Curtis Snow

My name is Curtis Snow, I have a 1978 280Z and I just replaced my alternator with a remanufactured 60amp one. I had Autozone test the old one and the alternator failed their test stand. I cannot get the new tested alternator to show more than 11.5 volts when the engine is running. The battery shows 12.65 volts. I know the voltage regulator is located inside the alternator. Question: What is the T (duel wire) plug used for? The plastic T connector that plugs into the back of the alternator. Where does the wires come from before the plug? I made sure all the connections are clean, including the fusible links and all the wires show continuity. The wires show battery voltage all the way to the positive lead on the alternator. I checked the ground cables as well. The battery is a year old and has been maintained over the winter. I tested the battery at autozone and it tested good. I went back to get a second alternator, even though the first one tested good at Autozone. I now am the proud owner of two good remanufactured alternators and both do not show a voltage from the positive lead on the alternator when installed. Can anyone help? Thanks