Humming fans may present multiple problems.
Ceiling fan motors use two separate windings to start and run the fan blades. The start windings have a capacitor to boost electrical power to the motor in order to start moving the blades. The capacitor can be thought of like a battery that stores electrical power to give the motor an extra push. A bad capacitor can cause the motor to hum, but not turn the blades. A few simple tests will tell you if the capacitor requires replacement, or if the entire ceiling fan motor is bad.
Instructions
Testing
1. Shut off the switch that supplies power to the ceiling fan motor. Most ceiling fans have two switches on the fan unit. Make sure the switch to the fan motor is off.
2. Turn the light on to the ceiling fan, if applicable. If the light illuminates, sufficient power is being sent to the ceiling fan. If the light does not come on, check the fuse or circuit breaker. Replace the fuse or reset the circuit breaker, and retest. If the fuse blows again or the circuit breaker trips, there is a serious electrical problem in the wiring of the fan unit. Contact a licensed electrician to correct the problem. If you do not have this problem, move on to Step 3.
3. Spin the fan blades by hand with no power being sent to the ceiling fan. If the blades do not turn freely and offer resistance, or if you hear a grinding noise, the bearings in the ceiling fan are bad. In many cases, bad bearings in the ceiling fan are extremely difficult to replace.
4. Turn on the power to the ceiling fan motor. While the motor is humming, spin the blades quickly in a clockwise direction. The motor will do one of two things: The blades will speed up and turn, or the blades will slow down because they're turning in the opposite direction of the fan's directional switch. Either of these results proves the fan capacitor needs replacing.
Capacitor Replacement
5. Shut off all to the ceiling fan circuit.
6. Remove the fan blades from the ceiling fan housing, following the manufacturer's instructions for assembly.
7. Pull the light kit from the ceiling fan housing. Disconnect the light kit's wire connections. Unscrew the fan's main housing, exposing the interior of the electrical connections and the ceiling fan's start capacitor. The capacitor may be round or square. Two wires lead from the capacitor device and connect to the fan motor. Make note of the wire colors and the connections.
8. Disconnect the wires from the capacitor. Install the new capacitor to the motor wires by twisting the two separate pairs of wires together with the wire pliers from the notes made in Step 3. Cover the bare wires with wire nuts.
9. Replace the main housing cover. Install the light kit and fan blades. Apply power to the unit. Test the light kit. Turn the ceiling fan motor on. If the ceiling fan still hums, the fan motor itself is faulty and needs replacing.
Tags: ceiling motor, circuit breaker, electrical power, power ceiling, bearings ceiling, being sent, being sent ceiling