Room Temperature Sensor Circuit - Air Conditioning System

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

DESCRIPTION

The room temperature sensor (cooler thermistor) is installed in the instrument panel to detect the cabin temperature which is used to control the heater and air conditioning system AUTO mode. The resistance of the room temperature sensor (cooler thermistor) changes in accordance with the cabin temperature. As the temperature decreases, the resistance increases. As the temperature increases, the resistance decreases.

The air conditioning amplifier assembly applies a voltage (5 V) to the room temperature sensor (cooler thermistor) and reads voltage changes due to changes in the resistance of the room temperature sensor (cooler thermistor).





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) Enter the following menus: Body Electrical / Air Conditioner / Data List.

(e) Check the value(s) by referring to the table below.

Air Conditioner





OK:

The display is as specified in the normal condition column.

Result:





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

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

2. INSPECT ROOM TEMPERATURE SENSOR (COOLER THERMISTOR)

(a) Remove the room temperature sensor (cooler thermistor) Removal.

(b) Disconnect the I57 room temperature sensor (cooler thermistor) connector.





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

Standard Resistance:





NOTICE:
* Hold the sensor only by its connector. Touching the sensor may change the resistance value.
* When measuring, the sensor temperature must be the same as the ambient temperature.

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

Text in Illustration





NG -- REPLACE ROOM TEMPERATURE SENSOR (COOLER THERMISTOR) Removal
OK -- Continue to next step.

3. CHECK HARNESS AND CONNECTOR (ROOM TEMPERATURE SENSOR (COOLER THERMISTOR) - AIR CONDITIONING AMPLIFIER ASSEMBLY)

(a) Disconnect the I77 air conditioning amplifier assembly connector.

(b) 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 ASSEMBLY Removal