Diagnosing a Bad Defroster Grid

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Prepping Glass for Defroster Repair....5

How to diagnose a bad defroster grid. Learn about rear defroster grids, diagnosing defroster problems, and stencil installation in this free video on car repairs.

Part of the Video Series: How to Repair a Rear Defroster
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Video Transcript

In this clip, we're going to talk about the proper way to diagnose and repair your rear defroster grid. In this step, I'm going to describe to you the functionality of your rear defroster grid. And, instruct you on how to diagnose any bad connections. Go ahead and pop the glass open right there and lift it up. What I have here, is my test light. What I'm doing is checking the continuity of all these little wires you see running across here. How the circuit works, is it's pretty much like a toaster. It feeds current through this side and out this side. And, uses these wires as resistance load. They actually heat up to a certain temperature and melt the ice or the fog on the rear windshield. I've already performed a visual inspection on all my defroster grid wires. And, actually found the bad spot. It's right here. What had happened, is this weather sealer had came down and water ran down the inside of it, actually rusted this bolt up. And, corroded away the metal paint that makes up that defroster grid element. I'm going to demonstrate another method with my test light. I'm going to put it on a good shiny ground. And, I can show you I have connection here. You see the light, light up? But, on the other side of the brake we've got nothing. And, just to show you that it still lights up we'll to the same one and one above. You're going to want to check the continuity all the way up these. Because, you may not see visually where it's bad at. The other way to tell is to turn it on, on a nice cold foggy day. And, you'll be able to see just by the performance which grids are not working. It may be possible that you have to repair more than one. That is the proper way to locate the failed defroster grid component.


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