Steering Wheel Blower Motor Switch
WARNING: This page is about a different car, the 2003 Oldsmobile Bravada, 2003 GMC Envoy XL, 2003 GMC Envoy, and 2003 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
A separate blower motor switch is mounted on the steering wheel to allow the driver to adjust the blower speeds. Power to the steering wheel controls is delivered from the body control module (BCM) through the rear wiper/washer switch supply voltage circuit. When the driver toggles the switch up or down, the voltage is sent through a series of resistors. That varied voltage is sent back to the BCM, through the remote radio control signal circuit. Once the BCM receives that varied voltage signal, the information is sent out over the class 2 serial data to the HVAC control module where the blower speed is adjusted.