OK, not certain, but this jumps out at me: Typically a switch is not designed to connect power (which you've sent to both low and high terminals) to ground (which you've connected to the common terminal). To me, as soon as you throw a switch in this setup you've got an automatic short. What you want is this: power - center terminal on switch high terminal - to accessory 1 power low terminal - to accessory 2 power Ground from battery to chassis and to the other terminal on each accessory. An example of what should be a working circuit: GROUND---BATTERY---FUSE---SWITCH CENTER---HIGH TERMINAL---LIGHT---GROUND The switch should not be involved in the ground at all. If it helps, think of the wires as pipes, switches as valves, and lights as turbines. Ask yourself if the water will flow to the turbine or just go back to the pool.