Instructables
It was a dark and stormy night. Snow has covered the entire car to a depth of several inches. It takes a few minutes to clear the snow, and by then the engine has warmed up enough to melt the frost clinging to the inside of the windshield, and has actually made inroads to the frost on the side windows. But the rear-window defroster clears only a narrow strip near the top and bottom  the window, leaving a wide strip of glass as translucent as a barrister’s door, and absolutely no visibility to the rear.

A worse scerio: The rear-window defroster grid has packed it in completely, requiring you to either drive blind (bad idea), or resort to scraping the rear window clear with your trusty wooden-handled snow scraper (really bad idea).

Now what?  This Instructable will help you identify and repair some of the most common rear-window defroster problems, as well as tell you how to avoid further damage to your defroster.  Try these repairs yourself, and save money and be safe this winter!  

This project was originally published in the January 2001 issue of Popular Mechanics.  You can find more great projects at Popular Mechanics DIY Central.

 
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Step 1: How to Damage A Defroster

Danger!

Let us make this perfectly clear: Do not try to scrape hard frost from a rear window equipped with a heater grid. The resistance wires are silk-screened, essentially painted, onto the glass. They are very easy to scratch, and will not work properly if the scratch breaks the continuity along the wire. This means that it’s possible for boxes, furniture or any other hard object one might place in a car to scratch the wire. Even a credit card can damage it. Don’t cram stuff into the back, and don’t let the load shift backward in your miinivan so that it touches the glass. If your window has a defroster grid, the only thing that should ever touch the glass is a soft cloth dampened with window cleaner. If you must clean the rear glass, scrub gently, and in the direction of the grid, not across it.

You don’t want to have to replace the glass to effect this repair. The compound-curve style of rear window is several hundred dollars, and a large hatchback’s backlite on, say, a Camaro, can easily top a grand or more. Add to this installation att the dealership or a glass shop—it’s definitely not covered by insurance.

MG Chemicals 8331 Two-Part Silver Conductive Epoxy will do the trick!

1 - Remove drivers side rear glass panel by using a panel popper.

2 - Remove tab from wire.

3 - Remove
solder on bottom side of tab that will attach to window. I initially
tried to use a solder gun but found using a drill gun with a wire brush
attached 'sanded' the excess off with ease.

4 - Clean tab and location on glass with rubbing alcohol. Make sure the new location is not the same one where the tab fell off.

5 - Use
a small vice grip to hold the tab. I found a great location where I was
able to use the back seat top cushion to jam the vice grip to help hold
the tab to the glass window. It was very sturdy.

6 - Grab a piece of
cardboard and a stir stick. Squeeze out epoxies at a 1 to 1 ratio(1 black
tube 1 white tube), I only ended up using maybe 1/4 of the tube. Stir
very well. It will take a while for the epoxy to harden, so no need to
rush.

7 - Use stir stick to generously apply the mix to the tab. (I put a
small amount on the bottom) Make sure you spread it around to contact
the circuit on the glass.

8 - Use a hair dryer to help harden the epoxy.
Very important: Don't mess with it while it is drying! I propped up a
hair dryer and set it to low heat since it was only about 6 inches away
from the tab. Left it on for 20 min. Came back and the epoxy had
hardened.

9 - Remove vice grip and reattach wire to tab

10 - Test with multimeter before reattaching panel.

FarhadJ13 months ago

LOL but how to repair ?

3366carlos6 months ago

great info, i hope i never need to repair mine.

doctorkb8 months ago

This 'ible is really about how to find the problem with a rear window defroster, not how to repair it.