If the rotor does not come lose,
1) make sure water is shut off at main
2) remove electrical connections
3) remove the stator (outer part that connects to electrical
4) remove the rotor housing with rotor.
5) soak rotor and housing in a small bowl half full of CLR.
6) remove after all little bubbles stop appearing.
7) hand turn rotor a little at a time in short strokes, working up to full 360 rotations.
8) replace all parts being sure to clean all mating surfaces.
Eriksen
January 2015