I had a series of electrical problems pop up all of a sudden:
Head light burnt out--replaced w/ 2 new headlights which lasted less than 1 hour before burning out.
Heater fan fuse blew out twice on "high"
Radio would quit playing at higher engine speeds, but OK at idle.
W/S/W were fast

This all began to happen over a short period of time. When I got home I put a voltmeter on it and it showed a charge at idle of about 15 volts, increasing to 18 at speed.
The alternator was a new Bosch ( not rebuilt) only a month old that I purchased from my local indie. Upon hearing the 18 volt charge, he agreed it was a bad alternator and replaced it under warranty.
Now the voltage ranges 13-14.5 or so. Everything else electrical seems to be back in order.
I suppose the radio shut itself off to prevent damage from over voltage.
While replacing the headlight, I found that the pot metal assembly that holds headlights was broken into two pieces. I got one from my local You-pull-it yard for $10. Everything os back to normal!

glad to hear you tracked it down-
seems that overvoltage situation has happened to a few members lately

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1984 300D Turbo - 231k....totalled 11/30/07 RIP