How to clean a window AC unit: filter, coils, fins and mold

Step by step: how to clean a window ac unit

Safety first. Unplug the air conditioner before you open or clean it, and keep water away from the control panel and wiring. Coil fins are sharp, so wear work gloves. A window unit is heavy and awkward: get a second person to lift it out, and never lean out of an upper-floor window to clean the back.

1. 1

   Unplug the unit

   Switch the AC off and pull the plug from the wall. Let it sit for a few minutes so the fan stops and any condensation drips out. Lay towels on the floor under the front of the unit.

2. 2

   Remove and wash the filter

   On most models the front grille is hinged at the bottom: grip it near the top on both sides and pull it toward you, then slide out the filter. Vacuum off loose dust, then wash it in warm water with a drop of dish soap, rinse and let it dry completely before you put it back.

3. 3

   Wipe the grille and front panel

   Wash the front grille and louvers with the same soapy water and a soft brush, or take the grille to a sink if it unclips. Dry it with a towel. Dust on the louvers blows straight into the room when the unit starts.

4. 4

   Vacuum the front (evaporator) coil

   With the filter out you will see the cold coil: rows of thin aluminum fins. Run the vacuum brush gently down the fins, in the same direction they run, to pull off the dust mat. Press lightly; the fins bend easily.

5. 5

   Spray the coil with a no-rinse cleaner

   Spray a no-rinse foaming coil cleaner evenly over the coil, following the can’s directions. The foam lifts grime and drains away with the condensation once the unit runs. Keep the spray off the control panel and wiring.

6. 6

   Straighten bent fins

   Where fins are crushed flat, slide a fin comb into the undamaged fins just above the bent spot and draw it gently down through them. Straight fins let air pass freely; large flattened patches choke airflow.

7. 7

   Deep clean the back coil and drain pan once a season

   With a helper, take the unit out of the window and set it on a table or outdoors. Remove the outer case, vacuum and spray the rear (condenser) coil, and scrub the base pan and drain channels with soapy water to clear slime. Rinse lightly, keeping water away from the motor and controls, and let it dry for a full day.

8. 8

   Reassemble and test

   Refit the case, the dry filter and the grille, reinstall the unit with a slight tilt toward the outside if your manual calls for it, and plug it in. Run it on cool for a few minutes: the airflow should feel stronger and any musty smell should fade.

Why does cleaning a window AC matter?

A clogged filter and dusty coils make the unit cool less, run longer and blow musty air. Cleaning both is the most effective maintenance a homeowner can do.

Consumer Reports notes that every room air conditioner has a filter behind the front grille that clogs with dust, which reduces airflow and efficiency. It advises taking the filter out a few times a season, vacuuming it, washing it in warm soapy water and letting it dry before reinstalling it, and replacing it if it is badly worn. Frigidaire’s instructions for its room air conditioners describe the same wash-and-dry routine, with vacuuming as an alternative, and point you to the manual for your model’s filter.

For coils, the ENERGY STAR maintenance checklist explains that dirty coils reduce a system’s ability to cool and make it run longer, raising energy costs and shortening the equipment’s life.

How do you clean mold out of a window air conditioner?

Small spots on the grille, louvers or base pan can be scrubbed off with soapy water once the unit is unplugged; mold that has spread across the blower wheel or insulation usually means professional cleaning or a new unit.

Mold grows where water sits, so the fix is cleaning plus moisture control. The EPA’s guide to mold says the key to mold control is moisture control, recommends gloves, goggles and an N-95 respirator to limit exposure while cleaning, and says that if the moldy area is less than about 10 square feet you can usually handle it yourself.

• Scrub the base pan and drain channels with warm soapy water, rinse and dry.
• Check the unit tilts slightly to the outside so condensation drains instead of pooling.
• Run the fan only for 10 to 15 minutes before switching off on humid days, to dry the coil.
• Do not run a visibly moldy unit in a bedroom; clean it or replace it first.

How often should you clean a window AC unit?

Clean the filter every two to four weeks while the unit is in use, and give the coils and inside a deeper clean once or twice a season.

Before storing it, clean and dry the unit fully so nothing grows inside over the winter. For central systems, see our guide to cleaning AC evaporator coils.

Mistakes to avoid

• Cleaning the unit while it is still plugged in.
• Putting the filter back while it is still wet.
• Blasting the coil with a garden hose or pressure washer and flattening the fins.
• Spraying cleaner or water onto the control panel and wiring.
• Running the AC without a filter, which lets dust coat the coil.
• Trying to pull a heavy unit out of an upstairs window alone.