I pulled this out of a unit about 2 months ago. BGE series, ran fine, no voltage - so the first place I went was the brushes, they were clean and within spec length but the slip rings had some carbon tracking. Started the unit, cleaned the slip rings with my stone while it was running, shut if off and checked ohms between the two slip rings. I had something like 10 Megohms... spec calls for 27 ohms.
The engine just happened to stop at the location you see pictured below and I could see the crack clearly now through the brush block window in the bell housing for the stator. So.. I dropped the unit, seperated the bell & stator, pulled the rotor and replaced both.
Your rotor may not be cracked but can still be shorted or open internally causing the problem. I have replaced dozens over the years and this is the first one I've seen cracked in this manner.
94-Newmar Kountry Star 40-KSDP
Spartan/Cummins 8.3C-300HP/Allison 3060 WTEC-II/25yr RV Tech RVIA Certified/Onan-Cummins Certified