Auxiliary Heating Operation
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2002 GMC Yukon XL, 2002 GMC Yukon, 2002 Chevrolet Tahoe, 2002 Chevrolet Suburban, and 2002 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
When an auxiliary warm air request is made the front auxiliary HVAC control assembly will send a high voltage signal to the auxiliary air temperature actuator on the auxiliary air temperature door position signal circuit. This voltage signal is a varied 12 volt signal. This signal is monitored by the logic incorporated in the actuator and it will move the actuator in the desired direction when a position change is requested.