Charging system on 1950 Allis Chalmers CA

Casper I

New User
I have an Allis Chalmers CA Tractor that I am trying to trouble shoot the charging system. It has a 6 volt, 3 brush generator with a cut-out relay mounted to the generator, with one wire going to the light switch. I bought a new light switch, it has a resistor and a fuse on it. I have a wiring diagram that shows the wire from the generator going to the resistor lug on the light switch, it shows first
position-low charge, second position-lights on, third position-high charge. With it wired as per wiring diagram it doesn't matter what position the switch is in the generator overcharges. I put a volt meter on the battery and it reads 8 volts. The amp gauge reads 12 amps. What would cause it to overcharge and how can I fix it?
 
What happens when you disconnect the "F" wire that runs from the generator to the resistor terminal on the switch?
 
I assume that the terminal on the generator that is wired back to the key switch lug that is connected to the resistor is called the F terminal wire. The terminal is not marked on the generator and that terminal is wired directly to one of the field winding. The other terminal on the generator is wired to the cut-out relay, that wire comes from the amp gauge and goes to one of the brushes. The second brush is wired to the opposite field winding. The third brush is wired directly to the frame of the generator. So, which is called the fixed brush? I found out by using my continuity tester that the terminal on the generator that is wired to the cut-out relay is grounded to the frame of the generator. Should it be grounded? Or is it shorted out and should not be grounded to the frame? Thank you for your info.
 
It should have low charge, High charge, then Lights on high charge. The third brush should be adjusted so when in high charge the voltage is about 7.4 volts
with a fully charged battery. It might be connected wrong. Jim
One like it?
 

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