GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Corvette 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 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).

  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.

Step

Action

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

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 review the HVAC operation and perform the necessary inspections?

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Manual

2

  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 3

Go to Engine Overheating

3

Important: For A/C compressor operation, 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 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 .
  6. Record the ambient air 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 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
  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 within 103 kPa (15 psi) of each other?

Go to Step 6

Go to Step 18

6

Is the HVAC control module inoperative?

Go to Step 17

Go to Step 7

7
  1. Start the engine.
  2. With a scan tool, observe the A/C Request parameter in the Powertrain data list.
  3. Place the air temperature switch in the coldest position.
  4. Turn the blower motor to the on position.
  5. Place the A/C request switch in the ON position.

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

Go to Step 11

Go to Step 8

8

Does the A/C request indicator illuminate?

Go to Step 10

Go to Step 9

9

Important: The blower motor must be in the ON position for this step.

  1. Turn the ignition ON.
  2. Test the blower motor off circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 36

Go to Step 29

10
  1. Turn OFF the ignition.
  2. 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 36

Go to Step 30

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 15

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 a good ground.

Does the test lamp illuminate?

Go to Step 13

Go to Step 25

13
  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 27

Go to Step 14

14

Does the test lamp remain illuminated with each command?

Go to Step 21

Go to Step 20

15
  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 16

Go to Step 24

16
  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 27

Go to Step 22

17

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 36

Go to Step 19

18

Test the ground circuit of the A/C refrigerant 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 36

Go to Step 26

19

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 36

Go to Step 29

20

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 36

Go to Step 30

21

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 36

Go to Step 30

22

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 36

Go to Step 23

23

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 36

Go to Step 28

24

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 36

--

25

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 36

--

26

Inspect for poor connections at the harness connector of the A/C refrigerant 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 36

Go to Step 31

27

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 36

Go to Step 32

28

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 35

Go to Step 33

29

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 36

Go to Step 34

30

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 36

Go to Step 35

31

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

Did you complete the replacement?

Go to Step 36

--

32

Replace the A/C compressor clutch relay.

Did you complete the replacement?

Go to Step 36

--

33

Replace the A/C compressor clutch coil. Refer to Compressor Clutch Plate and Hub Assembly Removal and Compressor Clutch Plate/Hub Assembly Install in Heating, Ventilation, and Air Conditioning.

Did you complete the replacement?

Go to Step 36

--

34

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

Did you complete the replacement?

Go to Step 36

--

35

Important:  Perform the reprogramming procedure for the PCM.

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls.

Did you complete the replacement?

Go to Step 36

--

36

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 4