Heated Glass Element: Description and Operation
CIRCUIT OPERATIONWhen the Ignition Switch is turned to "RUN," voltage is applied through the HVAC Fuse to the Rear Defogger Switch and the Rear Defogger Timer/Relay. When the Rear Defogger Switch is pressed, voltage is momentarily applied to the Rear Defogger Timer/Relay through CKT 292. When voltage is applied to the Rear Defogger Timer/Relay, the Rear Defogger Timer/Relay will close the internal contacts. The internal contacts remain closed until the defog cycle is complete or Rear Defogger Switch is pressed a second time.
When the internal contacts of the Rear Defogger Timer/Relay are closed, voltage is applied to the Rear Defogger Grid and indicator.
The Rear Defogger Timer/Relay contains an internal timer to control the time the internal contacts are closed. When the Ignition Switch is turned to "RUN" and the Rear Defogger Switch pressed for the first time, the defog cycle lasts 10 minutes and further operation will result in 5 minutes defog cycles. The defog cycle is reset to 10 minutes when the ignition Switch is turned to "OFF" and back to "RUN."