GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2004 🢒 GTO 🢒 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 2 A/C request outputs from the HVAC control assembly. One request comes from the mode switch when in the defrost mode and the other request comes from the A/C switch.

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 HVAC Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Manual

2

  1. Install a scan tool.
  2. Start the engine.
  3. Observe the ECT parameter.

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.

Does the A/C compressor operate?

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

Go to Step 4

4

Place the mode switch to the defrost position.

Does the A/C compressor operate?

Go to Step 18

Go to Step 5

5
  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.

Are the pressure values within specification for the ambient air temperature, and within 103 kPa (15 psi) of each other?

Go to Step 6

Go to Leak Testing in Heating, Ventilation and Air Conditioning

6
  1. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, observe the A/C high side pressure sensor parameter.
  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 7

Go to Step 21

7
  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. With a scan tool, observe the A/C request parameter.

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

Go to Step 9

Go to Step 8

8

  1. Stop the engine.
  2. Disconnect the body control module (BCM) connector C3.
  3. Start the engine.
  4. Place the blower motor switch in the maximum speed position.
  5. Place the A/C request switch in the ON position.
  6. Place the air temperature switch in the coldest position.
  7. Probe the A/C request signal circuit at the BCM connector with a test lamp that is connected to ground.

Does the test lamp illuminate?

Go to Step 28

Go to Step 18

9

Does the A/C request indicator illuminate?

Go to Step 11

Go to Step 10

10
  1. Stop the engine.
  2. Disconnect the BCM connector C1.
  3. Start the engine.
  4. Place the blower motor switch in the maximum speed position.
  5. Place the A/C request switch in the ON position.
  6. Place the air temperature switch in the coldest position.
  7. Probe the A/C request indicator signal circuit at the BCM connector with a test lamp that is connected to ground.

Does the test lamp illuminate?

Go to Step 28

Go to Step 19

11

With a scan tool, observe the A/C relay command parameter.

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

Go to Step 12

Go to Step 29

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 13

Go to Step 16

13
  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch.
  3. Connect a test lamp between the A/C compressor clutch supply voltage and ground circuits.
  4. With a scan tool, command the A/C compressor clutch relay ON and OFF.

Does the test lamp illuminate with each command?

Go to Step 24

Go to Step 14

14

Test the A/C compressor clutch supply voltage circuits 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 15

15

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

--

16

Test the A/C compressor clutch relay supply voltage circuits 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 17

17

Test the A/C compressor clutch relay control circuit 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 25

18

Test the A/C request signal circuit 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

19

Test the A/C request indicator circuit 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 20

20

Test the A/C switch supply voltage circuit 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 27

21

Test the ground circuit of the A/C refrigerant pressure sensor 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 22

22

Test the signal circuit of the A/C refrigerant pressure sensor 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 23

23

Test the supply voltage circuit of the A/C refrigerant pressure sensor 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

24

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 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 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 32

27

Inspect for poor connections at the harness connector of the A/C switch 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 compressor clutch coil. Refer to Air Conditioning Compressor 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 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

--

33

Replace the HVAC control assembly. Refer to Compressor Relay Replacement in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

Go to Step 36

--

34

Replace the BCM. Refer to Body Control Module Replacement in Body Control System.

Did you complete the replacement?

Go to Step 36

--

35

Important: The replacement PCM must be programmed.

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 2