farmall M Wiring Diagram

WayneMo

Member
Where can I find a wiring diagram for the M generator. Mine is one with only one relay coil mounted on the generator. I think the light switch is used to change the generator output. My relay box with the one coil has a resistor inside. It is equipped with a third brush inside. It is still 6 volt and I do not know the history of it. There is nothing in the shop manual. Surely someone has posted something here with the wiring diagram.
 
Thanks guys, I think I understand the wiring except for the field circuit. The diagram you posted shows the resistor inside the switch box. Mine is inside the relay box! I do not see how the light switch can bring the resistor in and out of the circuit with only one lead toward the relay box!
With only one relay inside the relay box, the only voltage regulation can only come from the 3rd brush location or by switching the resistor inside the relay box by bypassing it. I don't see how the one wire going to the light switch box can bring the resistor in and out of the field circuit!
 
Thats what the hi-charge position on the lite sw is for. Makesure the gen,cutout andlite sw all have a good ground to the pos side of the battery. Mite need clean all of the componets where they mount.You can adjust the third brush for charging out-put desired.
 
You're assuming that everything on your tractor is original and "correct." In the 75-ish years since it was built anything could have been done to the wiring. For all we know, someone who designs charging systems owned that tractor and improved it with his own design. Wiring modifications don't always have to be complete hack-jobs, though most were.

Bob M's diagrams show what the wiring is SUPPOSED to look like with factory correct parts. If you don't have factory correct parts then all bets are off.
 
If memory serves the resistor inside the cutout box was used only if the tractor came NOT equipped with factory lights. Otherwise it is "just along for the ride".

The charge control resistor is the larger wirewound resistor that's part of the light switch.
 
I think you are on to something! Maybe there are 2 charge resistors on this tractor! One in the relay box and one inside the light switch box. I have not seen what is inside the switch box and the tractor is at the home of a friend who I am trying to help.
This tractor has lights and they work but the ammeter does not show charge. I have the generator here and will go through it and clean it up before returning to the tractor and installing it. I will make sure the belt is tight and the generator is polarized. Then I will ground out the field and might run a wire from the field to the negative battery post to make sure it is grounded. Then if no charge, I will have to conclude the generator is defective! Sound right?
 

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