Rear Window Defogger

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Pressing Rear Widow Defogger button on the MTC or ATC head will defog the rear glass. See Fig 1 . The system will only operate when the ignition switch is in the run position. Once the Rear Widow Defogger button is pushed, the button indicator will light and the system will operate for a period of time and then automatically turn off. When the rear window defogger relay is ON, current is directed to the rear defogger grid lines. The heated grid lines heat the rear glass to clear the surface of fog or frost. Circuit protection is provided by a fusible link, located in the charging circuit for the heated grid circuit and by a fuse for the relay control circuit. The MTC or the ATC head sends a signal to the BCM, which indicates to the BCM that the operator wants the rear window grid to heat. An output wire from the BCM connects to the coil of the rear window defogger relay. The other side of the coil is connected to a fuse. The BCM turns on the relay by connecting the output line of the BCM to vehicle ground. The relay contacts will then close supplying vehicle power to the rear window defogger grid.

Fig 1: Identifying ATC Control Head

Courtesy of CHRYSLER CORP.