GM Service Manual Online
For 1990-2009 cars only

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

    • Heating
    • Ventilation
    • 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:

    • Mode operation
    • A/C compressor clutch operation
    • Fan operation
    • Discharge air temperature

The driver may select any of the following functions from the Heater-A/C control:

    • Interior temperature
    • Fan speed
    • One of eight different modes of operation

One of these modes is a fully automatic dual zone mode. In the fully automatic dual zone mode, the system determines the following conditions:

    • Air intake
    • Discharge locations
    • Fan speed
    • Discharge air temperature

The system determines these conditions from the following information:

    • The temperature that is selected by the driver or the passenger
    • Any information that is provided by the system's network of sensors

The passenger temperature control significantly increases or decreases the air discharge temperature on the passenger's side of the vehicle.

The passenger control is on the heater A/C control head. The passenger control is enabled by rotating the passenger temperature knob on the control head.