Ambient Temperature Sensor / Switch HVAC: Description and Operation

The ambient temperature sensor is a 2 wire negative temperature co-efficient thermistor. The vehicle uses the following air temperature sensors:
^ Ambient Air Temperature Sensor
^ Inside Air Temperature Sensor
^ Upper Left Air Temperature Sensor
^ Upper Right Air Temperature Sensor
^ Lower Left Air Temperature Sensor
^ Lower Right Air Temperature Sensor

The duct sensor temperature response is different from the ambient and inside sensors. A signal and low reference circuit enables the sensor to operate. As the air temperature surrounding the sensor increases, the sensor resistance decreases. The sensor signal decreases as the resistance decreases. The sensor signal varies between 0-5 volts. The IPM converts the signal to a range between 0-255 counts.

If the IPM detects a malfunctioning sensor, then the IPM software will use a defaulted air temperature value. The default action ensures that the HVAC system can adjust the inside air temperature near the desired temperature until the condition is corrected.

The HVAC control module displays the ambient air temperature value that it receives from the IPM. The scan tool has the ability to update the displayed ambient air temperature. The ambient air temperature value is displayed or updated under the following conditions: