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Tractor Talk Discussion Forum

Checking a Mag coil

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Bill in Mi

07-31-2005 10:18:30




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Does anyone know of an easy way to check an magnito coil to see if it is any good it is currently not firing at all




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Bob

07-31-2005 20:09:44




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 Re: Checking a Mag coil in reply to Bill in Mi, 07-31-2005 10:18:30  
You really can't check a coil (mag or Kettering ignition) with any degree of certainty with an Ohmmeter.

A single shorted turn in either the primary or secondary winding will greatly reduce spark output, but will not change the Ohmmeter reading enough to notice.

Coil testers "ring" the coil with a current pulse, and indicate the quality and length of it's "ringing" (oscillations) on a "BAD-GOOD" scale.

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Glen in TX

07-31-2005 19:02:03




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 Re: Checking a Mag coil in reply to Bill in Mi, 07-31-2005 10:18:30  
Bill, I can give you some ohm meter readings if you give me a mag and coil number. This still may or may not give you a true test. Magneto coils are tested on a coil tester by checking the primary and secondary coils and a load test and then sometimes the readings are borderline and have to be compared to a new coil also. If it gets warm and stops firing the coil is bad. If someone has hooked up battery voltage to it the coil is fried. The bearings must be good so the magnet rotor isn't rubbing inside housing or it won't fire or will fire intermittently. Need good clean properly set points and good condenser and check connections for shorts also. Cracks and tracking in the cap and dist. rotor can also short it out.

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Larry from MD

07-31-2005 12:16:47




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 Re: Checking a Mag coil in reply to Bill in Mi, 07-31-2005 10:18:30  
You can unkook the wires then hook up a good low voltage voltmeter.When you spin the mag you should get 2 to 3 volt reading.If it pases this test it still may not fire an engine repeatedly.



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