In-Cabin Temperature Sensor
The in-cabin or in-car temperature sensor is an (NTC), negative temperature coefficient sensor. This means that as temperature increases, resistance in the sensor decreases. Its signal voltage varies between 0 and 5 volts. The electronic automatic temperature control system's microprocessor uses this, along with the ambient temperature and sun load sensors input to adjust cooling load, fan speed, and volume according to different temperatures and conditions.
Visually inspect the aspirator tube to make sure it’s fastened to the sensor and vent system properly. The aspirator relies on suction from the vent system. It's this suction that causes the air sample to pass through the sensor. Also make sure nothing is blocking the vent, typically located somewhere by the A/C control panel. Many sensors contain an electric fan that can fail resulting in a poor and inaccurate sample. These sensors can be located in different areas throughout the vehicle.
Automotive air conditioning systems use NTC sensors to monitor air temperature. The In Car Temperature sensor (ICTS) is an NTC that monitors the air temperature of the passenger compartment. The ambient temperature sensor (ATS) monitors the air temperature outside of the vehicle. The EATC compares these values and makes output decisions based on the difference of these air temperatures.