Short answer: Turn the unit off, open the front panel, slide out the filters, vacuum or wash them in lukewarm water with mild soap, let them dry in the shade, and put them back. Wipe the outside of the indoor unit with a dry or damp cloth. Do not spray water inside it. Coil cleaning is a technician's job.
How often
Check the filters at least every few months, and more often if you run the unit a lot or have pets. The recommendations vary by maker:
- The Building America Solution Center (a Department of Energy program) says to clean ductless heat pump filters about every 3 months.
- Midea's owner's manual says every two weeks.
- Lennox says to look at the filters monthly during heavy use.
Your own manual has the right number for your model. If you have pets or dusty rooms, lean toward the shorter end.
What you need
- A vacuum with a brush attachment
- A sink, mild dish soap and lukewarm water
- A soft cloth
- A step stool, so you are not reaching or leaning
Cleaning the filters, step by step
Set aside about 20 minutes. Lay an old towel on the floor under the unit, because a little dust will fall.
These steps follow the Building America guide, the Midea manual and the Daikin user guide. Your unit may differ, so check your manual for how its panel opens.
- Turn the unit off. Use the remote or the power button. Midea's manual says to turn the unit off and disconnect power before cleaning or changing the filter.
- Open the front panel. On most wall units a hinged panel lifts up and out. Some units hold the filter on top with magnets. The manual shows which.
- Take the filters out. Press the tab and slide the filter out gently. You will feel a small click as it frees up. Midea warns not to touch the metal parts inside, because the edges are sharp.
- Vacuum first. Use the brush attachment to take off the loose dust.
- Wash if it is sticky or gray. Use lukewarm water and a mild detergent, then rinse. Daikin's guide allows washing with water or vacuuming. Midea says to use mild detergent and shake off the water.
- Do not use hot water. Daikin's guide says to soak in lukewarm water. Check your manual for a maximum temperature, because heat can warp plastic filters.
- Dry it in the shade. Midea says not to dry the filter in direct sunlight, because it can shrink. Let it dry fully before it goes back.
- Put it back. Slide it in until it sits right, close the panel, and turn the unit on. You will hear the beep and see the display light up, and the airflow should feel stronger than before.
If you have a small extra filter clipped onto the main one, Midea says to clean that one with a handheld vacuum, not water.
Wiping the indoor unit
Midea says to use only a soft, dry cloth, or a cloth soaked in warm water if it is very dirty. Do not pour or spray water into the unit. Midea warns that using water to clean the inside of the indoor unit can destroy insulation and cause an electric shock. Lennox also says not to clean the unit by spraying water directly onto it, and not to use benzene, thinner, alcohol or acetone, which can cause discoloration, damage, shock or fire.
The outdoor unit
You can keep the area around it clear. Do not wash the inside.
- Clear leaves, twigs and debris from around it by hand with the unit off
- Keep plants trimmed back (Trane says two feet, Lennox says 24 inches of open space on all sides)
- Do not spray water into the cabinet or chip ice off the coil
- Take care around the metal fins. Lennox warns the outdoor heat exchanger has sharp edges.
What not to do
- Do not take the unit apart to wash the coil or blower. Cleaning the indoor and outdoor units is part of a professional visit.
- Do not touch refrigerant lines or the electrical box.
- Do not run the unit with a wet filter.
Trane says a yearly professional visit should include cleaning the indoor and outdoor units, checking for refrigerant leaks, and checking electrical connections.
Signs the cleaning was not enough
If the unit still has weak airflow, a musty smell, or leaks after you clean the filters, read mini split leaking water, mini split not cooling or mini split filter replacement.
Routine care is part of the wider repair-or-replace decision. For service-life factors rather than a guaranteed replacement age, see how long mini splits last.
Sources
- Building America Solution Center: Clean ductless heat pump air filters
- Midea ductless split owner's manual
- Daikin user reference guide (air filters)
- Lennox mini-split user manual (cleaning cautions)
- Trane: Mini-split not cooling
- Lennox: Mini-split not working in heat mode
Follow your unit's own manual. This is general information.
