12 volt conversion on 8N

I recently got an old 8N-C . This is what is set up on the ignition system. Charging system disconnected. Dont see a regulator anywhere. May not be needed. It has a 12 volt coil on it and a resistor between it and the points.
Does anyone have any ideas what this guy was trying to do?

Looks to me like he was trying to convert to a 12 volt system but if so then what the resistor?

Im new at this so will need a lot of help.

Lots of good knowledge here but also post on the 9N-2N-8N
forum for a second opinion.

Just because the coil says 12 volts on it does not mean it is a true 12 volt coil. Many coils if you look close will say 12 volts external resister needed or 12 volts no external resister needed. So one has to look to be sure and then some do not give you a clue so they need to be checked with a VOM

Starting with the charging system:

Most 12v conversions use a 10SI Delco alternator.

If it has been converted to this type alternator, the regulator is internal.

There are 2 types of 10SI alternators, a standard automotive alternator with 3 wires.

There is a modified version that uses only 1 wire.

Both have a 1/4" stud electrical connection on the back, that wires directly to the positive battery cable.

If there is a 2 terminal plug on the back/side of the alt, that wires to the ignition through a resistor or diode, and to the battery terminal. See link.

If the terminal block on the back/side is covered with a rubber plug, it is a one wire, and only needs the battery stud wired to the battery. With any alternator, it is usually necessary to bring the engine to full governed speed to initiate the charge on start up.

Of course this is all assuming it has been converted to an alternator, and is the brand described. If it still has a generator, unless you are going for originality, replacing it with an alternator is the easiest, most economical, and reliable solution. With any alternator conversion, the system must be negative ground.



As for the coil, first determine what voltage the coil is designed to operate at. If there is a part number on the coil, research that, see if it requires a resistor.

If it says 6v, it needs a 1 1/2 ohm resistor.

If it says 12v resistor needed, it needs a 1 1/2 ohm resistor.

If it says 12v no resistor needed, it needs no resistor.

If there are no markings, you can test the resistance with an ohm meter. With the coil out of circuit, check across the + and - terminals. If 1 1/2 ohms, it needs a resistor. If 3 ohms, no resistor.

If in doubt, you can replace the coil with a NAPA IC14SB.

Also, if you keep the original coil and resistor, the resistor should be on the ignition switch side of the coil, not the points side.


While you are making these corrections, be a good time to look the rest of the wiring over. Very common to find crumbling insulation, farmer fixes, all kinds of problems with a tractor that age. The wiring is simple, don't be intimidated. With some internet research, Youtube, asking questions, you can do this!
Wiring Conversion

I bought the YT 12v conversion kit and followed JMOR's wiring pictograh and had zero trouble installing it or running it going on a year and 1/2. It had the 12v coil in the kit, no extra resistor needed, just used the stock one already in place. Has the one wire alternator.