Air Delivery
WARNING: This page is about a different car, the 2003 Pontiac Aztek and 2003 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.
The HVAC control module controls the mode actuator in order to distribute airflow to a desired outlet.
When the mode door is moved to the defrost position, the A/C compressor clutch engages and the recirculation actuator will be moved to the outside air position. Regardless of the mode setting, a small amount of air will be diverted to the defrost ducts to reduce windshield fogging. When the mode actuator sees an open in the control circuit, the actuator defaults to 6 volts and positions the mode door to the floor position. On start-up, the HVAC control module will place the mode door in the last selected position.