GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2007 🢒 Lucerne 🢒 HVAC 🢒 HVAC - 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 124°C (255°F).

  1. Placing the fan switch in the ON position, 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 module 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 perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install a scan tool.
  2. Start the engine.
  3. With a scan tool, observe the Engine Coolant Temperature Sensor (ECT) parameter in the Powertrain data list.

Does the scan tool indicate that the ECT parameter is above the specified temperature?

Go to Engine Overheating

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

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. Turn OFF the ignition.
  4. Install the J 43600 ACR 2000 Air Conditioning Service Center.
  5. Record the ambient 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 .

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

5
  1. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, observe the A/C High Side Pressure parameter in the Powertrain Control Module engine data 2 list.
  3. Compare the A/C High Side Pressure on the scan tool to the high side pressure value on the J 43600 .

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

Go to Step 6

Go to Step 16

6

Is the HVAC control module inoperative?

Go to Step 15

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 engine data 2 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 8

Go to Step 27

8

With a scan tool, observe the A/C Relay Command status in the powertrain control module (PCM) data list.

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

Go to Step 9

Go to Step 28

9

With a scan tool, command the A/C 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 10

10
  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 battery positive voltage 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 11

Go to Step 23

11
  1. Connect a test lamp between the A/C compressor clutch relay control circuit of the A/C compressor clutch relay and the coil side battery positive voltage supply circuit of the A/C compressor clutch relay.
  2. With a scan tool, command the A/C Relay ON and OFF.

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

Go to Step 25

Go to Step 12

12

Does the test lamp remain illuminated with each command?

Go to Step 19

Go to Step 18

13
  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Probe the switch side battery positive voltage 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

Connect a 10-amp fused jumper wire between the switch side battery positive 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 25

Go to Step 20

15

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 .

Did you find and correct the condition?

Go to Step 34

Go to Step 17

16

Test the ground circuit of the A/C refrigerant pressure sensor for an open. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 34

Go to Step 24

17

Test the ground circuit of the HVAC control module for an open. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 34

Go to Step 27

18

Test the A/C compressor clutch relay control circuit of the A/C compressor clutch relay for an open. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 34

Go to Step 28

19

Test the A/C compressor clutch relay control circuit of the A/C compressor clutch relay for a short to ground. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 34

Go to Step 28

20

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

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

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 34

Go to Step 21

21

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

Did you find and correct the condition?

Go to Step 34

Go to Step 26

22

Repair the switch side battery positive voltage circuit of the A/C compressor clutch relay. Refer to Wiring Repairs .

Did you complete the repair?

Go to Step 34

--

23

Repair the coil side battery positive voltage circuit of the A/C compressor clutch relay. Refer to Wiring Repairs .

Did you complete the repair?

Go to Step 34

--

24

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 .

Did you find and correct the condition?

Go to Step 34

Go to Step 29

25

Inspect for poor connections at the A/C compressor clutch relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 34

Go to Step 30

26

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 .

Did you find and correct the condition?

Go to Step 34

Go to Step 31

27

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 .

Did you find and correct the condition?

Go to Step 34

Go to Step 32

28

Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 34

Go to Step 33

29

Replace the A/C refrigerant pressure sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement .

Did you complete the replacement?

Go to Step 34

--

30

Replace the A/C compressor clutch relay. Refer to Relay Replacement .

Did you complete the replacement?

Go to Step 34

--

31

Replace the A/C compressor clutch. Refer to Air Conditioning Compressor Replacement .

Did you complete the replacement?

Go to Step 34

--

32

Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 34

--

33

Replace the PCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 34

--

34

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 4