Aircon Not Cold
Your aircon is running but the room stays warm. Three different faults look identical from where you sit — the fix depends on which one it actually is.
Why this happens
A quick summary of the most likely causes and what to look out for.
| Possible cause | What happens | Severity |
|---|---|---|
| Blocked Airflow | Blocked airflow can weaken cooling even when the unit is still running. | Simple fix |
| Refrigerant Leak | Refrigerant leak can make cooling fade gradually over weeks. | Needs assessment |
| Compressor or Start Fault | Compressor or start faults can leave you with wind but little real cooling. | Needs assessment |
1. Blocked Airflow
Your filter or evaporator coil is likely clogged. Cold air cannot reach the room properly even though the unit is running and the compressor is working. This is the most common cause of weak cooling and the cheapest to fix.
Signs to look for
- Airflow feels weaker than it used to.
- Cooling is uneven across the room.
- Getting gradually worse over weeks, not sudden.
How to tell this is the cause
What separates this from a refrigerant leak is that airflow feels noticeably weaker than before, not just less cold.
What the repair involves
A standard servicing or chemical wash clears the blockage and restores full airflow. Results are immediate once the obstruction is removed.
If someone recommends a gas top-up before checking airflow, push back. Both faults feel identical from the room. An airflow check costs nothing and should always come first.
2. Refrigerant Leak
Refrigerant is escaping through a leak in the copper piping or a connection joint. The unit still blows air at normal strength, but there is not enough refrigerant left to cool it — airflow feels the same as before; the missing piece is cooling capacity, not wind.
Signs to look for
- Cooling was fine before and has been getting worse over weeks.
- Room takes noticeably longer to reach a comfortable temperature.
- Airflow still feels normal in strength.
How to tell this is the cause
What separates this from blocked airflow is that airflow strength stays normal while cooling fades gradually over days or weeks.
What the repair involves
A pressure test locates the exact leak point. The joint or pipe section is brazed or resealed, and the system is properly recharged with refrigerant afterward.
Repeated top-ups without fixing the leak cost the same each time — the refrigerant drops back to the same level within weeks. The leak must be found and sealed first.
3. Compressor or Start Fault
The compressor cannot start or hold its load long enough to cool the room. The indoor fan still blows air normally — airflow feels fine, but no real cooling happens because refrigerant is not circulating through the system.
Signs to look for
- Outdoor unit sounds wrong: too quiet, humming then stopping, or cycling.
- Cooling stopped suddenly, not gradually.
- Running the unit longer makes no difference.
How to tell this is the cause
What separates this from a refrigerant leak is that the outdoor unit sounds wrong — too quiet, humming then stopping, or cycling unstably.
What the repair involves
An electrical draw test at the outdoor unit confirms whether the compressor or a start component like the capacitor has failed. If it is a capacitor, it can be replaced on the spot. If the compressor itself has failed, a full diagnostic report is provided before any major repair decision.
Compressor replacement is a major job — a smaller start component like the capacitor is sometimes the actual trigger. Confirm the root cause before approving major work.
Other Possible Causes
West-facing rooms in the afternoon, doors left open, curtains not drawn, and nearby heat-producing appliances can all push heat into the room faster than a standard unit can remove it. In these cases the aircon is working fine. The room is simply gaining heat faster than the system can extract it.
How to tell this is the cause
- Cooling feels weak only in the afternoon and improves at night.
- Other rooms on the same system cool normally.
- Airflow is strong and nothing has changed with the unit.
If this is the case, we will tell you on-site. No repair is needed — the conversation shifts to whether the unit is sized correctly for the room's heat load.
Help Us Diagnose Faster
Just observe, no disassembly required:
What to check before calling
| Check | Look for |
|---|---|
| Airflow strength | weak / normal / strong compared to before |
| Timeline | sudden / gradually worse over days / weeks |
| Outdoor unit | steady / humming then stopping / clicking / silent |
| Time pattern | weak all day / only during certain hours |
Cases like this
Related Reading
Guides, troubleshooting, and diagnostic case studies to help you make informed decisions.
Same situation with your aircon?
Tell us the symptom and the unit type. We’ll help you figure out what’s going on.
WhatsApp us