Subject: Re: [TR] Coil and spark plugs polarity

From: Tony Drews <[email-masked]>
Date: Sun, 09 Nov 2014 09:20:28 -0600

The center electrode will be the opposite of the ground that you're 
using.  Negative ground = positive center electrode, Positive ground 
= negative center electrode.  Has to be that way to produce a spark - 
otherwise there's no current flow.  I believe that the coil has a + 
and - connector but need to go look again to be sure.

Tony Drews

At 08:28 AM 11/9/2014, Andrew Uprichard wrote:
>List:  Is it true that it doesn't matter which way one wires the coil (for
>example after converting a car from positive to negative ground), but it is
>important that the center electrode of the spark plug is always negative?
>
>
>
>Andrew Uprichard
>
>Always learning something new...
>
>** [email-masked] **
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From: "Greg Lemon" <[email-masked]>
Date: Sun, 9 Nov 2014 09:52:15 -0600

No to number one, yes to number two, at least according to this article as I 
read it, and reversing the coil wires when you switch polarity is how you 
keep it that way.

The car will generally run fine wired either way, but if something else is 
marginal or a stronger spark is needed you get a better spark if it is wired 
to have the center electrode negative.

http://mgaguru.com/mgtech/ignition/ig104.htm

Greg Lemon
TR250

--------------------------------------------------
From: "Andrew Uprichard" <[email-masked]>
Sent: Sunday, November 9, 2014 8:28 AM
To: <[email-masked]>
Subject: [TR] Coil and spark plugs polarity

> http://autox.team.net/mailman/options/triumphs/[email-masked]

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From: Geo Hahn <[email-masked]>
Date: Sun, 9 Nov 2014 09:23:53 -0700

On Sun, Nov 9, 2014 at 7:28 AM, Andrew Uprichard <[email-masked]>
wrote:

> example after converting a car from positive to negative ground)...

Though spark polarity may be of little import -- it has always been my
understanding that coil polarity needs to be correct for the polarity of
the car.

IOW, on a positive ground car the little (white/black) wire from the coil
to the distributor should be connected to the coil post marked '+'.  Easy
to remember if you think about how that feed is an intermittent ground
(interrupted each time the points open).

Earlier coils were marked CB (contact breaker) and SW (switch) but as far
as I know those marks were made with positive ground cars in mind so
'CB'='+' and 'SW'='-'.

The ignition will still work with coil polarity reversed but I think the
points will not last as long.

OTOH, maybe this is just an old mechanics' wives tale that I believed and
am repeating.

Geo

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From: "dave n" <[email-masked]>
Date: Sun, 9 Nov 2014 11:46:41 -0600

most coils have a +  and a -

btw - if you hook up  a pertronix and wire the coil backwards, you will 
either be going back to points or buying a new one

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From: Mark J Bradakis <[email-masked]>
Date: Sun, 09 Nov 2014 13:48:57 -0700

> most coils have a +  and a -

Some have SW and CB - SW goes to the ignition switch, CB to the contact breaker.

mjb.