The fans in a central air conditioning unit play vital roles in the cooling process. There are two key fans, one each in the outside condensing unit and in the inside air handler. The condensing fan helps keep the condensing coils cooled while they convert gas refrigerant to liquid – a process that causes the coils to become hot. Inside the home, a fan cycles the air from your home across evaporator coils, which converts the refrigerant to a gas and becomes cold. Then, it pushes that cooled air out your vents.

Problems with your unit's fans can cause the system to overheat or cause inefficient cooling.

There are a few potential problems with your air conditioner fans and some are an easy fix, although you should always call in an air conditioning repair technician if you feel uncomfortable performing the fix yourself.

Loud Air Conditioner: Loose Fan

Does your outdoor condenser unit sound like a small plane taking off whenever the unit is running? The loud clanking sound might be the fan coming loose and wobbling as it rotates.

Turn off power to the unit using the fuse box. Remove the grated lid of the condensing unit and set it safely to the side. Locate the fan inside the unit and check to see that the fasteners are secure. Tighten any fasteners that seem loose. Return the lid, restore power, and turn the unit back on. Listen for the loud sound. No loud clanking? You fixed the problem.

Still hear clanking? Call an air conditioner repair technician. The bearings on the motor itself might be going out, which requires a complete motor replacement.

Fan Isn't Running: Electrical Issue

If either of the fans fails to run, you likely have an electrical issue. The suspect parts can include the fan motor, relay board, or control board. Do you have electrical experience? Dig out your owner's manual for details on how to check these components in your particular unit.

Don't have electrical experience or lost your manual? Call in an HVAC technician. You don't want to perform guesswork when it comes to electricity and your heating and cooling system. A wrong move could fry your system completely and lead to extremely costly repairs or replacements.

Fan Won't Stop Running: Electrical Issue Or Thermostat

Electrical issues can also cause the fan to run continuously if there's a short somewhere that won't let the fan sensor to switch the fan off. 

Before you call the HVAC technician, first perform a very simple check that could explain why the fan is constantly running. Make sure that the thermostat inside your home is set correctly. For example, make sure the unit is turned fully on or off rather than on fan mode. You should also replace the thermostat batteries periodically to make sure that your system is receiving the proper signals from your controls inside the house.

If these solutions don't work or you simply need more help, contact a professional like those at Mike Kearsley's All Service for assistance.