GM Service Manual Online
For 1990-2009 cars only

HVAC Mode Actuator

The HVAC Mode Actuator operates with the HVAC Mode Switch.

The following modes are the HVAC modes:

    • VENT
    • BI-LEVEL
    • FLOOR
    • FLOOR/DEFROST
    • DEFROST

The HVAC Mode Actuator Motor operates when an HVAC mode change is selected.

The HVAC Mode Actuator Motor drives the dampers open or closed in the HVAC ductwork segments.

This action provides the correct air handling mode path.

Vent Mode

The recirculating/fresh air actuator is activated when the switch is in the ON position.

The following actions occur when the recirculating/fresh air actuator is activated:

    • The recirculating/fresh air door opens completely.
    • Air is discharged from the upper air outlets.

As a result, the temperature of the air that is released from the upper air outlets is close to the temperature of the outside air.

Bi-Level Mode

The mode actuator is activated when the switch is in the ON position.

This action causes the mode control door to open halfway.

Airflow is divided between the upper air outlets and the floor air outlets.

Floor Mode

The mode actuator is activated when the switch is in the ON position.

This action causes the mode control door to open completely.

Most of the airflow is routed to the floor. The rest of the air is routed to the windshield outlets.

Floor/Defrost Mode

The mode actuator is activated when the switch is in the ON position.

This action causes the mode control door to open halfway.

Half of the airflow is routed to the floor. The other half of the airflow is delivered to the windshield outlets.

Defrost Mode

The mode actuator is activated when the switch is in the ON position.

This action causes the mode control door to open completely.

Most of the airflow is routed to the windshield outlets. The rest of the airflow is routed to the floor.

HVAC Recirculating Fresh Air Actuator

The HVAC Recirculating Fresh Air Actuator controls the amount of fresh air that enters the vehicle during the various HVAC modes.

    • The VENT mode provides 100 percent fresh air from outside of the vehicle.
    • The MAX A/C and the MAX HEAT modes provide a minimum of fresh air to the vehicle.
        These modes recirculate most of the vehicle inside air in order to quickly cool or warm the interior.

HVAC Temperature Actuator

The HVAC Temperature Actuator controls the amount of air from the Blower Motor that will be routed through either or both of the following components:

    • The A/C Evaporator Core
    • The Heater Core

The position of the operator temperature selection lever is translated into an electrical signal.

The temperature actuator controls a series of motor operated valves. The valves are driven into different positions. The positions provide more heating or cooling in response to the temperature selection.