Power window logic relay 1988 911 cab (what is the point of this?)

[rick-l]

I was thinking there was something wrong with my power windows because they work when the ignition is on or when the doors are open. People on the list have said they should work only after the ignition has been on and work until you open the door.

Instead of buying a new relay I was going to fix the old one. I drew out the schematic and to the best I can tell it behaves in the car exactly like the schematic says it should.

Look at that bizarre circuit whose only task is to turn on the relay when the door is open. WTF??? What is the point of that? I could think of many simpler ways to or those two signals together to operate a relay.

The PET says the relay in there should be a 944 615 116 00. The one I have in there is a 944 615 112 02 (with a build date of 9/11/1987). I wonder what should be in there?

Reverse engineered schematic (R10 just simulates the windows)


Simulation

[wolf]

It is indeed ment to work like that.

[Brad01mc]

Perhaps it's there so that you can operate the windows when you are putting up/down the top?

I had a BMW 325ic that required the windows to be down in order for the top to go up!

Anyway, just a guess.

Brad

[Mysterytrain]

I think the logic was so that you didn't have to get back into the car and put the key in the ignition if you decided to roll the windows up. Remember this was in the days before wireless remote entry and all the circuits they control. They are using the door pin to complete the ground so they needed a relay to handle the load. It would kinda tough installing a door switch that could handle 10 or 20 amps! They used the same logic with the footwell blower circuit if you think about it. So, the relay was state of the art for the early 80's..then in the later years they got really cool and added the delay circuit so that when you shut the car off..for example at a gas station, you could still roll the window down to meekly ask the attendant to fill the tank and hand over the 60 bucks.

[Super_Dave_D]

My 88 had the same issue and it was simply the door plunger switches. Very easy to replace those. I really didnt realize that it was a issue until my window switch went bad and got stuck in the down position one day thus killing my battery.

[charleskieffner]

my 1987 drivers window switch did the same thing. stayed in down position and killed battery. replaced switch....................life is good...........or was good.


fast forward 5 months later. lot boy at shop fires my car up to move out from inside shop. whatever he did ...............now NEITHER WINDOW goes up or down????

WTF???? what do i look for first??? fuse? relay? door plungers?????? i'll take a flying guess and try fuze when i get back to car tommorow.

what did clown lot boy do???

windows literally worked fine day before for 300 mile putt putt across central az thru winter wunderland!

[rick-l]

The fuse (Fusebox3 Fuse #1 wherever that is) is likely blown (not a good thing).

If not check this:

1. Door Open - 12volts on one side of fuse #1 (both sides if the fuse is good)
2. Door Closed Ignition Off - no power to fuse #1
3. Ignition On - 12 volts to fuse #1