Why Is My Rear Defroster Not Working?

Your car’s defroster is also known as a defogger.

Your defrosters are a system that helps to clear condensation and frost from your front and back windshields.

Since some weather conditions can cause rapid fogging of your car’s glad, defrosters are a safety feature by helping you maintain clear visibility while driving.

Recently we heard a story from a driver that his rear defroster was not working as he was heading back down the mountain after a long day of skiing. There were no other apparent problems with his car and he didn’t know what to do – as the winter weather made the use of defrosters necessary. Let’s take a look at how defrosters work and some common rear defroster problems.
Car driving on a snowy winter road surrounded by trees

Related: Safe Driving Tips for 2018

 

How Does My Defroster Work?

Front Windshield Defrosters

Your front defroster works by directing the warm air up through vents at the base of the windshield in order to clear condensation or frost. In cold weather, the defroster is most effective after the engine has warmed up and can send warmer air through the vents and onto the inside of the windshield.

In some cars the defrost position controls will also activate the air conditioning = compressor. Cooling the air with A/C first will remove more moisture from the air so it can do a better job clearing the windows.

Rear Windshield Defrosters

image of suv driving on snow packed mountain road
In most cars the rear defroster is electric. You will notice thin lines running across the rear window. These lines are electrical lines that are embedded in the glass. When you active your rear defrosted these electrical lines heat up. Your rear defrosted is activated by a separate button than the front defroster. You will notice the condensation or ice first clears up around these electrical lines until it dissipates throughout your rear windshield. The benefit of your rear defrosters being electrically powered is that they start working as soon as they are turned on, rather than having to wait for your engine to heat up.

 

Potential Causes of Rear Defroster Problems

Defroster Grid:

One of the electrical lines that make up your rear-defroster grid has been broken.

Defroster Tabs:

The tabs that bring electricity to the defroster grid may have been knocked off as their glue cracks over time or come lost after a window tiny application

Buttons & Knobs:

Over time the buttons or knobs that control your defroster may get stuck or stop working. In this case, the button may just simply need to be replaced.

Fuses & Wiring:

Defroster grids draw a lot of power and this could cause the fuse for your defroster to blow. Fuses can be tested and replaced by your mechanic.

 

What to Do If Your Rear Defroster Doesn’t Work

In the case of our customer at the beginning, he eventually realized his back windshield hatch was not closed all the way and it was a simple fix – close the hatch and his defroster started working again.

However, if your defroster isn’t working and it’s not such a clear simple fix – you need to bring your car into a professional. Your defrosters are necessary for safe driving in the winter months – and here in Colorado winter weather can be unpredictable well into the spring.

Whether it’s your front defroster, or your rear defroster the total car care specialists at AAMCO Colorado as here for all of your electrical and air-conditioning repairs. Schedule an appointment with one of Front Range locations today.

 

Schedule an Appointment

BOOK NOW

The information contained in this website, or any of our content, videos, and publications is for general information purposes only. Learn more about our information disclaimer »