Generator question

[WTC]

On the John T motor test, 12 volt generator motors without field
grounded but stops when the field is grounded. What is more than
likely the problem: field or armature?
Thanks for any info.

 

[John T]

Generally speaking good motoring means armature and brushes and bushings are likely okay, so Id suspect a field problem. There should be continuity through both fields connected in series, but NO shorting of field windings themselves to case frame ground.

John T