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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Equinox 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 HVAC Compressor Clutch Does Not Engage

Diagnostic Aids

The refrigerant temperature at the temperature sensor in the thermal expansion valve (TXV) controls cycling of the compressor clutch to prevent freezing of the evaporator core. The compressor is disabled when the temperature goes below 3°C (37°F) and vehicle speed is greater than 5 mph (8 km/h). The compressor is enabled when the temperature exceeds 4°C (40°F). The minimum cycling time OFF is 4 seconds. Refer to Air Temperature Description and Operation for a voltage temperature value table of the evaporator temperature sensor.

Test Description

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

  1. The A/C compressor relay output is disabled if the engine coolant temperature is above 96°C (205°F).

    2.

  2. Place the mode switch in any position except OFF, and place the air temperature control switch in a cold setting. Use the bi-level mode for consistent testing of the A/C system operation.

    3.

  3. The HVAC control module is inoperative if the module does not respond to any operator control requests.

    4.

  4. The compressor is disabled when the evaporator temperature goes below 3°C (38°F).

    5.

  5. Check the connection by removing and securely reinstalling before replacement of the HVAC control is considered.

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 if an A/C request has been made, and a powertrain DTC has not been set.

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Install a scan tool.
  2. Start the engine.
  3. Observe the Electronic Temperature Control (ETC) parameter in the Engine Control Data General Info-Inputs data list.

Does the scan tool indicate that the ECT parameter is above 96°C (205°F)?

Go to Engine Overheating in Engine Cooling

Go to Step 3

3

Important: For A/C compressor operation, the evaporator 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 clutch 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, then wait for approximately 2 minutes.
  4. Turn OFF the ignition.
  5. Install the J 43600 ACR 2000 Air Conditioning Service Center.
  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 the 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 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 control module (PCM) data list
  3. Compare the scan tool A/C High Side Pressure parameter to the high side pressure values on the ACR 2000.

Are the high side pressure values within 103 kPa (15 psi) of each other?

Go to Step 6

Go to Step 24

6

Is the HVAC control module inoperative?

Go to Step 16

Go to Step 7

7
  1. Start the engine.
  2. With a scan tool, observe the A/C Request Signal parameter in the powertrain control module (PCM) data list.
  3. Place the air temperature switch in the coldest position.
  4. 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 10

Go to Step 8

8
  1. Start the engine.
  2. With a scan tool, observe the A/C Request parameter in the body control module (BCM) data list.
  3. Place the air temperature switch in the coldest position.
  4. 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 9

Go to Step 18

9
  1. Turn OFF the ignition.
  2. Test the A/C request signal circuit for the following:
    3. • A short to voltage
    • A high resistance
    • An open

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 43

Go to Step 23

10

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 14

Go to Step 11

11
  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 of the voltage supply circuit with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 12

Go to Step 27

12
  1. Connect a test lamp between the control circuit and the coil side of the voltage supply circuit.
  2. With a scan tool, command the A/C compressor clutch relay ON and OFF in scan tool special functions.

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

Go to Step 29

Go to Step 13

13

Does the test lamp remain illuminated with each command?

Go to Step 21

Go to Step 19

14
  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Probe the switch side of the voltage supply circuit with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 15

Go to Step 26

15
  1. Connect a 10-amp fused jumper between the switch side voltage circuit of the clutch relay and the supply voltage circuit of the clutch.
  2. Turn ON the ignition, with the engine OFF.

Does the A/C compressor clutch engage?

Go to Step 29

Go to Step 22

16

Test the ignition 3 voltage circuit of the HVAC control module for the following:

    • A short to ground
    • A high resistance
    • An open

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 43

Go to Step 17

17

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 43

Go to Step 34

18
  1. Start the engine.
  2. Place the A/C request in the ON position.
  3. Measure the voltage on the request circuit at the BCM to a good ground.

Does the value measure near battery voltage?

Go to Step 31

Go to Step 20

19

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 43

Go to Step 35

20

Test the A/C request signal circuit for the following:

    • A short to ground
    • A high resistance
    • An open

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 43

Go to Step 23

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 43

Go to Step 35

22

Test the supply voltage circuit at the A/C compressor clutch relay for the following:

    • A short to ground
    • A high resistance
    • An open

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 43

Go to Step 25

23

View the evaporator voltage in the BCM scan tool data list under A/C sensor. Refer to Air Temperature Description and Operation for the evaporator sensor temperature to voltage conversion chart.

Is the Evaporator Voltage parameter greater than the voltage range of 2.45-2.55 volts which equals a temperature range of 36-38°F?

Go to Step 24

Go to Step 32

24

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

Did you find and correct the condition?

Go to Step 43

Go to Step 28

25

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

Did you find and correct the condition?

Go to Step 43

Go to Step 30

26

Repair the switch side voltage supply circuit of the relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 43

--

27

Repair the coil side of the voltage supply circuit of the relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 43

--

28

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 43

Go to Step 36

29

Inspect for poor connections at the 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 43

Go to Step 38

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 Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 43

Go to Step 39

31

Inspect for poor connections at the harness connector of the BCM. 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 43

Go to Step 41

32

Test the evaporator temperature sensor circuits for the following:

    • A short to ground
    • A high resistance
    • An open

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 43

Go to Step 33

33

Inspect for poor connections at the harness connector of the evaporator low temperature 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 43

Go to Step 34

34

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 43

Go to Step 37

35

Inspect for poor connections at the harness connector of the 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 43

Go to Step 42

36

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 43

--

37

Replace the evaporator low temperature sensor. Refer to Air Conditioning (A/C) Refrigerant Low Temperature Sensor Replacement in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

Go to Step 43

--

38

Replace the relay.

Did you complete the replacement?

Go to Step 43

--

39

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

Did you complete the replacement?

Go to Step 43

--

40

Replace the HVAC control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 43

--

41

Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 43

--

42

Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 43

--

43

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 4