Heater Temperature Sensor

Heater Temperature Sensor

The heater temperature sensor is a NTC thermistor that provides the ATC (automatic temperature control) module with a temperature signal from the air outlet side of the heater core. On manual systems, a single sensor is installed in the rear of the heater assembly casing, to the right of the center-line. On automatic systems, two sensors are installed, one each side of the center-line.

The ATC (automatic temperature control) module uses the input from the heater temperature sensor(s) to control the operation of the coolant valve(s).

The signal voltage from each heater temperature sensor is between 0 and 5 V. The ATC (automatic temperature control) module monitors the signal voltage and defaults to a temperature of 55 degrees C (131 degrees F) if it goes out of the range 0.173 - 4.890 V:
^ If the signal voltage is less than 0.173 V, the ATC (automatic temperature control) module assumes there is a short circuit to ground
^ If the signal voltage is more than 4.890 V, the ATC (automatic temperature control) module assumes there is an open circuit or a short circuit to battery.