Temperature Sensors

When the vehicle operator determines the desired temperature, the automatic system uses multiple sensors in order to achieve and maintain the desired temperature. The IPM software receives an input of the inside air temperature from the inside air temperature sensor assembly. A 5-volt reference signal is sent from the IPM to the inside air temperature sensor over the inside air temperature sensor signal circuit. A variable resistor inside the sensor varies the voltage. That varied voltage provides a signal to the software inside the IPM. As the air temperature increases, the resistance decreases. Remaining voltage from the inside air temperature sensor is sent back to the IPM ground through the low reference circuit.

The lower left air temperature sensor provides the IPM software with the temperature of the heat in the ductwork. A 5-volt reference signal is sent from the IPM to the lower left air temperature sensor over the lower left air temperature sensor signal circuit. A variable resistor inside the sensor varies the voltage. That varied voltage provides a signal to the software inside the IPM. Remaining voltage from the lower left air temperature sensor is sent back to the IPM ground through the low reference circuit.

The lower right air temperature sensor provides the IPM software with the temperature of the heat in the ductwork for passenger side temperature offset. A 5-volt reference signal is sent from the IPM to the lower right air temperature sensor over the lower right

air temperature sensor signal circuit. A variable resistor inside the sensor varies the voltage. That varied voltage provides a signal to the software inside the IPM. Remaining voltage from the lower right air temperature sensor is sent back to the IPM ground through the low reference circuit.

The upper left air temperature sensor provides the IPM software with the temperature of the A/C in the ductwork. A 5-volt reference signal is sent from the IPM to the upper left air temperature sensor over the upper left air temperature sensor signal circuit; A variable resistor inside the sensor varies the voltage. That varied voltage provides a signal to the software inside the IPM. Remaining voltage from the upper left air temperature sensor is sent back to the IPM ground through the low reference circuit.

The upper right air temperature sensor provides the IPM software with the temperature of the A/C in the ductwork for passenger side temperature offset. A 5-volt reference signal is sent from the IPM to the upper right air temperature sensor over the upper right air temperature sensor signal circuit. A variable resistor inside the sensor varies the voltage. That varied voltage provides a signal to the software inside the IPM. Remaining voltage from the upper right air temperature sensor is sent back to the IPM ground through the low reference circuit.

The ambient air temperature sensor provides the IPM software with the temperature outside the vehicle and displays that temperature on the HVAC control module. A 5-volt reference signal is sent from the IPM to the ambient air temperature sensor over the ambient air temperature sensor signal circuit. A variable resistor inside the sensor varies the voltage. That varied voltage provides a signal to the software inside the IPM. As the air temperature increases, resistance decreases. Remaining voltage from the ambient air temperature sensor is sent back to the IPM ground through the low reference circuit.

Because the sensor is mounted underhood, the sensor is affected by city traffic, idling, and hot engine restarts. A temperature memory feature is used in the IPM ambient air temperature programming that helps to provide greater accuracy under engine restart conditions.
^ If the engine coolant temperature is less than 10°C (18°F) above the ambient air temperature sensor reading, or if the engine has not been started in two hours, then the actual ambient air temperature sensor reading is displayed.
^ If the engine coolant is greater than 10°C (18°F) above the sensor reading, the memorized ambient air temperature is displayed. This is the last displayed temperature sensed when the engine was operating.

At vehicle speeds greater than 16 km/h (10 mph), the ambient air temperature displayed may be allowed to increase, but only after a built-in 300-second time delay which allows for ambient air to cool the sensor. The time delay begins when the vehicle speed reaches or maintains at least 16 km/h (10 mph). If the sensor reading is ever less than the displayed value, then the ambient air temperature changes are displayed as rapidly as possible.