GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Classic 🢒 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 air conditioning (A/C) compressor relay output is disabled if engine coolant temperature (ECT) is above 121°C (250°F). The engine coolant indicator will illuminate at this temperature.

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

Step

Action

Values

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

DEFINITION: The air conditioning (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 Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Start the engine.
  2. Observe the coolant temperature indicator.

Is the engine coolant temperature (ECT) indicator illuminated?

--

Go to Engine Coolant Temperature Indicator Always On in Engine Cooling

Go to Step 3

3

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 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, then allow the A/C system to equalize for about 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 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
  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 ACR 2000.

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

--

Go to Step 6

Go to Step 19

6

Is the HVAC control assembly inoperative?

--

Go to Step 10

Go to Step 7

7
  1. Start the engine.
  2. With a scan tool, observe the A/C Request parameter in the body control module (BCM) data list 2.
  3. Place the blower motor switch in the maximum position.
  4. Place the mode switch in the VENT position.
  5. 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 8

Go to Step 12

8

With a scan tool, observe the A/C Relay Commanded parameter in the Powertrain data list 2.

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

--

Go to Step 9

Go to Step 29

9

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 13

Go to Step 15

10

Test the ignition 3 voltage circuit 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 36

Go to Step 11

11

Test the ground circuit to the HVAC control assembly 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 27

12
  1. Start the engine.
  2. Place the A/C request switch in the ON position.
  3. Measure the voltage on the request circuit at the BCM to a good ground.

Does the voltage measure near the specified value?

12 V

Go to Step 28

Go to Step 17

13
  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 14

Go to Step 22

14
  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 25

Go to Step 18

15
  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 16

Go to Step 21

16
  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 25

Go to Step 23

17

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 complete the repair?

--

Go to Step 36

Go to Step 27

18

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 20

19

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 36

Go to Step 24

20

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 26

21

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

--

22

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

--

23

Test the control circuit of the A/C compressor clutch relay for an open or 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 29

24

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 36

Go to Step 30

25

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 31

26

Inspect for poor connections at the harness connector of the A/C compressor clutch coil. 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

27

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 36

Go to Step 33

28

Inspect for poor connections at 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 36

Go to Step 34

29

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

30

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 36

--

31

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 36

--

32

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

Did you complete the replacement?

--

Go to Step 36

--

33

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

Did you complete the replacement?

--

Go to Step 36

--

34

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 36

--

35

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 36

--

36

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 4