Mark, You should be able to do it using 2 diodes 1n4155 fast switching high current anode side to the coil and both cathodes to the tack. This should keep them from back feeding to the other coil.
>Mark Jones wrote, > My plane has a dual ignition and my tach is hooked up only to the primary coil. When I switch to the secondary coil, I loose the tach function. I would like to hook the tach up where it will function with either coil. Can I simply run a jumper wire to the secondary coil from the tach or how should this be done? > >
