<VV> GM Help needed, possible Corvair related

[Grant Young]

I am trying to figure out why the "Gen" light is on in my 1972 Cadillac. I have a newly rebuilt alternator, new battery and new wiring back to the firewall. I hooked up a simple battery/alternator testor and it shows that everything is fine.
This problem started shortly after I replaced the alternator the first time.
I disassembled it and found that a large plastic piece on the rotor had broken and sent pieces throughout the windings. Installing the second USA rebuilt alternator did not solve the problem, however. Any advise on where to look for the whatever is keeping the light lit all the time?
Thanks,
Grant