Toyota RAV4 Service Manual: Evaporator temperature sensor circuit

Description

The no. 1 Cooler thermistor (evaporator temperature sensor) is installed on the evaporator in the air conditioning unit to detect the temperature of the cooled air that has passed through the evaporator and to control the air conditioner. It sends signals to the air conditioning amplifier. The signals change in accordance with the resistance of the no. 1 Cooler thermistor (evaporator temperature sensor). 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 no. 1 Cooler thermistor (evaporator temperature sensor) and reads voltage changes as changes in the resistance of the no. 1 Cooler thermistor (evaporator temperature sensor). This sensor is used for frost prevention.

Wiring diagram

Inspection procedure

1. Read value of intelligent tester (evap fin temp)

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

Ok: the display is as specified in the normal condition column.

2. Inspect no. 1 Cooler thermistor (evaporator temperature sensor)

1. Remove the no. 1 Cooler thermistor.
2. Measure the resistance of the thermistor.

Standard resistance

Notice:

• Touching the thermistor even slightly may change the resistance value. Be sure to hold the connector of the thermistor.
• When measuring, the thermistor temperature must be the same as the ambient temperature.

Hint:

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

Replace air conditioning harness assembly