Join Date: Apr 2006
Thanked 176 Times in 173 Posts
Rep Power: 12
Grant, if you are measuring voltage in different places all with the same voltmeter, you will find the voltage directly on the alternator, from the positive output to the alternator frame (which is grounded) is the highest DC voltage. The regulator can only reduce that, and if the wiring is done correctly (yeah, sure) and the regulator has one "sense lead" that goes to the battery bank, you should be seeing 14.3-14.4 volts maximum at the batteries (+ to -) themselves.
It is possible the wiring is somehow wrong, or there may be an isolator in the lines, or the voltage sense lead may not be hooked up correctly. It is also possible that there's a bad diode in alternator, which allows some reverse current into the output. Most inexpensive multimeters will read that as an AC component and that can affect their reading when the leads are connected normally as opposed to reversed.
But before we start looking for zebras...doublecheck the wiring, make sure you are only using one meter, and that it is calibrated properly, or at least, that it reads something you can trust. Digital multimeters can be off by .3-.4 volts in either direction when you compare one to the next. If you have a known or trusted voltage source or other meter, you can compare the two and adjust the one you want to work with.