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, ground is supplied by the Multi-Function Alarm Module, turning on the "ON" Indicator and the rear Defogger. The rear window becomes warm to remove the condensation from the surface of the window.

The contact in the Multi-Function Alarm Module stays closed until the Rear Defogger Control Switch is pressed again, the timer cycle becomes complete, or the Ignition Switch is turned to "OFF."

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

The Multi-Function Alarm Module has a Vehicle Speed Sensor input from the Powertrain Control Module (PCM). If the Rear Defogger Control Switch is pressed while the vehicle is not moving, it will time out as noted above. If the Rear Defogger Control Switch is pressed while the vehicle is moving at or above 73 ± 5 kph (45 ± 3 mph), the timer in the Multi-Function Alarm Module will energize its contacts, but will not begin its time out. This results in the Rear Defogger remaining on as long as the Multi-Function Alarm Module sees the vehicle speed at or above 73 ± 5 kph (45 ± 3 mph.) If the vehicle speed goes below 73 ± 5 kph (45 ± 3 mph), the timer will begin its time out, and continue counting down until the vehicle speed increases to 73 ± 5 kph (45 ± 3 mph), 5 minutes has elapsed or the Rear Defogger Control Switch is depressed. The timer will not reset to 5 minutes every time the vehicle speed drops below 73 ± 5 kph (45 ± 3 mph,) but begins coming down from where it cuts off.