I have a three speed ceiling fan with light. It operates from a standard on/off wall switch. Fan speed is selected at fan. The fan and light were off and the wall switch was in the off position. All of a sudden the fan began emitting a loud buzzing sound. Tried turning the wall switch on and off repeatedly. Buzzing sound is constant whether the wall switch is in the on or off position. Blades move and light comes on when wall switch is turned on. No movement of fan or light when switch is off only the buzzing.

First turn off breaker to fan/light to see if buzzing goes away. That should confirm whether it is electrically caused.

If it goes away, remove switch and look for a bad connection there. Problem probably won't be in switch.

Remove fan/light from ceiling and look for something wrong there. Probably be something like wire nut came off a hot and is now arcing to ground.

If you don't see anything, post back and describe wires in switch and in ceiling box.