Hello,

I have a 300SD 1984 (126) with a difficult voltage regulation problem.

Initial symptoms would show a low charging voltage, and the alternator was replaced a year ago. The problem seemed to subside. In the last several weeks, I began getting overvoltage problems, where the voltage will rise from 12-18 depending on how fast the engine is spinning.

So I replaced the voltage regulator, now x 2 and the problem is STILL OCCURING....

Defective alternator??? Or is there something else responsible for voltage regulation on a 300SD????

I pulling out my hair on this one...can't take the car anywhere! The voltimeter must be accurate, as I have blew my headlights out from the overvoltage and the radio will stop responding during overvoltage readings...

Is there some other controller of voltage, or is there some kind of diode that could be causing this??? Again, the alternator is a dealer-factory rebuilt about 1-1.5 years old...

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1) 84 300SD 285K+ Miles (Ver Calif)
2) 84 300SD 175K+ Miles (Ver Federal)