Generator was charging, replaced VR, now gen has no output

(quoted from post at 18:04:40 03/08/18) I'm chasing electrical bugs, as usual... I have a formerly diesel 641, now with a gas 134 in it. It has the 12v generator from the diesel. I wasn't getting any battery charge. I tested the generator output (arm stud to ground) and it came in around 14v. I jumped all the wires between the gen and voltage regulator directly to the contacts on the regulator, and couldn't get it to charge. Finally, I took off the cover of the VR, pressed down the contact by hand, and the tractor immediately charged. 14v at the battery, ammeter reading about 30, lights brightened, all good. Did this several times over a couple days, generator never showed any sign of issue. So, I ordered a new voltage regulator from this site. (The shipping was very fast, thanks!) I put it in this morning, turned the tractor on, the ammeter climbed up to about 15 volts, for about two seconds, and then dropped down to zero. I tried all the connections etc and couldn't get it to charge again. I checked the generator again, and was shocked to find that it now wasn't producing a charge. The needle on the multimeter only rose to about 1 volt. I then removed the ARM wire from the generator, tested that stud again, and now it read about two volts. Repeated it a few times, and there's a clear difference between the voltage reading when the ARM wire is hooked up, and when it's not, but of course neither way indicates a working generator. What the heck is the problem?!

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(quoted from post at 14:20:46 03/08/18) That worked! But only for 30-60 seconds at a time......... I jump the ARM and F gen terminals, release, it stays charging for sometimes 30 seconds, sometimes 45, 60, but always breaks off again, with no change of rpm. I again jumped the field wire gen to VR, to bypass any potential bad spot, with no change.

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