Additional comment.  You might have asked 'If you had the 'pigtail' for a
couple of years why wasn't it installed?".  Simple answer:  If it ain't
broke, don't try to fix it.  It's a 30 second fix (after unloading the stuff
in back, I was on a trip) and by waiting for symptoms to appear and then
having the fix work the problem was defined.  If the problem had persisted
I'd have eliminated one possible cause and could have proceeded from there.
I also had on board an adjustable voltage regulator but when the alternator
failed (see my other post) I put in a stock regulator.  When troubleshooting
ONLY DO ONE THING AT A TIME.  I'll do the regulator upgrade later, I didn't
want to complicate the situation if the regulator/brush pack was not the
problem.