A-26A12-AI Coil Pack Primary Wire, 12', 12 Ga. (YLW)One New Aftermarket Replacement Coil Pack Primary Wire 12 Ft., 12 Ga. (Yellow) by A&I Products This 12 foot, 12 gauge yellow primary ignition wire is a bulk replacement wire for use in tractor and agricultural equipment ignition circuits. Primary ignition wire carries low voltage current from the ignition switch to the positive terminal of the ignition coil, energizing the coil's primary winding so the coil can generate the high voltage spark needed