HVAC Systems - Automatic

AMBIENT AIR TEMPERATURE SENSOR
The ambient air temperature sensor is a 2 wire negative temperature co-efficient thermistor. The vehicle uses the following air temperature sensors:
^ Ambient
^ Inside

A 5 volt reference and signal circuit enables the sensor to operate. As the air temperature surrounding the sensor increases, the sensor resistance decreases.

The sensor operates within a temperature range of 40°C (40°F) and 60°C (140°F). The HVAC control module receives a class 2 message from the Instrument Panel Cluster (IPC). The ambient air temperature sensor is mounted in the forward engine area of the vehicle. In this position, it is exposed to the airflow through the grill before it reaches the radiators. The sensor signal varies between 0 to 5 volts. The HVAC control module converts the signal to a working temperature range.

If the HVAC control module detects a faulty class 2 signal, then the control module 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 system is fixed.

Air Temperature Description And Operation:

The ambient air temperature is updated or displayed under the conditions: