The voltage would tend to drop if I turned the heater fan speed up, and go up if I turned it off.
As regulators seem to be "set", does it just sound like the alternator needs a strip and good clean?
Also, I have a pair of LED spotlamps, and I thought the idea was to allow loads of light for very little power. I think they are 20W each. Well when I turn those on, it can knock the volt meter reading right down to the low 10V area, knocking about 2V from the electrical system.

Ideas?