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Window air conditioner in a bright bedroom window, front grille off on a towel, a washed filter drying beside it

How to clean a window air conditioner

July 18, 2024•5 min read

To clean a window air conditioner, unplug it, take off the front grille, wash the filter in warm soapy water, vacuum the coil fins with a brush attachment, spray the coil with a foaming coil cleaner or mild soapy water, clear the drain channel, and let everything dry before you plug it back in. Plan on 30 to 45 minutes, plus filter drying time.

Central air is a different job. You handle the filter and the outdoor unit's surroundings, and an HVAC technician handles the rest.

What do you need?

A screwdriver, if your grille is screwed on
A vacuum with a soft brush attachment
A spray bottle of warm water with a few drops of dish soap
A foaming coil cleaner made for air conditioners (optional, but it does more than soap on a greasy coil)
A fin comb, for bent fins (cheap, sold at hardware stores)
An old toothbrush and a few microfiber cloths
Old towels for underneath

How do you clean a window air conditioner, step by step?

Unplug it. Not just off. Unplugged.
Take off the front grille. Many pop off with tabs at the bottom or sides; some have a screw or two. Lay it on a towel.
Slide out the filter. Vacuum the dust off, then wash it in the sink with warm water and a little dish soap. Rinse and stand it up to dry completely. A damp filter put back in grows mildew.
Vacuum the front coil. That's the grid of thin metal fins right behind the filter. Use the soft brush and move in the same direction as the fins, usually up and down, so you don't fold them over.
Spray the coil. Use the foaming coil cleaner as directed, or a light mist of soapy water. Let it sit for about 10 minutes. The foam and the dirt drain down into the pan underneath. Keep the spray away from the control panel and the wiring.
Straighten bent fins with the fin comb. Flattened fins block airflow just like a dirty filter does.
Check the drain channel. Look under and behind the coil for a tray or channel of standing water or slime. Wipe it out with a cloth and the toothbrush. That pink or black film is where a musty smell usually comes from.
Wash the grille in soapy water, rinse and dry it.
Wipe the cabinet and the window sill underneath. Dust and grime collect where the unit meets the sill.
Let it all dry, then put the filter and grille back and plug it in.

What about the back of the unit?

The rear coil, the one that faces outside, collects pollen, leaves and the fluff that floats around in late spring. If you can reach it safely from outside, brush and vacuum it the same way, then rinse it with a gentle spray.

If reaching it means leaning out a window or working on a ladder, don't. Take the unit out with a second person, clean it on a table or the driveway, and put it back in. Window units are heavier and more awkward than they look.

What if there's mold inside?

A little dark spotting on the grille or in the drain channel cleans off. Mold on the coil or the fan wheel behind it is a bigger problem, because the fan blows it straight into the room. If you can see dark buildup on the fan, or the musty smell comes back a day after cleaning, have it serviced or replace the unit.

Don't spray bleach into the unit. It can damage the coil and the fumes go right into the room the next time it runs.

How often should you clean it?

Filter: every two weeks while the unit runs every day. Your owner's manual may give a different schedule; follow it.
Full clean: when you put it in for the season and when you take it out.
Window sill and grille: a quick wipe whenever you dust the room.

How do you store a window unit for winter?

Clean it first, using the steps above, and let it dry for a full day. Store it upright, the way it sits in the window, so the oil in the compressor stays where it belongs. Cover it with a sheet or a breathable cover, not a sealed plastic bag. If it stays in the window all winter, an outdoor cover on the back keeps the cold air and the leaves out.

What can you do for central air?

Change or clean the filter. Check it once a month during the cooling season. When it's gray, it's done. A clogged filter makes the whole system work harder for less cool air.
Clear around the outdoor unit. Pull weeds, leaves and grass clippings away. Trim back shrubs so the unit has a couple of feet of open space on every side.
Rinse the outdoor fins gently. Turn off the power at the outdoor disconnect box first. Then use a hose on a gentle shower setting to rinse the pollen and dust out. No pressure washer.
Keep the supply and return grilles clear of furniture and rugs.

What to leave to an HVAC technician: the indoor coil, the refrigerant, the electrical parts, the blower, and a drain line that's backed up. A yearly service visit before the cooling season is the normal routine.

What does a house cleaning cover here?

On a Standard House Cleaning, RoutineCare, reachable surfaces and furniture are dusted and window sills and ledges are wiped.

Mold and mildew beyond surface cleaning stay off every one of our checklists.

See what's covered at House Cleaning. For the blinds that sit next to a window unit, see how to clean window blinds.

FAQ

How often should I clean a window air conditioner filter? Check it every two weeks while the unit runs daily and wash it whenever it looks gray. Follow your owner's manual if it gives a different schedule, and give the whole unit a full clean at the start and end of the season.

Can I use vinegar to clean my air conditioner? Diluted white vinegar is fine on the plastic grille and the filter, rinsed off afterward. On the coil, use a foaming cleaner made for air conditioner coils or a light spray of mild soapy water, and keep liquid away from the controls.

Why does my window air conditioner smell musty? Usually it's a dirty filter, standing water in the drain pan, or mold on the coil or the fan inside. Clean the filter, coil and drain channel first. If the smell stays or you can see mold on the fan wheel, have it serviced or replace the unit.

Can I hose down my outdoor central air unit? Yes, with the power off at the outdoor disconnect and the hose on a gentle shower setting. Never use a pressure washer on the fins, and leave the inside coil, refrigerant and electrical parts to an HVAC technician.