[Rev]

Actually, you can just use a test light. With everything off, there should not be any current flowing from the + battery post to the cable (alarm, clock, etc. disconnected and doors shut). If there is, then you may have a short somewhere. If that's the case, then just check one connection to the + battery one at a time to see which circuit is drawing amps ( lights the test lamp). Then at least you know which circuit is shorted or drawing amps. Trace it down from there.

Rev