HVAC Compressor Clutch Does Not Engage. Buick Century 2004

For 1990-2009 cars only

Makes 🢒 Buick 🢒 2004 🢒 Century 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 HVAC Compressor Clutch Does Not Engage

Test Description

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

The A/C compressor relay output is disabled if engine coolant temperature is above 121°C (250°F) for the L36/L67 and 124°C (255°F) for the LG8.

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 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

Values

Yes

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.

Did you perform the HVAC Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Manual

Install a scan tool.
Start the engine.
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?

3.1 L (LG8) 124°C (255°F)

3.8 L (L36/L67) 121°C (250°F)

Go to Engine Overheating in Engine Cooling

Go to Step 3

Important: The 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, then allow the A/C system to equalize for approximately 2 minutes.
Turn OFF the ignition.
Install the J 43600 .
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 parameter in the Powertrain Control Module engine data 2 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 18

Is the HVAC control module inoperative?

Go to Step 17

Go to Step 7

Start the engine.
With a scan tool, observe the A/C Request Signal parameter in the Powertrain Control Module engine 2 data list.
Place the air temperature switch in the coldest position.
Turn the blower motor to the ON position.
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 11

Go to Step 8

Does the A/C request indicator illuminate?

Go to Step 10

Go to Step 9

Important: The blower motor must be in the ON position for this step.

Turn ON the ignition.
Check the blower motor off circuit for short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?