Condenser Fan Motor Troubleshooting

The condenser fan motor is one of the most important components in an air conditioner (AC) system. It is these fans that blow the outdoor air across the condenser coil. This movement from air transfers heat from the refrigerant to the surrounding. As a result the refrigerant is transformed from a high pressure gas to a cool liquid with low pressure. The refrigerant is now ready for another cooling cycle.

You can see these fans inside the outdoor compressor/condenser unit. If the condenser fan is functioning at its normal pace then it will have 1725 rpm typically. Standing near the condenser unit, you will be able to feel air blowing outside from the unit. Here are some common problems that occur in condenser fan and its motor.

Condenser fan is not moving at all

This is very a common problem. The first thing that you should do in such a case is to check whether the outdoor unit is connected to power and whether the power is on. If it is on, check the thermostat. See if it is in cooling mode. Next, check if the compressor is working. If all these are fine then there could be some problem with the fan motor. The fan motor is damaged and the fans have shutdown thereby.

The condenser fans bearings could also have worn down. This can be checked easily by applying some tricks. Turn off the power to the air conditioner and take a long screwdriver and try to push the blades of the fan. If they spin freely, the bearings are fine. But you will need new motor.

Now check if the contactor is "pulled in". It is a switch located in the outdoor unit. If it is pulled in but the motor does not start then the motor is completely damaged and needs replacement. If the motoris humming and you are able to start the fan by pushing it with astick then you might needto change the capacitor.

Condenser fan runs only at an abnormally low speed

This can happen due to lots of reasons. One of the simple reasons could be low voltage. Also there can be circuit failure in condenser unit control board. There could be no power to the fan. They are running just because of the local breeze. It may be caused when the motor shaft to which fan blades are secure dis worn out or have moved from place. The fan belt gets stretched, cracked, and break due to normal wear-and-tear. This can reduce the fan speed or may stop it totally. You cannot mend the belt. But it can be replaced.

You should know that blower fan of condenser unit have single speed. Do not confuse it with blower fan found in the indoor air handler unit. The latter can have two or even more run speeds. Low speed in the outdoor fan is always unusual. A slow condenser fan can be the result of a non-working capacitor. There can be other reasons for slow moving fans as well. This condition can be also caused due to burned-out compressor motor. A non-working compressor will result in abnormally slow speed fans. Sometimes the unit can trip a breaker or blow a fuse in an attempt to start operation. This will result in shorting and burning the motor. In most cases the compressor is wired with 240Volts. As a result when there is an overcurrent in the compressor, it can trip in one leg of a two-pole breaker or in one of a pair of fuses. This will allow the circuit to keep running and the fan will move as a result. Generally low fan speed is caused by a fan motor in bad shape.

Noisy fans

This can be caused due some obstructions that are not allowing the fan blades to move smoothly. This also can be caused due to a failing motor.

Buzzing and humming fan motors

Check the fan for any damages. See if it is balanced in position. Ensure that it is secured to the shaft and there is no problem with the belt. If all these are fine then there could be a problem in the fan motor. It could be damaged due to overheating. There could be internal bearing failure as well.

The blades are bent and wobbling

Turn off the power. Check if the blade assembly is well secured to the shaft. A bent condenser fan should be replaced as it will put stress on the fan motor and destroy it. Minor bends can be corrected at home but if it is beyond such repairs then it should be replaced. Sometimes fan blades are broken and come loose from the shaft. In such cases the fan moves on the shaft but shaft is unable to turn the motor. The motor is usually damaged in this case and will need a replacement. If the motor is fine, then you would need to tighten one or more Allen screws that are present in the center bushing of the blower fan. This will secure the fan tightly to the motor shaft.

Sometimes the fan runs but intermittently. It keeps shutting after frequent intervals. In such cases check for disconnected and loose wires and components in the circuit board. Sometimes the fan runs and shuts off by tripping its thermal overload switch. The cause can lie in a short in the motor winding. The motor will continue to run due to the short.