Mmm! Tough question . . .
Couple thoughts come to mind - like how would you mount the 2nd coil?
If you put two coils on the end of one shaft, they would interfere
terribly with each other.
If you plan to switch out the second coil, then a switch would hardly
save you any time. You'd still have to remount the 2nd coil on
the end of the shaft.
If you want to keep two coils connected to the control box, and
move the "dead" one away from the active one, you could do that with
a switch.
I expect it would be messy though.
You'd have to study the screw-on connector for the coil.
Go to Radio shack and see if you can find a "Y" switch
connector box. That would do the trick.
You'd have to mount the switch to your control box.
If you cannot find, or if they do not make a Y switch,
you can make one yourself
but that's even messier - you'd have to cut and splice
the two coil cables, splay them out, and connect them
to a standard "Y" switch, making sure all the colored
wires go to the right places, then when you flip the switch,
change the "dead" coil to the end of the shaft.
That is so cumbersome . . . wondering if I understand
your question properly.
