GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2005 🢒 Sunfire 🢒 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 A/C compressor relay output is disabled if engine coolant temperature is above 121°C (250°F).

  1. There are two A/C request outputs from the HVAC control assembly. One request comes from the mode switch when in defrost or recirculation mode and the other request comes from the A/C switch. If there is an open in the A/C request circuit before the splice, the A/C may operate from the mode switch, but not from the A/C switch or vice versa.

    2.

  2. 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.

    3.

  3. Be sure to check both of the request circuits before the splice.

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 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. 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 in Engine Cooling

3

Important: The outside air temperature must be above 3°C (36°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.
  5. Cycle the mode switch through each position except OFF.

Does the A/C compressor operate in each mode position?

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

Go to Step 4

4

Does the A/C compressor operate with the mode switch in the defrost or recirculation positions?

Go to Step 5

Go to Step 6

5

Place the mode switch to the vent position.

Does the A/C compressor operate?

Go to Step 6

Go to Step 20

6
  1. Park the vehicle inside or in the shade.
  2. Open the windows in order to ventilate the interior of the vehicle.
  3. Turn OFF the ignition.
  4. Install the J 43600 ACR 2000.
  5. Record the outside air temperature at the vehicle.
  6. Record readings of the low and high side STATIC pressures.
  7. 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 specification for the ambient air temperature, and within 103 kPa (15 psi) of each other?

Go to Step 7

Go to Leak Testing in Heating, Ventilation and Air Conditioning

7
  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 8

Go to Step 22

8

Is the HVAC control assembly inoperative?

Go to Step 13

Go to Step 9

9
  1. Start the engine.
  2. With a scan tool, observe the A/C Request parameter in the Powertrain data list 2.
  3. Place the blower motor switch in the maximum position.
  4. Place the mode switch in the recirculation position.

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

Go to Step 10

Go to Step 15

10

Does the A/C request indicator illuminate?

Go to Step 11

Go to Step 25

11

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

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

Go to Step 12

Go to Step 34

12

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 16

Go to Step 18

13

Test the ignition 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 41

Go to Step 14

14

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 41

Go to Step 32

15
  1. Start the engine.
  2. Place the mode switch in the MAX A/C position.
  3. Probe the A/C request signal circuit at the body control module (BCM) with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 33

Go to Step 20

16
  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 17

Go to Step 26

17

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 21

18
  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 19

Go to Step 24

19
  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 27

20

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 41

Go to Step 28

21

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 41

Go to Step 23

22

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 41

Go to Step 29

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 41

Go to Step 31

24

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 41

--

25

Test the off blower motor control circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 41

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 41

--

27

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 41

Go to Step 34

28

Test the heater blower relay supply voltage circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 41

Go to Step 32

29

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 41

Go to Step 35

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 41

Go to Step 36

31

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 41

Go to Step 37

32

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 41

Go to Step 38

33

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 41

Go to Step 39

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 41

Go to Step 40

35

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 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 41

--

37

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

Did you complete the replacement?

Go to Step 41

--

38

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

Did you complete the replacement?

Go to Step 41

--

39

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 41

--

40

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 41

--

41

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 4