I apologize. When I wrote, "The regulator is solid state, so I think it was the brushes like Stu said.", I meant to say,"... like Toyvo said."
It is possible that with the brush hopping on the armature, that the regulator was attempting to compensate for the fluctuations in output, and thus proportionately clamped and passed the output as the brush hopped.
In control theory, this would be called a harmonic output, where the DC regulator is simulating an AC waveform, or wild hysteresis around the set point (14.4 VDC). When the brush lifts off the armature, the regulator reacts instantly to the drop in voltage, and slams open the output, giving a momentary reading of 16.5 VDC as the brush makes contact aagain.
We’ll never know for sure, I turned in the old alt as a core. Good riddance.
Thanks again, Dave
