Re: Ballist Resistor

Posted by KEB on May 20, 2007 at 21:28:57 from (72.19.170.5):

In Reply to: Ballist Resistor posted by CNKS on May 20, 2007 at 18:27:07:

By using a ballast resistor with a lower voltage coil, it is possible to apply the full battery voltage to the ignition coil for starting and then use the ballast resistor to limit current once the engine is running.

The idea is that by using a 6 volt coil on a 12 volt system, you can get a much hotter spark during starting, however, if you let the engine run continuously with 12 volts applied to a 6 volt ignition coil you'd have too much current flowing and would heat up the ignition coil plus fry the points in short order; hence the use of the ballast resistor.

If the tractor was originally designed to use a ballast resistor, there should be a second connection somewhere between the coil side of the ballast resitor and the (+) side of the coil, coming from a contact on the starter switch or the starter selenoid. The purpose of the second connection is to bypass the ballast resistor during starting and apply the full battery voltage to the coil, thereby creating a hotter spark.

If the tractor wasn't originally equipped with a ballast resistor, then it should have a 12 volt coil. Ballast resistors are also required for a 6 volt to 12 volt conversion unless the original 6 volt coil is replaced with a 12 volt one.

Yes, running a coil designed for use with an external resistor will fry the points in short order.

Hope this helps a little.

Keith

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