Heated Glass Element: Description and Operation

Rear Window/Power Mirror Defoggers

How the Circuit Works

Power Supply
Battery voltage is supplied at all times through fuse 14 (in the under-hood fuse/relay box) to the rear window defogger relay contacts.

Battery voltage is supplied at all times through fuse 7 (in the driver's under-dash fuse/relay box) to the driver's and front passengers MPCS units.

With the ignition switch in ON (II), battery voltage is supplied through fuse 30 (in the driver's under-dash fuse/relay box) to the rear window defogger relay coil and the climate control unit.

Defogger operation
When the rear window defogger/power mirror defogger switch is pressed, the climate control unit sends a signal through the B-CAN communication line to the relay control module and to the driver's MPCS unit.

The relay control module grounds the coil of the rear window defogger relay, providing battery voltage to the rear window defogger. This ground circuit of the rear window defogger relay coil is protected by fuse 2 (in the under-hood fuse/relay box).

The driver's MPCS unit provides voltage to the left power mirror defogger. The driver's MPCS unit sends a power mirror defogger operation signal to the front passenger's MPCS unit through the UART communication line. The front passenger's MPCS unit provides voltage to the right power mirror defogger.

The rear window defogger and mirror defoggers can be turned off by pressing the rear window defogger switch/power mirror defogger switch a second time or by turning the ignition switch to LOCK (0). The rear window defogger will also shut off after 5 to 40 minutes of operation (depending on the ambient temperature).