Originally Posted by Corley
This is correct, and one thing you should never do is to fire the coil without a path for the spark to follow to ground, or it will find it's own path. Like, for example, unhooking the coil wire or a plug wire, and snapping your points. That high voltage needs a path to ground, or it will find it's own path of the least resistance. If the path it finds is inside the coil, it will burn the insulation inside the windings, leading to coil failure. If the path it finds is across the output terminal insulator, it will burn a path, creating a carbon trail which will eventually ruin the coil. If you have a bad plug wire, it might cause a carbon trail inside the distributor cap. Not good...
Always provide a path or gap less than about 1/4" to protect the coil, if not, maybe you should buy stock in a coil mfg company instead. Yeah, they will take a few hits, but every internal arc does it's damage.
AND A POINT OF INTEREST: Coils are kind of weird. They can be 6v, and still need a resister, because they are actually 3v coils. They can be 6v on not need a resistor. They can be 12 Volt, and not need a resister or need a resister, because they have an internal resister or not. ETC. The only way to know you have the right coil for the application, is to purchase the correct one, and not rely on a marking that says 6volt or 12volt. Also, they can be for negative ground or positive ground systems, in either voltage, with or without an external resistor requirement. SO, purchase the correct coil, the markings on it won't keep you out of trouble. Not even measuring the resistance of the windings can keep you out of trouble.
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