[AT] grounded coil

Larry D Goss rlgoss at evansville.net
Wed Aug 29 10:43:53 PDT 2007


That's an OK assumption.  Some coil cases are a part of the circuit, others 
are not.  If the primary and secondary windings are shunted inside the case, 
then it isn't a part of the circuit, but if they're not, then the case has 
to be grounded in order to get spark at the plug.  Not all coils and 
ignition systems are equal.  Some have internal resistors, others don't, 
etc.  Several wiring diagrams I have for engines show the case as a part of 
the circuit and grounded.  What you're saying is true a lot of the time --  
maybe most of the time, but it's far from being universal.

Larry

----- Original Message ----- 
From: "Chris Britton" <c.britton at worldnet.att.net>
To: <at at lists.antique-tractor.com>
Sent: Wednesday, August 29, 2007 10:55 AM
Subject: Re: [AT] grounded coil


> Larry.. I'm making a big assumption here.. but I'm guessing we are talking
> about an ignition coil for a points style system.
>
> in that case.. the POINTS are the ground for the coil primary circuit!!!!
> When points open, you get spark.. having yuor coil grounded to the chassie
> would mean that you would NEVER have spark.
>
> Not a real good thing on a spark ignition system..... not to mention it
> would make the points useless... etc....
>
> The 'case' 'can' whatever material of the exterior of the coil itself 
> should
> be isolated/insulative.. and not be common to either the coil primary OR 
> the
> secondary...
>
> Soundguy
>
>>From: "Larry D Goss" <rlgoss at evansville.net>
>>Subject: Re: [AT] Grounded coil?
>>Be careful.  It depends on the coil and the design of the ignition system.
>>There are some systems that require the coil to be grounded.  Others 
>>don't.
>>To be on the safe side, I always make sure the coil is grounded.  We've
>>heard Farmer's mantra enough to all know it by heart -- Check the grounds,
>>check the grounds, check the grounds.
>
>>Larry
>
>
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