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Repairing Your Rear Window Defroster

It snowed last night. I mean it REALLY snowed last night...

» Warning!
» Doesn't Work At All
» Uh oh...
» Easy Repairs

Easy Repairs

Okay, so everything is working but you have a few lines of the grid not working. The lines don't work because there are breaks in them. So, we have to find these breaks. If you have a SUV or mini-van, the grid is easy to check. If you have a car you'll need to crawl into the back seat in a position the human body was not designed to be in. And if you want to see something really funny, watch a 250 pound, 6'3" man try to fit in the back seat of a small import.

Anyway, if you look from the inside out, you may see the breaks in the lines against the sky. Just start at one end and work your way to the other looking very carefully. If you can't see any breaks you will need to get out your test light or voltmeter. You need to keep in mind that when you check the defroster grid the voltage will decrease as you get closer to the negative side. In a line that has a break, the voltage will be the same until you get to the break and then disappear.

So with this in mind, lets start checking. First get a couple of pieces of aluminum foil. Wrap one end around the probes of your voltmeter or test light and leave the other end flat. This will let you check the grid without risk of further damage. I prefer to use a test light; I think it's easier. If you use a voltmeter the idea is the same. I clip the test light to a good ground and pressing the aluminum foil gently on the grid I watch the light. As you slide it from the positive side of the rear window defroster grid to the negative side, the light should grow dimmer as you go. If it stays bright then you are on a line with a break. As soon as the light goes out, you found the break. I have someone draw a circle on the outside of the glass with a marker so I don't lose this break while looking for others.

Once you find the breaks, repairing them is simple. You can buy a rear window defroster repair kit at most auto parts stores. Clean the area with alcohol. Don't use window cleaner since it might leave wax or silicone behind. Also, don't use paper towels with color or designs on it. The kit will have a self-stick template and a small bottle of conductive paint and brush. If the template is not the right size if the break is longer than the template, you can use masking tape to mask the lines.

Once the area is clean and masked off, shake, the bottle well, and simply paint across the line stroking along the line and not against it. Do all the breaks and then come back in a few minutes and give each break a second coat. Let it sit for 24 hours to allow the conductive paint to thoroughly dry and set.

Once you have all the breaks repaired, go back and check the rest of the lines you repaired since there may be other breaks a little further down. There's no rule that says only one break per line.

And that's it. Rear window defroster systems are pretty reliable and most times the worst thing that happens is a broken line, which you see, is very easy to repair.

» Part 1       » Part 2       » Part 3       » Part 4
Additional Information provided courtesy of and Warranty Direct
© 2000-2007 Vincent T. Ciulla

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