One wire alternator ?

[Ken Arms]

my 2 cents..the one wire GM alt on my ford naa tractor will some times need to be excited, in other words it wont charge at idle when the batt needs it, I have to rev up the engine to see the amp gauge go to +. There is also a balast in the circuit. My understanding is a GM three wire alt with a diode in the third wire will charge at idle and is the exciter wire. I'm no expert but I bought a 3wire for my 34 project. Ken