Air Conditioning System (For Automatic Air Conditioning System)

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 to detect the ambient temperature which is used to control the air conditioner "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 Techstream to the DLC3.
(b) Turn the ignition switch on (IG) and turn Techstream main switch on.
(c) Select the item below in the Data List, and read the value displayed on Techstream.

Data List / Air Conditioner





OK:
The display is as specified in the normal condition column.
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 Removal.
(b) Measure the resistance according to the value(s) in the table below.
Standard resistance:





NOTICE:
- Touching the sensor even slightly 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 HARNESS AND CONNECTOR (AMBIENT TEMPERATURE SENSOR - AIR CONDITIONING AMPLIFIER)




(a) Disconnect the A7 sensor connector.
(b) Disconnect the D37 amplifier 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 AIR CONDITIONING AMPLIFIER