Ambient Temperature Sensor / Switch HVAC: Testing and Inspection

CONTROL SYSTEM INPUT COMPONENTS





Ambient Temperature Sensor
The ambient temperature sensor is located on the radiator core support. It detects ambient temperature and converts it into a resistance value, which is then input to the EATC unit.

Ambient Temperature Input Process
The EATC unit includes a processing circuit for the ambient temperature sensor input. When a temperature increase less than 12 °C (20 °F) is detected by the ambient temperature sensor, the processing circuit allows the EATC unit to recognize the temperature increase after 80 seconds. When the temperature increase is greater than 12 °C (20 °F), 5 minutes is required.

As an example, consider stopping for a cup of coffee after high speed driving. Even though the actual ambient temperature has not changed, the temperature detected by the ambient temperature sensor will increase because the heat radiated from the engine compartment can radiate to the front grille area where the ambient temperature sensor is located.














TROUBLE DIAGNOSIS PROCEDURE FOR AMBIENT TEMPERATURE SENSOR CIRCUIT

SYMPTOM:
- Ambient temperature sensor circuit is open or shorted (40, 41, 42, or 43 is indicated on the EATC unit as a result of conducting Self-diagnosis).

ELECTRICAL COMPONENT INSPECTION








Ambient Temperature Sensor
After disconnecting ambient temperature sensor harness connector, measure resistance between sensor terminals 1 and 2, using the table.