Overcharging pretty much has to be the regulator or the connections to it. If no voltage is present at the battery sensing wire, the alternator goes into maximum voltage.

If there is a short in the regulator, the alternator maxes out as well.

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1984 300Sd 210k

Former cars:
1984 300D 445k (!!) (Strider) Original (and not rebuilt) engine and transmission. Currently running on V80 ( 80% vegetable oil, 20% petroleum products). Actually not, taking a WVO break.
1993 300d 2.5 275k. Current 120/day commuter
1981 300SD 188k (Hans) Killed by a deer