The Central Air Conditioner Fan Outside Is Not Turning & the Unit Has a Buzzing Sound

Debris

• Should debris become entangled with the fan motor or axle, the fan could fail to blow while the fan motor continues to run, which causes a humming or buzzing sound. Debris can enter the air conditioner unit through the intake grille and include such items as plastic bags, string, sticks or vines. To access the fan motor, panels of the air conditioner unit can be removed. If you see any debris within the unit, especially surrounding the fan axle or motor, it should be cleared away.

Fan Housing

• If the air conditioner condenser fan isn’t installed correctly, the fan may strike the sides of the fan housing, which can either slow the fan down or stop it from turning altogether. The fan motor will continue to run, which may cause damage and produce a buzzing noise. After panels of the unit are removed, you can spin the fan blades around a few times to see if any of them strike the housing. If they strike the housing, the fan should be uninstalled and reinstalled correctly.

Ball Bearings

• If the ball bearings in the fan axle are dry or grimy, the fan may fail to turn. While the fan is unable to function, the fan motor continues to run, causing a humming noise. If the fan doesn’t turn freely by hand with the power off, you can insert electrical motor oil into the ball bearing holes of the fan motor to lubricate them. A few spins of the fan will work the lubrication into the bearings and allow the fan to spin freely.

Thermostat

• A broken thermostat can activate the air conditioner’s internal compressor, which powers the cooling element, but fail to activate the condenser fan. A disconnection from the condenser fan or a malfunctioning thermostat could be the cause. One way to check the thermostat is to drop it to a setting lower than room temperature. If you hear a humming noise from the unit but the fan fails to turn, the compressor is activated without the fan, signaling a communication problem between the thermostat and the condenser fan.