B1411

AIR CONDITIONING SYSTEM: B1411/11: Room Temperature Sensor Circuit

DTC B1411/11 - Room Temperature Sensor Circuit

DESCRIPTION

The A/C room temperature sensor is installed in the instrument panel to detect the cabin temperature and control the heater and air conditioner "AUTO" function. The resistance of the A/C room temperature sensor changes in accordance with the cabin temperature. As the temperature decreases, the resistance increases. As the temperature increases, the resistance decreases.
The A/C amplifier assembly applies voltage (5 V) to the A/C room temperature sensor and reads voltage changes as the resistance of the A/C room temperature sensor changes. This sensor also sends appropriate signals to the A/C amplifier assembly. The room temperature sensor is integrated with the room humidity sensor.






WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. READ VALUE OF TECHSTREAM
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch ON and push the Techstream main switch on.
(c) Select the item below in the DATA LIST, and read the display on the Techstream.

Air Conditioner





OK:
The display is as specified in the normal condition.
Result:






C -- REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY
B -- PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE
A -- Continue to next step.
2. INSPECT AIR CONDITIONING AMPLIFIER ASSEMBLY





(a) Remove the A/C amplifier assembly with the connectors still connected.
(b) Measure the voltage according to the value(s) in the table below.
Voltage:





HINT: As the temperature increases, the voltage decreases.

Result:






C -- REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY
B -- PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE
A -- Continue to next step.
3. INSPECT A/C ROOM TEMPERATURE SENSOR





(a) Remove the A/C room temperature sensor.
(b) Disconnect the connector from the A/C room temperature sensor.
(c) Measure the resistance according to the value(s) in the table below.





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 ROOM TEMPERATURE SENSOR
OK -- Continue to next step.
4. CHECK HARNESS AND CONNECTOR (A/C ROOM TEMPERATURE SENSOR - A/C AMPLIFIER ASSEMBLY)





(a) Disconnect the connector from the A/C amplifier assembly.
(b) Measure the resistance according to the value(s) in the table below.
Resistance:






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