Mercedes: 1983 mercedes 300 d, turbo diesel, ground cables, low beams

Question
purchased this car with 90000 original miles, everythig in very good shape but some interesting ,possibly related problems; headlights go from dim to very bright and back to dim  while driving with low beams on, this happens occasionally, also i seem to burn out headlamps a lot, replaced them 3 times in a year; tachometer works sporadically; heater and A/C work sporadically; sometimes when you turn the radio on it comes on full blast even though the volume is not turned up all the way; inside courtesy lighting works sometimes; other bulbs seem to need replacing often; usually starts well but recently every other or third time my wife gets in she says she it won't start the first two tries then on the third try it won't turn over.
i think there must be something haywire in the electrical system but don't know where to start.
thanks
jonathan

Answer
#1. Clean all ground cables, replace the ground cable from body to transmission housing.
#2. Replace all fuses with NEW.
#3. Check the alternator belt condition/tension.
#4. Replace the voltage regulator.

Engine Electrical:
http://www.mercedesshop.com/shopforum/showthread.php?t=142401