B1412

AIR CONDITIONING: AIR CONDITIONING SYSTEM: B1412/12: Ambient Temperature Sensor Circuit
B1412/12 - Ambient Temperature Sensor Circuit

DESCRIPTION

The ambient temperature sensor is installed in the front part of the condenser to detect the ambient temperature and control the air conditioner "AUTO" mode. The sensor connected to the front light ECU (front controller) detects fluctuations in the ambient temperature. This data is used for controlling the room temperature. The sensor sends a signal to the air conditioning amplifier via the front light ECU (front controller). 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 front light ECU (front controller) applies voltage (5 V) to the ambient temperature sensor and reads voltage changes as the resistance of the ambient temperature sensor changes. The front light ECU (front controller) sends the read signal to the air conditioning amplifier via the CAN communication line.

HINT
This circuit uses the CAN communication line. Before performing the inspection, check that the CAN communication system is functioning normally.





WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. READ VALUE USING TECHSTREAM (AMBIENT TEMPERATURE SENSOR)

(a) Use the Data List to check if the ambient temperature sensor is functioning properly.

Air Conditioner





OK:

The display is as specified in the normal condition.

Result





B -- PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE Symptom Related Diagnostic Procedures

C -- REPLACE AIR CONDITIONING AMPLIFIER Removal
A -- Continue to next step.

2. INSPECT AMBIENT TEMPERATURE SENSOR





(a) Remove the ambient temperature sensor Removal.

(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 AMBIENT TEMPERATURE SENSOR Removal
OK -- Continue to next step.

3. CHECK HARNESS AND CONNECTOR (AMBIENT TEMPERATURE SENSOR - FRONT LIGHT ECU)





(a) Disconnect the B5 ambient temperature sensor connector.

(b) Disconnect the B14 front light ECU connector.

(c) Measure the resistance according to the value(s) in the table below.

Standard resistance:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE FRONT LIGHT ECU