Paul,
Makes sense, but in that case why do
themanufacturers put the CB / SW marks
(or + / - ) on the terminals?
Clive
===========================================
----- Original Message -----
From: <Dduncombes@aol.com>
To: <lawrie@britcars.com>; <mgt@autox.team.net>
Cc: <mg-mmm@autox.team.net>
Sent: Saturday, August 23, 2008 5:51 PM
Subject: Re: Coil theory
> Lawrie
> It doesn't matter which way any coil is wired with regard to the SW or CB
> terminals. When the points open there will still be a surge of current
> through
> the primary coil due to the condensor charging up, and the secondary in
> the
> coil will generate 20k plus volts at its terminal. Depending on the
> polarity
> of the primary coil connections, and therefore the direction of current
> flow
> in the primary, this high tension voltage will be positive or negative.
> When it gets to the plug it doesn't matter what it is because the
> potential
> difference across the plug will be at the worst case 20k minus 12 or at
> best 20k
> plus 12 - that will not affect the performance of the plug!!
> As a matter of interest my PA has been wired positive earth some time in
> the
> past but my old coil is wired in the normal way with the SW terminal
> being
> connected to the ignition switch (-ve) and the CB to the distributor
> (+ve).
> It runs perfectly, but the blower also helps!
> Regards
> Paul Duncombe
> UK
>
> Fellow listers - especially those of you who understand the ebb and flow
> of
> electrons....
>
> I've always been led to believe that coil polarity is important.If the
> car
> is wired negative ground, the "minus" terminal on the coil should go to
> the
> distributor for maximum spark voltage to be generated. However, today I
> presented myself with a puzzle which may be totally erroneous or may, in
> fact, need some explanation:
>
> If a coil was manufactured during the days when its intended cars were
> predominantly positive ground (example - a Lucas Sports Coil dated 1958),
> and has terminals marked "SW" and "CB" rather than "+" or "-", logically
> the
> "CB" terminal would be the "plus" terminal since the points take the
> current
> to a positive ground. Am I right so far? Or did Lucas make its Sports
> Coils
> to fit cars with either positive or negative ground?
>
> Now, if one wanted to put this coil into a car wired negative ground,
> would
> the "CB" terminal still go to the distributor? If reversing the polarity
> of
> the car also requires reversing the terminals on the coil (something I
> was
> told a long time ago), have we in fact now wired the primary voltage to
> the
> secondary circuit in the coil when we connect the coil the other way
> around?
>
> In short, are coils manufactured for particular polarity in a car and
> will
> their output voltage be reduced if they are wired backwards because the
> car's polarity has been reversed?
>
> Any and all insights will be appreciated!
>
> TIA,
>
> Lawrie Alexander
>
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