How to clean aircon filters: a 30-minute weekend job

It's 7am on a Sunday in July. You turn on the split system, expecting that steady stream of warm air. Instead, the unit rattles, groans, and pushes a puff of dust that smells like an old vacuum cleaner bag into the living room.

By the end of this guide, you'll have removed, cleaned, and reinstalled those filters in under 30 minutes, and you'll know exactly when to stop and call a professional.

Why cleaning your aircon filters matters

A split system air conditioner moves a staggering volume of air. Every hour the unit runs, it pulls the entire volume of a standard living room through its indoor coil. The mesh filters sit right in front of that coil to catch the dust, pet hair, and lint. When they clog, the system suffocates.

Here is what happens when the filter blocks up. The fan motor works harder to pull air, drawing more amps and driving up your power bill. The coil itself gets starved of warm room air, dropping below freezing. Ice forms on the copper piping. Eventually, the compressor cuts out on a safety trip, and you wake up to a cold house.

Regular DIY air conditioner maintenance comes down to this single task. If you do nothing else to your split system, clean the filters. It works. Mostly.

Tools and prep work

You do not need much. The toolkit is basic:

• A vacuum cleaner with a brush attachment
• A microfibre cloth or old tea towel
• Your laundry sink or a bucket of lukewarm water
• A Phillips-head screwdriver (rarely needed, but have one ready)

First, turn the aircon off at the remote. Then switch off the isolation switch next to the outdoor unit, OR turn off the dedicated circuit breaker in your switchboard. Doing both is the safest play. There are live electrical components behind the plastic fascia, and you do not want the unit kicking on while your hands are inside it.

Lay a drop sheet or an old towel on the floor directly beneath the indoor unit. When you pull the filters out, fine dust will fall. It always does.

How to remove the indoor filters safely

Most modern split system indoor units follow a similar design. You press the plastic front panel at the top or sides, and it clicks open, swinging upwards on a hinge.

The filters slide out. Usually there are two of them sitting side-by-side. They have a small plastic tab at the top edge. Grip the tab and pull them gently down and towards you. They should slide out of their tracking rails with minimal force.

If resistance occurs and they refuse to slide out, check underneath for a hidden securing clip. We've seen installations where the tradie screwed a support bracket slightly too close to the filter rail, pinching it. If that's the case, gently pressing the filter away from the bracket usually frees it. Brute force will just snap the plastic frame.

Take the filters outside or to your laundry. Give them a light tap over the bin to dislodge the loose dust.

The cleaning process

Start with the vacuum. Run the brush attachment gently over both sides of the filter mesh. This removes the bulk of the pet hair and heavy lint. Do not press hard. The mesh relies on the weave to catch particles. Deforming the plastic with aggressive vacuuming compromises the seal between the filter and the unit.

Next, take them to your laundry sink. Run lukewarm water over the dusty side of the filter. The water will run grey for a minute.

Do not use hot water. The plastic frames and the mesh itself can warp. Do not use detergent, and definitely do not use a high-pressure hose. Just let the water run through them. You will know they are clean when the water runs clear.

Gently shake off the excess water and pat them down with a microfibre cloth. Now, you wait. They must be completely dry before going back in the unit. Putting damp filters back into a dark cool space is how you grow mould. Air dry them flat in the sun for 20 minutes, or stand them upright somewhere warm for an hour if it is overcast.

While they dry, use your vacuum to clean out the inside of the unit where the filters sit. Use the brush attachment to sweep away dust on the plastic casing and coil fins. Avoid touching the aluminium fins directly if you can. They are razor-sharp and bend easily. If you bend a fin, it blocks airflow just like a dirty filter does. Ask three HVAC techs and you'll get three opinions on fin combs, but honestly we don't know why the manufacturers make them so fragile.

How to service aircon at home: reinstalling

Once the filters are bone dry, slide them back into the tracking rails. Push them up until they click or sit flush against the frame.

Close the plastic front panel. Listen for it clicking securely at the top and bottom edges.

Turn the isolation switch outside back on. Turn the breaker on. Then use the remote to turn the unit on.

Set it to your usual heating or cooling mode. Stand under it for the first two minutes. The air should flow smoothly without that musty smell. The unit should run quieter since the fan no longer works overtime to pull air through a wall of fluff.

Did a place in Marrickville last June — a post-war brick semi with a massive ducted system. The owners complained the house just wouldn't warm up. They'd cleaned the indoor return air vent, but the outdoor condenser unit was choked out by a banksia rose vine growing through the fence. Took us an hour to clear the foliage and hose down the coils. The house warmed up immediately. The owners assumed the system was dying. It was just suffocating.

The 3 signs your aircon needs a professional

Cleaning the filters handles 80% of basic aircon performance issues. But there are three red flags that mean you need to stop, shut the unit off, and book a licensed HVAC technician.

1. Ice on the unit or copper pipes

If you see ice building up on the large insulated copper pipe connecting the indoor and outdoor units, or ice on the indoor coil itself, you have a serious airflow or refrigerant problem. A dirty filter causes this, but if you have just cleaned them and the ice persists, the system is likely low on gas or has a leak. Running a frozen system will destroy the compressor.

2. Burning smells

A dusty smell when you first turn the unit on is normal. A sharp, electrical burning smell is not. Turn it off immediately. A burning smell indicates the fan motor is overheating, or the circuit board is failing. Wiring in older units degrades, especially in roof spaces where summer temperatures exceed 50 degrees Celsius. Do not keep running it to see if the smell goes away. It won't.

3. Strange noises

Split systems hum. They click when the compressor kicks in, and you hear a whoosh of air. They do not rattle, grind, or squeal. A grinding noise means a bearing is failing in the fan motor. A loud, persistent vibrating noise often means the indoor unit is pulling away from the wall mount. These issues require dismantling the unit to repair correctly.

If you hit any of these three, DIY maintenance ends. You need a licensed technician with manifold gauges and electrical testing equipment.

The Wenest take

In the homes we work in across Sydney, the version of this that actually fails is the outdoor unit. Everyone remembers the indoor filters, and for good reason. But the outdoor condenser sits quietly in the corner of the yard gathering dust. Leaves pile up against the back of the unit, and cobwebs choke the intake.

If a tradie won't quote a fixed price for a basic service, they don't know what they're doing. A proper service includes checking refrigerant pressures, testing electrical terminals, and hosing down the condenser coils. If you're not comfortable maintaining your split system alongside the rest of your household to-do list, that's where we step in. Coordinating the right tradespeople at the right time is exactly what Wenest handles for Sydney homeowners. Instead of relying on Hipages for one-off jobs and hoping the tradie shows up, our members get a reliable maintenance plan.

This article is general guidance only. Any electrical or gas work in NSW must be performed by a licensed tradesperson — see NSW Fair Trading for licence verification.

When you're putting together your seasonal home maintenance checklist alongside tasks like a Sydney winter laundry routine or figuring out who to hire when moving house, getting the aircon sorted is a priority. If you'd rather not be the one chasing a reliable HVAC tech at 5pm on a Friday, that's literally why we exist. Take a look at Wenest membership and let us coordinate the maintenance for you. Or just live with it. People do.