GM Service Manual Online
For 1990-2009 cars only

Temperature Control Knob


Object Number: 244225  Size: SH

The temperature control knob (1) controls the amount of air flow to the heater core, regulating the temperature of the air entering the vehicle.

When the temperature control knob is moved completely to the left or full COLD (blue) position, the air mix door closes in order to block the flow of air to the heater core.

When the temperature control knob is moved completely to the right or full HOT (red) position, the air mix door opens fully in order to allow the air to flow through the heater core.

Moving the temperature control knob between the full left and right positions allows the driver to adjust the passenger compartment temperature to the most comfortable level.

Mode Control Knob

The mode control knob (5) allows the driver to route the air into the passenger compartment through different outlets. The mode knob enables the selection of the following modes:

    • VENTILATION
       - Air is discharged from the IP air outlets.
       - Air quantity is controlled by the blower speed control knob.
       - Vehicle speed affects the air quantity when the fresh/recirc lever is in the FRESH position. The passenger compartment receives more air as the vehicle speed increases.
       - The passenger compartment receives some air even if the blower speed lever is in the OFF position.
    • BI-LEVEL
      • Airflow is divided between the upper air outlets and the floor air outlets.
      • Warmer air is delivered to the floor outlets than is delivered to the upper air outlets.
    • HEAT
      • Air is directed towards the floor outlet.
      • A small amount of air is directed towards the windshield.
    • HEAT/DEFROSTER
      • A portion of heated air is routed to the windshield.
      • The floor and side window outlets receive the remaining portion of air.
    • DEFROST
      • Most of the air is directed to the windshield.
      • The side windows and the floor receive a small amount of air.

Blower Speed Control Knob

The blower speed control knob (3) regulates the amount of air delivered into the passenger compartment. The blower speed control knob has 5 positions: OFF and speeds 1-4. The heater case contains the blower motor. The blower motor is located behind the right side of the IP.

Fresh/Recirculation Lever

The fresh/recirc lever (2) determines whether fresh outside air or recirculated passenger compartment air enters the vehicle's heater and ventilation system.

Moving the fresh/recirc lever to the recirculate position provides the quickest air delivery by closing the blower mode door. Outside air is not delivered to the passenger compartment in this position. Because the vehicle is equipped with a full-time outside air system, a small amount of outside air constantly enters the passenger compartment. Recirculate mode is helpful in heating up the passenger compartment faster. However, during normal heater operation use the fresh mode to prevent window fogging.