Cabin Temperature Sensor / Switch: Description and Operation

In-Car Temp Sensor:

DESCRIPTION
The Automatic Temperature Control (ATC) system uses various sensors which return 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 part of motorized aspirator assembly that is mounted in the instrument panel. A small fan (in the sensor) draws air through an intake in the instrument panel (behind the name plate). This air flows over a thermistor which measures interior vehicle temperatures. The ATC system then makes adjustments to maintain optimum passenger compartment comfort.

OPERATION
The In-Car Sensor will automatically turn on when a vehicle door is opened. If the door is left open, the In-Car Sensor will automatically turn off within approximately 5 minutes. If the door is then closed, but there is no ignition start, the In-Car Sensor will automatically turn off after approximately 2 minutes. After the vehicle has been driven, the In-Car Sensor will turn off immediately when the ignition is turned off. The aspirator motor in the In-Car Sensor operates whenever the ignition switch is on (even when the ATC system off button is pushed). If the In-Car Sensor is open or shorted on this system, the digital display will turn off. Then the system defaults to manual operation.

NOTE: The In-Car Temperature Sensor assembly is not serviceable and must be replaced if found to be defective.

CIRCUIT OPERATION
Power for the in car temperature sensor is supplied from the Body Control Module (BCM) on circuit C1O.

Circuit C57 is the sensor return and is spliced with the other sensors in the system.