What Causes Air Conditioner Filters to Be Black?

Dirty Air Filter

• Air conditioner filters are designed to block dirt, dust and other impure particles from entering the intake grille on the front of the air conditioner unit. Behind the intake grille, the filter sits as a shield to the internal fan and cooling elements. Sometimes, the filter acquires so much grime that it can look very dirty. The filter should be changed every two weeks or as per the air conditioner unit manual instructions. Some filters are reusable and washable, while other air conditioner units require a new filter for each change.

Cleaning The Filter

• A washable air conditioner filter is easy to clean. The front grille of the air conditioner can be opened by hand. Behind the grille, there is a fitted slot where the filter is situated. Grasp the filter and pull it gently from the area. Run warm water over both sides of the air filter, until all of the dirt disappears. If necessary, you can use a mild soap and warm water to clean the filter. Avoid damaging the filter during cleaning. If you damage the filter, replace it. Dab the filter with a towel, until it's completely dry. Allow the filter to dry completely before you reinstall it behind the grille. Close the grille.

Moldy Filter

• If the air filter is inserted into the air conditioner wet, it's possible mold might accumulate and grow on the filter, making it turn black. To avoid this, allow the air filter to dry completely. If you insert the air filter slightly wet, run the air conditioner "Cool" mode for an hour or two to dry out the air filter. If the air filter was dry when you inserted it and it still grows mold, run the "Dry" cycle on your air conditioner to remove moisture from the air. Condensation might gather inside the air conditioner, accumulate on the filter, and cause mold to grow. The "Dry" cycle is a dehumidifying cycle designed to leech humidity from the air inside the room.

Replacing The Filter

• If the air filter is black from mold or dirt and isn't reusable, you'll need to replace the filter. To avoid damage to the next filter, run the air conditioner's "Cool" or "Dry" cycle during humid climates, even if the weather is somewhat cool. Avoid running the air conditioner in temperatures under 60 to 65 degrees Fahrenheit, as this might cause the unit to freeze.