To clean an air conditioner filter, switch the unit off at the isolator, lift the front panel, slide out the mesh filters, vacuum off the dust or rinse them under lukewarm water, let them dry fully in the shade and clip them back in. Leading manufacturers such as Daikin and Mitsubishi Electric recommend cleaning the main air filters about every two weeks while the unit is in regular use.

Why clean AC filters matter

The filters behind the front panel of a wall mounted air conditioner catch dust, fluff, pet hair and pollen before the air reaches the indoor coil. As they clog, less air gets through. The unit has to work harder for the same cooling, the room takes longer to reach temperature, and running costs creep up. Manufacturers also warn that dirty filters reduce cooling performance and can cause odours.

Dust that gets past a blocked or missing filter settles on the coil and fan, where it holds moisture and can grow mould. That is the musty smell people notice when they first switch the unit on in spring. Keeping the filters clean is the simplest way to avoid it.

Filter cleaning is a quick owner’s job. Everything deeper inside the unit is covered by a professional air conditioning service, which we recommend once a year.

How often to clean your air conditioner filter

Check your own unit’s manual, as intervals vary by model and filter type. As a guide, based on manufacturer instructions:

Filter type	How often	How to clean	Replace?
Main mesh air filter	About every two weeks in regular use	Vacuum, or rinse with lukewarm water. Mild neutral detergent if dirty	Only if torn or damaged
Deodorising or photocatalytic filter (for example Daikin titanium apatite)	Around every six months	Vacuum, or soak in lukewarm water for 10 to 15 minutes. Do not wring	Daikin suggests about every three years
Air cleaning filter (for example Mitsubishi Electric MSZ-LN)	Around every three months	Soak in lukewarm water (30 to 40 degrees) for about 15 minutes, then rinse	When cleaning no longer restores it
Silver-ionised purifier filter (Mitsubishi Electric option)	Around every three months	Vacuum, or soak in lukewarm water	Mitsubishi Electric recommends yearly
Dust collection or air quality filters on some models	Do not wash	Washing reduces their performance	Daikin suggests about every six months

If the unit runs every day in a dusty room, a kitchen, or a home with pets, check the filters more often.

What you need

• A step ladder or sturdy step, as the unit is usually high on the wall
• A vacuum cleaner with a soft brush attachment
• A sink or shower, lukewarm water and a little mild washing up liquid
• A soft brush or old soft toothbrush
• A clean towel and somewhere shaded and airy to dry the filters

How to clean an air conditioner filter, step by step

1. Turn it off and isolate the power. Use the remote first, then switch off at the isolator or breaker.
2. Open the front panel. On most wall mounted units you lift the front panel at both sides until it clicks and stays up. Some panels unclip completely. Your manual shows how.
3. Remove the filters. Push each mesh filter up slightly to free the tab, then pull it down and out. Note which way round it goes.
4. Vacuum off loose dust. Use a soft brush attachment on the side where the dust has collected. For a lightly dusty filter, this may be all it needs.
5. Wash if needed. Rinse under lukewarm running water from the clean side, so dust is pushed back out the way it came. For greasy filters, use a little mild detergent in lukewarm water and brush gently. Do not use hot water, bleach or solvents.
6. Remove any extra filters. Take out deodorising or purifying filters from their frames and clean or replace them as the manual says. If a filter is marked not to be washed, do not wash it.
7. Dry them fully in the shade. Shake off excess water and let them air dry. Do not put them in direct sunlight, on a radiator or use a hairdryer, which can warp the plastic frames.
8. Wipe the front panel. Use a soft cloth dampened with lukewarm water, then dry it.
9. Refit the filters. Slide each one back in the right way round until it seats under the tabs. Make sure they are completely dry first.
10. Close the panel and restore power. Switch on and check it runs normally. If your unit has a filter reminder light, reset it as the manual describes.

Mistakes to avoid

• Running the unit with the filters out while they dry. Dust goes straight onto the coil. Wait, or buy a spare set.
• Refitting damp filters. Moisture in the unit encourages mould and smells.
• Using hot water. It can distort the frames so the filters no longer seal.
• Washing filters that are meant to be replaced. Some purifying filters lose their effect when washed.
• Spraying coil cleaner into the unit. Without rinsing and drain checks, residue can block the condensate drain and cause leaks.

When a clean filter is not enough

Clean filters solve a lot of weak cooling and smell problems, but not all. Call an engineer if, after cleaning, the unit:

• Still blows warm air or struggles to cool
• Drips water from the indoor unit
• Has ice on the pipes or the outdoor unit
• Smells musty even with clean filters
• Makes new rattling, grinding or hissing noises
• Shows an error code

These can point to a blocked condensate drain, a dirty coil, a low refrigerant charge from a leak, or a fan or electrical fault. Our air conditioning repair engineers can find and fix the cause. Only an F-gas certified engineer may check for leaks or handle refrigerant, and we are Refcom F-Gas registered (REF1024550).

What an annual service adds

A professional service goes well beyond the filters. The engineer cleans the indoor coil and fan, clears and tests the condensate drain, checks the outdoor unit and its airflow, checks electrical connections, and measures how well the system is performing so small problems are caught early. A system that is looked after uses less electricity, which our page on air conditioning running costs explains. If you are choosing a company to look after your system, our guide to choosing an air conditioning installer in Hertfordshire lists what to check, including F-gas certification.

What it costs with Vantage

In normal working hours there is no call-out fee. After the first hour, time is charged in half-hour steps, and parts are quoted before we fit them. Evening, weekend and overnight visits are charged at the out-of-hours rates. Every rate, including air conditioning servicing, is published on our prices page, so you know what you will pay before we arrive.

Frequently asked questions

How often should I clean my AC filter?

Daikin and Mitsubishi Electric both recommend cleaning the main air filters about every two weeks when the unit is in regular use. In a dusty room or a home with pets, check them more often.

Can I wash air conditioner filters with water?

Yes, the main mesh filters on wall mounted units are washable. Rinse them under lukewarm water, use a little mild detergent if they are greasy, and dry them fully in the shade before refitting.

Can I run my air conditioner without the filter?

It is best not to. Without the filter, dust goes straight onto the coil and fan, where it is much harder to clean and can lead to smells, poor cooling and a blocked drain.

Should I dry AC filters in the sun?

No. Manufacturers say to dry them in the shade. Direct sun or a radiator can warp the plastic frames so the filters no longer fit or seal properly.

Do I still need a service if I clean the filters?

Yes. Filter cleaning keeps air flowing, but it does not clean the coil, clear the drain or check the refrigerant and electrics. An annual service by an F-gas engineer covers those.

Air conditioning servicing in Hertfordshire, Bedfordshire and Cambridgeshire

If your air conditioning still smells, drips or struggles after a filter clean, or it is due its yearly check, our F-gas certified engineers can help. Visit our air conditioning servicing page or call 01462 506374, answered 24 hours a day, 7 days a week.