Ambient Temperature Sensor / Switch HVAC: Description and Operation

This sensor is located in front of the radiator. The sensor data is processed by the heater and A/C programmer and displayed on the heater and A/C control.

During periods of city traffic and idle conditions, engine heat can surround the area of the ambient temperature sensor and cause temperature readings that are higher than the actual ambient air temperature. To help eliminate these false readings, programming techniques are used to minimize unwanted temperature variations.

A temperature memory feature is used in the heater and A/C programmer ambient temperature programming to help provide greater accuracy under engine restart conditions. If engine coolant temperature is less than 10°C (18°F) above the ambient temperature sensor reading, or a two-hour ignition off timer has expired, then the actual sensed ambient temperature is displayed. However, if engine coolant is greater than 10°C (18°F) above the sensor reading, memorized ambient temperature is displayed. This is the displayed temperature sensed when the engine was previously operating. At car speeds greater than 32 km (20 mph), the ambient temperature display may be allowed to increase, but only after a built-in 80-second time delay which allows for ambient air to cool the sensor. The 80-second time delay starts when vehicle speed reaches or maintains at least 32 km (20 mph). If the sensor reading is ever less than the displayed value or if the vehicle speed is 72 km (45 mph) or greater, there is no delay and ambient temperature changes are displayed as rapidly as possible.