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TOPIC: windows and sunroof switch failure?

windows and sunroof switch failure? 26 Mar 2021 18:09 #21836


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I've got an 86.5 928S Auto, and just yesterday I went for a test drive on the suspension work I'd done and found that both windows won't go down and the sunroof won't open. No sound of struggling motors or anything like that, just nothing. The rear wiper works. The odd thing is that everything was working a month or so ago.
Anyone out there have an idea why these three items would all stop working at the same time?
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windows and sunroof switch failure? 28 Mar 2021 00:03 #21838


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Hello Vince,
If you don't have the factory workshop manuals, I suggest you download them. They're available in PDF format at no cost from this link:

www.ligeti.com/928/

The wiring diagrams are included. Looking to your 1986 model, there are fuses for the windows and sun roof (fuses 14 & 15). Check them, be sure there is no corrosion.



There is a relay for the window lifts (VI):


and looking at the wiring schematic with the relay



You can see that the relay VI supplies power to both the windows and sun roof. My guess is the problem is with the connection at the base of the relay VI or the relay has failed.

In the diagram I highlighted the 30 circuit which is always at 12V, and the 87 circuit which is switched.
Rich
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windows and sunroof switch failure? 28 Mar 2021 12:38 #21839


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Thanks for this, Rich.
I do have the complete set of manuals for the car, but I was short on time and feeling impatient when the issue popped up, so posted my question here.
You confirmed my suspicions - sort of. I was going to check fuses and clean everything up(dash pod is coming out soon anyway). I thought relay might be responsible, but wouldn't have guessed one relay for windows AND sunroof and thought it a long shot for two to quit at the same time.
I'll get on it and see what I find.
I appreciate your input!
Vince.
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