Turn off the power for the central air conditioning unit. You can usually do this in two different places: either at the main circuit breaker or at a separate breaker switch located somewhere near the air conditioner unit.
Locate the condenser unit, which is where the air conditioner fan is located. This part of the air conditioning system is placed typically on the outside of the building where the air conditioner is installed. These units are box shaped, and will have coolant pipes and electric cables leading back into the inside of the building.
Clean any dust or dirt off the outside of the condenser unit. Remove as many leaves or other fallen material as possible. If these make their way inside the condenser coils, they can cause the unit to work harder and possibly malfunction.
Remove the housing unit from the condenser to access the fan. This can differ from model to model, depending on the unit. On some models, for example, you may be able to remove the grill from the top of the unit. On other condensers, you may need to remove the entire housing. These grills and housings are usually held in place with screws or bolts. Remove screws with a screwdriver and bolts with a wrench or socket wrench.
Loosen the fan coupling nut in the center of the fan. Some fans may have a cap that you must first pry off before you can access the housing nut.
Pull the fan off the fan shaft.
Apply a light coating of machine oil to the fan shaft. Slip a new fan into place. Secure with the fan nut.
Replace the grill or housing for the fan.
Restore power to the air conditioner.