Air Conditioning System (For Automatic Air Conditioning System)

HEATING / AIR CONDITIONING: AIR CONDITIONING SYSTEM (for Automatic Air Conditioning System): B1412/12: Ambient Temperature Sensor Circuit

DTC B1412/12 - Ambient Temperature Sensor Circuit

DESCRIPTION

The ambient temperature sensor is installed in front of the condenser. It detects the ambient temperature to control air conditioning AUTO mode. This sensor is connected to the A/C amplifier and detects fluctuations in the ambient temperature. This data is used for controlling the cabin temperature. The sensor sends a signal to the A/C amplifier. The resistance of the ambient temperature sensor changes in accordance with the ambient temperature. As the temperature decreases, the resistance increases. As the temperature increases, the resistance decreases.
The A/C amplifier applies voltage (5 V) to the ambient temperature sensor and reads voltage changes as the resistance of the ambient temperature sensor changes.





WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. READ VALUE USING TECHSTREAM
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the Techstream on.
(d) Enter the following menus: Body / Air Conditioner / Data List.
(e) Check the value(s) by referring to the table below.

Air Conditioner





OK:
The display is as specified in the Normal Condition column.
Result:





C -- REPLACE A/C AMPLIFIER
B -- PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE
A -- Continue to next step.

2. INSPECT AMBIENT TEMPERATURE SENSOR
(a) Remove the ambient temperature sensor.




(b) Disconnect the ambient temperature sensor connector.
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance:





NOTICE:
- Hold the sensor only by its connector. Touching the sensor may change the resistance value.
- When measuring, the sensor temperature must be the same as the ambient temperature.
HINT: As the temperature increases, the resistance decreases (see the graph).

Text in Illustration





NG -- REPLACE AMBIENT TEMPERATURE SENSOR
OK -- Continue to next step.

3. CHECK HARNESS AND CONNECTOR (AMBIENT TEMPERATURE SENSOR - A/C AMPLIFIER)




(a) Disconnect the A/C amplifier connector.




(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:





Text in Illustration





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE A/C AMPLIFIER