Circuit/System Description
WARNING: This page is about a different car, the 2009 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.
The HVAC control module supplies the evaporator temperature and inside air temperature sensors with a low reference circuit and 5-volt signal circuit. The HVAC control module determines the voltage drop across the sensors, which is proportional to temperature. As the air temperature increases, the sensor resistance decreases. As the air temperature decreases, the sensor resistance increases. The inside air temperature sensor assembly has an internal fan that draws air across the sensor and is controlled by the HVAC control module. The internal fan motor is connected to body ground.