How To Track Down A Dead Short???

[newdad52001]

Good morning everyone..

Well, I'm back with the power drain problem.

A little over a week ago, I had issues with my 95 540i, Called BMW and they had me check the battery.. Ok, replaced battery (It was 6 years old) and this seemed to fix the issue.............. NOT..................

I went out of town for the weekend and this morning go out to start her up to head off to work, again.. dead as a doornail.

Does anybody have any tips / tricks to track down a dead short?

Thanks in advance for your time.

[Dirty_Tool]

i didnt read your original post so let me try to help with a little advise and please forgive me if im covring ground that was alrady covered.

First off let me explain that it is unusual for a dead short to cause a battery draw issue, a dead short is more likely to blow a fuse or fusible link which kills the circuit and shuts it down maning it isnt drawing any amperage.

So what you want to look for is any consumer which is drawing amperage with the key off, out of the ignition and all doors trunk etc closed. Basically reproduce th manner in which the problem occurs so lock the doors if necessary.

Now the best method for checking is installing an ampmeter inline with the battery and testing the draw. about 30-40 millamps is acceptable, any higher can cause the battery to drain down.

Now be sure to 1st check any aftermarket accessories which you may have installed. Disable them by pulling fuses or however you can.

Now lets say as an example you are measuring 100mA as a draw. What you want to do is leave the ampmeter connected and then begin pulling fuses until the draw goes down. If you pull a fuse and the draw goes below 30mA then youve found the problem then look to see what is on that fuse and start narrowing it down from there. Now lets say you pull a fuse and it goes down to 60mA, well then you may have more than 1 draw. leave that fuse out and continue until you get the draw under 30mA or 40 even would prob be ok.

If you get all the fuses out and the draw is still above spec then you will need to see what runs without a fuse which on that car I think is only the starter and alternator. In that case you would have to disconnect them individually and see if the draw goes away.

Anyway if need be I can get into more detail later but there are some tips to get you started.

P.S If you dont have an ampmeter then you can do this using a test lamp however it will obviously be much less accurate. What you would look for is a test light which is lit nice and bright = high draw so gett it to go nice n dim by pulling fuses to track down the problem.

Good Luck
DT

[maci4life]

my aftermarket alarm system with a self powered siren seems to do a good job of draining the battery, but not after a day or 2.

[newdad52001]

Dirty_Tool,

Thank you for your very in-depth and up front answer

I will take your advise and start looking into this or just due to time, I may take it to the local Euro car shop and have them go over it.

There is only one piece of aftermarket equipt. on this car and it is an alarm system. This system is very old and I don't even know if it works?? It was on the car when purchased and I am beginning to suspect that as the culprit...

I have never seen an alarm system that requires 2 gauge wire to run.... In the battery compartment there is a spur off the main line using 2 gauge wire to a huge fuse box... I think I should start there and just pull the fuse. (With an amp meter in place of coarse)

Again, thanks for your tips.. This really helps...

The users of this forum are always so helpfull!!! Can't believe that I have had 6 Beemers and I am just finding this site now??