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Farmall cub 6 volt will not charge wiring problems

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05-23-2020 09:59:25

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Hi all,
Just picked up this cub. Serial #5891. This is 6 volt with a magneto. When I got this it wouldn't charge. I looked at the harness and battery cables and most of the insulation on them all were deteriorated so I bought new ones and installed. So I got her to run but still no charging. So I checked the generator and did the battery to generator test and it did spin. Then I did check the regulator and it does check out. I also did the polarity test since the cables on the battery were negative ground and I changed it back to positive ground. I've looked at a couple of wiring diagrams on the site and wired it to the diagram. One thing that is wired is if I hook the light wire up to the regulator, the light switch begins to smoke!! I can get it to run, take off both battery cables and it still will run, just can't get it to charge. Any help will greatly be appreciated. I've also added some pics. Thanks guys.

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05-23-2020 11:13:52

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 Re: Farmall cub 6 volt will not charge wiring problems in reply to Dvss1, 05-23-2020 09:59:25  
I am answering this with real solutions. give me a half hour. Jim

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05-23-2020 11:40:27

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 Re: Farmall cub 6 volt will not charge wiring problems in reply to Janicholson, 05-23-2020 11:13:52  
Included is a modified diagram for your 1947 mid (first year) production Cub. Yours was equipped originally with a 4 position light switch. This is really 2 switches on one shaft. One switch controlled the generator charge by completing the field circuit to ground through a resistor, for low charge, or directly to ground for high charge. In both D and B positions of the light switch the gen stays in high charge.
You also have a Mag. This means that the engine will run with no battery because the mag creates its own electricity. to stop the engine the mag is shorted to ground. (by the way don't disconnect a battery while an engine is running, it can let the smoke out of expensive parts.)
Someone has put a voltage regulator on your tractor in place of the cutout relay. This means that the light switch is now going to be used only for the lights, and not for generator control. The lights were originally supplied electricity from a connection to the amp meter. they will now be supplied from the L terminal on the voltage regulator. (note!! the connection that powers the lights is not the one that is on the end of that lower resistor, that terminal is now abandoned and nothing should be attached to it.) The voltage regulator is fully in charge (pun intended) of the generator. When you have it wired like the picture, the last step will be to polarize the generator fields. Do this by connecting from the Voltage regulator Bat terminal, to the Voltage regulator Arm (or Gen) terminal. (not the Field). it will spark but hold the jumper for one second, and repeat one more time. This prepares the field iron poles to charge with positive ground.
The Gen Arm wires from the Generator to the VR and from the VR L and Bat wires should be 10 gauge amp gauge. The F on the gen to the regulator can be 12 gauge. The wire from the amp gauge to the starter switch should also be 10 gauge. The confusion is that the use of a voltage regulator is being spliced into a system that had a cutout, and the system also must compensate for the use of a mag. Third Party Image

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