Q: How Does a Car's Rear Defroster Work?

asked by on November 19, 2015

How does a car's rear defroster work?

Most vehicles have an electrical grid on the rear window that will warm the glass to clear fogging or frost. The rear defroster grid is applied to the inside of the glass by the manufacturer and actually conducts electrical current when it is turned on. There is typically a timer built in to the circuit that will automatically turn it off in 15 minutes or so, since it tends to get forgotten after the glass has cleared.

Larger vehicles like vans and SUV’s commonly have rear defrost capability built into their rear A/C and heating systems. These function are much like the defroster in the front but using dedicated blower fan which ducts direct airflow onto the rear glass. Should you run into any problems with this system, have a professional mechanic diagnose your defroster to accurately repair your vehicle.

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