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Purdy Swoft · 11-26-2019, 12:59 PM

I use the three OHM Pertronix flamethrower coil on my 12 volt converted 31 roadster . No resister is used or needed when a three OHM coil is used on a twelve volt system . No wires will need to be changed or reversed as long as it remains positive ground . . If a person feels that they need or must use a negative ground setup , reverse the wires at the coil and ammeter . The battery must be connected negative ground and you will be hooked up negative ground . I don't know what voltage is sent to the distributor but it works and I have had no problems with it .

If a 1.5 Ohm coil is used on 12 volts it will be necessary to use a resistor . Coils are rated in OHMs . In other words three Ohm for twelve volt will make a cleaner more ioriginal look without a resister .

There can be confusion between a six volt and twelve volt coil . When buying at a local parts house , I find it is best to ask for a coil in OHMs rather than volts Some counter people still won't know the difference and there will be NO telling what coil that you may end up with . Usually they will ask what year and model vehicle the coil is for . If you tell them the coil will be used on a model A Ford , they will usually tell you that they don't have one . This is why The OHM rating is sio important . I mostly order my coils from Pertronix and ask for three OHM for twelve volts or one point five OHM for six volts . .

11-26-2019, 12:59 PM	#5
Purdy Swoft Senior Member Join Date: May 2010 Location: Alabama Posts: 8,099	Re: 12 volt coil with resistor I use the three OHM Pertronix flamethrower coil on my 12 volt converted 31 roadster . No resister is used or needed when a three OHM coil is used on a twelve volt system . No wires will need to be changed or reversed as long as it remains positive ground . . If a person feels that they need or must use a negative ground setup , reverse the wires at the coil and ammeter . The battery must be connected negative ground and you will be hooked up negative ground . I don't know what voltage is sent to the distributor but it works and I have had no problems with it . If a 1.5 Ohm coil is used on 12 volts it will be necessary to use a resistor . Coils are rated in OHMs . In other words three Ohm for twelve volt will make a cleaner more ioriginal look without a resister . There can be confusion between a six volt and twelve volt coil . When buying at a local parts house , I find it is best to ask for a coil in OHMs rather than volts Some counter people still won't know the difference and there will be NO telling what coil that you may end up with . Usually they will ask what year and model vehicle the coil is for . If you tell them the coil will be used on a model A Ford , they will usually tell you that they don't have one . This is why The OHM rating is sio important . I mostly order my coils from Pertronix and ask for three OHM for twelve volts or one point five OHM for six volts . .