Hello Beryl,
The most likely cause is the suppressor in the foot control has fused, you need to open the foot control and take out the little square thing, no need to replace it, failing that when you open the foot control if you have a long ceramic tube the carbon discs inside the tube may have broken up and jammed together in which case a new foot control is needed but they are quite cheap, buy a YDK model.
drivewithken, June 2010
