So I just got my 40" light bar and I'm wondering how to wire it so the Spot and Flood functions. It didn't come with a harness. I was expecting it to come with 3 wires, 1 for ground, 1 for spot, and one for flood. But it only has power and ground wires. I've wired up auxiliary lights before but never a light bar. Would a universal light harness work? Do I need a 3 position switch? Any help is greatly appreciated.