My 2010 CVO Ultra Classic has been experiencing fluctuating voltage recently and I haven't been able to track down the problem. It may have started after I had the battery replaced at a local independent shop, but I don't think it is related.
When I start the bike, the voltage goes right up to about 14 to 14.5 volts and stays steady as long as the rpm's are above about 2,000. After riding 15 to 20 miles or so, the volt meter starts to fluctuate, and the longer I ride it the worse the needle swings. The stock gauge fluctuates rapidly between about 13 and 16 volts. Since I didn't trust the gauge, I taped a digital volt meter (DVM) to my gas tank to check it out, but the DVM showed similar behavior. With the DVM the voltage starts out steady at about 14.3 or so, but then once the fluctuations start the "average" reading starts to drop down into the 12 volt range with excursions as low as about 9 volts.
I have tried 3 different regulators, replaced the stator and rotor, and checked for broken wires, shorts, loose connections, etc. I even tried a different battery to see if that might be causing it, but so far no luck. All the parts I replaced tested OK according to the tests in the Electrical Manual for my bike, so I'm not too surprised that the new parts didn't make any improvement.
It seems like the fluctuations start after the battery reaches full charge. I tested this theory by putting it on the Battery Tender until it was fully charged and then taking it for a ride. Starting with the fully charged battery seems to reduce the amount of time needed for the voltage fluctuations to begin. So far it hasn't stored any codes either.
Has anybody run across this kind of thing before, or have any ideas? Is there anything besides the regulator that may have control over the charging system voltage? I’m hoping someone out there has experienced something like this before and has some good ideas…