Skip the auto shop - Our mechanics make house calls

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

asked by on

How does a car's rear defroster work?

A: Most vehicles have an electrical grid on th...

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.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: A/C stuck on floor and defrost will not change on any settings

Hello. You need to see if the mode door actuator is working. This actuator is on the evaporator case on the driver's side above the gas pedal. You have to remove the knee bolster for access. If this is the...

Q: If I have low coolant and my car won't blow cold air could that be the problem? I have freeon

Hey there, thanks for writing in about your 2003 C240 Mercedes-Benz. The low coolant light only means your engine coolant level is low in the engine cooling system. You may have a coolant leak. This has nothing to do with...

Q: How do I use the sun visors?

The sun visors are located above the two front seats, and help keep sun and glare out of your eyes. To use the sun visors, manually fold them down until they are blocking the glare. If the glare is entering...

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.