Room temperature sensor circuit

The 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 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 a voltage (5 v) to the room temperature sensor and reads voltage changes as changes in the resistance of the room temperature sensor.

1. 1
   Read value of intelligent tester (room temp)
2. 2
   Connect the intelligent tester (with can vim) to the dlc3.
3. 3
   Turn the ignition switch on and turn the intelligent tester main switch on.
4. 4
   Select the item below in the data list, and read the value displayed on the intelligent tester.

   

2. Inspect cooler thermistor (room temperature sensor)

1. 1
   Remove the room temperature sensor.
2. 2
   Measure the resistance of the sensor.

Standard resistance

• 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.

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

3. Check wire harness (room temperature sensor - air conditioning amplifier)

1. 1
   Disconnect the e21 sensor connector.
2. 2
   Disconnect the e37 amplifier connector.
3. 3
   Measure the resistance of the wire harness side connectors.

Standard resistance