[dmjlambert]

And what RustyPile says about placement of the sense wire is solid info. If you place the sense wire at a point in your harness where you want the voltage to be steadiest, the alternator will produce output that results in 14.6 volts at that point. If you power your volt gauge from that point also, you would be measuring the ability of your alternator to adapt to different current demands. There's always voltage drop along wiring, especially wiring with a lot of current flowing in it and with resistance of connectors along the wire.