The 1986-89 300E's have an alternator that is too small. Only 65-70A max output.

Sounds like you are having an under-charging problem. You need to watch voltage while driving. Radio Shack offers a cigarette lighter volt meter.

WE always try to up-grade those cars with the 1990 & later alternator (80+A).

All you need is the later alternator (Bosch AL66X) & wiring harness 124-542-45-26 ($62 LIST new). OR get the harness from a bone yard!

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