1988 300SEL ~250Kmi. When the key turned to on and the engine not yet started, the oil level, washer level, and battery lights all light up. Starts and runs fine for about 5 min charging normally with system voltage above 13V. Then headlights dim and system voltage starts dropping to about 12V and the car will eventually stall even if driving.

Try to restart, when the key turned to on and the engine not yet started, the oil level, washer level, and battery lights all do not light up. The car starts and runs fine but system voltage remains ~12V and slowly decreases even at high RPM.

I put the battery on change and try to start and the cycle repeats itself.


Help..............

Either a bad voltage regulator OR alternator.

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