Why is my aircon not cold but the fan is working?

The fan and the cooling are two separate things. The fan blows air whatever else is wrong, so air out of the vent tells you nothing about whether the unit is cooling. Nine times out of ten the air is passing over a coil too dirty to take heat out of it.

Does topping up gas fix an aircon that is not cold?

Only if gas is actually the problem, and it usually is not. A sealed system does not consume refrigerant, so a low system has leaked. We check for the leak before we put gas in, because topping up a leaking system buys a few weeks and then you pay again.

Will a general service make it cold again?

Often, yes — if the cause is a choked filter or a dusty coil, cleaning it brings the cooling back the same day. If it turns out to be low gas or a failed part, we will tell you on the day rather than after taking payment.

How often should I service my aircon?

Every three months for a typical Singapore home. Units running nightly in a bedroom, or in a home with pets, do better on a slightly shorter interval. A chemical overhaul is usually once a year, not every visit.

We offer same-day servicing, subject to team availability. If it is urgent — a leak, or a unit that has stopped altogether — tell us and we will try to fit you in. Otherwise we book you the next available slot, usually the following day. We are open 8am to midnight every day including public holidays.

Aircon not cold but the fan is running

If air is coming out but it is not cold, the most common cause in Singapore is a filter and coil choked with dust, not low gas. A general service is $50 for one unit and often fixes it. If the dirt has hardened on, an overhaul is $130. Gas only after a leak check.

Written by Wilson Lee, owner and lead technician at LM Brothers Aircond · 10 years in the trade · Reviewed 21 August 2026

The same aircon drainage tray and blower wheel before and after cleaning: mould and grime on the left, clean parts on the right

Why it happens

Your aircon does not make cold air. It takes heat out of the air in your room, carries it outside through a pipe, and dumps it there. The cold you feel is what is left once the heat has been removed.

That heat gets picked up by the aluminium fins behind the front cover, which are cold to the touch when the unit is working. Air has to pass right through them. When dust builds up on the filter and settles between the fins, less air gets through and the air that does get through barely touches cold metal. The fan sounds the same. The air comes out lukewarm.

The same thing happens outside. The outdoor box has to release that heat into the open air. If it is choked with dust or has no space around it, the heat has nowhere to go and cooling stops.

Not cold, or not cold enough?

There is a real difference between a unit blowing warm air and a unit losing a fight. On a hot afternoon with sun on the windows, a unit that normally holds 24 degrees may sit at 26 and run without stopping. That is not a fault. Neither is a bedroom unit failing to cool a whole living room, or a room with the door left open.

A rough test: shut the room, close the curtains, set it to 24 and give it 30 minutes. If the room comes down and stays down, the unit is fine and the room is the problem. If the air at the vent never turns properly cold no matter how long it runs, something is wrong and the rest of this page applies.

What causes it, and what fixes each one

Choked filter and dusty coil
By far the most common cause, and the first thing we check. Dust mats over the filter and settles on the fins behind it, so barely any air reaches the cold metal. Cooling fades over months rather than stopping overnight, and the airflow usually feels weaker too.
The fix: A general service. Filters and cover washed properly, blower wheel cleaned where the model allows, drain vacuumed, then we run it and check the air is cold before leaving. Aircon general servicing in Singapore
Dirt that has hardened onto the fins
On a unit that has gone a year or two without attention, the dust mixes with damp and grease and sets hard between the fins. Washing the filter will not shift it, and neither will a normal service, because you cannot reach it with the unit on the wall.
The fix: A chemical overhaul. The unit comes off the wall and apart, and every part is flushed rather than wiped. We will tell you honestly if a service would have done instead. Aircon chemical overhaul in Singapore
The outdoor unit cannot get rid of the heat
The condenser outside is often forgotten. Fins packed with dust, a fan not spinning, or the box boxed in by a service yard rack or a neighbour's junk with no clearance. The room cools a little, then stops improving.
The fix: Clearing and cleaning the outdoor coil, and moving whatever is blocking the airflow around it. If the outdoor fan is not turning, that is a repair, not a clean. Aircon general servicing in Singapore
Low refrigerant, because it leaked
Real, but less common than the number of gas top-ups sold would suggest. A sealed system does not use gas up. If it is low, it has escaped somewhere. Signs are air that is cool but never cold, cooling that faded over months, ice on the pipework, or a hissing sound.
The fix: We pressure-check and trace the leak first, then tell you what we found and what it costs to fix. Refilling without finding the leak just sells you the same job again in a few weeks. Aircon gas top-up in Singapore
The compressor is not kicking in
If the indoor fan runs but the outdoor unit never starts, or starts and cuts out after a minute, the cooling is not happening at all. Usually a failed capacitor, a fan motor, or a contactor. Sometimes the breaker trips when it tries.
The fix: A diagnostic visit. Capacitors are a cheap part and a common fix. A failed compressor on an old unit is the one case where we will tell you replacement is the better spend. Aircon repair in Singapore
It is set to fan or dry mode
Worth stating because it happens weekly. Fan mode blows air and cools nothing, and dry mode cools very gently. A remote that got reset is all it takes.
The fix: Set it to Cool and 24 degrees. Free, and no call needed.

The same aircon stripped down before and after a chemical overhaul: a grey, clogged coil and a grimy drainage tray on top, the same parts clean and bright below

What you can check yourself

Check the mode and the set temperature: The remote should say Cool, not Fan and not Dry, and the temperature should be below the room temperature. Set 24 and give it 15 minutes.
Take out the filters and rinse them: The front cover lifts up and the filters slide out — no tools, no wiring. Rinse them under the tap until the water runs clear, let them dry fully, then slide them back. If cooling improves, you just saved yourself a call.
Look at the outdoor unit: From a safe spot, check the fan is spinning and there is space around the box. Move anything leaning against it. Do not put your fingers near the fan, and do not spray water into it.
Check the isolator and the breaker: If the outdoor unit is dead, look at the switch beside it and the aircon breaker in your DB box. Only flip it if your hands and the switch are dry. If it trips again straight away, leave it off and call.

When to call someone

Ice on the pipes or on the fins inside the unit
The breaker trips whenever the aircon runs
A burning or hot electrical smell
Water dripping from the unit as well as the poor cooling
The outdoor unit humming but not starting, or cutting out after a minute
Cooling still poor after clean filters and 30 minutes in a closed room

What it costs

Most of the time this ends as a cleaning job, and that is the cheap outcome. A general service is $50 for one unit and drops to as low as $20 a unit when we do several in the same visit. No GST, and 90 days of workmanship warranty on the job. The full ladder is on our pricing page.

If the dirt has set hard, a chemical overhaul is $130 for the first unit and $88 for each one after. Nobody should be sold an overhaul for a unit that only needs a service — if a service will bring your cooling back, we will say so and charge you the lower price.

If you do not know what is wrong and want us to diagnose it, the call-out is $50, or $120 for VRV and VRF systems, and it is free if we go on to do the work. Parts and gas are quoted after we have looked, never before.

See the full price list