Evaporator Temperature Sensor

The evaporator temperature sensor contains a thermistor. The resistance of this thermistor varies by a specific amount based on the evaporator core temperature. The HVAC module measures a voltage ratio between the reference voltage it supplies to the sensor and the sensor voltage to determine this resistance and the associated evaporator core temperature.

As the evaporator core removes heat and moisture from the airflow moving through the evaporator core fins, the removed moisture condensates on the exterior of the evaporator core. The HVAC module uses input from the evaporator temperature sensor to prevent this moisture from freezing on the exterior of the evaporator core, and inhibiting airflow through the evaporator core fins. When the evaporator core temperature drops to a temperature near the freezing point of water, the HVAC module will switch off the A/C request signal to the IC. The A/C request will be switched back on when the evaporator core temperature rises to an acceptable level.

The evaporator temperature sensor electrical connector is located outside of the heater core and evaporator core housing behind the glove compartment, with the sensor pigtail leading into the housing to the sensor probe which is inserted between the evaporator core fins.