Is a model a generator like a model t.I can not get my generator to charge in my model a,it motors just fine with 6 volts positive ground but wont put out any volts at all.Seems like i had this trouble with a model t gen and it wouldnt read on a digital meter.
Your digital meter is the first problem.
Assuming there is no short or open circuit it could be worn brushes or the third brush could be out of adjustment. Try moving the third brush first then attack the generator with an ohm meter. I forget which way to move the third brush but try both ways and move it a large amount. The brushes are worn out if the springs are bottoming out on the brush holders.
Worked on a Model T gen, tested it all ways to Sunday that I could, every thing checked good, it too motored. No matter what I did would not to gen. Swapped the armature, boom good to go!
Maybe You need to flash it to wake it up ? Like I have done with a old farmall generator that wouldn't gen. worked like a champ one flash and it started working.
P.S. I forgot I did the same thing on a 51 Chevy 6 volt generator one flash and it was working