[stackj]

I have had the switch problem in my '67 model too. I replaced the master and alternator switches. I broke open the switches and you'd be surprised how dirty the 35 year old contacts were. That carbon buildup seems to make the alternators hunt for stability. After replacing the switches the problem went away.

There are four switches in series with the field input to the regulators. Take a look at the technical data page of this web site for a simplified electrical charging diagram. It may not be exactly like your aircraft but may help a little with troubleshooting.