6V to 12V - Using an Ignition Reducer

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The NAPA coil does not need a resistor.

If you are using an original style 6 volt square coil, you need enough resistor to where the voltage to the coil is approximately 3 volts... WHERN THE POINTS ARE CLOSED. If the points are OPEN, the circuit will read battery voltage.

This IS electricity in it's most basic form... and the basic rules apply... they ALWAYS apply.

Have fun.... duey

I was not 100% clear on my original post so this may clarify....
Terminal Block (aka Resistor) - Understood to be required for any 12V converstion.
Ignition Resistor (aka Voltage Reducer) - this is what I want to clarify - is this device required for a 12 volt conversion in which I would be using a 12 volt coil?

I appreciate everyone's thoughts and ideas - I am a better plumber than an electrician.

The 4 ohm 12 volt coil will not work with a OEM Ballast. These require the Dell .5 ohm.

I would just measure the Ohms of Your Coil and if its 2.5 Ohm (it seems most are this type) You would use the OEM Ballast & an Ignition resistor of a fixed value (near) ~1.0 ohm.

If you have an Ammeter on your Dash just bump your starter until you read Max Discharge(points Closed) and the correct current will be closer to three (3) than it is to two (2). This will be the same for "ALL" the front Mount coils regardless of voltage applied.

Hope this Helps,

oem 6v front mount coil, on a 12v system needs the OEM balalst resistor AND a dropping resistor similar to an 8NE10306.

non-oem 12v front mount coil on a 12v system = read packaging that came with coil. There are at least a couple kinds out right now. Some like a 1/2 ohm dropping resistor made with a couple 1-ohm resistors paralleled together.. Some like the OEm ballast resistor.

If your 12v coil came with no info.. then complain to the supplier.. you paid good money for it.. the least they could do is have manufacturer info / specs listed for it. if in doubt.. use the the OEM ballast resistor and see what performance you get.

Soundguy

On the front mount with 6 volt coil you need a balast resistor -- the convient place to mount one is on the terminal block.

On a front mount 6 volt square can coil using a 12 volt system you need both the original balast resistor AND a voltage reducing resistor. If you use a "12 volt" coil you need about 1/2 ohm of resistance to limit the current flow so as to not melt your coil. (It's because it IS a 12 volt coil and your alternator puts out about 14.5 volts when running). You need one rated for 20 watts (or more) else it is gonna melt.

You can think of voltage as pressure and amps as flow. Resistors work as restrictors in the line.
If you have pressure and no flow through a pipe as when it is shut off down stream then you will have the same pressure on both sides of the restrictor -- if the water is flowing then you will have a pressure drop accross the restriction (oriface). That is why you should get battery volts at the coil with the points open and less than that with them closed.

(You can also think of the spark system as a water hammer situation -- Shut off a large flow of water fast and bang the pipes rattle and a big pressure surge happens)

HTH Roger in Michigan

You see, there are 12V coils that require NO resistor; then there are coils used on a 12V vehicle that still need a resistor.

What I understand is that if you use the recommended NAPA coil (Dell or someone will have the exact part number, or you can search this site), you won't need one. If you use anything else, you'll have to make the call yourself based on any tech data you can find on the coil.

I know this is technically a "non-answer", but it really DOES depend...

Good luck. Someone here'll add the detail you need, I'm sure.