Circuit Description

WARNING: This page is about a different car, the 2004 Pontiac Aztek and 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.

The mode actuator is an electronic device that incorporates a stepper motor and feedback potentiometer. The HVAC control module controls the mode door position by sending a control signal to the actuator. The signal's value is dependent upon the desired mode selected by the vehicle occupants. As the actuator moves, the potentiometer produces the actual door position signal that is sent to the HVAC control module. The HVAC control module continues to command the actuator to move until the desired and actual values are equal. The door directs airflow through the outlets as selected by the vehicles occupants.

The HVAC control module commands the actuator through it's full range. The HVAC control module stores the learned minimum and maximum position values. The travel range value is calculated by subtracting the minimum and maximum position values. Then the HVAC control module compares the travel range, minimum and maximum values to calibrated value ranges. If the travel range value is less than or equal to the maximum calibrated limit and greater than or equal to the minimum calibrated limit, then the calibration is considered successful. The HVAC control module continuously compares the actual actuator position to the calibrated minimum and maximum position values.