Cabin Temperature Sensor / Switch: Description and Operation

ATC IN-CAR TEMPERATURE SENSOR
The Automatic Temperature Control (ATC) In-Car Temperature Sensor returns electrical signals to the Body Control Module (BCM). The In-Car Temperature Sensor is used on ATC equipped vehicles only. The In-Car Temperature Sensor is made up of two parts. One part is the in-car sensor motor fan assembly and the second part is a temperature thermistor. The in-car sensor motor fan assembly attaches to the back of the ATC Control head. This assembly has a small fan and a motor which draws air through the intake on the front of the ATC control. The in-car sensor thermistor is located inside of the ATC Control Head. Air drawn from the passenger compartment by the in-car sensor motor-fan assembly, flows over the thermistor. The in-car sensor thermistor changes resistance with air temperature. The BCM measures this resistance and calculates the temperature of the air drawn into the ATC Control. The ATC system then makes adjustments to maintain the optimum passenger compartment comfort. Refer to the ATC Sensor Motor-Fan Operation table for when the ATC Sensor is operating.

ATC SENSOR MOTOR-FAN OPERATION
The in-car sensor motor is an integral part of the Control Head and not a separate serviceable part. The ATC Control Head must be replaced if there is a fault relating to the motor. See Diagnosis and Testing for proper check of airflow. The In-Car Sensor Thermistor is part of the ATC Control Head and not a separate serviceable part. One must replace the ATC Control Head if the ATC self-diagnostics indicates a fault code. See Self-Diagnostics for information on diagnosing wiring and thermistor.