Aircon Not Cold? Here's What to Check First
Singapore heat and an aircon that won't cool is a bad combination. Before assuming the worst, run through these checks in order — the majority of "not cold" complaints have a simple cause that you can rule out in 10 minutes.
Check these first (in order)
The air filter
A clogged filter is the single most common cause of poor cooling — and the easiest to fix for free. The filter sits behind the front panel of your indoor unit. Open it, pull out the filter, and look at it.
If it's grey, packed with dust, or you can't see light through it, that's your problem. A clogged filter chokes the airflow over the evaporator coil, dramatically reducing cooling efficiency. In extreme cases it causes the coil to ice over.
The outdoor compressor unit
The outdoor unit is where the heat exchange happens. Two things commonly go wrong with it:
- Power switch tripped — there's usually an isolator switch on the wall near the outdoor unit (or in your DB box). Check it hasn't tripped. Reset and try again.
- Blocked airflow — the outdoor unit needs clear space to expel heat. If it's boxed in by plants, drying racks, or stored items, it overheats and the compressor shuts down on protection mode. Clear the area and wait 10–15 minutes for it to reset.
Temperature setting and mode
It sounds obvious, but confirm the remote is set to Cool mode (not Fan or Dry), and that the set temperature is below your room temperature. If the room is 28°C and the aircon is set to 28°C, it won't cool — it'll just run the fan.
Also check the remote's batteries. A weak battery can cause the aircon to receive incorrect settings without showing an error.
How long since the last service
If the filter is clean but cooling is still weak, the evaporator coil itself is likely fouled. Dust, mould, and grease accumulate on the coil fins over time, reducing heat exchange efficiency. This isn't something you can fix at home — the coil needs to be cleaned by a technician.
If it's been more than 3 months since your last service, or over a year since a chemical wash, a dirty coil is the likely culprit.
Signs it's a refrigerant problem (needs a technician)
If the above checks don't reveal anything, the problem may be low refrigerant. Unlike a dirty filter, this isn't a DIY fix — refrigerant handling requires a licensed technician.
Signs pointing to refrigerant:
- Ice forming on the refrigerant pipes near the indoor unit — white frost on the copper pipes is a clear sign
- Unit runs but air is barely cooler than room temperature even after 30 minutes
- Hissing or bubbling sound from the indoor unit
- Cooling declined gradually over weeks rather than dropping suddenly
- Higher electricity bills — a refrigerant-starved compressor works harder and draws more power
When to call a technician immediately
Some causes of poor cooling indicate a more serious problem that shouldn't be left running:
- Burning or electrical smell — turn off the unit at the isolator switch and call a technician. Do not run it.
- Loud grinding or rattling noise — usually a failing fan motor or loose blower wheel. Running it longer risks more damage.
- Unit keeps shutting itself off — the compressor is going into protection mode repeatedly. Usually overheating, low refrigerant, or an electrical fault.
- Ice on the coil or pipes — turn the unit off and let it thaw before calling. Running an iced unit can damage the compressor.
Ran through these checks and still not cold? Tell us what you found and we'll diagnose it over WhatsApp — usually within the hour.
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