Keith,
I'm with you on that one buddy, been trying to track down what drains
mine for a few weeks now Here's what i have compiled thus far, and of course check your alternator,
battery cables etc (I assume you have already, but you gotta ask!)
Tach I don't know about, maybe you should pull the instrument cluster and see
if maybe the tech dislodged something after the SIL battery repair.
As for the OBC light,This
shows you how, a PITA, but very doable. I think the key is not to have
fat fingers!.
Hope this helps you.Jim Ladd
84 318i
Bimmers Librarian, and Sweet Pickles Bus Driver