HVAC Compressor Clutch Does Not Engage. Buick Century 2001

For 1990-2009 cars only

Makes 🢒 Buick 🢒 2001 🢒 Century 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 HVAC Compressor Clutch Does Not Engage

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

The A/C compressor relay output is disabled if engine coolant temperature is above 124°C (255°F) for the LG8 and 121°C (250°F) for the L36.

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.

The HVAC control assembly 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

Values

Yes

Schematic Reference: HVAC 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.

Did you perform the HVAC Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Automatic

Install a scan tool.
Start the engine.
With a scan tool, observe the engine coolant temperature (ECT) parameter in the Powertrain data list.

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

3.1L (LG8) 124°C (255°F)

3.8L (L36) 121°C (250°F)

Go to Engine Overheating in Engine Cooling

Go to Step 3

Important: Ambient air temperature must be above 3°C (38°F).

Start the engine.
Place the blower motor switch in the maximum speed position.
Place the A/C request switch in the ON position.
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

Park the vehicle inside or in the shade.
Open the windows in order to ventilate the interior of the vehicle.
If the A/C system was operating, allow the A/C system to equalize for approximately 2 minutes.
Turn OFF the ignition.
Install the J 43600 ACR 2000.
Record the ambient air temperature at the vehicle.
Record readings of the low and high side STATIC pressures.
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 specifications for the ambient air temperature, and within 103 kPa (15 psi) of each other?

Go to Step 5

Go to Leak Testing in Heating, Ventilation and Air Conditioning

Turn ON the ignition, with the engine OFF.
With a scan tool, observe the A/C high side pressure sensor parameter in the powertrain data list.
Compare the A/C high side pressure on the scan tool to the high side pressure value on the ACR2000.

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

Go to Step 6

Go to Step 16

Is the HVAC control assembly inoperative?

Go to Step 15

Go to Step 7

Start the engine.
With a scan tool, observe the A/C Request parameter in the Powertrain data list.
Place the air temperature switch in the coldest position.
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 8

Go to Step 27

With a scan tool, observe the A/C Relay Command status in the Powertrain Data List.

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

Go to Step 9

Go to Step 28

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 10

Turn OFF the ignition.
Disconnect the A/C compressor clutch relay.
Turn ON the ignition, with the engine OFF.
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 11

Go to Step 23

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.
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 25

Go to Step 12

Does the test lamp remain illuminated with each command?

Go to Step 19

Go to Step 18

Turn OFF the ignition.
Disconnect the A/C compressor clutch relay.
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 14

Go to Step 22

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.
Turn ON the ignition, with the engine OFF.

Does the A/C compressor clutch engage?

Go to Step 25

Go to Step 20

Test the ignition 3-voltage circuit 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?