Re: Which coil is used when coil splitting humbuckers?
You can wire it once and hear the difference. The coil closest to the bridge is brighter, this annoys some people who prefer the one farthest from the bridge which is throatier. Just wire it up, hear, and then loosen the ring screws and flip the coil, listen and decide which position you like.
Once you have decided make sure the bucker screws are closest to the bridge, you may have to rewire.
Just leave enough cable on the bucker so that you have enough space to flip it and hear the difference.