When they get dirty, they won't make a solid connection and the motors won't get power. I've taken them apart and cleaned them, but it's almost impossible to do without losing some of the little springs, fingers, or bearings that are precariously balanced into place during assembly. I've found what works best is to put some towels under the seat and spray the inside (there are holes on the switch assembly) with some aerosol brake parts cleaner, while jiggling the switches. Cleans them right up!