Get the alternator checked before you just replace it -- it may just need a new voltage regulator/bush holder, which is MUCH cheaper. You definitely have an overvoltage problem! Don't drive it til you fix it, or you will fry the electronics and lamps!

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!