Theory Of Operation

The Panel and Floor Duct Temperature Sensors are negative temperature coefficient thermistor type sensors. 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. As the temperature gets colder, the resistance is higher. As the temperature gets warmer, the resistance is lower. The HVAC Module applies a low current, 12-volt signal to the signal circuit and measures the voltage drop across the thermistor. The lower the temperature, the higher the voltage drop. 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.

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

• Temperature Sensor Signal
• Sensor Ground