Theory Of Operation

The Panel and Floor Duct Temperature Sensors are negative temperature coefficient thermistor type sensors. As the sensor gets colder, the resistance is higher. As the temperature increases, the resistance is lower. The HVAC Module applies a low current, 5-volt signal to the signal circuit and measures the voltage drop across the thermistor. The lower the temperature, the higher the voltage drop.

There are two circuits between each duct temperature sensor and the HVAC Module:

• Temperature Sensor Signal
• Sensor Ground

The duct temperatures are monitored by the HVAC Module to make sure each temperature door is allowing the correct air temperature to enter the desired zone within the cabin.

The HVAC Module monitors the temperature sensor signal circuit for voltages that are out of normal operating range. If a problem is detected, a DTC will be set.