resistor on 12 volt system

Kent

Look at your coil. See if you can still read the writing on the side of the can. It should say if a resistor is needed or not.
May say one of the following..... ..
12v no external resistor required
12v external resistor required

As mentioned by another poster NAPA sells a 12v coil that can be wired straight to 12v's. The resistor is built into the can. Local store sells them for $16.99.
For this amount of money I would just buy it for the piece of mind of knowing I have the correct part installed.

Q I dont know what all could happen.

A If its a 12 volt tractor and you use ONLY a 6 volt coil with no external series voltage dropping (12 to 6) Ballast Resistor, it will run fine for a while buttttt t the coil may get so hot you cant hold your hand on it and/or the points will burn up prematurely.

Q I dont think the coil is a 12 volt coil. Being it is 12 volt, it needs a resistor on the coil, right?

A RIGHT otherwise see the above

Theres so many different coils out there but my general best guess answer is to measure the coils primary ohms resistance between its lil + and - terminals with a good ohm meter on the low R x 1 scale and if its around 1.25 to 2 ohms its a 6 volt coil but if more like 2.5 to 3.5 ohms its a 12 volt coil or else as posted below if it smells hot after some time or you cant touch it, probably a 6 volt coil (needs external ballast)

John T

I had the ballast resistor fail (went open) on my 12 volt converted Super M last December. As we desperately needed the tractor I jumpered across the resistor so the coil was on 12 volts. The tractor started right up

After a few minutes of running the coil was so hot it could not be touched. But it continued to run like this continuously for 8 hours. Afterward I opened the distributor and found the points nearly completely burned up. However the 12 volt diet seemed not to have damaged the coil.

That evening I installed a new resistor and points - the tractor's been running fine ever since.

...Bob M

• Hobby farm

One way to check, hook a voltmeter set to read 12 Volts DC to the batt in terminal on the coil. If it reads 12 V then close the points or ground the lead going to the points. If the voltage on the input side of the coil drops to about 6 colts then there is a resistor somewhere between the input of the coil and the 12V supply. If it does not drop from 12V to about 6 volts with the other side of the coil grounded and you do not have a 12 volt coil you need to get one. simplest way is to just find a 12V coil at napa and put it in there.