Automatic Air Conditioning System

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

DTC 12 - Ambient Temperature Sensor Circuit

DESCRIPTION

The sensor connected to the clock detects fluctuations in the ambient temperature that is used for controlling the interior temperature. The sensor sends a signal to the A/C amplifier via the clock.





WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. INSPECT CLOCK ASSEMBLY





(a) Check the difference in ambient temperature between the value displayed on the clock assembly and the actual temperature.
OK:
The ambient temperature displayed on the clock assembly and the actual ambient temperature are almost the same.

HINT: The temperature displayed on the clock assembly and the actual temperature detected by the sensor may differ when the ambient temperature rises significantly (such as when the vehicle stops immediately after start-up).

NG -- INSPECT CLOCK ASSEMBLY (TH+ - SG)
OK -- CHECK HARNESS AND CONNECTOR (CLOCK ASSEMBLY - A/C AMPLIFIER)
2. INSPECT CLOCK ASSEMBLY (TH+ - SG)





(a) Remove the clock assembly with the connector still connected.
(b) Turn the ignition switch to the ON position.
(c) Measure the voltage according to the value(s) in the table below.
Standard voltage:





HINT: As the temperature increases, the voltage decreases.

Result:





C -- CHECK HARNESS AND CONNECTOR (CLOCK ASSEMBLY - A/C AMPLIFIER)
B -- PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE
A -- Continue to next step.
3. INSPECT A/C AMBIENT TEMPERATURE SENSOR (COOLER (AMBIENT TEMP. SENSOR) THERMISTOR)





(a) Remove the A/C ambient temperature sensor (cooler (ambient temp. sensor) thermistor).
(b) Measure the resistance according to the value(s) in the table below.





Standard resistance:





NOTICE:
- Even slightly touching the sensor may change the resistance value. Be sure to hold the connector of the sensor.
- When measuring the sensor temperature must be the same as the ambient temperature.

HINT: As the temperature increases, the resistance decreases (see the graph).

NG -- REPLACE A/C AMBIENT TEMPERATURE SENSOR
OK -- Continue to next step.
4. CHECK HARNESS AND CONNECTOR (CLOCK ASSEMBLY - A/C AMBIENT TEMPERATURE SENSOR)





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





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE CLOCK ASSEMBLY
5. CHECK HARNESS AND CONNECTOR (CLOCK ASSEMBLY - A/C AMPLIFIER)





(a) Disconnect the connectors from the clock assembly and the A/C amplifier.
(b) Measure the resistance according to the value(s) in the table below.
Standard resistance:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE AIR CONDITIONING AMPLIFIER