The armature needs to be tested on a growler, a non working armature can pass the buzz test for shaots on a growler, the other test on a growler is a bar to bar output test using amp meter---some growlers have them built in, this tests the armature under a load ----just checking resistance is not as good
look close at the solder connections where the wires of the windings attach to the commutator ---the solder connections go bad from thermal cycle fatigue and overheating (running generator not connected to the battery, too high of charging amperage)---when you took it apart was there any little silver splotches on the field coils across fron commutator---thrown solder
i have fixed many poor performing armatures by resoldering the commutator
the growler with the armature on it make a transformer, the a generator armature makes about 10-15 amps depending on the growler ---if you don;t have the ammeter you can use a wire to make a bar to bar spark test , the armature will need to be rotated and the test done at the same position, the position varies depending on the type of winding but you are looking for each bar to be the same as others tested in the same position, starter armatures can be tested the same way but the anp reading is much smaller--2-5 amp, voltage readings can be misleading because you can have voltage through a bad connection----until there is a load
the growler/armature is an AC transformer, use AC scale on stand alone meter
