It’s 2pm, the room is warm, and the aircon is humming along like nothing is wrong. Annoying. The first thing many people hear is “top up gas lah”. Sometimes that’s right. Often it isn’t.
Here are the seven causes I see most, roughly from most to least common.
1. Dirty filters
The easiest one. If the filters are clogged with dust, air can’t get through, and the room never cools properly. Pop the front cover open and look. If they’re grey and fuzzy, rinse them with water, let them dry, and put them back. Free fix.
2. A dirty coil or blower
Behind the filters is the coil, and below it the blower (the long round fan). When these get coated in grime, the aircon blows weakly and the air feels lukewarm. A filter rinse won’t reach this; it needs a proper servicing.
3. The remote is on the wrong mode
Don’t laugh, it happens to all of us. Check it’s on cool, not fan or dry, and the temperature isn’t set to 28.
4. The outdoor unit is choked
The compressor outside needs to breathe. If it’s packed in with plants, boxes or dust, it struggles to push the heat out. Clear the space around it.
5. Low gas (refrigerant)
Gas doesn’t get “used up” like petrol. If it’s low, there’s usually a small leak somewhere. Signs include ice on the copper pipes and air that never gets cold even after a clean. This is where a gas pressure check matters.
6. A tired capacitor or fan motor
If the outdoor unit hums but doesn’t start properly, or the fan spins slowly, a part may be failing. That’s a repair job, and topping up gas won’t fix it.
7. The unit is too small for the room
If it has never cooled well since day one, the unit may simply be undersized for the room. Worth knowing before you spend on fixes.
What we do on a visit
We check airflow and gas pressure, clean what’s dirty, and explain what we found in normal words. If gas is genuinely low, a top-up during a servicing is $38. If it isn’t, we tell you that too.
Dirty coils and filters are common reasons, so aircon servicing is a sensible first step.
Aircon still warm? WhatsApp us “my aircon is not cold” and we’ll help you work out the cause. More on gas on our gas top-up page.