12V coil resistor needed?

Bob in Tennessee · Jul 24, 2015

My ongoing project 841 was converted to 12V at some point and I am in the process of installing new harness. Since I don't have a 6V generator, I will go back with 12V one wire alternator with internal regulator. My question is do I need a resistor between 12V power source and coil? My assumption is no but before I hook up I want to ask those who have done that.
Thanks
Bob

JMOR · Jul 24, 2015

(quoted from post at 12:35:54 07/24/15)
My ongoing project 841 was converted to 12V at some point and I am in the process of installing new harness. Since I don't have a 6V generator, I will go back with 12V one wire alternator with internal regulator. My question is do I need a resistor between 12V power source and coil? My assumption is no but before I hook up I want to ask those who have done that.
Thanks
Bob

ome coils need resistor, some don't. No way to even guess unless we know what coil you have! Primary coil resistance is the determining factor.

Bob in Tennessee · Jul 24, 2015

I got my answer. I will need a resistor because I can't confirm that my round coil is a 6V or a 12V which I am understanding doesn't really have an internal resistor it just has double the windings which causes resistance. Mechanically inclined but electrically challenged.

JMOR · Jul 24, 2015

(quoted from post at 12:51:06 07/24/15) I got my answer. I will need a resistor because I can't confirm that my round coil is a 6V or a 12V which I am understanding doesn't really have an internal resistor it just has double the windings which causes resistance. Mechanically inclined but electrically challenged.

ell, maybe you got it. Shotgun approach has its limits. TOO much resistance can result in hard starting & insufficient spark energy to run correctly or at all at high temperatures.

dmbinva · Jul 24, 2015

get an IC14SB coil from NAPA about 20 bucks , no need for an external resister then

Texasmark1 · Jul 25, 2015

MF service manual says breaker points are rated for 5 amps at break. With a 12v system that's up around 13.5 when running, 13.5v/5 amps = 2.7 ohms. That's the total resistance in the circuit from the ignition key to the tractor frame.....ground......aka battery return. So, either the coil has it or you add a resistor to get it. Auto parts stores around here carry ballast resistors including the ones with multiple terminals so you can get the right resistance.

souNdguy · Jul 25, 2015

Adding a resistor to one when not needed will cause issues too.

Measure, don't guess..

12V coil resistor needed?

Bob in Tennessee

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JMOR

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Bob in Tennessee

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