Heated Glass Element: Description and Operation

With the Ignition Switch in "RUN," voltage is applied to the Rear Defogger Control Switch. When the Rear Defogger Control Switch is pressed "ON," voltage is applied to the Rear Defogger Timer-Relay. The contact closes, providing voltage to the ON Indicator and the Rear Defogger. The rear window becomes warm to remove the fog from the surface of the window.

The contact in the Rear Defogger Timer-Relay stays closed until the Rear Defogger Control Switch is pressed again, the timer cycle is complete, or the Ignition Switch is turned to "OFF."

The first time the Rear Defogger Control Switch is pressed, the Rear Defogger Timer-Relay allows the Rear Defogger to operate for approximately 10 minutes. Each time after that when the Rear Defogger Control Switch is pressed, the Rear Defogger Timer-Relay operates for approximately 5 minutes. The Rear Defogger Timer-Relay resets to 10 minutes when the Ignition Switch is turned "OFF."

The Rear Defogger Timer-Relay has a Vehicle Speed Sensor input from the ECM. If the Rear Defogger Control Switch is pressed while the vehicle is not moving, the Timer-Relay will begin its time out, energize the relay contacts and stay on for about 10 minutes. If the Rear Defogger Control Switch is pressed while the vehicle is moving at or above 45 +/- 3 mph, the timer in the Rear Defogger Timer-Relay will energize its contacts, but will not begin its time out. This results in the Defogger remaining on as long as the Rear Defogger Timer-Relay sees a vehicle speed at or above 45 +/- 3 mph. If the vehicle speed goes below 45 +/- 3 mph, the timer will begin its time out and continue counting down until the vehicle speed increases to 45 +/- 3 mph, 10 minutes has elapsed or the Rear Defogger Control Switch is depressed. The timer will not reset to 10 minutes every time vehicle speed drops below 45 +/- 3 mph, but begins counting down from where it left off. The timer does not reset every time the Ignition Switch is switched off, the timer times out, or after the Defogger is turned off.