A few weeks back when I turned in the disposal switch in the kitchen nothing happened. I switched it off and checked the unit, all seemed fine. I tried the switch again and it worked fine. After that when switching on the disposal I would have to switch it on-off-on to get it to work. A couple days ago I did the on-off-on and saw a spark behind the plate. Now in order to get the disposal to run I have to hold the switch all the way on, if I let go the switch is still in the on position, but the disposal doesn't work. Any help much appreciated!