Crazy electrical gremlin - car sometimes totally dead, until shaken or door slammed

[Bill R.]

There is also a couple of other places i would check that come to mind..... There is a ground disconnect point behind a plastic cover in front of the battery on the carpeted section that the rear seat sits on. Take that cover off and check the ground connection there. I think your e34 also has a connecting point under the dead pedal where they originally had a battery disconnect switch when the car was being transported from the factory, the switches are removed at the dealer but the connecting point is still there and if it worked loose or got corrosion on it it could have an effect also.

[shogun]

here are pics of that ground wire on the rear seat
OJs Autobahn - 21_groundwire_exposed
under this cover
http://www.ow.no/gallery2/main.php?g...3e48eee6dae665
OJs Autobahn - 19_groundwire_cover

[ericole]

here are pics of that ground wire on the rear seat
OJs Autobahn - 21_groundwire_exposed
under this cover
http://www.ow.no/gallery2/main.php?g...3e48eee6dae665
OJs Autobahn - 19_groundwire_cover

I've always wondered why that plastic piece was there, but never had enough interest to check. WHY is it there? thanks, I'll check it this week/end while off for Thanksgiving. Also check the voltage stuff as mentioned.

[Mordan]

I've never considered my car a DIY vehicle. So you are saying that without this voltage reader in my cigarette lighter I should not post questions to this forum?

Sorry my friend but if it is not a DIY vehicle what are you doing here? Just drop your car at the dealer/mechanics and be done with it.

@genphreak. My euro cars don't have OBCs giving me all that stuff.

[ericole]

Can you show me where to see the schematic you mention? There was only one fusible link that we were able to find in my 1995 E34. thanks

[ericole]

I wanted to update b/c I haven't written anything in a while and I hate finding these forums and never seeing if the problem is resolved or not, so I don't want to leave this thread undone.

This hasn't happened in a while, so like happens with things like this I've sort of ignored it (especially since our new house has gotten into the final stretch and there have been things we've needed to do with that). 3 nights ago we were all going somewhere and my wife turned they key - dash lights, then fully dead. A full blow gremlin attack. She waited, tried again, same thing. Did that a few times until the key turn got no response - as if no battery existed in the car. We shook the car, slammed driver's side door, etc. Got lights a couple of times but that was it. Finally got my son out of his car seat in the back and noticed that when I opened the rear passenger door the interior lights came back on - they were off before that. Slammed his door shut and she was able to get the dash lights again, but no start. Started troubleshooting and found out that with either back door opening or closing the interior lights would come back on and we'd get the dash lights part - but no starting.

I called my mechanic since I was in the middle of a gremlin battle to get his thoughts. He suggested I take the back seat out, which I had already done to begin looking around. Battery terminals all still good, clean, etc. He recalled an old 7 series he had worked on that had the same strange behavior. He took off the negative wire, moved it around and reattached it in a different orientation on the terminal. That car never had the problem again. I forget why he said he tried that, but before I did that I tried to start the car. Voila - with the back seat out, and me having done nothing else, the car started right up!!! I did go ahead and move the negative wire like he suggested. I drove a couple of days with the seat out and haven't had any problem.

I did note that when I start the car that I hear some kind of relay or whatever click in the back seat area. Lots of other things seem to be controlled from there as well (I noticed the windshield wipers for one).

Anyway, it does seem that it is definitely localized in the back seat area. I checked to see if any kind of wire or wiring harness was in a place that the seat itself should be interfering with it. As best I can tell, everything is where it should be from the factory design. There is really no way to see this directly, but I can't imagine that the seat touches the battery. I assume it's all designed so that the battery comparment is deep enough to keep that from happening. My seat isn't damaged in any way, so it's not flexing down beyond where it should - at least I wouldn't see how it could.

So that's my last status - any thoughts?
thanks

[shogun]

on cars with anti theft/ drive away protection the car will not start when the seat is out and the drive away protection is on. Those cars have a microswitch on the cover of the battery and when the seat is lifted, the microswitch acts = no power. You can check all the details of wirings and parts which are under rear seat in the ETM = electronic troubleshooting manual, there are even pictures of those items at the end of the ETM under parts location views, select the correct one for your built year here
E34 (1988 to 1995 5 Series) Wiring Diagrams
E34 (1988 to 1995 5 Series) Wiring Diagrams
1988 e34_88.pdf (10,476,973 bytes) e34_88.zip (8,451,206 bytes)
1989 e34_89.pdf (10,863,822 bytes) e34_89.zip (8,588,005 bytes)
1990 e34_90.pdf (14,676,816 bytes) e34_90.zip (11,295,570 bytes)
1991 e34_91.pdf (18,332,496 bytes) e34_91.zip (13,399,412 bytes)
1992 e34_92.pdf (15,153,055 bytes) e34_92.zip (11,963,569 bytes)
1993 e34_93.pdf (15,214,090 bytes) e34_93.zip (11,994,722 bytes)
1994 e34_94.pdf (15,860,270 bytes) e34_94.zip (12,448,814 bytes)
1995 e34_95.pdf (15,392,094 bytes) e34_95.zip (11,897,304 bytes)

[Tiger]

If you lost complete power as in no battery at all, it is definitely the fusible links... there are a couple of them back there and some hidden.

The most basic is clean the battery clamps and battery terminal with the battery terminal wire brush thing.

I might even change the ground cable because it is so easy and cheap. Wires does go bad when corroded inside the wire insulation... more common in engine compartment but not really inside the car... still very cheap job.

[Dave M]

Thanks for posting an update to your story and ignoring the odd heckle from members that feel obliged to flex their inernets muscles. Seaking help is necessary to becoming a DIY'er.

Dave

[ericole]

I'm not really sure what to take from this other than wiring diagrams - hopefully identifying another fusible link. There is no microswitch on my battery. The car starts and runs fine with the seat out.