I had a similar issue with my ole Renegade. Got a replacement knob, Oxix-Ada I think, and the inner 'D' sleeve didn't hold up to the torque of revolving the fan switch. Lacking a set screw on the stock knob, I went down to the local Rat Shack and went through their knob bin 'till I found one with a set screw~99 cents and no problems since