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acolatse
03-16-2006, 09:48 PM
My 1999 750iL could not hold its battery power. I replaced the batteries (2 in this car) a couple of months ago when the car would not start. A week ago, it refused to start again. The mechanic said he replaced the altenator. This moring it refused to start agian. Also not functioning for a couple of months on this car are:
1. the passenger side mirrow would not adjust anymore with a change of the gear to reverse.
2. the blue high beam light indicator takes a second to react
3. the seat warmers not functioning (no light when you press the seat warmer button)
4. stearing wheel takes a few seconds to adjust when the car is started

I believe these are all related to the car losing its power.

Any ideas? Help
-a

shogun
03-17-2006, 12:08 AM
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.

Written by Javier, and slightly changed by me to fit such question in general.
Hope that helps.

3. the seat warmers not functioning (no light when you press the seat warmer button)
Have you checked the fuse?

As for item one I would first disassemble the switch to see if there is any oxydation.

Kalevera
03-19-2006, 06:00 PM
I've seen this or something very much like it once before..trying to remember the exact details. It turned out to be the general module.

I believe the specifics of it were that the car wouldn't go to sleep -- after about 30 seconds of closing trunk/doors with the engine off, I think it is on the e38s, the current draw should drop significantly. It should drop again after 15 minutes or so. If it doesn't, then the batteries die after a short while.

One thing to do is monitor battery draw over a time period of about 20 minutes to assure that the car is actually going to sleep. The E31/E38 cars with two batteries, especially the late E38s (late '99 and up) with electrically heated cat converters, are very sensitive to battery condition. Immediately past the two batteries is a switch block that determines how current is routed to the car (EKAT cars devote one battery to the heating of the cats almost exclusively); I seem to remember something about that block and corrosion issues, but it's been a few months since I've worked on one.

In all likelihood, it'll be necessary to get the car on a good diagnostic computer to pinpoint the exact draw. It's a very complex car.

best, whit

joshua43214
03-20-2006, 02:06 PM
Unfortunately you have what can be one of the most frustrating car problems to isolate. Electrical problems in general can lead the inexperienced to heavy drinking and tracking down a parasitic draw on even and old chevy can drive people to extremes, let alone a 750il. To make matters worse, I believe your year had an isolator as well. I will give you a few hints to get started, but I strongly recomend that you find someone who is both skilled with electrical problems and is familiar with the 750il if you don't locate the problem rapidly.

Do all your testing with only 1 battery installed, disconnect the negative terminal from both batteries and the positive from 1 battery. us a jumper cable from the loose positive cable to the other hooked up positive, be very careful to lay every thing on insulated surfaces, your rubber floor mats are good for this. Hook up your AMPmeter as described already to a GOOD chasis ground.

You will need to access both under hood and in trunk, so before you hook up your ampmeter, open both and bypass the the switches, make sure key is removed from ignition. Also when you hook the ampmeter up, you can see a pretty high volt/amp spike as the computors power up, make sure you have a meter able to handle a fair amount of amps or use a shunt with an accurate meter, a $15.00 toy meter from radio shack may not be accurate enough for using a shunt.

After you have hooked up the meter, go drink a cup of coffee and relax for a while, In theory, the car should go to sleep inabout 15 minutes, but I would give it 2 hours or more if possible.

If everything is ok, you should see a few miliamps of draw, enough to keep radio and clock memory alive, as well as the monitoring circuits for the alarm and ignition. If you see more than a few mili amps, something is creating a parasitic draw and needs to be isolated, a large draw is a good indication that the car is not going to sleep, this could be caused by it believing anything from a door being open to the key being in the ignition, or possibly even a computor failure. If you have a moderate draw, pull each fuse 1 by 1 and and check the draw, on some circuits it can take a couple moments for the draw to go away.

If you are lucky, you will isolate the circuit at the fuse box and can then do pin point testing of everything on that circuit.

these problems very often have very simple answers, but finding them can be very very frustrating.
I have seen intermitant issues with your model not going to sleep properly.
Faulty alternators are a common cause of this, don't assume your's is ok because its new, especialy if its a reman unit from a discounter.
The dealer can monitor every thing in the car with all doors closed, but they may not have a tech that is familiar with an older model like yours.
Many electrical only shops, employ parts hangers and are in the business of only selling batteries and alternators.
BMW specialists are your friend in this, The techs that do this type of work for a living are rare and the know they occupy the top of the food chain with drivability techs. They expect to be payed well and they are, expect a large labor bill if the problem can't be found easily.