I have a Casablanca ceiling fan with a variable speed switch that no longer works. I think it is the rheostat and would like to replace that with a 3-speed switch. Can this be done? It's the switch on the fan itself. There is no wall switch, the fan is wired hot. The fan has no light, just the switch chain on 1 side & the rheostat dial on the other. Switch & motor both work fine. The 3 wires from the unit to the switch box are black, blue & white. on the the rheostat there are 2 wires, black & white. The switch has 3, black, blue & red. Original hook up was black supply to black switch, blue supply to white rheostat & black rheostat to red switch. The white supply & blue switch wires were both capped off & not connected to anything.The 3 speed switches I see say 4 wire although 1 said either 3 wire or 4 wire.