How to Fix an Air Conditioner That Is Not Cooling
When your air conditioner is running but not actually cooling the room, it's one of the most uncomfortable problems to deal with — especially in a Sydney summer. Before you call a technician, there are several things you can check yourself that might resolve the issue.
1. Check the Air Filter
A dirty air filter is the number one cause of reduced cooling performance. When the filter is clogged with dust and debris, airflow to the indoor unit is restricted and the system can't cool effectively. Locate your indoor unit's filter (usually behind the front panel), remove it and clean it under running water. Let it dry completely before reinstalling. If the filter hasn't been cleaned in months, this alone may fix the problem.
2. Check the Thermostat Setting
It sounds basic, but confirm your thermostat is set to COOL mode and the target temperature is lower than the current room temperature. Also check whether the fan is set to AUTO rather than just FAN — running on fan-only mode blows air without cooling it.
3. Check for Blocked Airflow
Make sure furniture, curtains or other objects aren't blocking the indoor unit's vents. The unit needs clear airflow to distribute cool air around the room. Also check that the outdoor condenser unit isn't blocked by plants, leaves or debris — the condenser needs good airflow to dump heat outside.
4. Check if the Outdoor Unit Is Running
Go outside and confirm the outdoor condenser unit is actually operating when the system is switched on. If the fan on the outdoor unit isn't spinning, there may be an electrical fault or the compressor may have tripped out due to overheating or a refrigerant issue.
5. Check for Ice on the Coils
If the indoor unit is frosting over or you notice ice on the coils or pipes, this indicates restricted airflow (from a dirty filter) or a refrigerant issue. Turn the system off and let it thaw completely before restarting. If it ices up again quickly, you likely have a refrigerant leak — this requires a licensed refrigerant technician.
6. Consider the Size of the Unit
If your air conditioner is undersized for the room, it will run constantly but struggle to reach your target temperature. As a rough guide, a 2.5kW unit suits rooms up to 20m², 3.5kW for up to 35m², 5kW for up to 50m² and 7kW+ for larger spaces.
When to Call a Technician
If cleaning the filter and clearing obstructions doesn't help, the issue is likely a refrigerant leak, a failed compressor or an electrical fault — all of which require a licensed technician.
Oceania Appliances stocks split system air conditioners from Daikin, Mitsubishi, LG, Hisense and more. Free delivery across Sydney.