"battery drain" 1988 BMW 735i

[donaldashworth]

["battery drain" 1988 BMW 735i]

I recently purchased a 1988 BMW 735i with 197k miles from the orginal owner last weekend. Some time

back, the engine's main bearing was replaced, and pretty much the entire engine was overhaulled. The

body also has a new pearlescent white paint job.

The orginal owner decided to sell car after all of this work because quite regularly the battery would

completely drain itself "while running". The car runs great, the battery just dies everyonce in a

while.

Last night, I connected two wires to the battery and routed them outside of the vehicle and let the car

set for an hour. Later I connected my fluke and I am measuring a 0.01 milliamp draw...nothing

practically. So, unless I have an intermittant parasitic leak, I believe the problem may be caused by

the regulator or altenator.

I started the car and let it warm up, and then disconnected the battery. The car remained running on

the altenator. This does not mean the altenator is not defective, but it's not completely dead either.

My question is this; how would one proceed at this point? I do not want to take the car to a

dealership. I can spend 38.00 and replace the regulator, and 180.00 or so on a rebuild altenator later.

I have 2003 BM 325i and I am strapped for cash. The 735i (having a new paint job and rebuilt

motor...and all of the maintenance records) was too good of a deal to pass up. I would rather make

educated guesses on parts replacement rather than non-educated ones.

Can anyone think of any other diagnostic treatment, asside from taking the altenator for a diagnostic

check up at Autozone?

Thanks,
Don

[18wheelerbob]

Hello Don, I guess I wasn't the only person last weekend who didn't let a good deal go by. You mention of an 2003 325i, I'm sure you had serviced the car at a dealership at least once. Drop by and speak to the service manager on one of those visits, I'm sure they will be gladly to give you advise. If not wait like I'm waiting to get my questions answered. or www.BMWTECHINFO.COM (expensive) or try www.cardoctor.com ( $20.00 bucks) and hope for a correct answer?
Good luck, 18wheelerbob ( another weekend shopper)

[shogun]

finding the power drain - for beginners


If you are a beginner in electric issues, this walks you through it, hopefully:

I'll try to make it simple, ...

The meter should have an A scale (Ampere) for reading current. Preferably, a High amp one (10A for example). In some of them, this high amp scale requires the red plug of the wire probes to be connected in a different hole. We do not know the magnitude of the current involved, so in order to preserve the meter, it is better to start reading in this high amp scale.

Disconnect the ground (negative) lead to the battery (electronic devices in the car will loose status when battery is unplugged, so you will need radio code for example), connect the positive (Red) meter probe to the negative thick wire to the battery, and connect the negative (Black) probe of the meter to the negative battery post. Be sure that the probes are inserted in the proper holes in the meter for the readings (Amp) you intend to take.

If you have a leak as you assumed before, you should have a significant reading in the meter (maybe/sometimes more than 50 milli amps, > 0.05 Amp). If the selected scale do not allow you to have a clear reading of the leaking current and you want to change down scales, do so. Remember that some meters require to select a new hole in the meter for the red probe in order to select a lower Amp (Current) scale.

Once your meter is properly set and you have a good steady reading of the leaking current, proceed to remove, one by one, the fuses on the fuse box. Keep an eye to the meter in order to identify which fuse removal is dropping down the current in the meter. The leaky circuit is feed by that fuse.

Investigate what devices are associated to that fuse, plug the fuse back, and start disconnecting all devices one by one until you get again a reading drop. That device would be the culprit.

But in case of our E32 the complete electronics come to a rest/sleep modus after about 16 minutes. That means that you should not open the door again for example but keep it locked for checking. Therefore open the rear windows and the hood, remove rear seat and then lock the doors and wait 16 minutes. Then you have access to the battery and the fuses thru the rear windows.
If the door is unlocked, the GM is again on stand-by modus and maybe others.
When all is 'sleeping' usual drain is 30-50 mA.

The wiring diagram for E32 cars are here:

http://shark.armchair.mb.ca/~dave/BMW/e32/

Download this one.

It has fuse charts, power distribution, ground cable distribution etc.
Best is you study these almost 700 pages and print out the most important ones for this task.

When you have identified the fuse(s) in question and need more help, please let us know in detail what you have done, what disconnected etc., details are very important. There are people here on the board which can guide you thru it.

Good Luck

[donaldashworth]

This afternoon I disconnected the negative battery terminal and place my digital volt meter between the battery negative terminal and the body ground. I set my DVM on mA/A (DC) and the display would vary between .38 and .45 mA.

I let the car rest for 30 minutes and began pulling fuses one at a time under the hood. I eventually reached fuse 20 (the plastic fuse cover labels fuse 20 as “Instrument cluster, heater”)

My Bently Manual describes fuse 20 as…

Anti-theft system (DWA)
Automatic climate control (IHKA)
Brake pad warning
Instrument cluster check control
On board computer
Park, tail, marker, under hood lights
Power windows
Sunroof


I am not certain if this is .38 ~ .45 mA is the normal draw across fuse 20 when the car is idle.

Also, occasionally the fuel and temp gauges on the instrument cluster do no resister. When this happens, the digital readout does not work either. Usually, after I drive the car around a bit, the instrument cluster returns. Not always though.

And the SRS light always flashes. I am not certain what is causing this. I checked out the left and right collision sensors…they seem ok.

One thing I noticed today is the speaker/chime has been disconnected. I reconnected the speaker/chime and, event with the windows and doors closed and the car was turned off and at rest, the speak chime would go off (one ding) every few minutes. I am not certain if this was due to my bumping/touching the car while taking fuse readings or not. I have to assume that the previous owner disconnected this because it kept going off. I went out side a few minutes ago, and I could hear the speaker/chime sounding.

The previous owner said that the electrical problem (parasitic battery drain) began when he drove through a water puddle at high speed. He could not diagnose the problem, and his solution was to put a negative terminal “quick disconnect” on the battery.

At this point, if the .38 ~ .45 mA current draw across fuse 20 is normal, I would think that I should begin understanding why the speaker/chime is sounding. I am leaning towards disabling (if possible) the “Anti-theft system”.

[shogun]

I already asnwered your question here
http://forums.bimmerforums.com/forum/showthread.php?t=1172186

[dabinfamous]

check the positive lead to starter... seems like a good place for a short... worked for me cost $11 cad

[shogun]

unfortunately he never told us how the problem was solved, that was back in 2009 when he started the thread

[626daimond]

i have a bmw 1991 735i and i have problems with the battery the batery is brand new and i charge the batery and the car starts the next day i wont to start it it wont start and i took the batery to pepboys they said the batery was good what can the problem be ???? help

[shogun]

If you do not tell us the whole problem in detail, then it is difficult to help you.
Because here you mention that you installed an alarm system and then your problem started
Bimmerforums - The Ultimate BMW Forum - View Single Post - E36 E36 OEM alarm/keyless entry system
copied:
[QUOTE]i need help i bought a viper alarm for my bmw 1991 735i i instaling it and i didnt know what wires to connect so i just took it off and 2 days later the car didnt want to start it will onley strat with the jump strat and the battery is brand new what can i do to fix it plase reply /.\ ?????[626daimond/QUOTE]