The condenser unit fan is a blower that moves outdoor air across the condensing coil found in the outdoor compressor/condenser unit. The movement of outdoor air across the condensing coil transfers heat to outdoor air and allows high pressure/high temperature refrigerant inside the condensing coil to condense from a gas back to a liquid refrigerant.
The condenser fan is visible inside of the outdoor compressor/condenser unit such as the unit shown in our sketch at left, an in our other photos on this page. Our central A.C. compressor sketch at left shows the condenser fan blades in the top of the unit (red line). The green line marks a common location for the fan control circuitry, and the blue line marks the fan motor.
Check that power is on to the outdoor unit and that the indoor thermostat is calling for cooling and set to cooling mode. If the compressor/condenser unit has power and the compressor motor appears to be able to start and run normally but the outdoor compressor/condenser fan itself won't turn on, the fan motor may be overheated or damaged
A condenser fan that won't start when power is turned on, but whose blades will spin easily when power is off may have a worn fan motor shaft bearing. You may detect this by noticing that you can wobble the fan motor shaft (when power is OFF) or you may notice that you can pull the shaft in and out of the motor (loose end-play).
If the condenser unit fan won't start at all, check for power to the unit and to the fan motor and that all of the controls are calling for cooling (or heat pump operation); check for loose, disconnected wires; Check for a frozen fan motor (motor won't turn manually when power is off).
Possible low voltage at the equipment; possible condenser unit control board circuit failure
Also possibly there may be no power to the fan and fan blades are moving due to local breeze blowing through the unit. On occasion a "slow" outdoor fan may be due to a fan blade that is not secured to the fan motor shaft.
A slow condenser fan (or air handler unit fan) could be caused by a bad start-run capacitor.
Check for a fan blade hitting an obstruction in the unit; possible failing blower fan motor.
If the fan itself is balanced and undamaged and secured to the shaft and the fan motor buzzes or hums the motor may be damaged, overheated, have an internal bearing failure, or the motor may be hard starting.
Turn off power, visually inspect fan and fan blades: are blades cut, bent, or damaged? Is the fan blade assembly secured to the fan motor shaft? A bent condenser fan causes stress on the blower fan motor shaft and can destroy the motor. Minor bends can be corrected manually; damaged blades need to be replaced.
Turn off power and assure that the fan blade is secured to the fan motor shaft. If the fan spins on the motor shaft and the motor shaft won't turn the motor may be seized and need replacement. If the fan motor is OK one or more allen screws set into the center bushing of the blower fan itself may need to be tightened to secure the blower fan to the motor shaft.
Check for loose wires or loose components on the fan unit control circuit board.
A blower fan may run for a brief while after the compressor motor has stopped but if the outdoor fan never stops check for a problem with the control board wiring or circuit.
Could be a bad start-run capacitoror a bad control board.
