At the very least check your battery earth & also the voltage regulator earth. Are you still on the fragile original CE unit or have you changed to the more robust HD unit? Fluctuating voltage seems to indicate a regulator fault.
With my HD regulator the voltage reads about 14.4 all the time even with all lights on provided the engine is a little above idle speed. With the failing CE unit & headlamps on the voltage slowly fell.
Tim
