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12 volt coil |
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Ken in Texas
Orange Level Joined: 11 Sep 2009 Location: Henderson, TX Points: 5919 |
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Posted: 03 Dec 2009 at 9:02am |
I'm trying to scrounge up a 12V coil for a C with a Batt ignition. I can only find free coils that say " for use with external resistor". Will they work without a resistor? Is the resistor the condensor looking thing with one wire right at the coil on a Dodge? If I have to use it, what pole does the resistor wire connect to? I'm presumeing The 6 volt coil has to be changed when converting to a 12 volt system .
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Goose
Orange Level Joined: 07 Oct 2009 Location: Melrose, Wis Points: 2471 |
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Ken, I bought a simple generic 12 volt coil at Farm and Fleet for about $12. It was in the automotive section. It didn't need a resistor and it works great on my WD. Never had a problem. |
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Brian Jasper co. Ia
Orange Level Joined: 11 Sep 2009 Location: Prairie City Ia Points: 10508 |
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Before I converted my CA to electronic ignition, I had a coil from a Kohler K301 engine on it. The Kohler coil didn't use a ballast resistor on the single cyl engine and I never did on the CA either. Worked just fine.
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"Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford
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Gerald J.
Orange Level Joined: 12 Sep 2009 Location: Hamilton Co, IA Points: 5636 |
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The will work without a resistor, for a while. But they will burn the points from too much current and will eventually fail from too much current in the coil. You need the ballast resistor with resistance about the same as the low voltage winding of the coil to use those coils on 12 volts.
Most any vehicular coil without a resistor (most likely a 60s or earlier vintage Ford coil will do, providing its later than about 1955 to avoid being 6 volts or later to avoid being solid state ignition) will do just fine. NAPA is reputed to have a suitable 12 volt coil needing no resistor for maybe $15. Gerald J. |
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B26240
Orange Level Joined: 21 Nov 2009 Location: mn Points: 3860 |
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Ken I have used several NAPA coils with no problems, ask for one that says 12 volt no external resistor required. Mark L
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Coke-in-MN
Orange Level Access Joined: 12 Sep 2009 Location: Afton MN Points: 41567 |
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Most GM coils from 1955 on and many Chrysler coils also used a external resistor to drop coil voltage to around 8V. GM did away with the external resistor by using a resistor wire from the ign switch in later years.
For starting the coil picked up voltage from the starter lug on solonoid of Delco starter which was 12V when key was turned to start. When engine started the wire from ign to coil was run through resistor to increase point life.
As far as wire , either end as resistor is not polarity sensitive, but points and coil are as they need to be same polarity to ground as the battery is. So marking on the coil to ground should be same as battery.
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Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something.
"Challenges are what make life interesting; overcoming them is what makes life meaningful." |
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Osage_Orange
Orange Level Joined: 11 Sep 2009 Location: SW MO Points: 1593 |
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If you just want to "tinker" with all your used parts, the DC current through the coil and points with the engine shut off should be approximately 3 Amps (it will be less when the engine is running). This will prevent overloading the ignition system and preserve the life of the points and coil. You can sort through ballast resistors and coils until you find a combination that gives the above values. If you just want to get the job done and move on, go to an auto parts store and buy a coil that is labeled "12V, no external resistor required".
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Why is there never time to do it right the first time, but always time to go back and fix it?
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Steve in NJ
Orange Level Access Joined: 12 Sep 2009 Location: Andover, NJ Points: 11788 |
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When running a 12V conversion with a 4 cylinder engine, you need 2.7-3.3 ohms of resistance in the Ignition circuit for the engine to run correctly and not burn up the points. Stay away from external ballast resistors. They didn't work under the hood of 60's auto's, they sure as Hell ain't gonna last to long hanging off the side of a tractor out in the elements. Mother nature plays havoc with those things. We offer a 3.0 ohm coil with built-in resistor. You can also purchase one from Napa or your local auto parts store. Just tell them you want a 3.0 ohm coil with built-in resistor. Your done.....
Steve@B&B |
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