For 1990-2009 cars

Perform one of the following procedures in order to attain temperature control:

• | Adjust the wobble plate in the V5 compressor (Buick).

• | Run the A/C compressor (Oldsmobile).

• | Direct the system air either through or around the heater core.

When the A/C compressor is not running, the air flowing through the system may be heated above the outside air temperature. The air may not be dehumidified or cooled below the outside air temperature. When the A/C compressor is running, the following changes occur to the air flowing through the system:

• | The air is cooled.

• | The air is dehumidified.

• | The air is heated in order to bring the vehicle interior to the desired temperature.

When the A/C is requested, the heater and A/C programmer send a request for the A/C compressor to the powertrain control module (PCM). The compressor is turned on when the following conditions exist:

• | The outside temperature is above 5°C (41°F).

• | The PCM does not sense a low refrigerant level condition.

• | The system is in any operating mode except for the following modes:

• | OFF

• | ECON

• | VENT

The system air is then cooled and dehumidified.