1988 300E Strong Surging and Electrical System Fluctuations
 

My 300E, a manual transmission model, has begun to experience engine surging as the temperatures have dropped here recently, and, along with the engine (and speed) surging there is a brightness fluctuation of the head lights and dash lights. I suspect the voltage regulator has given up the ghost, but don't understand how that would cause the engine to surge. Anyone else ever have this same experience? Any fixes? Thanks, Jim

Just to finish out this topic for anyone else having similar symptoms, it was the voltage regulator. At idle it was turning out 19 Volts DC and less than half a Volt AC, and at speed it was likely tripping the OVP relay, which shuts off the fuel pump, among other items. So the varioius protected items would shut off and wait for the engine rpm to drop low enough to bring the voltage below the threshold for the OVP interceding to protect various items. Which showed up as surging and bucking. Battery may have been damaged too, so I rinsed the area with a copious dousing with water and baking soda.

All is back to normal. The new voltage regulator is a Bosch item made in Spain, I believe, while the old one was a wierd brand I never heard of before, god knows where it was made. It looked fine, more than half the brush length still there.
Jim