B1412

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

DESCRIPTION

The thermistor assembly is installed in the front part of the condenser to detect the ambient temperature and control the air conditioner. The thermistor assembly is connected to the combination meter assembly and detects fluctuations in the ambient temperature. This data is used for controlling the room temperature. The thermistor assembly sends a signal to the air conditioning amplifier assembly via the combination meter assembly. The resistance of the thermistor assembly changes in accordance with the ambient temperature. As the temperature decreases, the resistance increases. As the temperature increases, the resistance decreases.

The combination meter assembly applies a voltage (5 V) to the thermistor assembly and reads voltage changes as changes in the resistance of the thermistor assembly. The combination meter assembly sends the read signal to the air conditioning amplifier assembly via CAN communication.





WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. CHECK CAN COMMUNICATION SYSTEM

(a) Use the Techstream to check if the CAN communication system is functioning normally Diagnosis System.

OK:

CAN DTC is not output.

NG -- GO TO CAN COMMUNICATION SYSTEM Diagnosis System
OK -- Continue to next step.

2. READ VALUE USING TECHSTREAM (AMBIENT TEMP SENSOR)

(a) Use the Data List to check if the thermistor assembly is functioning properly Scan Tool Testing and Procedures.

Air Conditioner





OK:

The display is as specified in the normal condition column.

Result





C -- READ VALUE USING TECHSTREAM (AMBIENT TEMPERATURE)

B -- REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY Removal

A -- PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE Symptom Related Diagnostic Procedures

3. READ VALUE USING TECHSTREAM (AMBIENT TEMPERATURE)

(a) Use the Data List to check if the thermistor assembly is functioning properly Scan Tool Testing and Procedures.

Combination Meter





OK:

The display is as specified in the normal condition column.

NG -- INSPECT THERMISTOR ASSEMBLY
OK -- Continue to next step.

4. REPLACE COMBINATION METER ASSEMBLY

(a) Temporarily replace the combination meter assembly with a new or normally functioning one Removal.

NEXT -- Continue to next step.

5. CHECK FOR DTC

(a) Clear the DTCs Reading and Clearing Diagnostic Trouble Codes.

(b) Check the DTCs Reading and Clearing Diagnostic Trouble Codes.

OK:

DTC B1412 is not output.

NG -- REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY Removal

OK -- END (COMBINATION METER ASSEMBLY IS FAULTY)

6. INSPECT THERMISTOR ASSEMBLY

(a) Remove the thermistor assembly Removal.





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

Standard Resistance:





Text in Illustration





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

HINT
As the temperature increases, the resistance decreases (refer to the graph).

NG -- REPLACE THERMISTOR ASSEMBLY Removal
OK -- Continue to next step.

7. CHECK HARNESS AND CONNECTOR (THERMISTOR ASSEMBLY - COMBINATION METER ASSEMBLY)

(a) Disconnect the A18 thermistor connector.

(b) Disconnect the C50 meter 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 COMBINATION METER ASSEMBLY Removal