The inside air temperature sensor is located in the heater and A/C control behind a small grille. In this position, its exposed to the air that is present in the passenger compartment. This provides a sample of the inside air temperature.

The sensor is a thermistor used to control the signal voltage at the heater and A/C control. The heater and A/C control supplies a reference voltage (about 5 volts internally) to the sensor and measures the voltage drop in the circuit to obtain a temperature signal. This signal is an input that tells the heater and A/C control how much cooling or heating will be required to delver to the passenger compartment. After an initial start-up, the heater and A/C control uses the temperature input from the inside air temperature sensor for automatic control. Eventually the temperature input from both air outlet temperature sensor's overrides the input from the inside air temperature sensor and becomes the primary temperature input to the heater and A/C control.

When the inside air temperature is cold, the thermistor resistance is high; therefore, the heater and A/C control will receive a high signal voltage input. If the inside air temperature is hot, the thermistor resistance is low, the heater and A/C control will receive a low signal voltage input.

The numbers below refer to the step numbers on the diagnostic table.

2. Determines if the malfunction is present.

3. The inside air temperature sensor is internal to the heater and A/C control unit. Replace the heater and A/C control unit to repair the malfunction.