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rear defrost problem help!!

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Old 01-25-2006, 10:12 PM
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Default rear defrost problem help!!

every time i turn on the rear defrost it doesnt shut itself off and if idont shut it off myself it eventually dies along with the power seat. ive checked the fuse and it getas really hot before they shut down .ive replaced it but it doesnt help any other suggestions to what might be the cause??
Old 01-26-2006, 11:57 AM
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Sounds like it's time to start checking the wiring. Have you installed anything electrical lately? Mine's not working right now and I haven't gotten around to checking the wiring yet. I know my problem started after installing some other guages so I'm starting in that area first.
Old 01-26-2006, 01:17 PM
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no actually i havent install anything , at first i thought maybe one of the filaments on the back window had been cut but i cant find any breaks. the wiring on that could be fun to trace too.
Old 01-26-2006, 03:33 PM
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The rear defroster is a common problem with F-bodies. I have a friend with an '01 formula and I have a '00 TA. Both of our cars will active the rear defrost, click it off early then the defrost will not work unless we let it cool for 5+mins at which point it only runs for maybe 20 sec at a time. He took his in to a dealer. They replaced the breaker, did a TSB recommended procedure that involves swapping out terminals in the fuse box, replaced the heater head unit, replaced some kind of timing unit, and now they're actually replacing the rear window. (essentially they're replacing everything.)

Alternatively he told me he found something online about people swapping the breaker out with a fuse and it fixing the problem.

Sounds like your problem could be this "timing unit"
Old 01-26-2006, 04:46 PM
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sounds like u might be right wheres this timing unit located?
Old 01-26-2006, 05:23 PM
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while we're on the subject of this...one of the filaments i think it is...the lines that come across the window is burnt out or something and doesn't defrost in that certain spot...is there any way to fix this particular problem? just curious...thanks guys
Old 02-01-2006, 10:10 PM
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I have the same problem. Does the fuse fix take care of it? What amp rating does the fuse need to be?
Old 02-02-2006, 12:35 PM
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Originally Posted by Mike44138
The rear defroster is a common problem with F-bodies. I have a friend with an '01 formula and I have a '00 TA. Both of our cars will active the rear defrost, click it off early then the defrost will not work unless we let it cool for 5+mins at which point it only runs for maybe 20 sec at a time. He took his in to a dealer. They replaced the breaker, did a TSB recommended procedure that involves swapping out terminals in the fuse box, replaced the heater head unit, replaced some kind of timing unit, and now they're actually replacing the rear window. (essentially they're replacing everything.)

Alternatively he told me he found something online about people swapping the breaker out with a fuse and it fixing the problem.

Sounds like your problem could be this "timing unit"
Did the dealer trace the wiring from the front of the car all the way back to the rear glass? Apparently the wiring runs under the seat and through some other spots were some people have experianced the wiring getting pinched and then having problems with the defrost.


One thing to test that might help narrow down the problem somewhat..can you adjust your power seat while the defrost is on or during that period where it doesn't want to turn on? The power seat and the rear defrost is on the same circuit. From the reading I've done, if the seat still works, the problem is someplace starting with the wiring under the seat and running to the back glass...somewhere in that area. If the seat doesn't work, the problem is someplace between the seat forward (bad fuse, problem with a wire towards the front of the car..) I haven't heard anything mentioned before about a timing unit...so no clue if there's a timing unit or if it's bad on how it would affect the seat...
Old 02-02-2006, 06:03 PM
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Ok, I went to work this morning, ran the defrost...sure enough, it (and the seat) quit a minute later. Stopped at the gas station and popped open the fusebox cover. When I tried to yank out the defrost/power seat circuit breaker it burned the f#ck out of my fingers!!! I mean, this thing was nearly as hot as a soldering iron! After letting it cool enough to pull it, I popped in a 30 amp fuse. Problem solved, works like a champ. Thanks a bunch guys! You rock!

Unless you like your fingers well done, don't touch the breaker right after it fails!

Last edited by thunderdan74; 02-02-2006 at 06:10 PM.
Old 02-02-2006, 06:56 PM
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yah thats what mine does its hotter than hell after a minute ,but what was the original fuse a 20 or 25 and why would it have to be a 30 now to work?
Old 02-02-2006, 07:04 PM
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Hope the circuit breaker that you replaced with the 30 amp fuse was rated 30 amp as well. If not, you might be melting wiring.
Old 02-03-2006, 04:08 AM
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I'll double check but i think it's a 20 amp breaker...might wanna put a smaller fuse in there
Old 02-03-2006, 06:46 PM
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Originally Posted by Sebring 00
Hope the circuit breaker that you replaced with the 30 amp fuse was rated 30 amp as well. If not, you might be melting wiring.
Yes it was a 30 amp breaker. Thanks, though.
Old 02-06-2006, 06:25 AM
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I had the same problem. the defrost and seat would quit after about 90 seconds, when it cooled off they would work again. replaced the breaker with fuse with the same rating. works perfect now and its been years since I did it.
Old 02-10-2006, 11:57 PM
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Were is the breaker for this located?
Old 02-11-2006, 05:47 AM
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Originally Posted by Jimmy P
Were is the breaker for this located?
same question for me? Can someone post a pic to be more exact Thanks guys
-Ivan
Old 02-11-2006, 05:54 PM
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It is in the fuse box on the side of the dash. Second or third one down on the left side labeled seat/defrost. Turn on your defrost and let it overheat and touch a few of them silver boxes in there. You'll find it soon enough!
Old 02-12-2006, 04:15 AM
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Thanks guys I tried that today and everything worked perfectly.
-Ivan




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