The 1978 Corvette rear window relay is an electrical switch that opens and closes under the control of another electrical devise. The defroster is activated or deactivated through this relay when the rear window defroster switch is pressed. It will also automatically deactivate when the relay's programmed timing cycle ends.
Original 1978-79 Corvette rear defroster systems were flawed from the factory. If the defroster was on with the ignition switch in the run or accessory position and the ignition switch was then switched to the off position, the defroster would continue to operate until the programmed time cycle ended. This would reduce battery life and could potentially cause a weak battery to go dead.
In 1980 Chevrolet corrected this flaw. This relay/timer along with an adapter wire (included) that runs from the defroster switch to the relay timer will update your defroster system to 1980 Model operating the specs. This is the same update that was provided to dealers as an update kit. It was not provided as a "recall" repair, but as an update kit that could be sold and installed on a customer's Corvette. The adapter wire must be installed and used along with this relay/timer or the system will not operate at all.
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