I have an 87 Skyhawk Wagon, and up until about a week ago the rear defroster was working fine. It has since ceased to defrost with the cold and snow.
I checked the leads/lines running across the back, and they all seem fine.
I took a test light to the power wire on the rear hatch and came up with no power, however the dash switch lights up, and I can hear the relay click on and off when I hit the switch.
I can not find which fuse it is, or even if it has a fuse (shouldn't it??); none of the fuse names seem to make sense for a rear defroster...
I know on newer cavaliers that they have a green wire/module that goes bad underneath the driverside carpet that you can bypass with thicker gauge wire, does the Skyhawk have anything similar?
Any help would be greatly appreciated. Thank you!
I have an 84 so will share what I have out of the service manual. Power is provided through the "gages" fuse. Do you have access to a service manual? If not, please send me an email to email@example.com and I will forward you a pic of the defogger troubleshooting page.
Thank you for the quick reply! I will certainly check the gauges fuse tomorrow. If that fuse were blown though, wouldn't the gauges not work as well..?
And as for a service manual, I do have a Hanes manual buried in my tools somewhere; I'd imagine that will work just as well? I'll probably email you anyway.
Thank you again!
I have both the shop service manual and the electrical manual, so if the problem continues after what Paul gets you from the service manual, I might have something more.
I wouldnt know what Im looking at, but Id try.
i just had this happen to my 88 plymouth shadow. check the wires that go from the body of the car to the tailgate. from years of opening and closing the wires broke. old brittle wires plus this exteme cold make them very fragile. in my experiance with rear defrosters if you have power to the switch and can hear the relay it is more than likely farther down stream. you can also do continuity check of the grid itself to rule that out. hope you have a warm garage to work in, this weather is brutal on man and machine alike. rear defrosters are one of those things you dont really appreciate untill you suddenly dont have it. kind of like a garage door opener or tv remote. can you imagine actually getting out of your car to close the garage door or getting off the couch to change the channel? its like going back to the stone age!!
If your gauges work the fuse should be ok.I did try to read thru my true shop manual (gm) and it is so much info I got tired.Anyway in your main fuse box there should be a actual circuit breaker #3 which is for PWR ACC 30amp which in turn is for the rear window defog,power door locks,or power seats.My big manual has steps to trace the issue and there are grounds that are relevant to this particular option.I was too tired to read more and I worked today so this is all for now.My cheapo chiltons lead me to the fuse block pic and while the #8 in the block is for gauges and yeah rear defog is listed in that as to what applies to this fuse.I could check my car but,no rear window defog option or pwr locks etc.Just a thought on quick checks.I need more time to understand the diagrams to pinpoint things.
Just my 2 cents - I'd suggest checking at the rear window and make sure you are getting voltage back there with a test light or VOM. If you got voltage there there must be a break in the window traces . Next I would be looking at the wiring where the hatch opens like John Galt mentioned. Unfortunately those wires are buried inside these rubber boots. one on each side. There just might be a possibility you might have a simple ground issue as well....since one side of this wiring must be carrying current back to ground. Symptom should be voltage on both sides of window if the ground isn't working.
These 2 places are the high risk areas for failure. If you do have a breaker gone be careful as the defroster is one of the parts of the electrical that carrys a lot of current. A short might be the cause of the breaker failure.
Got some photos this morning . These are some areas for you to double check for problems.
This is where the wires are always bending and might have fatigued and broken - there are 2 of them.
Check to see that both wires are still connected to the glass too. I measured my voltages today. The one on the drivers side measured 12V.
and the one on the passenger side measured .2V looks like I may not have a great ground on that side. Hmmm.
I also found that the liftgate striker plate makes a perfect place to ground your tester to check for current or voltage back here.
Thank YOU orlen for those pics.I will scan in the details of the rear defrost maybe tue,wed from my gm shop manual.The voltage you said is kinda low imo on recall of my quick learn in my book tonight.I can say the black wire on the pass side term is defog is suppose to be 0 volts,middle of defog grid (yes the middle) 5-7 volts and the black wire on the driver side grid should be 10volts.This is in order exactly I will download a scanned diagnostic of the actual diagram and the print how to later this week.The system varies based on sedan,coupe,wagon to some degree.I am sooo tired done.0
Wow you guys rock, thanks for the pictures!
