GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Oldsmobile 🢒 2001 🢒 Aurora 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 HVAC Compressor Clutch Does Not Engage

Diagnostic Aids

The Mitsubishi scroll type A/C compressor carries an internal thermal cut off switch. The thermal cut off switch normal operation is to open and disable the compressor under extreme load and temperatures above 155°C (311°F). The internal thermal cut off switch is non-serviceable.

Test Description

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

  1. Placing the mode switch in any position other than OFF, along with placing the air temperature control switch in a cold setting, activates A/C operation. For the purpose of this and future steps where A/C operation is necessary, bi-level mode is used for consistent testing.

    2.

  2. The HVAC control assembly is inoperative when the module does not respond to any operator control requests to enable the A/C compressor. The blower motor may still operate independent of the A/C controls.

    3.

  3. The A/C compressor relay output is disabled if engine coolant temperature is above 121°C (250°F) for the LX5 and 126°C (259°F) for the L47.

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

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 mode switch in the defrost 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 3

3
  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, then allow the A/C system to equalize (about 2 minutes).
  4. Turn OFF the ignition.
  5. Install the J 43600 ACR 2000.
  6. Record the ambient air temperature at the vehicle.
  7. Record readings of the low and high side STATIC pressures.
  8. Compare the low and high side pressure values with the allowable limits for the recorded ambient air temperature. Refer to Air Conditioning (A/C) System Performance Test in Heating, Ventilation and Air Conditioning.

Are the low and high side pressure values within the allowable limits for the recorded ambient air temperature, and within 103 kPa (15 psi) of each other?

Go to Step 4

Go to Leak Testing in Heating, Ventilation and Air Conditioning

4
  1. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, observe the A/C High Side pressure sensor parameter in the powertrain data list
  3. Compare the A/C high side pressure on the scan tool to the high side pressure value on the ACR2000.

Are the high side pressure values with 103 kpa (15 psi) of each other?

Go to Step 5

Go to Step 20

5

Is the HVAC control module inoperative?

Go to Step 19

Go to Step 6

6
  1. Start the engine.
  2. With a scan tool, observe the Commanded A/C parameter in the Powertrain data list.
  3. Place the air temperature switch in the coldest position.

Does the scan tool indicate that the Commanded A/C parameter is ON?

Go to Step 13

Go to Step 7

7

With a scan tool, observe the A/C Clutch (Desired) parameter in the DIM A/C Information list.

Does the scan tool indicate that the A/C Clutch (Desired) parameter is ON?

Go to Step 8

Go to Step 9

8

With a scan tool, observe the A/C Clutch (Actual) parameter in the DIM A/C Information list.

Does the scan tool indicate that the A/C Clutch (Actual) parameter is ON?

Go to Step 13

Go to Step 34

9

With a scan tool, observe the Control Head (Desired) parameter in the DIM A/C Information list.

Does the scan tool indicate that the Control Head (Desired) parameter is ON?

Go to Step 10

Go to Step 12

10

With a scan tool, observe the Pressure Status parameter in the DIM A/C Information list.

Does the scan tool indicate that the Pressure Status parameter is Normal?

Go to Step 11

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

11

With a scan tool, observe the Temperature Status parameter in the DIM A/C Information list.

Does the scan tool indicate that the Temperature Status parameter is OK?

Go to Step 31

Go to Engine Overheating in Engine Cooling

12
  1. With a scan tool, observe the A/C Control Head (desired) parameter in the DIM A/C information list.
  2. Place the mode switch in the defrost position.

Does the scan tool indicate that the A/C Control Head (desired) parameter turn ON and OFF with each command?

Go to Step 30

Go to Step 33

13

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 14

14
  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 15

Go to Step 27

15
  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 29

Go to Step 16

16

Does the test lamp remain illuminated with each command?

Go to Step 23

Go to Step 22

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 a good ground.

Does the test lamp illuminate?

Go to Step 18

Go to Step 26

18
  1. 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.
  2. Turn ON the ignition, with the engine OFF.

Does the A/C compressor clutch engage?

Go to Step 29

Go to Step 24

19

Test the ignition 3-voltage circuit of the HVAC control module 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 21

20

Test the ground circuit of the A/C pressure sensor for 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 28

21

Test the ground circuit of the HVAC control module for 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

22

Test the control circuit of the A/C compressor clutch relay for 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 34

23

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 34

24

Test the A/C compressor clutch supply voltage circuit at the A/C compressor clutch 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 25

25

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

26

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 42

--

27

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 42

--

28

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

29

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 38

30

Inspect for poor connections at the instrument panel integration module (IPM). 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 35

31

Inspect for poor connections at the dash integration module (DIM). 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

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 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 42

Go to Step 40

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 Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 42

Go to Step 41

35

Replace the IPM. Refer to Instrument Panel Module Replacement in Body Control Systems.

Did you complete the replacement?

Go to Step 42

--

36

Replace the DIM. Refer to Dash Integration Module Replacement in Body Control Systems.

Did you complete the replacement?

Go to Step 42

--

37

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

Did you complete the replacement?

Go to Step 42

--

38

Replace the A/C compressor clutch relay.

Did you complete the replacement?

Go to Step 42

--

39

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 42

--

40

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

Did you complete the replacement?

Go to Step 42

--

41

Important:  Perform the programming procedure for the PCM.

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls-3.5L or Powertrain Control Module Replacement in Engine Controls-4.0L.

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 3