Strange electrical issue

jrwilson · jrwilson's Garage

Just today when I got in my car and started it up, I tried to roll down the windows and they weren't working - any of the switches. While I was driving I heard the buzz of the warning buzzer for a tiny bit, and then when I got where I was going and turned the car off then on again, the windows worked.

Just had the same thing happen - started up, windows didn't work. I thought maybe a grounding issue in the door wiring but I couldn't feel any issues. Turned the car off, made the buzzer go, started up and windows worked again.

Is the buzzer connected to the windows or something?

Anjizkit · Anjizkit's Garage

The buzzer comes when the car door is open and the ignition is on.

I think the windows won’t go down when the car door is open and ignition is on. I Don’t remember since I don’t have the car near me. Try to close the door and see if the window works.

Sent from my iPhone using Tapatalk

jrwilson · jrwilson's Garage

Okay, some new info. The windows start working again after a bit of driving, no connection to the buzzer as far as I can tell. Are windows on a relay?

mike sampsel · mike sampsel's Garage

Quote:

Originally Posted by jrwilson

Okay, some new info. The windows start working again after a bit of driving, no connection to the buzzer as far as I can tell. Are windows on a relay?

Windows operate with the key in the on position (door open or not). The power windows have a relay.

The buzzer is off if the doors are closed and the seat belt is fastened with the key in the ignition. Doors open or seat belt off the buzzer goes also to remind you of the key in the ignition and off, "key in contact warning". The buzzer goes if the driver seatbelt is not in place and the key is in run position.

There is a seat belt relay too, which configures the doors, seatbelt, key buzzers and Pbrake SB warning light.

GH85Carrera · GH85Carrera's Garage

It is also normal that the windows will roll up or down after shutting off the car, until you open the door. So you can park, kill the engine, and still roll the windows up or down if you have not opened the door. Once the door is opened and the interior lights come on, the windows are no longer powered, until the key is turned back on.

wazzz · wazzz's Garage

Quote:

Originally Posted by GH85Carrera

It is also normal that the windows will roll up or down after shutting off the car, until you open the door. So you can park, kill the engine, and still roll the windows up or down if you have not opened the door. Once the door is opened and the interior lights come on, the windows are no longer powered, until the key is turned back on.

I think this is correct for older models, but on later models they changed the behavior.

On my 88 windows will roll up and down when engine is cut off only if a door is open.
Opposite behavior.

gtc · gtc's Garage

Next time it happens, pull a window switch out of the door and see if you have 12v at the red wires.
I had the same issue, the cause was severed wires in the window harness between the fender and the door. The harness was getting pinched when the door was fully open due to bad door stays. New harnesses are available from the dealer, but it was quite a PITA since i had to remove the door to get to the plug in the fender.

mike sampsel · mike sampsel's Garage

Quote:

Originally Posted by GH85Carrera

It is also normal that the windows will roll up or down after shutting off the car, until you open the door. So you can park, kill the engine, and still roll the windows up or down if you have not opened the door. Once the door is opened and the interior lights come on, the windows are no longer powered, until the key is turned back on.

Not on a 78, maybe on my 2018 GTS though, actually per the Bentley diagram all SC's need the key in run or in ACC for the relay to get power.

Cheers

Carrera are IDK because they are not in the 78-83 Bentley

spoke · 08-02-2023, 08:43 AM

Window up/down switches are notorious for becoming resistive because of dirt and oxidation and may or may not allow the windows to function. I've had to take the switches apart on my '86 930 and clean them with emery cloth and contact cleaner. Worked very well after that.

darrin · 08-02-2023, 08:54 AM

Quote:

Originally Posted by wazzz

I think this is correct for older models, but on later models they changed the behavior.

On my 88 windows will roll up and down when engine is cut off only if a door is open.
Opposite behavior.

gilles -- does your dome light illuminate when you open your driver's door?

wazzz · wazzz's Garage

Quote:

Originally Posted by darrin

gilles -- does your dome light illuminate when you open your driver's door?

Yes.

jrwilson · jrwilson's Garage

Quote:

Originally Posted by spoke

Window up/down switches are notorious for becoming resistive because of dirt and oxidation and may or may not allow the windows to function. I've had to take the switches apart on my '86 930 and clean them with emery cloth and contact cleaner. Worked very well after that.

When it happens none of the window switches work, either door.

timmy2 · timmy2's Garage

J51 Relay may be loose in socket, causing it to work intermittently. Try spreading the pins with a razor blade run down the slots.

spoke · 08-04-2023, 03:28 PM

Quote:

Originally Posted by jrwilson

When it happens none of the window switches work, either door.

It could be the wires going from the door to the chassis. I recently had the alarm go off all by itself when the door was open wide. Turns out 2 wires were crossing each other in the door jamb. All the power to both windows goes into the driver door.

Pop one of the switches out on the driver door and with power on, measure 12V on the power pins of the switches.

jrwilson · jrwilson's Garage

So, I pulled the cover off the fuse box and a bunch of the relays were partially out of their sockets! I have no idea how that happened. I pushed them in and when I'm back in the garage I'll do what timmy2 said and expand the pins a bit on each one.

I hope that was the issue! Thanks to everyone as always for the amazing help, this forum is gold.

spoke · 08-05-2023, 01:18 PM

About relays, a while back I was having trouble with the idle getting higher and higher having to close the throttle more and more. While investigating, I found the AAR was not working because it was not powered. Tracing the power on the schematic, found the AAR is powered by one of the fuel pump relays in the front trunk fuse panel. Opened the fuse panel cover and the relay was just sitting there on the cover. Plugged it back in and everything was fine. Relays positioned on their sides have a tendency to work loose.