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Farmall & IHC Tractors Discussion Forum
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H 4 mag coil

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Paul G. in Mn

07-23-2006 12:58:13




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I am working with my mag and wondering when I take my meter on the oms setting sound turned on should I have a beep when I touch on lead to the wire going to the condentor and the other to the case? Is that a sign of a bad coil?




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Bob

07-23-2006 13:05:54




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 Re: H 4 mag coil in reply to Paul G. in Mn, 07-23-2006 12:58:13  
YES, it should "beep". NO, it does not indicate a bad coil.

With the breaker points OPEN, the coil's primary winding is connected to ground at one end, and the points/condensor at the other end, so the meter WILL show conductivity to ground, through the coil's primary winding.

It is IMPOSSIBLE to accurately evaluate the condition od a coil with an Ohmmeter. Yes, and Ohmmeter will catch a DEAD short, but even one shorted turn in one of the coil's windings will greatly reduce spark output.

Coil are tested with a machine that RINGS thme with and AC current, and displays the condition of the coil depending upon how it RINGS (oscillates).

Think of a "good" coil as a bell that rings when struck.

A "bad" coil is much like a cracked bell that gives a dull "thud" when struck, instead of a bight note. A shorted or partially shorted coil acts the same way, electrically, and that is what the coil teater displays.

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Bob

07-23-2006 13:11:13




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 Re: H 4 mag coil in reply to Bob, 07-23-2006 13:05:54  
GOOD GRIEF...

I tryed backing ip to correct several "typos", and posted the message THREE TIMES.

Here's the corrected version:

YES, it should "beep". NO, it does not indicate a bad coil.

With the breaker points OPEN, the coil's primary winding is connected to ground at one end, and the points/condensor at the other end, so the meter WILL show conductivity to ground, through the coil's primary winding, to ground.

It is IMPOSSIBLE to accurately evaluate the condition of a coil with an Ohmmeter. Yes, an Ohmmeter will catch a DEAD short, but even one shorted turn in one of the coil's windings will greatly reduce spark output.

Coil are tested with a machine that RINGS them with an AC current, and displays the condition of the coil depending upon how it RINGS (oscillates).

Think of a "good" coil as a bell that rings brightly when struck.

A "bad" coil is much like a cracked bell that gives a dull "thud" when struck, instead of a bight note. A shorted or partially shorted coil acts the same way, electrically, and that is what the coil teater displays as coil condition.

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