83SC: Odd electrical windows issue

Deschodt · 08-31-2009, 09:37 AM

I've had a few electrical window failures of late... but odd ones, which is why I'm posting, in case someone's seen something vaguely similar and could point me in the right direction...

First one seemed like a bad switch on the driver side, so I replaced it and all was well for a while. Then I could not operate the passenger window from the driver side's other switch, but I still could from the passenger side, which then "sometimes" restored functionality to the driver side switch ??? Huh ?

Anyway, replaced that one too and was fine for another while...

Now the driver side one is bad - again. And when it gets bad, all 3 switches are bad! But get this, if I turn the car off for a while and try again a few hours later, more often than not it works again, and if ti does, then all 3 work again !

This morning my driver side window would not go up... I turned it off, checked the fuse, nothing. Came back at lunch and it went up... 5 minute later, nothing again !

This ON/OFF bevahiour is puzzling me (OK, it's actually pissing me off). I've ordered 3 new switches (Porsche @$35 each) from our host and will recheck the connections, but.... does this erratic behavior suggest anything else ? A wiring error, a bad motor, a bad ground? Where are the grounds for this thing anyway ? I pulled the offending switch out of the door (still connected). nothing burned, nothing warm... Truly puzzled !! I'm starting to think it's at the fuse box for all 3 to fail (And I've replaced switches for nothing)

sailchef · sailchef's Garage

Testing the switches is easy enough with a test light and a battery.

It sounds like there is a short somewhere in the harness. tracking down a short is never any fun but you will probably find that is what it is. I would start looking at all the wiring that actually "moves" and can become chaffed, like the wiring going thru the door into the cabin, it's almost 25 years old and may be worn thru or cracked and brittle.

Anyway, that's where I'd start, Good luck.

Deschodt · 08-31-2009, 10:19 AM

Agreed, but wouldn't a short have popped my fuse at least once ? I'm really confused by this on/off thing. My headlights did the same for 6 months till I figured out it was a relay connection that was loose...

this car has been the most reliable piece of automobile I've ever owned for 12+ years, but this year it's falling apart ;-)

sailchef · sailchef's Garage

It's a lot of aggrevation but how about starting with the little spade connectors that go into the switch. maybe one of them is broken just enough to cause problems. Clean each one with alchohol and a q-tip.

Have you actually pulled the motors and tested them on the bench ? Couldn't imagine both going bad at the same time but stranger things have happened.

Start with the things that are easily accessible and not difficult to trouble shoot.

Sounds like patience is going to be your number 1 tool.

Mysterytrain · 08-31-2009, 11:23 AM

There is a relay after the fuse that feeds all three switches. You might want to swap that out. From the relay the power goes into the driver's door via a plug in harness. There might be some 'funk' on the connector. It can be removed and given a dose of contact cleaner. The connector is located at the rear of the driver's side front fender. Not the easiest task in the world but it can be done. Lastly, the new switches are pretty crappy.

86 911 Targa · 08-31-2009, 03:57 PM

Greg,

Take a look at this.......

The P/W relay is very accessable from the fromt.

Pull the relay, and clean the connections.

Then, you might want to "wiggle" the relay while in the socket, and try your windows.

Good luck,

Gerry

p911dad · p911dad's Garage

I have a similar problem in our 84' Carrera. If the car is left out in the hot sun, the passenger side switch likely won't work, but the driver side switch controlling the passenger side does. I have replaced all the window switches. When it is cool, both sides work. No clue what is wrong..

Deschodt · 09-01-2009, 03:33 AM

I had no idea there was a relay there, thanks for the picture, easy enough to get to !!!

Yeah the puzzling part to me is when the driver side door switch for the passenger side does not work, yet the passenger side switch does, and then that "Resurrects" the driver side one too.... Gremlins I tell you !!! At any rate, I have a spare relay and 3 new switches coming in, we'll see...

Mysterytrain · 09-01-2009, 04:11 AM

That relay behind the dash allows the windows to operate when the ignition is turned off and one of the doors are opened. The main relay is on the front fuse panel. One has no effect on the other, if they are both the old style round relay. The more modern cars have a 'multifunction' type relay that powers the doors and allows for the windows to operate with the ignition off.
Does your car allow you to operate the power windows with the ignition off?