The ceiling fan and ceiling fan light are on two separate wall switches: 14/3 Type-NM with black wire to fan switch in one gang wall box & red wire for the fan light in other gang wall box) I would like to replace the single pole switch to the ceiling fan with a Lutron variable speed switch. I would like also to change the single pole for the ceiling light to a Lutron light dimmer for CFL/LED (Lutron DVCL-153P). Although the combo switches for fan speed and fan light in single gang box are nice, I would prefer for these controls to remain in separate gang boxes otherwise it would look funny with a blank plate over one of the gang boxes!
There can be problems with changing a single speed fan to a variable speed (not using the different motor windings and a remote) I have replaced several fans that the customer put a speed control in instead of using the motor taps and a remote. Both of the fans had over heated and smoked the stator windings. The problem is trying to slow a motor that is on high speed winding but not getting the full AC waveform caused over heating in the first case the fan actually caught fire and the device was an actual motor speed control, the next time I was called on a fan with a dimmer controll the fan had smoked and opened the stator winding. Both of these fans were on the high speed (at different homes) with those experiances I would get a remote and use the windings in the fan made to run at different speeds. I have only seen this a few times and that is not a lot of failure data but would consider it the same as putting a dimmer on a switched outlet (a code violation).
Ceiling fans with lights ? Yes you CAN indeed install a variable speed switch for the fan and a dimmer for the lights, provided you have a 3 conductor with ground wire from that switch box to the fan...
Typically, it would be a 14-3 w/ ground. If you have this going to your fan, then you are good to go.