These are total guesses but could the Aux be for a guage? Or maybe a jumper to another Actuator?
Were there three wires hooked up before?
Since this is a solonoid for it to do its job it needs to have a large post from the power wire, and another large post that goes to the captains call. Then there are two smaller wires. One is ground and the other is the "trigger" wire. So from your description you are missing a wire. Now there is another configuration. That is that the ground triggers the solonoid, so the switch would be ground. If that is the case then you have a power in and a AUX out and a ground that goes to the help for your switch. Hope that helps