GM Service Manual Online
For 1990-2009 cars only

Air enters the heater and ventilation system where it is heated as necessary before being discharged through the proper ducts and outlets into the passenger compartment. Within the heater case, doors guide the airflow in response to the positions of the temperature lever and the mode lever in the heater control unit.

The mode lever operates the air flow control doors. The doors route the heated, unheated, fresh, or recirculated air through the various ducts and outlets. The following list identifies the duct locations:

    • The right IP duct
    • The left IP duct
    • The center IP duct
    • The right window defroster duct
    • The left window defroster duct
    • The windshield defroster nozzle duct
    • The center floor duct

The following list identifies the outlet locations:

    • The right IP louver
    • The left IP louver
    • The center IP louver
    • The right window outlet
    • The left window outlet
    • The right windshield defroster nozzle
    • The left windshield defroster nozzle