Heated Glass Element: Description and Operation

DEFOGGER CIRCUIT OPERATION
When the Ignition Switch is turned to "RUN," voltage is applied through the CLUST Fuse to the HVAC Control Assembly and through the INDIC Fuse to 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.

TIMER RELAY
When the internal contacts of the Rear Defogger Timer Relay are closed, voltage is applied to the Rear Defogger Grid and Indicator.

RUN CYCLE
The Rear Defogger Timer Relay contains a solid state 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."