Test F: The Defrost System Is Inoperative
PINPOINT TEST F: THE DEFROST SYSTEM IS INOPERATIVEF1-F2:
F2-F5:
F5-F8:
F8 Continued:
Normal Operation
Under normal operation the heated backlight power relay receives power from circuit 185 (BK) and 326 (WH/VT). When the rear window defrost switch is depressed on the dual automatic temperature control (DATC) control unit, a ground signal is sent to the instrument cluster module (ICM) through circuit 688 (GY/LB). When the ICM receives ground through circuit 688 (GY/LB), the ICM grounds circuit 1009 (DG/VT) to activate the heated backlight power relay. Power is then sent to the rear window defrost grid through circuit 186 (BN/LB) from the heated backlight power relay. The rear window defrost grid then receives ground through circuit 1205 (BK) to chassis ground.
Possible Causes
- Inoperative ICM
- Inoperative DATC
- Inoperative heated backlight power relay
- Open in circuits 185 (BK), 186 (BN/LB), 326 (WH/VT), 688 (GY/LB), 1009 (DG/VT) or 1205 (BK)