How to Clean Air Conditioner Filters in a Canberra Home

Why a clean filter matters more in Canberra

Canberra is often called Australia’s allergy capital. ANU researchers who run the Canberra Pollen count put allergic rhinitis at nearly a third of the population, and the tree pollen season starts as early as August, with grass pollen peaking through late spring and into summer. Add bushfire smoke in a bad summer and dust from a dry one, and the filter in your air conditioner catches a lot more here than it would in Sydney.

The filter is the only thing between that air and the indoor coil. When it clogs, airflow drops, the fan works harder, and the coil cannot transfer heat properly. The US Department of Energy puts the energy savings from swapping a clogged filter for a clean one at 5 to 15 per cent of the unit’s consumption. On a ducted system heating a Canberra house through July, that is real money. In cooling mode, a starved coil can also ice over, which is when people ring us about water dripping from the indoor unit.

And there is the smell. A filter thick with pollen and dust holds moisture, and a musty smell when the unit starts is usually the first sign it has been left too long.

How to clean a split system filter, step by step

Step 1: Switch the unit off

Turn it off at the remote and wait for the louvres to close. If you are nervous about it, switch off the isolator next to the outdoor unit as well. Never open the panel while the fan is running.

Step 2: Lift the front panel

On most Daikin, Mitsubishi Electric and Panasonic wall units, the panel hinges up from the bottom edge and clicks into a raised position. It should not need force. If it does, check for small tabs at each end.

Step 3: Slide out the filters

There are usually two, one on each side, with a small tab or handle. Pull gently down and out. If you see a smaller secondary filter (often black or blue, labelled deodorising, catechin or PM2.5) clipped to the main mesh, take note: those are not washable. They get replaced, not rinsed.

Step 4: Vacuum, then rinse

Vacuum the dusty side with a brush attachment to lift the loose layer. Then rinse under lukewarm water from the clean side so the dirt washes out the way it came in. A drop of mild detergent and a soft brush will shift kitchen grease. No hot water, no bleach or harsh cleaners, and no scrubbing; the mesh warps and tears.

Step 5: Dry in the shade

Shake off the water and stand the filters somewhere shaded with airflow. An hour or two is usually enough. Direct sun warps the plastic frame, and a damp filter put back in the unit is how mould gets started.

Step 6: Refit and run

Slide the filters back until they click, lower the panel, and run the unit on fan for ten minutes. Wipe the louvres and the outside of the panel with a damp cloth while you are there. If the airflow is noticeably stronger than before, the filter was overdue. 

What about ducted return-air filters?

A ducted system does not have filters at every outlet. It has one filter (sometimes two) at the return-air grille, which is the large vent that pulls air back into the system, usually in a hallway ceiling or high on a wall. Unclip or unscrew the grille, slide the filter out, and clean it exactly as you would a split system filter: vacuum, rinse, dry in shade, refit.

Because one filter handles the whole house, it loads up faster than you would expect. Monthly is a sensible rhythm in a Canberra winter when the system runs every day. Some return-air filters are disposable media rather than washable mesh. If yours tears or will not come clean, a technician can supply a replacement during the annual service.

How often should you clean the filter?

Every two to four weeks when the system runs most days, which in Canberra means June to August and December to February. Weekly to fortnightly through pollen season, roughly August to January, especially if anyone in the house has hay fever or asthma. After any day of bushfire smoke. Fortnightly year-round if you have pets that shed. For a unit used only occasionally, clean it at the start of each season and every six to eight weeks while it is in use.

Signs a filter is past cleaning

• You cannot see light through the mesh after washing
• Tears, holes or a warped frame that no longer sits flat in its slot
• A musty smell that comes back within days of cleaning
• Weak airflow even with a clean filter, which points to a dirty coil rather than the filter itself
• Ice on the indoor coil or water dripping from the indoor unit in cooling mode

Replacement mesh filters are cheap and brand-specific. The model number is on a sticker under the front panel. Secondary filters (deodorising, PM2.5, carbon) are replaced every 6 to 12 months depending on the brand.

What you can do yourself, and when to call a professional

The filters, wipe the panel and louvres, clear leaves and grass from around the outdoor unit so it can breathe, and check that the condensate drain outside drips when the unit is cooling.

Clean the indoor coil (the fins behind the filter, which need a proper coil cleaner and are easy to damage), flush the condensate drain and tray, clean the barrel fan where mould collects, check electrical connections and, above all, anything to do with refrigerant. Handling refrigerant without an ARC licence is illegal in Australia, and a unit that has lost charge needs the leak found and fixed, not a top-up.

Book a professional service once a year, ideally in spring or autumn before the extreme weather. In Canberra, our service partner Climate Plus handles split and ducted servicing on (02) 6185 5151. Climate Master, ARC licence AU36036, handles new installs and replacements. Our split system air conditioner Canberra page explains when a tired unit is worth replacing rather than servicing, and our Canberra air conditioning services page covers the rest.

Frequently Asked Questions

Can I run the air conditioner without the filter while it dries?

No. Dust goes straight onto the indoor coil, which is far harder to clean than a filter and usually means a chemical coil clean later. Wait an hour or two for the filter to dry, or clean it in the evening when you are not using the unit. If you rely on the unit heavily, a spare set of filters lets you swap and go.

Why does my air conditioner still smell musty after cleaning the filter?

The smell is usually mould or bacteria on the indoor coil, in the barrel fan or in the drain tray, not on the filter. It is common in Canberra homes that run cooling all summer and then leave the unit off through autumn. A technician can do a coil clean and flush the drain. Running fan-only for 20 minutes before switching off dries the coil and slows the return.

Do split system filters need replacing or just cleaning?

The main mesh filters are washable and last for years if you dry them in the shade and do not scrub them. Small secondary filters (deodorising, catechin, PM2.5 or carbon) are not washable and are replaced every 6 to 12 months depending on the brand. Check the manual for your model; the brand and model number are on a sticker under the front panel.

Does a dirty filter really increase the power bill?

Yes. The US Department of Energy puts the savings from replacing a clogged filter with a clean one at 5 to 15 per cent of the unit’s energy use, because the fan works harder and the coil transfers heat less efficiently. On a ducted system heating a Canberra home through winter, that is a measurable slice of the bill, and the same clogged filter can ice the coil and trigger a fault.

If the filter is clean and the unit still smells, leaks or struggles, book a service with Climate Plus on (02) 6185 5151. If it is time to replace the system, Request A Quote from Climate Master on (02) 6228 1126.

About the Author

Climate Master, Heating, cooling and hot water specialists, Canberra, 30+ years

Climate Master is a Canberra heating, cooling and hot water business with more than 30 years of serving Canberra and Queanbeyan, installing and replacing gas, electric, and heat pump hot water systems.