D2 5U voltage regulator box

looking for ideas, the charging system is not working, looking at the diagram its pretty simple, 3 wires to the regulator and generator, I wired it direct and bypassed the switch and amp meter and got nothing, the generator has resistance so I am assuming its likely good, anyone played with the regulator box? I assume it has contacts, tomorrow I am going to see if the contacts are clean and not corroded

is there ant test method to figure what is failing

thanks

First polarize the generator. This establishes the magnetic field required to generate and ensures it is the correct polarity (negative ground).

If they does not result in it generating voltage at high rpm, you can short the field to bypass the regulator and test for voltage output on the armature terminal of the generator.