New Member with a question

[Hal Dewey]

Hi Everyone,

I'm a new member of the forum and a recent, first-time BMW owner (1989 525i, 137K original miles). I've heard great things about this site and have read many helpful postings. My question goes out to anyone who might have some suggestions. If I don't start my car for 2 or more days, the battery dies. I found this out the hard way after returning home from a week-long trip to find that I couldn't unlock my doors. Many people tried the by-pass trick on the passenger door to no success. A very persistent and careful AAA guy finally "broke" into my car after 45 minutes of attempts. The battery is new and in good condition, but after some testing, I was told that there is some sort of electrical draw that is sapping the battery. It was recommended that I run the car past 2000 RPM's daily to prevent battery from losing charge. It always takes 2 tries to lock my doors, the locks pop back up after the first try. Could this have something to do with the battery drain? Other than that, the car seems to be great. I rent at the beach so do not have a garage that I can hook a charger up while I'm gone and can't always find someone to drive the car while I'm away. Any help would be most appreciated as I'm not gifted mechanically.

Thanks, Hal D.

[Paul in NZ]

my guess is a short circuit at the trunk hinge wiring or one of your door actuators is fried and is somehow drawing current all the time.

[shogun]

Since practically every hollow space within an 8/7/5 is host to a control unit, many with memory and sensors, it is no wonder the E31/32/34 has such a high resting current drain. About 1 amp/hour drain about every 20 hours. Here's the figures:
With the trunk/luggage compartment lights off:
1.) Driver's door open: 4.8 - 5.0 Amps
2.) Driver's door closed: 4.1 Amps for 20 seconds then reduced to approx. 450-470mA for next 16 mins. then reduced to approx. 50mA
With the trunk/luggage compartment lights on:
1.) Driver's door open approx. 6.1-6.4 Amps
2.) Driver's door closed--approx. 5.9-6.1 Amps for 20 seconds, then reduced to approx. 2.5 Amps for the next 16 mins, then reduced to approx. 50mA

Hope that helps when searching. :)

But that all does not drain your battery completely.
Paul's idea might go into the right direction, as this is a known cause of problems.
Check the cables at the the trunk hinge wiring. For sure you will find something.

The unlocking also could be a problem of a defective microswitch in the doors and the trunk.
You can also install a multimeter between the battery and the battery cable and the pull fuse after fuse till it drain drops. By this method you can allocate the area where you have to look for.
Also check lights/switches in glovebox, trunk etc.

[632 Regal]

have the alternator checked, if it has a bad diode it will constantly drain the battery.

[Jose]

Next time you've got a dead battery and you can't open your doors, try removing your license plate illumination( two small philips screws ) and giving it some juice with the help of another batery/car and a jumper cable. This should enable you to open your doors.

[Hal Dewey]

my guess is a short circuit at the trunk hinge wiring or one of your door actuators is fried and is somehow drawing current all the time.

Thanks Paul, I'll have it checked out.
Hal D.

[Hal Dewey]

Since practically every hollow space within an 8/7/5 is host to a control unit, many with memory and sensors, it is no wonder the E31/32/34 has such a high resting current drain. About 1 amp/hour drain about every 20 hours. Here's the figures:
With the trunk/luggage compartment lights off:
1.) Driver's door open: 4.8 - 5.0 Amps
2.) Driver's door closed: 4.1 Amps for 20 seconds then reduced to approx. 450-470mA for next 16 mins. then reduced to approx. 50mA
With the trunk/luggage compartment lights on:
1.) Driver's door open approx. 6.1-6.4 Amps
2.) Driver's door closed--approx. 5.9-6.1 Amps for 20 seconds, then reduced to approx. 2.5 Amps for the next 16 mins, then reduced to approx. 50mA

Hope that helps when searching. :)

But that all does not drain your battery completely.
Paul's idea might go into the right direction, as this is a known cause of problems.
Check the cables at the the trunk hinge wiring. For sure you will find something.

The unlocking also could be a problem of a defective microswitch in the doors and the trunk.
You can also install a multimeter between the battery and the battery cable and the pull fuse after fuse till it drain drops. By this method you can allocate the area where you have to look for.
Also check lights/switches in glovebox, trunk etc.


This is really helpful, thank you for the suggestions.
Hal D.

[Hal Dewey]

have the alternator checked, if it has a bad diode it will constantly drain the battery.


I will Jeff, thank you.
Hal D.

[Hal Dewey]

Next time you've got a dead battery and you can't open your doors, try removing your license plate illumination( two small philips screws ) and giving it some juice with the help of another batery/car and a jumper cable. This should enable you to open your doors.

Very helpful, thank you.
Hal D.

[pong]

Next time you've got a dead battery and you can't open your doors, try removing your license plate illumination( two small philips screws ) and giving it some juice with the help of another batery/car and a jumper cable. This should enable you to open your doors.

uhmmm... i couldnt imagine this... where do i connect it? (btw front or rear?)

[Jon K]

Literally pop your license plate lights out (rear) and hook up another car battery + to + and - to -, this will act like a battery in parallel with the whole car, allowing for you to unlock the doors. This is just a remedy to a dead battery, not fixing yoru problem. Check your trunk harness. The lock popping up is a sign that a wire in your trunk harness is SPLIT. Follow the the left side trunk hinge back until you see the big hunk of wiring, fix all your split wires... i bet one is grounding out, draining your battery.