Hi -- I've been off the list for a while and I hope this hasn't been
recently covered, but...why do ignition coils have polarity?
Backgound: I recently installed a Crane ignition system on my TR-3A.
Also, this car has a Lucas Sport Coil and is positive ground. The coil
is marked with polarity on the terminals (+/-).
With the points system, I had to connect the "hot" lead (the lead from
the battery via the ignition switch) to the positive terminal on the
coil. The negative terminal went to ground, via the points.
With the Crane system, you connect the positive terminal on the coil to
ground along with the red lead from the module. The yellow lead, which
the module switches off and on, goes to the negative terminal. (The
lead from the switch goes to a third lead from the module.)
So, that made me wonder. Why does a coil have polarity (and also, why
it seems reversed with the Crane vs points systems)?
Thanks!
Chris Amley
1959 TR-3A
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