Rear Window Defogger Operation

CIRCUIT OPERATION
The rear window defogger system uses a relay located in the junction block. This relay is protected by two fuses and controlled by the HVAC control. When the operator pushes the ON switch for the rear window defogger, a signal is sent to the HVAC control and the control supplies a ground path for circuit C14.

This causes the coil side of the relay to energize, connecting circuit A4 to circuits C15, and C16. The C16 circuit is protected by a 10 Amp fuse located in cavity 12 of the junction block, and used to supply power for the power mirror heaters.

The A22 circuit that is used to power the coil side of the relay is protected by a 10 Amp fuse located in cavity 8 of the junction block and is HOT in the RUN position only

The A4 circuit, which is used to supply power to the contact side of the relay, is protected by a 40 Amp fuse located in cavity 1 of the Power Distribution Center (PDC) and HOT at all times.

Circuit C15 connects from the relay to the rear window defogger grid. Ground for the grid is supplied on circuit Z1, and terminates at the liftgate ground.

The rear window defogger grid consists of two BUS bars and grid lines that form a parallel circuit. When current flows through the grid the grid lines heat up and transfer the heat to the window.

When the system is in operation a Light Emitting Diode (LED) located in the A/C-Heater control is illuminated.