Here's a dousy for you

[Keith Hardman <khardman@xxxxxxxxxxxx>]

Long story. And shows what a little inattention can do for you. I
recently rebuilt the engine on a 1987 325. During overhaul, I thought
I'd put a trickle charger on the battery. Without paying any attention
to the correct polarity of the battery, I hooked the I presume dead
battery up backwards on the charger (negative to positive etc.), the
whole time the negative cable was disconnected but the positive which
was hooked up to the negative lead off of the charger putting negative
voltage on the cars positive circuitry. I hope you have followed me so
far. I did not notice this until the arc that was drawn got my attention
whenever I went to lay the negative cable back down on the battery. I
discharged the battery using a 12 volt light and proceeded to recharge
the battery correctly. After recharge, I installed the battery on the
car and once again drew quite an arc when laying down the ground
connection. I tried the lights, ignition, horn, etc. and nothing worked.
When I put a meter on the positive and negative post in the engine
compartment there was minimal (approximately 2-3 volts on the system).
The negative cable was a little warm but not hot. I removed the cables
from the battery and checked voltage and it was about 6 volts. My next
move is to get another battery but I am sure there is now a problem in
the cars electrical system. My question is what all could I have toasted
or where do I need to start troubleshooting this problem? I don't know
if keeping a negative charge on the positive circuit throughout the car
without a return leg hurt anything or not. I'm at a standstill on what
to check or try. I possible could have burnt something up when I laid
the negative lead down on the battery but not sure where to start
checking or how. Could you give me any idea where to start or any system
to follow to check all of this out? This whole project started after my
son ran the car without oil after knocking a chunk out of the oil pan
about 18 months ago. 
One more hint. I tried jumpering the leads from my other cars battery
and when trying to connect the two negatives together there is the
familiar big arc even with no load on the BMWs system other than what I
have no control over. I have found no blown fuses in the fuse box in the
engine compartment. I don't know how to check out the relays in the fuse
box. I know I couldn't be that lucky though.

Thanks a bunch for trying to help on this problem. After 18 months, I'm
ready to take the car for a spin.

Keith

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