Mitsubishi Repair: mitsubishi alternator, prong plug, model a ford

Question
I am running a Mitsubishi alternator on my  1931 Model A Ford and it is not
charging the battery.  I just put this alternator on and have just noticed that the
frame has a place to put a 2 prong plug into. The case is marked with a IG by
one prong and an L by the other.  Is it necessary to have these two prongs
hooked to anything?  I am just taking 12 volts from the BAT terminal.

Answer
Arthur,
The "IG" terminal is for the ignition switch that turns the voltage regulator on.  The "L" terminal grounds the circuit to the warning lamp.  I have no idea what the electrical system on a Model A requires, so unfortunately I'm unable to tell you if you need to use these terminals or not.  Sorry I couldn't be more help.
Good luck!