Thank you for the offer on the wiring harness; maybe another day (although I hope not).

It turns out it was neither the alternator nor the harness -- it was the ignition coil.

Again, in case anyone is interested, the symptoms were rough idling, with a very pronounced vibration, followed a day or two later with the engine dying with electrical power remaining.

A new ignition coil cured it all.

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1995 E320 (2009 - current)
1985 300TD Turbo black (2007-current)
1983 300TD Turbo red (2008-2009)
1972 280SE (2004-2007)
1977 300CD (2003-2004)
1976 240D (1999-2003)