GM Service Manual Online
For 1990-2009 cars only

The inside air temperature sensor is a temperature-sensitive resistor similar to the outside temperature sensor. As cabin air temperature increases, resistance decreases. As cabin air temperature decreases, resistance increases.

A fan located in the in-vehicle air temperature sensor housing continually draws passenger compartment air over the sensor. This condition increases the accuracy of the temperature reading.

The electronic climate control (ECC) module monitors the vehicle temperature signals and uses this information in order to help determine command signals.

Upper and Lower Outlet Temperature Sensors

The heater and A/C temperature sensors are used in order to monitor discharge temperatures from the heater and A/C outlets. These sensors are located in the heater and the A/C ducts. The ECC module monitors the discharge temperature sensors and uses this information in order to help determine command signals.