Inspect your wiring under the front of the engine, and to the back of the alternator. There are a few possibilities, all in this area- you could have lost a belt for hte alternator, wrapping itself up in the pulley and damaging wiring, or maybe trashing the other belt.
The alternator might have bad mount bushings and not be running true, with similar results.
On a 1988 245 recently I fixed the oil light wire, alt charging wire, alt main wire, and alt ground wire- all were thrashed by a bad belt. Your symptoms seem similar to his- the exception being that your car still runs. His didn't when the small red wire (alt charging) grounded out against the block.

Pull off the splash pan, if in place, and have a look.
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Rob Bareiss, New London CT ::: Roterande Fläkt Och Drivremmar!