John S. Markowitz

OK- a little background.

1991 928S4 Automatic, 116K, well kept, had for years...
I am not much of a mechanic but have a regular Porsche BMW mechanic who is usually very capable but the present issues can't seem to be resolved.

The work that was JUST done to the car all at once in case it could be linked to problems:
*Replaced torque tube (previous one sheared off!)
*All new CV boots
*Replaced just the black face of instrument cluster with a good used one (original was delaminating)
*Coolant sensor replaced
* Also, when I brought it in, the passenger side mirror movement was out in one direction, and passenger window was also somewhat intermittent

On getting the car back all back together these intermittent electrical Gremlins began:
* Passenger Window suddenly and intermittently rolls down an inch on its own and then neither window works
* intense clicking will start under the Driver seat- control module I believe and sounds like relays clicking
* Interior lights work intermittently
* It will keep clicking and drain battery unless fuse# 25 is removed or battery is disconnected. Then when re-connecting the battery (or reinserting the fuse), everything works fine again.....but not for very long. Its as if there is a temporary "re-set"

Other oddities/clues
* Passenger window has rolled down on its own when the window switch is completely disconnected and when the key is not in the ignition.
* The express window deal- when key is turned in door and held, only works to roll down Passenger window (at least when everything else is working)
* the original passenger mirror positional issue (just one direction) seems to come and go with other problems

What's been investigated:
Both door panels have been off and a few suspect wires re-soldered etc, window motors checked, and window switches checked
-Wiring Harness checked
-Seat control module has been out and cleaned/checked, all connections checked
-Door Pins have been cleaned/checked
-all fuses checked

I found some posts here related to the window issues and the clicking of the module under the Driver's Seat but did not find any clear resolution to the issue- even with a new module in one instance.

Please help me get my beautiful car back on the road before I jump out the window !!!!!!!!!!

John

jcorenman

The first question is always "What was the last thing you fixed". The problem here of course is that the answer is "lots of stuff".

This might be key:

Fuse 25: Inside lights, Diagnostic connector, Instrument cluster ...

I would start there, make sure the instrument cluster is properly reassembled and connected.

Porsche985

Yes- good places to start looking for Lord Lucas.

Alan

You sure you mean this? The key held in lock position causes the pass window -> sunroof -> drivers window to close in sequence. Nothing to do with the locks causes the windows to open...?

Alan

Alan

If you have intermittent operation of the mirrors I'd suspect damaged (broken) wires in the hinge pass through area. Check that the window motors work properly when powered directly (via a 15A fuse). If yes then it is likely the motors wires are getting shorted to ground - I'd suspect a similar break & shorts in the wiring in the same location. With this module both the motor wires will normally be at 12v.

Shorting the motors wire to ground will cause the unit to disconnect the relays for over-current protection - it may not last long cycling like this - the relay terminals will likely be getting damaged by the current overload.

Alan

The Forgotten On

It honestly sounds like the module itself has failed. Try borrowing a known good one and see if your issues go away.

Alan

I would not volunteer a good unit to be tested in this car - given the symptoms - I'd do the opposite - test your unit in an otherwise good car. I'd suspect it will work OK. But you need to find another '90+ car.

Alan

John S. Markowitz

Hi All

I believe the problem has been resolved-I waited a few days to post because the problem was intermittent and wanted to be relatively sure it was fixed before posting.

Thank you for all your input- it gave me much to consider and track and all of it was useful.

There were 2 issues I found that could have been contributory having to do with connections to the module I had not noticed before:
1) I noticed that the upper black plug into the module, though plugged in all the way, actually remained quite loose- even to the touch it would wiggle. I did a short videoclip so you could really appreciate the issue but my mp.4 file is wrong for this site. I just added a still below showing the connector in question. I have no idea how this module plug-in came to have so much play and wiggle

The FIX: Nothing too sophisticated- wrapped some cable ties around it to hold it firmly in place

2) After unplugging the Black module plug I got a very good look at one of the connectors from the wiring harness- I believe the one that goes to the sunroof. In any case, the wire just before the female side of the white connector had an area that was completely flattened- looked like a cobra's head (pic below)! I assume the wire had been run over by the seat after being routed incorrectly? The insulation was all still intact, but it looked completely suspect.

The FIX: Removed this piece of the wire, soldered and shrink-wrapped. Bundled in cloth tape and oriented well out of the way of seat tracks etc

Before and after pics below..(excuse the quality)

So nothing earth-shattering here and I still don't know if it was both issues or just one causing about 3 weeks of 928 grief but I sincerely hope this helps somebody out there to just examine these as possibilities early on if they start to experience this kind of electrical weirdness!!

John S. Markowitz

Hi Alan

Didn't mean to ignore your query- I was trying to post what my mechanic had passed along to me and may have gotten that incorrect. In any case, thank God, the issue was finally resolved.

BTW: I have appreciated much from your informed posts over the years so thank you!

John

Alan

I'm quite sure it was the large plug looseness that was giving your issues not the single wire. Odd that it was loose though...

A new one to look for in future.

Alan

John S. Markowitz

Hi Alan

I managed to convert my mp4 clip. Its short and Blink and you'll miss it but I wanted to show how loose this thing was.

I have no idea why it was so loose, this is a 2nd owner well taken care of car and that module has never been messed with as far as I know. The brown plug below it was also not as tight as you would expect but not nearly as bad.

Much time was spent chasing other possibilities- maybe people can start with an easy one!

John