I have a Montgomery MG set installed a rebuilt hoist motor car first would run on inspection. Car no longer will run. I checked armature voltage and I’m only getting 35-45 vdc off generator motor is rated for 200v . When I read resistance on my fields I’m getting 15ohms shop said they should be 87ohms any ideas in which direction I should go from here? This is an old Montgomery where they use a shunt motor in damping circuit. I believe car is late 60 early 70s