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・Fair and transparent pricing

Get a quote

What others are asking

Q: Defroster not working

Hi, the problem could be the defroster grid has separated from the main power clip/tab. To reattach the tabs, remove the metal clip out of the connectors and use a tab repair kit to repair the problem. Replace the separated...

Q: Air conditioning not working.

There are innumerable things that can go wrong with the A/C system and so the best thing to do is request an air conditioning system inspection and the responding certified mechanic will get this resolved for you. The most likely...

Q: Window not working

Hello! That is a problem that several owners of the 350Z have faced. I personally have repaired three 350Z windows, and all three had a malfunction of the driver's side window; in each case, the cause was the driver's side...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...