The new switch does require an additional electrical wire.
Can you wire a ceiling fan to a dimmer switch.
Connect the blue wire to the red wire.
Your power supply line the black wire should be feeding both switches and those switches power the fan black or the light blue.
Follow the manufacturer s instructions to hook up your dimmer fan switch at the switch box.
These typically require you to leave the white neutral wires in the switch box undisturbed and connect.
With a situation such as this it would be best to have a separate 3 wire cable from each ceiling fan to the switch box just in case the desired method of control will be changed.
Connect black fan wire to the black ceiling wire.
A dimmer switch for the lights will be available in several watt sizes.
To do this method the wire from your wall circuit to your light has to have 3 wires.
If you replace with a blank plate wire nut the black from supply to this black and again cap the red.
An example of this is that the motor in your fan could be damaged and rendered useless.
If it s more than just a dimmer you might keep it in a box for if you can use it later.
By all means you can connect a ceiling fan directly to a dimmer switch but you may run into problems along the way.
You can install a ceiling fan light dual dimmer switch to operate the fan speed and light intensity from the original wall switch location.