Most likely your generator is not working,
may need new brushes, and maybe armature turned.
bearings are replaced at this point at times.
Get the armature tested for open or shorts, the same with the Field windings.
I would start with the Brushes, and see if that takes care of it, see how far they are worn down
Polarize the generator after installation.
Best read up on a automotive electrical book before starting work.