The DA plug designed for regular production 10/12SI GM alternators has two numbered wires:
#1- Goes to the ignition switch (on) and should have a diode/and or idiot light (a common #194 indicator works great) in series to prevent run-on when shutting off. This light will also warn of low charging issues.
#2- This is output voltage monitoring that goes to the same distribution lug/location the main feed from the alternator goes to, NOT the battery. This ensures the approx. 14.4V output of the alternator is at the distribution point and not just at the rear of the alternator, to eliminate/minimize any voltage drop. This is especially important with rear battery locations, like two of my cars.
I don't know about your Powermaster, but the one I bought a few years ago was labeled one OR three wire, and it came with a DA plug. Curious how the regulator can operate one OR three wire, I talked to their tech support and found out the operation is ONE wire, but allows a stock production vehicle DA to be plugged in, without voltage monitoring. I then sold the Powermaster and bought a rebuilt 3-wire 12SI from our local re-builder in town for about 1/2 the cost because I wanted the advantages of 3-wire operation.
So, I'm not sure if your #1 DA lead will function with a diode or a #194 lamp, because the one I had would not.
You might want to learn more about the advantages of a GM 3-wire 10/12SI like I did, through the text and pictures provided by Mark Hamilton @ M.A.D. Enterprises.
http://www.madelectrical.com/index.shtml
Actually they are 4-wire, because of the suggested and important case ground.
IMO, the ONLY advantage of a one wire is less /easier wiring. These were designed more for constant rpm/stationary usage, not automotive.