Another problem, is every time someone works on our RV. They pull the knob down and turn the fan on with the knob, then they must close by pushing the knob up and using the switch in the cabinets or something. Sometimes the covers are torqued down so tight to bite into the seal hard and motor struggles to open it. Other times, the knob is still down and switch won't do anything. Then other times motor will only open half way or not at all. have to open it all the way and let the motor cycle to open position and push knob up. Maybe not exactly spot on descriptions but they screw them up just about every time.
