Clive
Fair question but I'm unsure about the answer! Perhaps it came down to
insignificant technicalities. Does anyone else know?
Paul
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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