GM Service Manual Online
For 1990-2009 cars only

The dual zone A/C system performs the following functions:

    â€¢ Heating
    â€¢ Ventilation
    â€¢ Air conditioning

The dual zone A/C system is controlled by vacuum and electronic circuits. Both electronic and vacuum circuits determine air intake and discharge locations. Electronic circuits also control the following functions:

    â€¢ Mode operation
    â€¢ A/C compressor clutch operation
    â€¢ Fan operation
    â€¢ Discharge air temperature

The driver may select any of the following functions from the front HVAC control assembly:

    â€¢ Front interior temperature
    â€¢ Fan speed
    â€¢ One of eight different modes of operation for the front seating area

The passenger may select any of the following functions from the rear HVAC control assembly:

    â€¢ Rear interior temperature
    â€¢ Fan speed
    â€¢ One of five different modes of operation for the rear seating area

The system determines these conditions from the following information:

    â€¢ The temperature that is selected by the driver or the rear passenger (s)
    â€¢ The mode position that is selected by the driver or the rear passenger (s)
    â€¢ Any information that is provided by the system's network of sensors

For more information on the front HVAC control assembly operation. Refer to Control Assembly Description .

For more information on the rear HVAC control assembly operation. Refer to Control Assembly Description .