[Sprint60]

Sounds like a bad ground at the V/R. May I suggest checking the braid cable on the back side of the regulator? It fixes ground across the vibration isolator and has a bad habit of getting loose or corroded. Also, check the ammeter, if the glass is cracked and it's been sitting outside it'll be toast.

I had similar problems with one of the 147s when I was working out the issues with it: Wound up cleaning and putting in new brushes and bearing in the S/G.
Installed a whole new wiring harness - the original was all rotted out.
Gave the V/R a good working over and found the bad ground strap.
Still had intermittent problems that turned out to be in the ammeter - replaced with a genuine IH part made in America (purchased from Steiner).
At that point everything started working well and all that was needed was to adjust the V/R. Still works good.

I've had lots of problems with new ones; they work briefly then quit. I'd much rather clean and troubleshoot an old one than mess with the four pole ones that are about all you can get new now-a-days. That's just me; I'm sure Jonathon will blast me for that opinion. Asbestos suit on and ready!