This past weekend, I decided to tackle a problem I've been having with my fairing voltmeter. I have it wired directly to the battery, routed through a waterproof switch on the inside surface of the fairing...that way I can cut off power while the bike is parked. But the voltmeter was giving my strange readings while running down the road at speed, showing below 13v at times, moving around, and finally over time, edging up towards 13.5v. The alternator light never comes on, so I dismissed these readings; also the bike starts crisply so I figured I was getting good charging at the battery. I've used my hand-held voltmeter to confirm that. But if I'm dismissing the fairing meter, why even have it??
I decided to look at the grounds within the left-side pocket of the fairing. I have the Luftmeister fairing with the voltmeter and a clock. Each has a backlight for power. So, just for these two gages, there's power as well as a ground wires. What I had done was to take all of the ground lugs for each of these gages (power and lights) and couple them together with a single bolt/nut through them. A pigtail lug and wire was also part of this stackup which ran out of the bottom of the fairing to the bolt at the ignition coil. A common ground wire for both gages.
I began to wonder if the ground return path for all both gages (remember, two for power and two for the lights) was overwhelming the single ground wire to the coil. The gages have maybe 16-gage wire while the single ground wire is more like 20-gage wire...not sure of the size, but it was clear that the size of the single ground wire was smaller. There's not a lot of current running through these two gages, but still I wondered about the size difference.
So, what I did this past weekend was take the stackup of ground lugs apart and clean them with some RatShack cleaner. I also interleaved internal tooth star washers to help bite into the lugs. I retightened the bolt/nut that holds all of these together. Then I went for a ride.
Holy cow! Once up to speed, the voltmeter read between 14.0 and 14.1v the entire time, dipping a bit when coming to a stop. Now that's what I call a good charging voltage...and a proper reading voltmeter. I'm sure glad I did that! Prior to this, I had always just ignored the voltmeter, certainly since the alternator light never came on at speed. But now, I guess I'd better pay attention! It actually works!!