How often should I clean a window air conditioner?

Rinse the filter every two to four weeks during the cooling season — it takes two minutes and is the single biggest thing for airflow and efficiency. Do a full deep clean (coils, fins, drain pan, blower) once a year, ideally before you put it in the window each spring, and again if it starts smelling musty or cooling weakly. A unit that runs all summer in a dusty or pollen-heavy area benefits from a mid-season coil rinse too.

Why does my window AC smell musty?

That smell is mold and mildew growing on the damp evaporator coil and in the drain pan — the AC condenses water out of the air, and that moisture plus trapped dust is an ideal breeding ground. Cleaning the coils, clearing the drain, and washing or replacing the filter removes it. To prevent it coming back, run the fan-only mode for 10 to 15 minutes after cooling to dry the coil, and keep the filter clean.

Can I spray water inside a window air conditioner?

Yes, carefully, but only when it is unplugged and removed from the window. The coils and aluminum fins are designed to get wet — that is what condensation and rain do — so a gentle hose rinse or a spray bottle is fine. Avoid soaking the electrical parts: the fan motor, the control board, and the compressor terminals. Let everything dry fully before reinstalling and plugging back in. Never spray a unit that is still plugged in.

What can I use to clean AC coils?

A commercial no-rinse coil cleaner (often a foaming spray) is the easiest and is made for the job — it loosens grime and drains away with the condensate. A mild solution of dish soap and warm water in a spray bottle also works for light dirt. Avoid harsh solvents or bleach directly on aluminum fins, which can corrode them. After cleaning, straighten any bent fins with a fin comb so air flows freely.

Is it worth cleaning a window AC or should I replace it?

Cleaning is almost always worth it first — a clogged filter and dirty coils can cut cooling output dramatically, so a good clean often restores a unit that seemed to be failing. Replace it only if the compressor is failing (it runs but never cools even when clean), the unit is more than 8 to 10 years old and inefficient, or the housing is corroded. A clean, well-maintained window unit easily lasts a decade.

How to Clean a Window Air Conditioner: A DIY Guide

Written & researched by Derek Holt Home & Appliances Editor

Updated August 2026

Over-the-shoulder view of a person adjusting a wall thermostat in a warm hallway, in soft early-morning light

Affiliate Disclosure

Some links on this page are affiliate links. As an Amazon Associate, we earn from qualifying purchases — at no extra cost to you. We do not buy, test, or physically handle the products we cover; our rankings come from aggregated owner reviews, ratings and expert consensus. Commissions never change our verdicts. How we rank · full disclosure.

Cleaning a window air conditioner is a straightforward DIY job — plan on an hour or two, near-zero cost, and no special skills. Unplug it, pull it out, wash the filter, clean the coils and straighten the fins, clear the drain, and let it dry. A clean unit cools better, runs cheaper, and stops smelling musty — the mold on a damp coil is what causes that odor. The only real cautions: always unplug first, and keep water off the electrical parts. This is pure maintenance, no wiring involved.

We never buy, test or physically handle the products we rank; recommendations come from aggregated owner reviews and expert consensus, described in how we rank. More at the heating and cooling hub.

How to Clean a Window Air Conditioner Fast and Easy

Tools and materials

Coil cleaner (no-rinse foaming type) or dish soap and warm water in a spray bottle.
A fin comb to straighten bent aluminum fins, a soft brush, and a vacuum with a brush attachment.
A garden hose or spray bottle, a screwdriver, and old towels.
A helper — window units are heavy and awkward to lift out safely.
If cooling is still weak after cleaning, compare replacements in our best tower fan and portable-cooling picks.

Wide environmental view of a person adjusting a wall thermostat in a warm hallway, in soft early-morning light

Step 1: Unplug and remove the unit

Unplug the AC — never clean it while it is powered. With a helper, remove it from the window and set it on a sturdy table or the floor over towels. Take off the front grille and slide out the filter. Remove the outer housing screws so you can reach the coils inside.

Step 2: Wash the filter

Rinse the reusable filter under warm water with a little dish soap until the water runs clear, and set it aside to dry completely. A clogged filter is the number-one cause of weak cooling. If the filter is disposable or torn, replace it. Never reinstall a damp filter — it breeds mildew.

Low-angle view of a person adjusting a wall thermostat in a warm hallway, in warm late-afternoon light

Step 3: Clean the coils and fins

Vacuum loose dust off both coil faces with the brush attachment, working along the fins, not across them, so you do not bend them. Spray coil cleaner (or the soapy solution) onto the evaporator (indoor) and condenser (outdoor) coils and let it sit per the product directions. If you can move the unit outside, a gentle hose rinse flushes the loosened grime — keep water off the fan motor, control board, and compressor. Straighten any flattened fins with the fin comb.

Step 4: Clear the drain and pan

Wipe out the base pan where condensate collects, and clear the drain channel or weep hole at the back so water drains instead of pooling and breeding mold. A pipe cleaner or a shot of water flushes a clogged drain. A little diluted vinegar in the pan discourages regrowth.

Three-quarter view of a person adjusting a wall thermostat in a warm hallway, in bright midday sun

Step 5: Dry, reassemble, and reinstall

Let every part dry fully — hours, not minutes, especially the coils and filter. Reassemble the housing, slide the dry filter back in, and reinstall the unit in the window with your helper, tilting it very slightly outward so condensate drains outside. Plug in and test on cool; the air should blow noticeably colder and cleaner. Run fan-only for a while after each use going forward to dry the coil.

Common mistakes

Cleaning it plugged in. Always unplug first.
Spraying water on the motor or control board. Keep electrical parts dry.
Reinstalling a damp filter or coil. Let everything dry fully to avoid mildew.
Bending the fins. Vacuum and comb along the fins, not across.
Ignoring the drain. A clogged drain pools water and breeds the musty smell.

When to call a pro

Cleaning is fully DIY. Consider a repair tech or replacement if the unit still will not cool after a thorough clean (a failing compressor or low refrigerant — refrigerant work is licensed-only, never DIY), if it trips the breaker, or if you smell burning. Refrigerant handling and any electrical repair inside the unit are professional jobs.

How to Clean a Window Air Conditioner