the A/C Request Signal parameter is Yes?

Go to Step 32

Go to Step 26

9

Does the scan tool indicate the A/C Compressor Cycling Switch parameter is Normal?

Go to Step 11

Go to Step 10

10
  1. Turn OFF the ignition.
  2. Disconnect the A/C low pressure switch.
  3. Connect a 3-ampere fused jumper between the low A/C pressure sensor signal and the ground circuits.
  4. Start the engine.
  5. With a scan tool, observe the A/C Compressor Cycling Switch parameter.

Does the scan tool indicate the A/C Compressor Cycling Switch parameter is Normal?

Go to Step 29

Go to Step 22

11

With a scan tool, command the A/C compressor clutch relay ON and OFF.

Does the A/C compressor clutch relay turn ON and OFF with each command?

Go to Step 17

Go to Step 12

12
  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Using a test lamp that is connected to a good ground, probe the coil side of the voltage circuit of the A/C compressor clutch relay .

Does the test lamp illuminate?

Go to Step 13

Go to Step 27

13
  1. Connect a test lamp on the A/C compressor clutch relay between the control circuit and the coil side of the voltage circuit.
  2. With a scan tool, command the A/C compressor clutch relay ON and OFF.

Does the test lamp turn ON and OFF with each command?

Go to Step 28

Go to Step 14

14

Does the test lamp remain illuminated with each command?

Go to Step 16

Go to Step 15

15

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

Did you find and correct the condition?

Go to Step 40

Go to Step 33

16

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 40

Go to Step 33

17
  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Probe the switch side of the voltage supply circuit of the A/C compressor clutch relay with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 18

Go to Step 19

18
  1. Connect a 10-ampere fused jumper between battery positive voltage and the supply voltage circuit of the A/C compressor clutch.
  2. Turn ON the ignition, with the engine OFF.

Does the A/C compressor clutch engage?

Go to Step 28

Go to Step 24

19

Repair the switch side of the voltage supply circuit of the A/C compressor clutch relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 40

--

20

Test the ignition 3 voltage circuit of the HVAC control module for a short to ground, for a high resistance, or for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 40

Go to Step 21

21

Test the ground circuit of the HVAC control module for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 40

Go to Step 31

22

Test the signal circuit of the A/C low pressure switch for a high resistance or for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 40

Go to Step 23

23

Test the ground circuit of the A/C low pressure switch for a high resistance or for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 40

Go to Step 33

24

Test the supply voltage circuit at the A/C compressor clutch for a short to ground, for a high resistance, or for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 40

Go to Step 25

25

Test the ground circuit of the A/C compressor clutch for a high resistance or for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 40

Go to Step 30

26

  1. Turn OFF the ignition.
  2. Reconnect the A/C high pressure switch.
  3. Test the both A/C request signal circuits of the A/C high pressure switch for a short to ground, for a high resistance, or for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 40

Go to Step 33

27

Repair the coil side of the voltage supply circuit of the A/C compressor clutch relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 40

--

28

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 40

Go to Step 34

29

Inspect for poor connections at the harness connector of the A/C low pressure switch. 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 40

Go to Step 35

30

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 40

Go to Step 37

31

Inspect for poor connections at the harness connector of the HVAC control module. 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 40

Go to Step 38

32

Inspect for poor connections at the harness connector of the A/C high pressure switch. 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 40

Go to Step 36

33

Inspect for poor connections at the harness connector of the powertrain control module (PCM). 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 40

Go to Step 39

34

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 40

--

35

Replace the A/C low pressure switch. Refer to Air Conditioning (A/C) Low Pressure Switch Replacement in Heating, Ventilation, and Air Conditioning.

Did you complete the replacement?

Go to Step 40

--

36

Replace the A/C high pressure switch. Refer to Air Conditioning (A/C) High Pressure Switch Replacement in Heating, Ventilation, and Air Conditioning.

Did you complete the replacement?

Go to Step 40

--

37

Replace the A/C compressor clutch coil. Refer to Air Conditioning Clutch Coil Removal and to Air Conditioning Clutch Coil Installation in Heating, Ventilation, and Air Conditioning.

Did you complete the replacement?

Go to Step 40

--

38

Important: Perform the calibration procedure for the HVAC control module.

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

Did you complete the replacement?

Go to Step 40

--

39

Important: Program the PCM.

Replace the Powertrain Control Module (PCM). Refer to Powertrain Control Module Replacement in Engine Controls-4.8L, 5.3L, and 6.0L or Powertrain Control Module Replacement in Engine Controls-8.1L.

Did you complete the replacement?

Go to Step 40

--

40

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 4