Aircon Filter
The air filter is the most accessible part of your aircon — and the most commonly neglected. A blocked filter is behind a significant share of weak cooling and water leak complaints. Checking it takes under a minute.
What This Part Does
The air filter sits at the front of the indoor unit, in the path of air being drawn in from the room. Its job is to catch dust, hair, and particles before they reach the evaporator coil.
Without the filter, dust would build up directly on the coil fins. That buildup is far harder to remove than a dirty filter — it requires chemical washing and takes significantly longer.
The filter protects the coil and keeps indoor air quality reasonable. It also keeps the system's airflow resistance low, which directly affects cooling performance and energy use.
How You Would Notice
The most obvious sign is weaker than usual airflow from the unit. The fan runs but the output feels reduced. The room takes longer to reach temperature or never fully cools.
A severely blocked filter causes the coil to get too cold. Ice forms on the indoor unit or the connecting pipe. When the unit shuts down, the ice melts and water leaks from the front.
You can usually see a blocked filter without opening anything. Pull the front panel of the indoor unit up and look at the mesh screen. If it is grey or you cannot see the coil behind it, it needs cleaning.
- Weak airflow from indoor unit — fan running but output reduced
- Room takes longer than usual to reach set temperature
- Ice or water appearing from the indoor unit
It Might Not Be The Filter
If the filter is clean and airflow is still weak, the coil itself may be dirty. Fine particles that pass through the filter over time build up on the coil surface. This requires a professional clean, not a filter rinse.
A failing indoor fan motor reduces airflow regardless of filter condition. If the fan sounds normal but output is low, the motor may be losing speed.
Low refrigerant also reduces cooling without affecting airflow noticeably. If filter, coil, and fan are all clear but the room still does not cool, refrigerant pressure needs to be checked.
How We Check
We inspect filter condition as part of every service visit. A dirty filter is cleaned or replaced. If the filter is clean but cooling is still weak, we move to the coil.
We assess coil condition visually after the filter is removed. Surface contamination on the coil confirms the issue goes beyond the filter. Deep contamination needs a chemical wash, not just wiping.
We also check airflow output at the unit with the filter clean and coil clear. If airflow is still below expectation with both components in good condition, the fan motor is the next check.
For units that had a blocked filter for a long time, we inspect the drain pan and float switch. Ice melt from a frozen coil can overflow and partially block the drain.
What We Find And What Happens Next
A blocked filter is the most common finding on a weak-cooling visit. It often coexists with light coil contamination. Both resolve in the same service visit.
| Finding | Next Step |
|---|---|
| Filter blocked, coil surface clean | Clean filter, retest airflow |
| Filter blocked, coil contaminated | Clean filter and chemical wash coil |
| Filter clean, airflow still weak | Check fan motor and coil condition |
| Filter clean, cooling still poor | Refrigerant pressure check |
About The Repair
Filter cleaning is the one maintenance task most users can do themselves between professional visits. Pull the filter out, rinse it under running water, let it dry fully, and replace it. This is safe and recommended.
Do not use a wet filter — moisture drawn into the coil encourages mould growth. Make sure it is fully dry before reinserting.
If the filter is physically damaged — torn mesh, broken frame — it should be replaced rather than cleaned. A damaged filter lets particles through and defeats its purpose. Replacement filters are available for most common brands.
After Replacement
After a filter clean, airflow should return to normal and the room should reach temperature within a reasonable period. If it does not, the coil needs to be assessed next.
We run the system after every filter clean to confirm airflow has improved and no ice is forming. Ice that forms even with a clean filter means the cause is deeper — coil contamination or refrigerant.
We record filter condition at every visit. A filter that is heavily blocked at short intervals tells us the environment is dusty or the service schedule needs to be more frequent.
When We Tell You To Wait
If the filter looks light grey but airflow is normal and the room is cooling well, wait for the next scheduled service. A lightly dusty filter does not significantly restrict airflow.
If the filter is visibly dark and airflow feels reduced, clean it before the next service. This is a task most users can do without calling a technician.
If cleaning the filter does not improve airflow, contact us. The coil or fan motor needs to be looked at, and that is not a DIY task.