Evaporator Temperature Sensor

Before testing the rear evaporator temperature sensor, verify that the front A/C system is operating correctly by performing the ATC Function Test using the DRBIII(R) scan tool. Use a volt/ohmmeter to test the sensor. For circuit descriptions and diagrams, refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, details of wire harness routing and retention, connector pin-out information and location views for the various wire harness connectors, splices and grounds.

1. Turn the ignition switch and the front A/C switch to the On position. Place the rear blower motor switch in either low or high speed position. Check for voltage to the rear evaporator relay from the rear evaporator temperature sensor. If OK, go to Step 2. If not OK, repair the open or shorted evaporator temperature sensor circuit as required.
2. With the ambient temperature between 20 to 30° C (68 to 90° F), start the engine and run the rear air conditioning system. The rear A/C solenoid valve should cycle open and closed. Use a voltmeter connected to the output side of the sensor for this check. If the A/C solenoid valve fails to cycle in these temperatures, replace the faulty rear evaporator temperature sensor.

NOTE: If the ambient temperature is above 32° C (90° F) the rear A/C solenoid valve may not cycle due to the high heat load. This condition is normal.