12 volt conversion question

[John T]

Not a flame, just best info: 12v coils operating on 14 volts do not have actual resistors in them. They are designed with wire size and number of turns to operate on the higher voltage, just like a 12v lightbulb instead of a 6v lightbulb when converting to an alternator. Jim

X2 and Ditto. While some old cars actually used coils that had discrete stand alone resistors thermistors tucked away inside the can I never saw any old tractor coils 6 or 12 volt that had internal resistors. John T

 

[Janicholson]

i ran my 12 volt tractor with a 6 volt coil and no added resistor for ~ 8 years. the coil's still good.

Some 6v coils are close to 2 ohms actual primary resistance. Some systems only deliver 11 volts to the coil through the switch and wiring, Sometimes reality is good despite what could happen. Jim

 

[Geo-TH,In]

@buickanddeere - Please explain. I don't understand this statement. zuhnc

That's easy. Double the voltage you double the amps.
Heat is same as power. Watts = volts x amps.
2 times the voltage times 2 times the amps = 4 times the power. 4 times the power, 4 times the heat.

 

[HFJ]

Some 6v coils are close to 2 ohms actual primary resistance. Some systems only deliver 11 volts to the coil through the switch and wiring, Sometimes reality is good despite what could happen. Jim

the extra resistance has my money on it. my system delivers 12+ to the coil and has since i converted it. it wouldn't run with the ceramic blob- that turned out to be 3.5 ohms. i pulled it out and let it run, waiting for the coil to burn up. it never did

i still have the resistor - anyone need one that won't let their tractor fire?