Get your air conditioner ready for summer: filters, service and a 10-minute test

To get your air conditioner ready for summer, clean the filters, check that the indoor and outdoor units are clear, run a short test and book the annual service with a qualified technician. The first two take about 20 minutes and you can do them yourself. The service, which covers the refrigerant circuit and electrical parts, is a job for a professional. Do all of it before the first heatwave, because that is when technicians have the longest waiting lists.

Season note: this applies to whichever hemisphere you are in. If summer is a few weeks away where you live, start now; if it is already hot, do the filters today and book the service as soon as you can.

Step 1: clean the filters

Dust-clogged filters are the most common reason an air conditioner cools badly. Air struggles to get through, the unit works harder and the room takes longer to cool. In most homes the filters should be cleaned every two months while the unit is in use, and more often with pets, dust or smokers in the house.

1. Switch the unit off and unplug it or turn it off at the breaker.
2. Open the front panel and slide the filters out. The manual shows how.
3. Vacuum the dust off, then wash the filters with lukewarm water and a drop of dish soap. Do not use hot water or harsh chemicals unless the manual says so.
4. Let them dry completely in the shade before putting them back. A damp filter is a source of musty smell.

The air conditioner filters page explains the rhythm in more detail.

Step 2: look at both units

• Indoor unit. Wipe the front and the air outlet with a damp cloth. Check that the louvres move freely and that nothing blocks the airflow, such as a curtain or a shelf.
• Outdoor unit. Remove leaves, cobwebs and anything stored against it. It needs space around it to release heat. Do not use a pressure washer or bend the metal fins; if they look flattened or dirty, let the technician deal with them.
• Drain. Look at the condensate hose or tray. If water drips inside or the hose is kinked, mention it at the service.

Step 3: run a 10-minute test

Set the unit to cooling at a low temperature and let it run. Check that:

• cold air comes out within a few minutes;
• there is no strange smell, rattle or ice on the pipes;
• water drains where it should, not onto the wall;
• the remote and display work.

If something is off, write it down. It gives the technician a starting point and may save you a second visit.

Step 4: book the annual service

The yearly service is the part you should not do yourself. A qualified technician checks the refrigerant circuit, the electrical connections, the condenser and the internal cleaning. Never open the unit, handle refrigerant or touch the wiring on your own. What the service includes depends on the model and the country, so ask what is covered when you book. If you rent, check your contract: the landlord often covers the service, while filters are usually the tenant's job (more in who is responsible for what when renting).

Don't forget the ceiling fans

Ceiling fans and the air conditioner work well together: a fan makes a room feel cooler, so you can set the thermostat a little higher. Dust builds up on the blades over winter. Switch the fan off, wipe each blade with a damp cloth or an old pillowcase (it traps the dust instead of scattering it) and stand on a stable step ladder, not a chair.

Keep it up all summer

Cleaning the filters once is not enough: they need a reminder every two months while the unit runs. HouseKiper schedules the filter cleaning, the annual service and the fan cleaning for you, so the date does not slip by. You can see all of the seasonal tasks in the summer home maintenance checklist and the complete checklist.

How often should I clean my air conditioner filters?

Every two months while the unit is in use is a good general rhythm, and more often if there are pets or a lot of dust. Your manual may suggest a different interval.

Can I clean the air conditioner myself?

You can clean the filters and the outside of the units yourself. The internal parts, the refrigerant circuit and the electrical connections should only be handled by a qualified technician.

When should I book the air conditioner service?

Before the first hot weeks, ideally at the start of spring or early summer. Technicians are much easier to book before the heat arrives.

Why does my air conditioner smell musty?

Usually because of damp, dirty filters or standing water in the drain. Clean and fully dry the filters first. If the smell stays, ask a technician to clean the internal parts.