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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