Join Date: Feb 2014
Location: Topeka, Kansas USA
Voltage Goes Down as RPMs Go Up?
I just wanted to ask real quick before I set off on a full set of tests from the guide. I recently acquired a Vulcan. I haven't ridden more than a block yet. I'm still waiting for decent weather and for parts to arrive. I want to get all the maintenance up to date (oil change, clean air filters, lube the drive line, change the plugs, etc.). After reading about charging problems that come up with these bikes, I thought I'd better do quick test and see if I'm charging before sinking anymore money in this thing.
I connected my meter to the battery terminals. I keep all my bikes on a trickle charger so the the resting voltage at the time was about 13.2. I started the bike. At an idle (~1000 - 1100 RPM) I get 14.4 volts at the battery. As I rev the engine up the voltage drops to about 13.5 at 5K RPM.
This is a$$ backwards to everything I've read. The fan was off during the tests, just didn't run it enough for it to come on since it was less than 20F in the garage at the time.
It's a stock 89, no mods, no extra lights. About 26K miles. I imagine the ignition system is pulling the voltage down as the RPMs qo up. But shouldn't the regulator compensate for that (if it's functional)? It seems the stator is capable of making over 14 volts.
I wouldn't be worried if I only had battery voltage or maybe a little less at an idle and the voltage increased along with the RPMs. But this is really weird.
Topeka, Kansas, USA