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. The HVAC control module is inoperative when the module does not respond to an operator control request.

    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 assembly 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. When the blower motor is in the OFF position, a voltage is applied to the OFF blower motor control circuit. The A/C system will not operate if a voltage is applied to the OFF blower motor control circuit.

    12.

  12. 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 if an 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 Symptoms - HVAC Systems - Manual

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 request switch in the ON position.
  4. Place the air temperature 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 not in direct sunlight.
  2. Open a window in order to ventilate the interior of the vehicle.
  3. If the A/C system was operating, then wait for approximately 2 minutes.
  4. Turn OFF the ignition.
  5. Install J 43600 .
  6. Record the ambient temperature at the vehicle.
  7. Record readings of the low and 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 assembly 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 22

8

Important: Ensure that the blower motor switch is not in the OFF position during this step.

  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 33

Go to Step 27

9

With a scan tool, observe the A/C Compressor Cycling Switch parameter in the Engine Data 2 data list.

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 low pressure switch signal and ground circuit.
  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 30

Go to Step 23

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. Probe the coil side voltage supply circuit of the A/C compressor clutch relay with a test lamp that is connected to ground.

Does the test lamp illuminate?

Go to Step 13

Go to Step 28

13
  1. Connect a test lamp between the control circuit and the coil side voltage supply circuit of the A/C compressor clutch relay.
  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 29

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 41

Go to Step 34

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 41

Go to Step 34

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

Does the test lamp illuminate?

Go to Step 18

Go to Step 19

18

  1. Connect a 10-ampere fused jumper between the switch side voltage circuit of the A/C compressor clutch relay 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 29

Go to Step 25

19

Repair the switch side 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 41

--

20

Test the ignition 3 voltage circuit of the HVAC control assembly 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 41

Go to Step 21

21

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

Did you find and correct the condition?

Go to Step 41

Go to Step 32

22

Important: Ensure that the blower motor switch is not in the OFF position during this step.

Test the OFF blower motor control circuit 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 41

Go to Step 32

23

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 41

Go to Step 24

24

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 41

Go to Step 34

25

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 41

Go to Step 26

26

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 41

Go to Step 31

27

  1. Turn OFF the ignition.
  2. Reconnect the A/C high pressure switch.
  3. Test the A/C request signal circuit 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 41

Go to Step 34

28

Repair the coil side 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 41

--

29

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 41

Go to Step 35

30

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 41

Go to Step 36

31

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 41

Go to Step 38

32

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 41

Go to Step 39

33

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 41

Go to Step 37

34

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 41

Go to Step 40

35

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 41

--

36

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 41

--

37

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 41

--

38

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 41

--

39

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

Replace the HVAC control module. Refer to Heater and Air Conditioning Control Replacement .

Did you complete the replacement?

Go to Step 41

--

40

Important: Program the PCM.

Replace the PCM. Refer to one of the following procedures:

    •  Powertrain Control Module Replacement in Engine Controls-4.3L
    •  Powertrain Control Module Replacement in Engine Controls-4.8L, 5.3L, and 6.0L
    •  Powertrain Control Module Replacement in Engine Controls-8.1L

Did you complete the replacement?

Go to Step 41

--

41

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 4