If that is a TC and maybe some others it has a little tear drop shaped part on the side of the hammer by the halfcock notch, it sounds like it must be stuck or broke or packed up with crud. If it does not have a fly[ the little part we are talking about] then loof by the half cock notch for a machined out spot wit a little hole in the deepest part of the V if that whats there and there is no little part its been lost. If there is no little part and no cut out then you have to do some changeing of springs or machineing to correct the problem. Lee