what if it's only a slightly slipping belt? That could account for the rpm fluctuation,,, but,,, why is the auto pilot acting up and why doesn't the alternator put out less if the belt is slipping?

Another thing to check,,,, I'll tighten the belt and see if it's different. If it works it still needs a new tach for the hour meter.

Thanks for reminding me. A slipping belt has happened before. It's a 130 amp alternator with only a single belt. (highest output they make with one belt. it should really have 2 belts)