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Farmall & IHC Tractors Discussion Forum
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Farmall H coil 6 volt/ 12 volt difference?

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Farm w/Junk

07-20-2004 05:20:57




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Hi my tractor was running on 12 volts last summer and my coil went out so i put a 12 volt coil on it. It ran good and started nicely. Now that I have switched it back to 6 volt it starts hard but runs good if you get it started. Would the 12 volt coil not work as good as it should with 6 volts? What is the difference? Its from OEM tractor parts and looks like the original but is 12 volt. Should I order a new coil? Thanks
Matt

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Pete

07-20-2004 14:20:53




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 Re: Farmall H coil 6 volt/ 12 volt difference? in reply to Farm w/Junk, 07-20-2004 05:20:57  
Use the right coil AND condenser it is always
the best option.



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rustyfarmall

07-20-2004 07:13:02




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 Re: Farmall H coil 6 volt/ 12 volt difference? in reply to Farm w/Junk, 07-20-2004 05:20:57  
I assume that the 12 volt coil you have uses an internal resistor? If so, then by running a six volt system, you would be getting only three volts, so you would want to get a new coil. On the other hand, if the 12 volt system used an external resistor for the coil, then all you need to do is remove that resistor.



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Allan in NE

07-20-2004 07:30:14




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 Re: Re: Farmall H coil 6 volt/ 12 volt difference? in reply to rustyfarmall, 07-20-2004 07:13:02  
And,

Reverse the coil's polarity if you went back to a positive ground.

That plug firing backwards could make it a little hard to start....but would probably run pretty good after she pops off.

Allan



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Jed

07-20-2004 06:22:44




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 Re: Farmall H coil 6 volt/ 12 volt difference? in reply to Farm w/Junk, 07-20-2004 05:20:57  
The 12 volt coil doesn't know any difference. If you put 6 volts across it , it will perform quite well. A coil is simply a winding. If you run a 12 volt system, simply add a chrysler resistor on the hot wire to the coil. They sell for about $3 to $5 at any autoparts. All they do
is reduce the voltage by 50%.



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K-Mo

07-20-2004 10:12:38




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 Re: Re: Farmall H coil 6 volt/ 12 volt difference? in reply to Jed, 07-20-2004 06:22:44  
The coil won't care too much but the spark plugs will. For example, if a 12 volt coil with 12 volts applied supplies 30,000 volts to the spark plugs then applying 6 volts to the 12 volt coil will supply 15,000 to the plugs. Your right, to use a resistor with a 6 volt coil in a 12 volt system. Back in the late '50s and proir to electronic ignitions, a lot of the 12 volt systems by-passed a resistor during starting and then placed the resistor in the circuit after starting, there by giving a hotter spark for good starting.
K-Mo

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