GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2000 🢒 Century (China) 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 HVAC Compressor Clutch Does Not Engage

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Placing the mode switch in any position other than OFF, 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 Compressor Control Schematics

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 review the HVAC operation and perform the necessary inspections?

Go to Step 2

Go to Diagnostic System Check

2

Important: The 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 3

3
  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 approximately 2 minutes.
  4. Turn OFF the ignition.
  5. Install the ACR 2000.
  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 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 4

Go to Leak Testing in Heating, Ventilation and Air Conditioning

4

Is the HVAC control module inoperative?

Go to Step 13

Go to Step 5

5
  1. Start the engine.
  2. With a scan tool, observe the A/C Request parameter in the Engine Data 2 data 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 parameter is YES?

Go to Step 6

Go to Step 23

6

With a scan tool, observe the A/C Relay Command status in the Engine Data 2 data list.

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

Go to Step 7

Go to Step 24

7

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 11

Go to Step 8

8
  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 9

Go to Step 20

9
  1. Connect a test lamp between circuit 459 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 21

Go to Step 10

10

Does the test lamp remain illuminated with each command?

Go to Step 16

Go to Step 15

11
  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 12

Go to Step 19

12
  1. Connect a 10-amp fused jumper wire between the switch side voltage circuit of the A/C compressor clutch relay and circuit 59 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 21

Go to Step 17

13

Test circuit 41 of the HVAC control module 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 29

Go to Step 14

14

Test circuit 1450 of the HVAC control module for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 29

Go to Step 23

15

Test circuit 459 of the A/C compressor clutch relay for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 29

Go to Step 24

16

Test circuit 459 of the A/C compressor clutch relay for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 29

Go to Step 24

17

Test the circuit 59 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 29

Go to Step 18

18

Test circuit 1050 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 29

Go to Step 22

19

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 29

--

20

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 29

--

21

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 29

Go to Step 25

22

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 in Wiring Systems.

Did you find and correct the condition?

Go to Step 29

Go to Step 26

23

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 in Wiring Systems.

Did you find and correct the condition?

Go to Step 29

Go to Step 27

24

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 29

Go to Step 28

25

Replace the A/C compressor clutch relay.

Did you complete the replacement?

Go to Step 29

--

26

Replace the A/C compressor clutch coil. Refer to Air Conditioning Clutch Coil Removal and Air Conditioning Clutch Coil Installation in Heating, Ventilation, and Air Conditioning.

Did you complete the replacement?

Go to Step 29

--

27

Replace the HVAC control module. Refer to Control Assembly Replacement .

Did you complete the replacement?

Go to Step 29

--

28

Important: Perform the programming procedure for the PCM.

Replace the PCM. Refer to Powertrain Control Module Replacement/Programming in Engine Controls-2.5L and 3.0L

Did you complete the replacement?

Go to Step 29

--

29

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3