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rear defroster help needed

 
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tsbrewers
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2005 Chevrolet Impala


PostPosted: Sun Nov 11, 2012 10:24 pm    Post subject:  rear defroster help needed Reply with quote

hey all, I am trying to get my rear defroster working again on the '05 impala.

To try and save some time, I am pretty sure I have it narrowed down to the wiring AFTER the relay and breaker. There is a dark green wire that comes out of that panel that is for the defroster/heated mirrors (that work great still), but I am not getting any power at the connectors at the rear window. I have continuity all over the rear window, IE from each tab to the other, but I can not get power to these tabs from the front of the vehicle.

Basically, I am trying to figure out the wiring path from the front to the rear. From what I can tell, the green wire goes to the radio antenna module, then I think comes out black and goes to the window??

Brew
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Dirtyharry
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2004 Chevrolet Monte Carlo


PostPosted: Thu Nov 15, 2012 6:41 pm    Post subject:  Impala defrost issues. Reply with quote

Hey there,

I'm a new user (a dirty, dirty 04 Monte SS owner), BUT I am, what would you say WELL-VERSED in these defroster issues! (Our cars have a lot of similarities) I had a bunch of stuff go wrong with my defroster. The green wire coming out of the fuse box on your Impala goes all the way to the back window radio antenna module with no connectors according to the wiring diagram for an Impala. (If you need to run a new wire, that would make it easy; just be sure to use the same size wire because that's a 30 AMP circuit.)

Have you checked to see if your green wire shows signs of burning at all coming out of the fuse box? Mine had burned from the fusebox to about 1.5 inches from the fusebox as well as burned the fusebox itself where the green wire pin attaches. I ended up bypassing the entire fusebox and running the 30 amp circuit breaker and relay outside of the fusebox but then I had to rewire 2 radio wires as well. Plus if you have heated seats and heated mirrors bypassing the fusebox affects that as well. GM doesn't have a "fix" either for the issue. The wiring gets hot and overheats the fusebox and the wire and a new right side fusebox is $230 from GM. So theoretically the whole cluster-F&#* could happen all over again!!

OH, I almost forgot! I also had to replace the antenna/defogger module as well because once I fixed my wiring I had a good 12 volts at the antenna module but no voltage coming out. I got an AC/Delco new antenna module delivered from Amazon for $33.

Well, hopefully this helped you out and if not, let me know here.

DH
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tsbrewers
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2005 Chevrolet Impala


PostPosted: Thu Nov 15, 2012 8:48 pm    Post subject:   Reply with quote

Yup, that does help. I did have the burnt wire problem too which started it all. I cut off the burnt end, and about 3" of the green wire, crimped and soldered on a new end on a new section of wire, and soldered that to the existing green wire. I got continuity from the relay plug to the green wire so I figured I had the burnt part fixed. But when I ran a jumper from the #30 socket to the #87 socket (where the relay goes) I was not getting juice to that green wire then for some reason. For giggles I ran 12v directly to the green wire and where the connector is on the rear window it got VERY hot.

Which told me a few things, the wiring to the window is good, but when I re-connected the tab on to the rear window, I used WAY too much epoxy? and that was heating up too much. I basically gobbed it on to make sure the tab stayed. Unfortunately, I think that makes it collect too much juice and gets very hot.

SO, I am thinking/hoping, I just need to chisel? off the big gob of conductive epoxy I used to re-connect the tab to the window and re-do it more carefully and not use too much epoxy. Then I "hope" that might fix all the problems I am having.

One concern I have is that I can get continuity to the green wire from the relay, but once I apply power, I no longer seem to have that connectivity. So I am not sure if the built in breaker is sensing too much power draw (remember big gob of epoxy) and opening up?

I hope some of that makes sense.
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Dirtyharry
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2004 Chevrolet Monte Carlo


PostPosted: Fri Nov 16, 2012 12:32 pm    Post subject:  Defogger issues... Reply with quote

I'm not sure if running that jump wire where you did is going to help you or not. The way the circuit works is you have 2 "feed" wires going into the right junction block: A red 60 amp wire (hot at all times) coming from the underhood fuse box (circuit 1042) feeding the rear defog relay, and an orange wire coming from the BCM for "load management" (circuit 480) feeding the relay. Then you have the dark green wire coming out of the relay (circuit 1927), that runs to the rear defrost/antenna circuit. The other circuit (193) is a white wire that comes from the HVAC control head.

I have heard using too much of anything (epoxy or those defroster line repair kits "solder") isn't good for the rear defroster. I've been told the system is designed to have the two soldered leads at both sides of the rear glass and the defroster grid itself and you have to be careful adding anything that's not supposed to be there. When I was a tech way back we used to use scotch tape to fix the lines of the defrost grid once we knew where the "open circuit" was, (usually caused by a scratch from people tossing crap in the back window!), by using just a touch of the metallic paste stuff just as thin as the defroster line was and then pulling the tape off carefully. I have heard from a few places that you can only really do a few repairs on the grid before they recommend installing a whole new rear window. The glass does get hot to the touch and that is normal but I've also heard of hot spots in the glass causing back windows to blow out as well.

Good luck in your repair dude!

DH
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tsbrewers
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2005 Chevrolet Impala


PostPosted: Fri Nov 16, 2012 7:56 pm    Post subject:   Reply with quote

Thanks. We jumped the green wire and the rear window wasn't getting warm at all, but as soon as (my wife) touched the spot where we "fixed" the loose connector, it almost burnt her.

We fixed the loose tab once before and it worked fine for a couple years, then it quit working again. I tried to pull off the wire from the tab, and broke it loose again, so I gobbed it on there again. When that didn't work, I found the burnt connector on the green wire. I am wondering if my last fix of the tab (what was much neater) overloaded it too, just more slowly.

Anyway, I am thinking I need to remove all the extra silver epoxy and do it again with much less. Then give it a try. I will report back my findings. Thanks for the help.

Brew
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