I have this same issue with my '94 ultra.. Mine with brakes and turnsignal on bounces between 10.5v and 12.5v; with just a turnsignal it bounces from 12v-14v... This is at idle with a brand new battery... I was thinking of getting a new charging system over the winter and replacing just because... But I'm working just fine as long as I have some road time before I have to shut down..