Haven't driven my 87 in a couple of months, needed to put a new set of tires on it and get an alignment. My father tried to start it a few days ago and the battery was completely drained. We pulled the battery and recharged it, and the car will start now. However, when connecting it, there's a large spark present when connecting the ground side, as if there's an existing load on the system (and by appearances, something more than just an interior light, etc.). We pulled each fuse in the underhood fuse box one at a time, and tapped the cable on the ground post. The arc never went away (it's large enough that it generates a bit of smoke and marks the post - play with it long enough and you could probably weld the cable to the post. The battery light on the dash is on constantly (even without the key in the ignition).

Any ideas on how to trace the source of the load/battery drain/dash light?

__________________
1987 Mercedes 300D