Im having the same problem. I also replaced my belt and the issue persisted.
You can read my post on it:
Voltage Regulator again??? 1987 300TD

I will have my resolution posted as soon as I have a resolution.

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1987 300TDT - 195,000 (Original #14 head)
1993 190E 2.3 - 105,000
1981 300D - 250,000