busted rear window defogger, 1991 GT - Ford Mustang Forum
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post #1 of 4 (permalink) Old 04-25-2005 Thread Starter
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busted rear window defogger, 1991 GT


My rear window defogger hasn't worked in a while. Some scumbag busted rear my window last December, so I thought I might get lucky and the new glass, with it's new element should do the trick. Still nothing.

When I click it on via the switch, the light on the switch lights, but the rear window doesn't defog. I can see that it's plugged in. The lighter works, and I think it's on the same fuse.

Can anyone point me to some info on how to fix this?


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post #2 of 4 (permalink) Old 04-25-2005
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I can not find my manual right now, but I think there is a relay that is ?behind? the glove box. You might want to check that and make sure that it was not zapped when the window was broke out. I will look for the shop manual more in a bit, I am in need of it too.

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post #3 of 4 (permalink) Old 04-25-2005 Thread Starter
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It wasn't working for a year or so before the window got busted. Would have been nice to have the inconvenience of the broken window pay off with a new element that worked.
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post #4 of 4 (permalink) Old 04-27-2005
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You have all but eliminated the heating element as the culprit. Prove it by placing a test light between the two leads at the glass. If it lights there, then the element is at fault. If not (and I suspect it won't) then the trouble is upwire someplace.

If you can find the relay that LqDFx is referring to, then check on both sides of that to see if power goes in and power goes out. If power comes out of that, then it is somewhere between the relay and the heating element; which usually means a busted or poorly grounded wire. Also, they could have snuck in another fuse someplace.

Hearing that the lighter works off the same fuse circuit is good news. Hearing that the indicator light still works is good news. I highly doubt that the switch, or energy supply side of the circuit is the problem. If that relay exists, it is most likely the suspect.
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