difference between a 6 and 12 volt coil

Clem Clement said:
How do I tell the difference between a 6 v olt and 12 volt coil on the bench? Clem
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Clem, if you have a way to test OHM , a 6 volt coil should be around 1.5 ohm and a 12 volt would need to measure around 3.0 ohm This would be an internally resisted coil to use on a model A.
 
I have always wondered.
Can u use a 12V coil in a 6V car?
What would happen if u did; say in an emergency.
Thanks boys.
Manuel in Oz
 
if the coil is not an interally resited coil, it uses the full 6v, it will work but as was stated weak spark, most 12v coils use a resister on or in them which brings the voltage down to around 9v
 
Manuel said:
I have always wondered.
Can u use a 12V coil in a 6V car?
What would happen if u did; say in an emergency.
Thanks boys.
Manuel in Oz
Click to expand...
It all depends on the OHM. Coils are seldom referred to in volts now days. I bought a coil from one of the TOP model A vendors. There was a sticker on the coil that had been painted over, out of curiosity, I used some mineral spirits to remove the paint from the sticker. The sticker stated 12 volts. Purdy Swoft, who prefers the Pertronics flamethrower coils.
 
I guess I'm dumb. I've tried measuring resistance of several coils and I'm getting readings the continuously change. I've used 2 meeters. I'm measuring across the two terminals, right? Guidance please.
Clem in northern VA with few clouds and no storm.
 
If you order a new 6v coil from synders you will get a 12v coil ,It will work no problem over 5k still great fire
 
A coil doesn't know what voltage is applied to it. An ignition coil is a basic inductor. There are a given number of primary wire windings around a proporsional given number of secondary windings. Both windings are in there but they are insulated from each other by oil on the old ones and by epoxy on the newer ones. A given number of primary windings will have a resistance value like a wire wound resistor will. Most coils are rated by there primary resistance, Condensers are matched up in a given microfarad capacitance rating to the resistance of the coil's primary winding taking into consideration the system voltage being applied. The condenser you use has to be rated to work with the coil you use to make the system function at peak efficiency. If they aren't matched well the spark output will suffer. If you use a coil that was designed to have a ballast resistor then it will work better with that configuration. Late manufacture coils with epoxy insulation can work at higher temperatures but they should still be matched with a condenser that will make them work at peak efficiency to keep them running cooler & lasting longer. The points will last longer too.

There are several good threads on this board about ignition sytems and matching components.

Kerby
 
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