I was working like crazy, and today was my day off but of course, the high is 11F... and with no garage I did not want to freeze to death. I have a garage at work (at a lovely 62 degrees), and when it's slow I can usually work on my own stuff w/o any problem (hopefully tomorrow!). I'll keep you guys posted.
I'm going to slice open those two rubber boots on the lift gate and inspect/ test the wires there as a next step. I guess I'll just use generous amounts of electrical tape when I'm done?
Ps good tip on the striker as a ground haha. I'm going to use that from now on back there.
While you are in the neighborhood you can check the area there where the Liftgate attaches to the Hinge Pads. I noticed some rust creeping in around my pads this year - and that is why you notice the generous amounts of fresh paint all along under the Liftgate in a couple of the photos. You can't really get to anything there without removing the Liftgate, and you can't get the Liftgate off without removing those Defroster Wiring. I guess you have to drop the Headliner to get at those Defroster Wires. Ahhh the joys of Wagon ownership...LoL
So this ole Country Bumpkin just cleaned up best as he could and used a whole lotta rust inhibitor and later plenty of enamal. I had to lower the Liftgate some to get deep inside as I went - while crouching ever lower under the Liftgate as I painted.
So far so good.
I will scan the technical things in wed I was busy today working on my maytag washing machine.It far less complex but the issue I have is a pain.
I'd say we piled on this one pretty well. GO TEAM!
Orlen - great pics - I don't have a hatch so I can't help with that. I sent him the troubleshooting pages out of my 84 Shop Manual.
Ron - I am dealing with an issue on my washer as well. My wife likes to stuff the poor thing and burns out clutches so no high spin. It is an easy fix but a pain in the butt. Always something
So I checked the 'gauges' fuse, but as the gauges are working as well, so is the fuse. If I take it out, I lose all my gauges and the button for the defroster will not click on.
I checked the back of the switch, and it seems a thick gauge purple wire with a white stripe carries the current to it. It gets power from the switch, which I'm going to guess is a good thing (see photo).
From there.. I'm going to take a gander that there is a break in the line somewhere... Which is not so good.
Also if I remove the PWR ACC 30amp relay, the defroster does not click on either. But with it back in it works (it's the only non-fuse on the fuse block).
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From there, I checked the rear door wires, thinking there could be a break in them if power is coming from the switch. First attached photo is the rubber boot opened, but that wire was fine and not broken... I also tested it with the test light in the boot, and no power...
I also tested inside the door panel before and after the connector going from the purple wire to the black one (see photo), but neither side had power...
Any suggestions on where to go from here?
The switch gives power, but no power in the rear. Wires in the rear hatch (on the driver side, did not check passenger side) have no power, and seem fine w/o any breaks... I'm not sure where to go from here.
Thank you guys for the support so far!
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Also, rear hinge latches seem pretty rust free! The car sat in a garage for a good chunk of it's life.
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I am running out of thinking power.I will revisit this thurs when I am not tired.The switch coming on is good this means the breaker is ok,seems like either the 192 plug in the back which feeds from the quarter area up may be loose yeah purple wire,or maybe your grounds need to be removed and cleaned on quick thought.No ground No power.I want swear to this being whooped.
My suspicions are now on the relay timer. The contacts might be gone inside it. Wonder where that bugger is????
No doubt - knowing GM - every make and model probably has it in a different location
I agree with the relay timer as the next step. The manual indicates it is under the dash. I don't have one so can't help much more than that.
This is a good learning exercise for me as both my J's have this option.
As seems so often , once again I can share the difference between the Pontiac and the Chevy. The Pontiac has the Defroster switch on the right side of the steering column while the Chevy has it on the left hand side.
Success! So while driving today to get some coffee and brainstorming on what to do next about the defogger.... I noticed my rear windshield fogging up from the rain we've had here. I decided to turn it on, in the slight hope that it would work, and IT WORKED!
I'm not sure what exactly did it... I had taken both the PWW ACC Breaker and 'Gauges' Fuse out a few times... and the weather warmed up a bit... maybe the combination of both??
Regardless, it works again!
I want to say THANK YOU to everyone! You guys have been so helpful with diagnosis, diagrams, and overwhelming support.
Well keep this stuff in mind if it poses a problem later for reference.Glad it worked and my nephews car well still leaks water and I know generally what the issue is.In short I suspect the tail light seal itself and plan on replacing all four seals on his lights as this appears to be a common issue on his models and others.Coool