How to Fix Your Rear Defroster

rear window

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How to Repair a Broken Rear Defroster Line

Back window of a car

 Morten Falch Sortland/Getty Images

If you think about it, your rear defroster is a pretty amazing accessory to your vehicle. For decades, drivers were forced to drive without any view out of their rear windows if the weather caused their windows to fog. Sure, there was the warm air blowing from the defrost vents at the base of the windshield, but this had little, if any, effect on the back window at the far end of the cabin. If you had kids, you could pass a cloth to the back seat and give orders to keep the rear window clear. Car seats were optional in those days.

Then along came that curious grid of wiring across your back window. A button on the dash activated the system, and right before your eyes, you saw the fog disappear. Ice would melt, snow stayed away. It was a small miracle. Some cars actually tried versions of this on the windshield, but it proved a bad idea. But the defroster became standard issue for rear windows, and the world was a better place. That is until something put a little nick or scratch in one of those delicate lines across the glass. Then, the system stopped working. It was widely accepted in the car business that a car more than 5 years old would likely have an inoperative rear defroster.

The days of having to live with a non-functioning grid of defrost lines are over. The latest defroster repair kits are amazing, addressing almost every possible problem that can arise in your system. The first step is always troubleshooting. You need to figure out why your defroster isn't working. The complete repair kits come with diagnostic tools like a special test light, too. Before you start repairing, you should check your fuse to be sure it's not a simple blown fuse problem. The two most common problems with rear defrosters are:

  •  A break in the conductive lines.
  • The deterioration of the spades that connect the grid to your car's wiring.

Both of these can be repaired, and we will teach you how.

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Repair a Damaged Rear Defroster Grid

Ready for repair
Tape off the section of the rear defroster to be repaired.

photo: Matt Wright

If you've tested your rear defroster using the best testing methods and have located a break in your defroster lines, proceed with your repair. The first step is to tape off the repair area. There is blue painter's type tape supplied with your kit, but if you need extra you can use the standard hardware store blue tape. As you tape around the damaged section, keep the untaped area as slim as possible. This is where you will be repainting your defrost lines. If the space is huge, your line will be huge. It will still function, just look bad.

With the area carefully taped off, repaint the line. Let the paint dry thoroughly (I'd wait 24 hours) and then give it a try. 

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How to Repair a Broken Wiring Stud in your Rear Defroster

Special conductive epoxy
Mix a batch of conductive epoxy to reattach the spade plug.

photo: Matt Wright

You may think that a broken wiring stud (or spade) connector on your rear defrost grid means that you will never have a rear defogger again. But the new kits have repair parts you can use to repair this and anything else wrong with your system. If you've tested your rear window grid and found a bad spade connector or stud, the first step is to get the old one off (if it's still hanging on) and clean the area under it. This can be done with the emory cloth included in your repair kit. Next mix up a little of the conductive epoxy and use it to reattach a new stud to the glass. Be sure you get it in the same spot as the one you removed. Allow it to dry for 24 hours and give your defrost a try.

Tip: It's also a good idea to have a circuit tester handy to be sure you have a proper ground for the system.