Hitachi internally regulated alternator
I did the same job as you are describing last year. I had to go through a battery to find out you absolutely need wiring on BOTH of those connections you are describing as a T. You can't get the alternator to begin charging without one of them and it won't regulate to 14.5v without the other one.The one that turns the alternator on can be the neg. wire from the "charge" lamp. After switching the alternator on this circuit is opened internal to the alternator and the lamp goes out. The other is the "sense" wire which it needs to regulate the voltage to under 14.6 volts. As I found, the 16v it maxes out at without this wire connected will boil/kill/make cheese of a battery over time. I was told by the shop where I bought the alternator that this "sense" terninal could be permanently wired to positive, but I ran it through my ignition switch anyway. I was suspect of leaving the sense wire powered permanently after the bad advice they gave me that lead me to leaving the sense wire off completely. I'd like to hear from any "experts" on this because I don't like the idea of the extra connections and contact point in the "sense" circuit I have that may not be necessary.Sorry, I didn't write down which one was which. Trial and error was my method. Take the charge light wire and hook it up to one of them, leave the other one empty. Start the engine and check the voltage. If it's on the wrong one, the voltage will stay at battery voltage, if it's on the right one you'll see over 15 volts. Get it on the right one and then hook up the "sense" wire to the other one. Start the motor and read voltage and you should see 14-14.6 volts.BTW, after installing the alternator, I did some reading and most people advise against these internally regulated alternators in boats, I forget why.