The Topic reads 1-wire to 3-wire so I assumed you swapped out your 1-wire and have put a 3-wire in.
The BATT wire and the #2 wire both go to power ... but using the BATT connection for voltage sensing, as many do (because it's easy to just jump the #2 wire around to the back of the alternator), is not only lazy but a real good way to get a totally inaccurate reading for the built-in regulator!
What you'll see in my image-link (see my above post) is the BATT connection (charge) and the #2 wire (regulator/voltage sensor) are both connected to a terminal block on my firewall.
I'm getting a full 14 volts from the battery to my terminal blocks and feeding all my major components from there ... therefore, the #2 wire is sending a very honest reading of how much voltage those major components are getting and the regulator is doing an excellent job because of that.
The #1 wire simply goes to the ignition.
