Road Temperature Sensor: Description and Operation

Fig. 10 Ambient Temperature Sensor:

AMBIENT TEMP SENSOR
The ambient air temperature sensor is hardwired to the HVAC control and the HVAC control sends out a J1850 message to the overhead console. The ambient temperature sensor is a variable resistormounted to a bracket that is secured with a screw to the right side of the radiator yoke, behind the radiator grille and in front of the engine compartment.

The ambient temperature sensor cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.

The ambient temperature sensor is a variable resistor that operates on a five-volt reference signal sent to it by the HVAC control head unit. The resistance in the sensor changes as temperature changes, changing the temperature sensor signal circuit voltage to the HVAC control head unit. Based upon the resistance in the sensor, the HVAC control head unit senses a specific voltage on the temperature sensor signal circuit, which it is programmed to correspond to a specific temperature.