Shut off the power supply to the air conditioner.
Remove the screws from the access panel for the evaporator coils with a screwdriver.
Attach a soft brush attachment to your vacuum hose.
Vacuum the coils of evaporator to remove any dust and debris.
Pour one part bleach diluted with 16 parts water down the vent tee connected to the evaporator unit, using a funnel. This removes any clogs.
Remove the cover from the main housing of the air conditioner, using a screwdriver.
Pull out the air filters. Replace them with the same filter type if they are dirty. This prevents dirt from collecting on the evaporator coils.