Series III V12 charging issue

Hi , I’m currently working on a 1971 V12 . When the car came in the ignition light would stay on even with the key out. I traced out to a bad alternator. Had the alternator rebuilt, now the car is still discharging and ignition light is on while running. I’ve swapped out the voltage regulator with one from a car that was working fine still no dice. Anyone run into this?
Many thanks
Dan

You indicated originally the alternator tested bad. How does it test now that it has been rebuilt?
Tom

I’m getting an output of 3 amps off the alternator. The current doesn’t change as I increase RPM’s as the manual suggests would be a faulty voltage regulator. I’m stumped on this one

I struggled with alternator issues for a while. Once a bad alternator damaged a new regulator. Eventually I gave up and had a modern Delco remy installed. No issues ever since