Jack Look at the switches in the "Shoe Box" on the right side of the head there are at least three switches in it that run on cam's on the end of the back gear quill you should find one of them with the arm bvroken of bent out of adjustment I fought this for a while and finaly a $6.00 micro switch fixed it . With the lig off and call for a tool /speed change that requires back gear and you should see the cam try to turn and lock in if you twist the cam with a screwdriver it should lock in Good luck Kevin