My pull switch broke coming out of my fan, it was a 3 speed switch, when I opened the cover to see the switch it only has two black wires coming out of it one goes to an electrical nut the other black wire goes up into the base of the fan. When I go to Lowe's to buy one they only have for a 3 speed fan switch a 4 wire hook up. And mine only has two wires going to the switch. What do I need to do.