I piggy backed a set of under counter lights to the side screws of the disposal switch. When I turned the disposal on it ran slower and the lights grew dim and stayes dim after I turned the disposal off. The disposal continued to ran very slowly as well when I turned it off then it stopped. It wasn't spinning because of operation it was still being powered with a reduced current. I've taken the wires off the switch but I'd like to know what happened here.