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 ECM detects fluctuations in the ambient temperature. This data is used for controlling the room temperature. The sensor sends a signal to the A/C amplifier via the ECM. 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 ECM applies voltage (5 V) to the ambient temperature sensor and reads voltage changes as the resistance of the ambient temperature sensor changes. The ECM sends the read signal to the A/C amplifier via CAN and body multiplex communications.





WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. READ VALUE USING TECHSTREAM

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Select the item below in the Data List, and read the display on the Techstream.

Data List / Air Conditioner





OK:

The display is as specified in the normal condition.

Result





C -- REPLACE AIR CONDITIONING AMPLIFIER

B -- PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE
A -- Continue to next step.

2. INSPECT AMBIENT TEMPERATURE SENSOR





(a) Remove the ambient temperature sensor.

(b) Measure the resistance of the sensor.

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
OK -- Continue to next step.

3. CHECK WIRE HARNESS (AMBIENT TEMPERATURE SENSOR - ECM)





(a) Disconnect the B5 ambient temperature sensor connector.

(b) Disconnect the A53 and E83 ECM connectors.

(c) Measure the resistance of the wire harness side connectors.

Standard resistance:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE ECM