GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2003 🢒 Savana 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 HVAC Compressor Clutch Does Not Engage

Diagnostic Aids

The engine is idling at a low unstable RPM.

Test Description

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

  1. The A/C compressor output is disabled if the engine is idling at a low unstable RPM.

    2.

  2. The A/C compressor relay output is disabled if engine coolant temperature is above 121°C (250°F).

  1. The HVAC control assembly is inoperative when the assembly does not respond to any operator control requests.

Step

Action

Value

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

DEFINITION: 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 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. Set the parking brake.
  3. Place the vehicle in drive and allow the engine to idle.
  4. Observe the engine RPM.

Does the engine idle at a steady RPM?

--

Go to Step 3

Go to Rough, Unstable, or Incorrect Idle and Stalling in Engine Controls - 4.8L, 5.3L, and 6.0L or Rough, Unstable, or Incorrect Idle and Stalling in Engine Controls - 4.3L

3

  1. Install a scan tool.
  2. Start the engine.
  3. With a scan tool, observe the ECT parameter in the Powertrain data list.

Does the scan tool indicate that the ECT parameter is below 121°C (250°F)?

--

Go to Step 4

Go to Engine Overheating in Engine Cooling

4

Important: 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 5

5
  1. Park the vehicle inside or in the shade.
  2. Open the windows in order to ventilate the interior of the vehicle.
  3. If the A/C system was operating, allow the A/C system to equalize for approximately 2 minutes.
  4. Turn OFF the ignition.
  5. Install the J 43600 ACR 2000.
  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 6

Go to Leak Testing in Heating, Ventilation and Air Conditioning

6

Is the HVAC control assembly inoperative?

--

Go to Step 8

Go to Step 7

7
  1. Start the engine.
  2. With a scan tool, observe the A/C Request Signal parameter in the Engine Data 2 data list.
  3. Place the A/C request switch in the ON position.

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

--

Go to Step 10

Go to Step 11

8

Test the voltage supply circuits to the HVAC control assembly for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 42

Go to Step 9

9

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

Did you find and correct the condition?

--

Go to Step 42

Go to Step 33

10

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

--

Go to Step 17

Go to Step 12

11
  1. Turn OFF the ignition.
  2. Disconnect the A/C high pressure switch.
  3. Connect a 3-amp fused jumper wire 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 parameter is YES?

--

Go to Step 34

Go to Step 13

12
  1. Turn OFF the ignition.
  2. Disconnect the A/C low pressure switch.
  3. Connect a 3-amp fused jumper wire between the A/C low pressure switch signal and ground circuit of the A/C low pressure switch.
  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 31

Go to Step 15

13
  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, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 42

Go to Step 14

14

Measure the voltage from the A/C request signal circuit at the PCM.

Does the voltage measure near the specified value?

B+

Go to Step 35

Go to Step 33

15

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

Did you find and correct the condition?

--

Go to Step 42

Go to Step 16

16

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

Did you find and correct the condition?

--

Go to Step 42

Go to Step 35

17

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 18

Go to Step 20

18
  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 a good ground.

Does the test lamp illuminate?

--

Go to Step 19

Go to Step 28

19

Connect a 10-amp fused jumper wire between the switch side voltage circuit of the A/C compressor clutch relay and the A/C compressor clutch supply voltage circuit of the A/C compressor clutch.

Does the A/C compressor clutch engage?

--

Go to Step 30

Go to Step 23

20
  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 a good ground.

Does the test lamp illuminate?

--

Go to Step 21

Go to Step 27

21
  1. Connect a test lamp between the control circuit of the A/C compressor clutch relay 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 30

Go to Step 22

22

Does the test lamp remain illuminated with each command?

--

Go to Step 25

Go to Step 26

23

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

Did you find and correct the condition?

--

Go to Step 42

Go to Step 24

24

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

Did you find and correct the condition?

--

Go to Step 42

Go to Step 32

25

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

Did you find and correct the condition?

--

Go to Step 42

Go to Step 35

26

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

Did you find and correct the condition?

--

Go to Step 42

Go to Step 35

27

Repair the coil side voltage supply circuit of the A/C compressor clutch relay for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 42

--

28

Test 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 42

--

29

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

Did you complete the repair?

--

Go to Step 42

--

30

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 42

Go to Step 36

31

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 Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 42

Go to Step 37

32

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 42

Go to Step 39

33

Inspect for poor connections at the harness connector of the HVAC control assembly. 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 42

Go to Step 40

34

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 Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 42

Go to Step 38

35

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 42

Go to Step 41

36

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 42

--

37

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 42

--

38

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 42

--

39

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

Did you complete the replacement?

--

Go to Step 42

--

40

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

Did you complete the replacement?

--

Go to Step 42

--

41

Important:  Perform the programming procedure for 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

Did you complete the replacement?

--

Go to Step 42

--

42

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 5