Hello Sherry,
Peel off the rubber on the bottom of the control, the rubber may be brittle by now so be careful, once you have peeled the rubber off there is a screw in the middle, undo the screw, you make break a bit of the plastic off but don't worry it can be glued back on, you can now open the control, it may be some carbons broken inside, if it is you will need a new foot control, you don't have to buy Singer you can get any replacement the best one is YDK and they are cheap enough, very easy to wire in.
Ken
drivewithken
September 2009