Circuit/System Description
WARNING: This page is about a different car, the 2019 Buick Cascada, 2018 Buick Cascada, and 2017 Buick Cascada. However, it is still accessible from the selected car via links, so may be relevant.
Doors in the HVAC case assembly are used to control air flow. The HVAC control module operates the doors through the use of actuators, with one actuator being used for each door. Each actuator is a 5 - wire stepper motor.
With the switches and dials on the HVAC controls, air temperature door position, mode door position and recirculation door position can be selected. The selected values are passed to the HVAC control module via serial data.
The HVAC control module supplies a 12 V reference voltage to the stepper motors and energizes the 4 stepper motor control circuits with a pulsed ground signal. The stepper motors move the appropriate doors into the calculated positions, in order to reach the selected setting.