Aircon Troubleshooting · Singapore · Updated July 2026
Why Is My Aircon Not Cold?
If your aircon runs but doesn’t blow cold air, it’s almost always low refrigerant, a clogged or frozen coil, a dirty condenser, or simply the wrong setting. Here’s how to tell which — and how we fix it.
The short answer
An aircon that runs but won’t cool has usually lost its ability to move heat. Low refrigerant is the single most common cause, followed by a clogged or frozen indoor coil or a dirty outdoor condenser. Always check the basics first — that it’s set to Cool (not Fan/Dry) and the filter is clean. If it’s still warm after that, it’s a refrigerant or electrical fault that needs a technician.
Quick diagnosis by symptom
Match what you’re seeing to the likely cause and typical fix.
| What you notice | Likely cause | Typical fix |
|---|---|---|
| Air is slightly cool but weak | Low gas (leak) | Gas top-up + leak check |
| Cools then turns warm; ice on pipes | Frozen coil / low gas | Gas check + chemical wash |
| No cold air, indoor unit runs | Clogged / mouldy coil | Chemical wash |
| Weak cooling, outdoor unit hot | Dirty condenser | Condenser cleaning |
| Blows warm air, won’t cool at all | Capacitor / compressor fault | Repair (diagnosis first) |
| Runs non-stop, never reaches set temp | Undersized unit (BTU) | Right-sizing advice |
Common causes — and the fix for each
From most to least common in Singapore homes.
Low gas (refrigerant leak)
The most common cause. When the gas leaks out, the system runs but can’t carry heat away — so air feels weak or only slightly cool. Often paired with ice on the copper pipes or a hissing sound.
Gas top-upClogged filter or cooling coil
A dirty filter or mould-caked indoor coil blocks airflow, so cold air can’t get out. Common in Singapore’s humidity if the unit hasn’t been deep-cleaned in a while.
Chemical washFrozen cooling coil
Low gas or restricted airflow makes the coil ice over. Cooling works briefly then stops as the ice blocks airflow, and recovers once it melts — a tell-tale “cools then warms” cycle.
Chemical washDirty outdoor condenser
The outdoor unit pushes your room’s heat outside. When its coil clogs with dust, heat can’t escape and cooling fades — even if the indoor unit looks clean.
Condenser cleaningWrong mode or temperature setting
If the unit is set to “Fan” or “Dry” instead of “Cool”, or the temperature is set too high, it blows room-temperature air. The simplest and most-missed cause — free to fix.
Free — see the checks belowFaulty thermostat or temperature sensor
A failed temperature sensor misreads the room, so the unit stops cooling early or never ramps up. Needs testing and a part replacement.
Aircon repairFaulty capacitor or compressor
If the compressor won’t start — usually a failed capacitor, sometimes the compressor itself — the system can’t cool at all and air stays warm. This needs diagnosis with proper tools.
Aircon repairUndersized unit for the room (BTU mismatch)
A unit too small for the room (or an open, sunny, crowded space) runs non-stop but never reaches the set temperature. Common after a renovation or room change. We can advise on the right capacity.
Ask us about sizingAgeing or end-of-life unit
After ~10 years, compressors lose efficiency and older gas types may be obsolete. Repeated faults and weak cooling despite servicing can mean replacement is the better value.
Aircon repairAircon still not cold after servicing?
Frustrating — you just paid for a service and the room still isn’t cooling. It happens more often than you’d think, and it usually means one of four things:
1. The settings got changed during the service
Technicians test units in different modes, and it’s easy for an aircon to be left in “Fan” or “Dry” mode afterwards. Thirty seconds with the remote — set it to Cool, 24°C or below — rules out the most common (and free) explanation.
2. The problem was never dirt in the first place
A standard service is a clean — filters, coil surfaces, drainage. If the real cause of weak cooling is low gas (a refrigerant leak) or a failing part like a capacitor, cleaning won’t touch it. This is the most common reason a service “doesn’t work”. Ask for a gas pressure check — it takes minutes and settles the question.
3. The unit needed a deeper clean than it got
Once mould and grime cake hard onto the cooling coil, a routine wipe-down can’t clear it — the coil needs to be stripped and washed with cleaning solution. If the unit hasn’t had a deep clean in over a year and airflow still feels weak, a chemical wash is the honest next step, not another basic service.
4. Something was missed or knocked loose
It’s rare, but a filter seated crooked, a panel not clipped back, or a sensor nudged out of place can weaken cooling right after a visit. Whoever did the service should make this right — call them back first; a reputable company will return at no charge. If you’d rather have fresh eyes on it, we’ll diagnose the actual cause and quote you before any work starts.
What you can check yourself first
These are free and safe to try before booking a visit.
- 1Set the mode to “Cool” (a snowflake icon) — not “Fan” or “Dry” — and drop the temperature to 24°C or below.
- 2Replace the remote batteries; a weak remote can fail to send the cool command.
- 3Remove and rinse the washable filter — a clogged filter chokes airflow.
- 4Check the outdoor unit isn’t blocked by laundry, boxes, or debris, and that the breaker hasn’t tripped.
- 5Switch the unit off for 30 minutes — if a frozen coil thaws and cooling briefly returns, you likely have low gas or a dirty coil.
How to keep your aircon cooling properly
Most weak-cooling call-outs come down to a dirty filter, a clogged coil, or a slow gas leak left too long. A little upkeep prevents nearly all of them.
- Service the unit every 3–4 months — a clean filter and coil keep airflow strong so cooling stays full.
- Rinse or replace the washable filter monthly; a choked filter is the fastest way to lose cooling.
- Keep the outdoor unit clear of laundry, boxes, and debris so it can push heat out.
- Book a gas pressure check if cooling slowly weakens over weeks — catching a small leak early avoids compressor damage.
- Right-size the unit for the room when renovating or changing its use, so it isn’t fighting a losing battle.
The simplest safeguard is routine aircon servicing — it keeps the filter, coil, and condenser clear so the unit cools at full strength.
When to call a technician
If the air is still warm after the checks above, the problem is inside the sealed system — low refrigerant, a clogged coil, or an electrical fault — and none of those are safe or possible to fix without tools and training. The longer a unit runs low on gas, the harder the compressor works, which can turn a cheap top-up into an expensive compressor replacement.
We diagnose the exact cause on-site, tell you the price before any work begins, and can usually fix it the same day — book a same-day aircon repair anywhere in Singapore.
Other aircon problems
Aircon not cold — FAQs
Why is my aircon running but not cold?
Why is my aircon blowing warm air?
Why does my aircon cool then turn warm after a while?
Does aircon gas run out over time?
How much does it cost to fix an aircon that is not cold?
Can I fix my aircon not being cold myself?
My aircon was just serviced but still isn’t cold — why?
Why is my aircon not cold after a chemical wash?
Still not cooling? We’ll sort it today.
Same-day diagnosis across Singapore. We confirm the price with you before any work begins.