rear window defogger HELP!
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Le Mans Master
Joined: May 2004
Posts: 5,866
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From: Hellinois
Finalist 2020 C4 of the Year - Modified
rear window defogger HELP!
I know I have lots of areas I am not real good at but electrical is definitely at the top of that list. My '85 has no rear window defog, it shows power at the black/red wire and the ground is good on the other side. My drivers side mirror gets very warm but the passenger side and the rear window have nothing. The switch and timer are both okay and working properly. I'm thinking I will start at the passenger side mirror first and if I can't find anything there I have no idea where to go next. I have the fsm, in fact I have two of them but I am not making much sense out of the diagrams.
Safety Car
Joined: Sep 2004
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From: Mission Viejo CA
Is that wire connected to the hatch lift rod? _____.
12 v. at the top connector of the lift rod? ____.
Is the wire to the grid on the hatch glass okay? ____.
12v. at the place on the hatch glass where the wire is soldered to the RH side of the grid? ____.
12 v. at the place on the hatch glass where the wire is soldered on the LH side of the hatch glass? ____. (This should be NO!)
If YES, your ground connection is defective between this wire on the LH side and the ground wire at the bottom of the LH lift rod.
If the ground connection checks out okay, the grid may have major damage.
Testing the RH mirror heater will require removing the mirror mechanism from the mirror housing. Do you need that mirror heater?
Thread Starter
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
Let's start at the black/red wire. 12 v. there? Yes!
Is that wire connected to the hatch lift rod? __yes___.
12 v. at the top connector of the lift rod? _yes___.
Is the wire to the grid on the hatch glass okay? __yes__.
12v. at the place on the hatch glass where the wire is soldered to the RH side of the grid? __yes__.
12 v. at the place on the hatch glass where the wire is soldered on the LH side of the hatch glass? _no___. (This should be NO!)
If YES, your ground connection is defective between this wire on the LH side and the ground wire at the bottom of the LH lift rod.
If the ground connection checks out okay, the grid may have major damage.
i have not went over every inch of the grid but it seems to be intact
Testing the RH mirror heater will require removing the mirror mechanism from the mirror housing. Do you need that mirror heater?No, if I can get the rear defog to work the RH mirror is no big deal.
Is that wire connected to the hatch lift rod? __yes___.
12 v. at the top connector of the lift rod? _yes___.
Is the wire to the grid on the hatch glass okay? __yes__.
12v. at the place on the hatch glass where the wire is soldered to the RH side of the grid? __yes__.
12 v. at the place on the hatch glass where the wire is soldered on the LH side of the hatch glass? _no___. (This should be NO!)
If YES, your ground connection is defective between this wire on the LH side and the ground wire at the bottom of the LH lift rod.
If the ground connection checks out okay, the grid may have major damage.
i have not went over every inch of the grid but it seems to be intact
Testing the RH mirror heater will require removing the mirror mechanism from the mirror housing. Do you need that mirror heater?No, if I can get the rear defog to work the RH mirror is no big deal.
Last edited by Midnight 85; Jan 22, 2017 at 03:26 AM.
Safety Car
Joined: Aug 2013
Posts: 4,429
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From: Minneapolis Mn
IIRC if you disconnect at least one end of the leads on the rear window defroster you can OHM the thing and check for continuity. If it doesn't check out and you can find the break, there is a conductive paint like material that can be used to bridge the gap.
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Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
Thank you, that was going to be my first thing to do today. It almost has to be that.
Thread Starter
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
A big thanks to you guys who offered help, the defogger works great, the spade terminal on the bottom driver's side was loose and slipped right off when I pulled it. I had been there a dozen times but I was probing the sides instead of pulling on it. Another case of the simplest things causing trouble. The passenger mirror still does not work and for now I can accept that but I am **** about things like that. If it is on the car it better work or I won't relax until it does.
