Hi,
If you have not solved the charging system problem, I’ll try to help out. After looking over wiring diagrams for the alternator circuits. I think I have a few things for you to check. I hope I don’t give bad info.

The early model circuits with an ammeter is as follows
I terminal of the regulator is not used.
A+ terminal of regulator is connected to the battery terminal of starter relay.
S terminal of regulator is connected to the ignition terminal of the ignition switch; the switch is feed from a shunt style ammeter that is in series of the battery feed to the alternator
Ground should be common between the alternator and the regulator.
Seeing the ammeter has been removed just connecting the two ends together should not cause the system to start working.


The wiring should be put into a warning lamp configuration.
I terminal of regulator connect to a 15ohm load (Lamp, make sure your lamp is in working order) and continue to the ignition switch (ACC side).
A+ terminal of the regulator connects to the battery terminal of starter relay.
S terminal of regulator connects to STA of alternator.
F terminal of regulator connects to Field terminal of alternator.
Ground should be common between the alternator and regulator.

I hope this helps you