Converting a Ford 8N from a 6 volt to 12-volt electrical system may not be as difficult as you might expect. For one, this conversion does not require you remove the wiring -- as long as the wiring is satisfactory -- you only need replace the electrical components. There are many advantages to making this conversion. In particular, you will be replacing the 6-volt generator with a 12-volt alternator. Generators can not recharge a battery at idle speed or at low RPM -- an alternator can. Additionally, you can put a solid 12-volt battery in the Ford 8N that will be capable of starting in cold weather.
Remove the 6-volt lights and the light assemblies. Use a screwdriver to remove the light cases seated in front of the bulbs. Push in on the bulb 1/8 of an inch, twist counterclockwise a quarter turn and pull out the bulb. Back out the screws attaching the light assemblies to the frame of the tractor. Pull the assemblies from the frame and detach the wiring with your screwdriver.
Detach the electrical wires from the generator and regulator with your 1-inch flathead. Remove the cables from the 6-volt battery with the proper wrench from your set. Remove the 6-volt fuses from the fuse box by hand.
Replace the lights and assemblies with the 12-volt versions. Replace the 6-volt fuses with 12-volt fuses.
Grind off the regulator mount, the battery mount, and the generator mount. Weld the new alternator mount in the same place the generator mount was located. Weld on the regulator mount if you did not buy an alternator with an attached regulator. Weld on the new battery mount.
Check the electrical wiring for damaged sheathing. Replace any wires that have exposes copper. Connect the wires that ran to the generator to the new alternator as well as the wires that attach to the regulator. Reverse the leads on the ammeter by switching the wires on the terminals. Connect the ballast resistor to the coil if your tractor starts via an ignition. Reconnect the cables to the battery. Your tractor has been converted to a 12 volt.