Heated Glass Element: Description and Operation

The rear window defogger system consists of a tinted glass that has a number of horizontal ceramic enamel compound element lines and two vertical bus bars baked onto the inside surface during the glass forming operation. The feed wire or terminal is soldered to the bus bar on the side. The ground terminal is soldered to the right side. The system is used to melt ice or snow from the exterior surface of the rear window or to clear up condensation from the interior surface of the rear window.

Under some conditions, heat from the glass may not be detected by touch. The length of time required to remove interior fog from the back glass are functions of temperature, atmospheric pressure and number of passengers.

This system uses an instrument panel mounted switch with an integral indicator lamp. The on/off function of this system is manual.

The system operates with the ignition in the RUN position.

When the rear defog switch is placed in the ON position, the switch provides a ground path for current through the coil of the rear defog relay. The switch also provides a ground path for current through an LED indicator lamp in the switch assembly. When the relay coil is energized, current flows through the rear defogger element to ground. There is no timer in the system. The rear defogger remains on as long as the switch remains in the ON position.

A variable power density grid pattern is used on the rear defogger grid. The power density in the center section is greater than the power density to either side of the center section. This design results in faster clearing of the center section.