something electrical is depleting the battery

We are having an electrical problem with our 1994 325ic that has depleted two perfectly new batteries. About 4 weeks ago I attempted to start the car but it was completely dead. After fully charging the battery the car started and I thought everything was fine. But by the next day the car was completely dead. It seems obvious that something in the car is staying on which is depleting the battery within 6-10 hours of being fully charged. Brought it to the BMW dealer 4 weeks ago and they cannot find the source of the problem. Thank goodness it's a spare car. Where do we go from here? This problem may be simpler than everyone is making it but we need some 'out of the box' ideas. PLEASE HELP!!!

Testing a battery draw issue normally requires a amperage meter.

You could try using a 12 volt bulb by using the bulb in place of the fuses.

Pull the fuse and insert the wires to the bulb.

Any circuit drawing power will light the light

Then correct the issue causing the battery draw.

Kind of a shady deal but it does work.

PS: BMW used that for years to provide an idiot light on the dash.

Later,

Testing a battery draw issue normally requires a amperage meter.

You could try using a 12 volt bulb by using the bulb in place of the fuses.

Pull the fuse and insert the wires to the bulb.

Any circuit drawing power will light the light

Then correct the issue causing the battery draw.

Kind of a shady deal but it does work.

PS: BMW used that for years to provide an idiot light on the dash.

Later,


You do not mention if you have a cell phone charger or rader detector plugged into the cig lighter..sounds stupid but I left mine plugged in all the time and had a similiar problem..turns out there was a short in my cord and was draining the battery! It never smelled or got warm enought to think it was anything other than the sun warming it up...I pulled it out of the cig lighter and no more drain.
FYI, all cars with computers and clocks, car alarms, etc drain power all the time, you mention this is a 'spare car'. If you are not driving it for more than a few days you should disconnect the battery. There are aftermarket quick disconnect battery terminals just for these reasons.

Testing a battery draw issue normally requires a amperage meter.

You could try using a 12 volt bulb by using the bulb in place of the fuses.

Pull the fuse and insert the wires to the bulb.

Any circuit drawing power will light the light

Then correct the issue causing the battery draw.

Kind of a shady deal but it does work.

PS: BMW used that for years to provide an idiot light on the dash.

Later,

KC, we used a Fluke 88 multimeter and found a draw on the battery of 3000ma. BMW says that a 17ma draw is standard on a 24/7 basis. Now they can confirm that the additional 2983ma draw is ample enough to cause the batttery depletion. The BMW mechanic said that draw begins 4-6 hours after the car has been shut down. Now, for the next challenge. They think it's a module of some sort, possibly in the instrument cluster, ABS, or 'main brain' computer module. The bad news is...there are lots of modules which means lots of troubleshooting that adds up to a whole lot of labor charges. I urged them and they have agreed to call Tech Support at BMW. Is there anything here that rings a bell with you. I'm getting desperate for some good news.

DME relay maybe stuck on, check this out,
RE: DME relay live when ignition off - drains battery
Posted: Apr 8, 2002 11:45 AM Reply


RE: DME relay live when ignition off - drains battery Guest User
Dear Mano,

The DME relay is turned on and off via the DME ECM (terminal 27). Check for
a constant ground at terminal 85 (0.5 mm brown wire) of the relay socket
with the relay removed. If the ground is always there, relay won't shutoff.
Check for chaffing or shorting to ground on this wire. The other possibility
is a faulty relay. If the relay sticks closed, everything will stay powered,
regardless of a ground signal. Complete DME Relay(or Master Relay) testing
information is given in the Bently repair manual.

I have never seen a delayed power draw.

There is only one issue I can even imagine causing this type of issue.

In the main instrument cluster is a board called a SI, Service Interval board. It is equipt with a battery. It does a periodic charge.

You could disconnect both of the main cluster connections to verify.

http://e30m3performance.com/maintenance/SI_Board/SIBoard-10.jpg

SI Board Swap Out

Last but not least - the SI Board. Above is a new SI Board with lithium batteries and below is the old one. Note the blown battery on the old SI Board (green circle). The light blue rectangle shows the actual service indicator LED's which appear on your dash display. These LED's are mounted on a separate circuit board which must be pulled out of the old SI Board and plugged into the new one. This is an easy task. The purple arrow shows the orientation of the SI Board relative to the driver.


If it fails to reset then you need batteries.

Varta battery 500RST OE part.

Radio Shack: part number 23-191: $6.49 for set of two; they come w/solder tabs on them.

1.2 volts / 700mAh

Charge fully B4 installation on SI board.

Consider mounting batteries "remotely" under dash, etc. in separate holder for easy removal in future (i.e. not pulling the console out and apart); you can buy a plastic holder at RS. Run leadwires from holder to SI board connections. Makes life easy if you ever need to replace batteries again.

From Radio Shack, get:
1) You'll need a twin AA battery holder ($3)
2) 2 AA NiCAD rechargeable batteries ($6)


Here is a step by step procedure for the cluster assembly.

http://e30m3performance.com/maintenance/SI_Board/SI_Board.htm



Later,