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

The air conditioning amplifier applies voltage (5 V) to the cooler thermistor (front room temperature sensor) and reads voltage changes as the resistance of the cooler thermistor (front room temperature sensor) changes. This sensor also sends the appropriate signals to the air conditioning amplifier.





WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. READ VALUE USING TECHSTREAM (ROOM TEMPERATURE SENSOR)

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Air Conditioner / Data List / Room Temperature Sensor.

(e) According to the display on the Techstream, read the Data List.

Air Conditioner





OK:

The display is as specified in the normal condition.

Result





C -- REPLACE AIR CONDITIONING AMPLIFIER Removal

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

2. INSPECT COOLER THERMISTOR (FRONT ROOM TEMPERATURE SENSOR)

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





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

Standard Resistance:





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

(c) Reinstall the cooler thermistor (front room temperature sensor).

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

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

(a) Disconnect the H16 cooler thermistor (front room temperature sensor) connector.





(b) Disconnect the H24 air conditioning amplifier connector.

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

Standard Resistance:





(d) Reconnect the air conditioning amplifier connector.

(e) Reconnect the cooler thermistor (front room temperature sensor) connector.

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE AIR CONDITIONING AMPLIFIER Removal