Hello Linda,
The carbons may have broken away in the foot control, it woul dbe cheaper to get another control, try YDK they are very easy to fit and the most common replacement foot control, if you don't have a local shop try Leicester or www.sewingonline.co.uk/instructions
Ken
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix sewing machines.