Power windows problem - solved

[Motzking1]

Hi everybody I'm new here having a bit of trouble with my 1991 750IL. Well actually I got it about 3 months ago and have been slowly working out all the links, there was quite a few. Broken power seats, vibration at freeway speed, diff pinion seal leak, trans program error, eml light. I got all those fixed and behind me. Got a small pile ahead of me but today I'm a bit stumped on the power window problem. So here we go here's my best description of the problem. Sometimes they work and when they do everything works. Sometime shortly after starting and driving the power windows stop working. When this happens all windows stopped working and the sunroof. If I stopped the vehicle and cycle the key ones from off to on they come back on and they're working again until they fail. The time from start up to fail can from 20 seconds to sometimes days. So I got a wiring diagram and I started at the center console window switch. With engine running I got the grounds were they should be at all times. When the problem is NOT present I have14.1 volts on all the non grounded pins. If I ground these hot pins the windows move up or down according to their respective pin. When the problem IS (Windows not working) occurring I have about 9.4 volts static. A good 5 volt drop no load. So I hit the wiring diagram and Chase the circuit on the power side. It would appear that everything in the general module where the power should come from for the switch gets its power on-line number 30. At least according to my alldata wiring diagram. But as much of the wiring schematic as I print out I cannot determine where pain 30 gets its power from? I guess that's my big question if anyone knows what fuse or circuit supplies power to that line 30? I can see that fuse 17 in the front power distribution box feeds the general module also fuse 44 in the rear rear power distribution box. But they do not appear to feed the line 30. Any help would be greatly appreciated

[XAlt]

http://twrite.org/shogunnew/diagnosi...ralmodule.html

[shogun]

here is a German function diagram for the E32 ZKE, http://www.e32-schrauber.de/bmw/daten/zke/bild11.jpg
Fensterkontakte (Fenster geschlossen) = window contacts, window closed
item 11 is all related to FH = Fensterheber = window, and SHD = Schiebe Hebe Dach = sunroof
http://www.e32-schrauber.de/bmw/s-zke.htm

there is an internal overload protection inside the GM, below I translate the part of the ZKE German info I posted the above.

Fensterheber und SHD:
Das Relais schaltet ab

-wenn laenger als 60 Sekunden ein Strom von ueber 36A oder
wenn laenger als 0.3 Sekunden ein Strom zwischen 36 und 60A oder (Ueberlastung)
-wenn laenger als 0.1 Sekunden ein Strom groesser als 60A fliesst (Kurzschluss)

Um die Laststromkreise TSH/ZV/ZS/FH/SHD sicher vor Ueberlast zu schuetzen, wurde zusaetzlich zur 30A Sicherung eine elektronische (reversible) Stromsicherung eingebaut.
Im GM wird der Spannungsabfall am RM gemessen, und je nach Spannungsabfall (Stromschwelle) unterbricht das Sicherheitsrelais den Laststrom .

Die Abschaltwerte der 30A Sicherung werden dabei nicht erreicht (diese wurden nur dann schmelzen, wenn ein Defekt an der elektronischen Sicherung vorliegt).
Die Ansprechschwelle dieser elektronischen Sicherung ist so gelegt, dass immer vor Ueberlast der angeschlossenen Steuerungen automatisch abgeschaltet wird.
Ein automatisches Wiedereinschalten erfolgt nach 60 Sekunden!!!!
Jedoch nur dann, wenn diese Verbraucher abgeschaltet waren bzw kein Kurzschluss vorliegt. Ein automatisches Wiedereinschalten kann 6 x erfolgen bei eingeschalteter Kl. 15. Diese Sperre wird aufgehoben durch Ausschalten der Kl. 15.
Um die Ausloeseschwelle beim gleichzeitigen Einschalten mehrerer Verbraucher nicht zu erreichen, koennen bei der FH-Steuerung gleichzeitig nur 2 gleichzeitig angesteuert werden. Werden mehrere Tasten gleichzeitig betaetigt, so werden nur die zwei ersten Befehle ausgefuehrt. Sollte bereits bei 2 eingeschalteten FH die Ueberlastgrenze ueberschritten werden, so wird ein FH abgeschaltet. Dabei haben die FH vorne Vorrang.

short Engl. translation:

The relay switches off

-if there is longer than 60 seconds a current of about 36A or if longer than 0.3 seconds a current between 36 and 60A, or (overloading)
-if longer than 0.1 seconds, a current greater than 60A flows (short circuit)

To protect the load circuits, TSH / ZV /ZS / FH / SHD from overload, there was installed in addition to that an electronic fuse 30A (reversible).
In the GM the voltage drop is measured at the RM, and depending on the voltage drop (current threshold) interrupts the safety relay is the load current.

The switch off values of the 30A fuse will not be reached here (it would just melt when there is a defect in the electronic security).
The threshold of this electronic fuse is positioned so that is always switches off automatically before overload of the connected controllers.
An automatic restart is only possible after 60 seconds!!
But only if these consumers were turned off, or there is no short circuit.
Automatic resetting can be made 6 times when terminal 15 is switched on.
This lock is released again by switching off the terminal 15.

wiring diagrams in detail are here http://shark.armchair.mb.ca/~dave/BMW/e32/

Also check for broken wires in the wire loom from A-pillar to door

[Motzking1]

Thank you very much. I am real close to finding the problem. I got it traced back to the GM. Pulled the case off the GM and put in back in. When I loose the windows if I wiggle the GM the voltage drop goes away. If I take a screwdriver and seat the connectors of the GM gently the problem is gone. So it's either in the contacts of the plug of the GM or there is a loose solder joint or crack in the board. It gets tight in there to get test equipment but I will find it. Visually the board looks good, no cracks. I got it down to an inch or less now, I will get it! Thank you for your help!

- - - Updated - - -

So if I understand this correctly the current is determined by voltage drop not actual current?
So a bad connection causing a voltage drop could trigger the protection?

[shogun]

Here you have the GM pinout to see which pins are in charge for that http://www.bimmerboard.com/forums/posts/1229510/

Also pull out the RM relay module next to the GM, remove the cover and check the relays inside, because maybe when you wiggle the GM also the RM is moved

[Motzking1]

Problem solved! It's been 3 days and not only do my power windows work flawlessly my mysterious alarm going off problem is solved also. The problem was the GM was not fully seated in the connectors. Cleaning the contacts with a small wire brush and electrical contact cleaner and fully seating the module eliminated the intermittent voltage drop. Thank you Shogun for your help!