HVAC Compressor Clutch Does Not Engage. Buick GL7 (Export) 2000

For 1990-2009 cars

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
DEFINITION: A/C compressor clutch will not engage when an A/C request has been made and no Powertrain DTC are set.
1 | Did you review the Compressor Controls Circuit Description and perform the necessary inspections? | -- | Go to Step 2 | Go to Symptoms
2 | Verify that the HVAC compressor clutch does not engage. Does the HVAC compressor clutch operate normally? | -- | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3

3

1. Turn the ignition switch to the OFF position.
2. Install both the high and low A/C freon pressure gages.
3. Read the freon pressure with the engine off.

• | Freon pressure in the high and low sides should equal each other after the A/C system has come to rest.

• | Freon pressure will fluctuate depending on ambient temperature.

• | Proper clutch operation depends on correct refrigerant charge, low freon charge will shut off A/C compressor operation.

Are the high and low side freon pressures below the specified value?

345 kPa (50 psi)

Go to Leak Testing in Heating, Ventilation and Air Conditioning

Go to Step 4

4 | Are the high and low side freon pressures above the specified value? | 690 kPa (100 psi) | Go to Step 5 | Go to Step 6
5 | Evacuate and recharge the A/C system according to proper freon fill specifications. Has the A/C system been recharged properly? | -- | Go to Step 25 | --
6 | Check for a short to ground in circuit 59. Refer to Circuit Testing in Wiring Systems. Is a short present? | -- | Go to Step 7 | Go to Step 8
7 | Repair a short to ground in circuit 59 between the underhood accessory wiring junction block and the A/C compressor clutch coil. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Step 25 | --

8

1. Remove the A/C CLU relay from the underhood accessory wiring junction block.
2. Disconnect the A/C compressor clutch coil connector. Refer to Air Conditioning Clutch Coil Removal .
3. Connect a 10A fused jumper between the ignition feed terminal for the switch side of the A/C CLU relay and underhood accessory wiring junction block connector C1 terminal F8.
4. Connect a DMM between the A/C compressor clutch coil connector terminal B and ground. Refer to Circuit Testing in Wiring Systems.
5. Turn the ignition switch to the RUN position.
6. Measure the available voltage at the A/C compressor clutch coil connector terminal B.

Is the voltage within the specified values?

B+

Go to Step 10

Go to Step 9

9 | Repair a poor connection or an open in circuit 59. Refer to Wiring Repairs or Connector Repairs in Wiring Systems. Is the repair complete? | -- | Go to Step 25 | --
10 | Using a DMM, measure for continuity between terminal B of the A/C compressor clutch coil connector and ground. Refer to Circuit Testing in Wiring Systems. Is the resistance to ground less than the specified value? | 0 - 2 ohms | Go to Step 12 | Go to Step 11
11 | Repair a poor connection or an open in circuit 1050. Refer to Wiring Repairs or Connector Repairs in Wiring Systems. Is the repair complete? | -- | Go to Step 25 | --

12

1. Disconnect the Powertrain Control Module (PCM) connector C2.
2. Reinstall the A/C CLU relay.
3. Connect a 10A fused jumper between the PCM connector C2 terminal 39 and ground.
4. Turn the ignition switch to the RUN position.
5. Using a DMM, measure the voltage between the A/C compressor clutch coil connector terminal B and ground. Refer to Circuit Testing in Wiring Systems.

Is the voltage within the specified values?

B+

Go to Step 13

Go to Step 14

13

1. Remove the fused jumper from the PCM connector C2 terminal 39 and ground.
2. Reconnect the A/C compressor clutch coil connector. Refer to Air Conditioning Clutch Coil Installation .
3. Reinstall the fused jumper between the PCM connector C2 terminal 39 and ground.
4. Turn the ignition on.

Does the A/C compressor clutch engage?

--

Go to Cooling Insufficient - Air Conditioning (A/C) System

Go to Step 24

14

1. Turn the ignition switch to the OFF position.
2. Remove the A/C CLU relay.
3. Using a DMM, measure for continuity between the PCM connector C2 terminal 39 and the underhood accessory wiring junction block connector C1 terminal F7. Refer to Circuit Testing in Wiring Systems.

Is there continuity?

0 - 2 ohms

Go to Step 16

Go to Step 15

15 | Repair a poor connection or an open in circuit 459. Refer to Wiring Repairs or Connector Repairs in Wiring Systems. Is the repair complete? | -- | Go to Step 25 | --
16 | Replace the A/C CLU relay and retest the A/C system. Refer to Compressor Relay Replacement . Does replacing the A/C CLU relay correct the concern? | -- | Go to Step 25 | Go to Step 17

17

1. Disconnect the heater-A/C control connector C2.
2. Connect a DMM between the PCM connector C2 terminal 22 and the heater-A/C control connector C2 terminal B. Refer to Circuit Testing in Wiring Systems.
3. Measure circuit 762 for resistance between these two connectors.

Is circuit 762 resistance between the specified values?

0 - 2 ohms

Go to Step 19

Go to Step 18

18 | Repair a poor connection or an open in circuit 762. Refer to Wiring Repairs or Connector Repairs in Wiring Systems. Is the repair complete? | -- | Go to Step 25 | --

19

1. Connect a DMM, between the PCM connector C2 terminal 22 and ground. Refer to Circuit Testing in Wiring Systems.
2. Measure circuit 762 for continuity to ground.

Is circuit 762 continuous to ground?

--

Go to Step 20

Go to Step 21

20 | Repair a short to ground in circuit 762. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Step 25 | --

21

1. Disconnect the DMM.
2. Reconnect all connectors back to their respective modules.
3. Install the scan tool to the diagnostic link connector.
4. Start the engine and allow it to idle in park.
5. Select the area of the scan tool which will read HVAC button output status.
6. Depress the A/C button on/off several times.

Does the scan tool read the A/C request being sent by the HVAC control head?

--

Go to Step 22

Go to Step 23

22

1. Check connections between the PCM and the underhood accessory wiring junction block.

Important: Perform the reprogramming procedure for the PCM.

2. If OK, replace the PCM.

Is the repair complete?

--

Go to Step 25

--

23 | Replace the heater-A/C control. Refer to HVAC Module Assembly Replacement . Is the repair complete? | -- | Go to Step 25 | --
24 | Replace the A/C compressor clutch coil. Refer to Air Conditioning Clutch Coil Replacement . Is the repair complete? | -- | Go to Step 25 | --

25

1. Turn the ignition switch to the OFF position.
2. Reconnect all connectors/components disconnected.
3. Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 3