Bill - the switches do connect inputs to ground to signal the functions of the switch - this is not the ground supply to the unit nor should this create any additional (significant) current - unless there is a problem with the controller.

Simon - Fuse 18 is the Flap Controller feed (only) (MY '90 correct?) seems it must be related to this - would suggest the flap relay has an issue - pull the flap relay (with flaps open) - if you reinsert fuse - is everything still good (a check to see nothing else is connected to that fuse...)

Previously you said pulling the window module solved the problem... is this a secondary problem or is this now the only problem (e.g. reinstall the old window controller and windows OK and drain now gone?)

Alan

 

Hi there,

Alan, if I forgot to mention, my car is a 1991 car. This makes fuse 18 part of the window controller circuit for sure.
Yes, pulling the module itself does solve the problem, but I was making sure this was the sole cause of the problem. I've sent an email round a UK 928 mailing list to see if anyone local would mind me borrowing theirs to be sure it is the controller that is the problem.
Is there even anything else on that circuit that could cause a problem? I'm only unsure because a 928 guy in the UK I spoke to said he thought it was very rare for these units to fail.

Cheers
Simon

 

Note that I had the same problem (and one or two others with the windows and sunroof) and a new control unit did not resolve the drain or other issues. There was a relay inside that wouldn't unlatch until all power was removed, but the box itself was not the issue. The box is over $200 US. See if you can find one to borrow locally. If not I can ship my extra one to you on loan.

Note that if you have a buddy with a 90+ 928, the control box can be accessed by moving the seat all the way forward. There are a couple of 10mm nuts that hold down a cover plate. They can be removed pretty easily with a Gearwrench. Once those are out, the plate comes loose, and the box can be unplugged and removed. The seat does not need to be removed.

In the meantime, it would be worth trying to determine is there is a wire harness or other issue that could be responsible.

 

So, if I replace the box and find that this relay is sticking here also, how do you go about resolving it? How would I check for a problem with the wiring harness?

Cheers
Simon

 

Bill, should the windows still work with the box pulled? My mechanic seemed to think so, and when the fuse is pulled for the box, the alarm works intermittently. There is evidence that someone has fitted another alarm in the past, and apparently that has been dis-armed. Could have someone crossed a few wires, and caused all of these problems? How would I go about finding out? Should I really give this to a pro?

 

This unit failed on my '91 - finally exhibiting greater than 0.5A static current draw - but not before it killed both of the window motors.

How many 90-95 928s are there in the UK? As in: the boxes are probably rare to start with. They are approaching 20 years of service. I suspect we'll see more of them fail.

It's a shame the VW part didn't work out. Hmmmm..... maybe someone could open it and figure out which wires need to be cut to make it work like the 928 part?

 

I don't see how the windows could work w/o the box. I would be looking at then add-on alarm wiring for tie-ins to the window/sunroof system wiring.

 

We did, there were a different number of relays inside...

Bill, I wouldn't attempt something like that myself, but I know a man who would!

 

.... for a fee of course

I will try and find a new unit, and see how we do...

 

Having problems with window control module on the 93 GTS. Adding this info ----
Original unit is 928 618 240 00.
This unit part number does not exist in the Porsche system. I know it is correct as I have seen it on a number of 90 and later cars.
Checking in PET and the controller is a 928 618 040 00. As Rawky found out under the sticker 928 618 040 00 is the VW part number 191 959 875X. A new unit 928 618 040 00 seemed to work but I lost the closing of windows and sunroof from the door and hatch locks. Sent it back to where it came.

Other interesting findings - besides the three rectangular connectors to the unit there are two barrel connectors, both are white in color and one is small diameter and the other larger. The larger barrel connector is already unconnected, however if you connect it the driver’s window and sunroof open and close together. I did see this listed as a feature on some cars to other countries.
The smaller connector is connected for the US/Canada market and does not allow one touch up on the driver’s side only. If you disconnect it the one touch up feature is activated.

Hope this helps someone else in the future