Why is my aircon suddenly so loud?

If it changed overnight, look for something physical first — a cover left unclipped after a filter clean, a filter not pushed in, an object on top of the unit. If it got louder gradually, that is dust building up unevenly on the fan and it needs a clean.

Is a noisy aircon dangerous?

Most are not. A rattle or a drone is a nuisance, not a hazard. Take it seriously if there is a burning smell, if the breaker trips, or if there is a loud buzz outside while the fan or compressor is not starting. Switch it off at that point rather than keep running it.

Will servicing stop the noise?

It depends what you are hearing. A drone or a rumble from a dirty blower wheel usually goes quiet the same day. Grinding and screeching are worn bearings, and a service will not touch them — anyone who tells you a clean fixes a grinding motor is selling you a clean.

Why does my aircon make noise when it starts?

A thump and then a hum from the outdoor unit as the compressor kicks in is normal, as is a short hiss or gurgle in the pipes. A brief squeal on start-up that then settles is not — that is a bearing beginning to dry out, and it gets worse.

The outdoor unit is the loud one. Is that different?

Yes, and worth knowing before you book. Outdoor noise is usually a loose panel or bracket, a worn fan bearing, or an electrical buzz from a failing capacitor. Only the first is cheap, so we diagnose it rather than guess.

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 making noise — what each sound means

What you hear decides what it costs. Rattles and a low drone are usually a loose cover or a dirty blower wheel, and a general service at $50 a unit normally clears them. Grinding or screeching is a worn fan motor, which is a repair and gets quoted first. Gurgling is often nothing at all.

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

One blower wheel in three stages: fins packed solid with black grime, then mid-wash with the loosened dirt scattered across the floor, then clean with every fin clear

Why it happens

The fan inside your aircon is a long plastic drum with rows of little blades, spinning fast and close to the casing around it. It leaves the factory balanced. Dust does not land on it evenly — it cakes thicker on one side — and once one side is heavier, the drum wobbles as it turns. You hear that as a drone that rises with the fan speed.

That drum spins on bearings at each end, packed with grease. After years of running most of the night in a climate that is damp every day, the grease dries out and metal starts running on metal. That is the grinding or the squeal, and cleaning does not bring the grease back.

Everything else is the casing. An indoor unit vibrates gently the whole time it runs, and that works plastic clips loose over the years. A cover not fully snapped in, a filter sitting slightly proud, or a loose screw on the outdoor bracket will all buzz or tap.

Sounds you can safely ignore

Some of these sounds are the unit working as it should. Water trickling or gurgling behind the indoor unit is condensation running down the drain pipe, and you hear it more in humid weather. Soft ticking as the unit cools or warms up is the plastic casing expanding.

Outside, a thump then a steady hum when the compressor starts is normal, and so is a brief hiss from the pipes in the first minute. The rule that works: a sound that has always been there, and is not getting louder, is almost certainly fine. A new sound, or one getting worse, is worth looking at.

What causes it, and what fixes each one

Rattling, tapping or vibrating
The cheapest kind of noise and the most common. Usually a front cover not clipped back properly after a filter clean, a filter that has not slid fully home, or something resting on top of the indoor unit. Outdoors it is often a loose bracket bolt or a panel screw.
The fix: Often free — reseat the cover and the filter, clear the top of the unit. If it is the outdoor bracket or a panel, we tighten it on any visit.
Droning, rumbling or a whooshing that has got louder
A deeper, constant noise that changes pitch with fan speed. This is the blower wheel carrying an uneven load of dust and wobbling as it spins. It creeps up over months, and usually comes with weaker airflow and a musty smell.
The fix: A general service. The blower wheel is cleaned where the model allows, along with the filters and cover. If the grime has set hard in the blades, a chemical overhaul strips the unit down and flushes it. Aircon general servicing in Singapore
Grinding, screeching or a metallic squeal
This one is not a cleaning problem. It is dry or worn bearings in the indoor fan motor, or the same in the outdoor fan. It often starts as a squeal for the first minute and settles, then over a few weeks becomes constant. A motor left running like that eventually seizes.
The fix: A repair. We come out, confirm it is the motor rather than something touching the fan, and quote parts and labour as one number before we start. Aircon repair in Singapore
Buzzing or repeated clicking
A buzz at the outdoor unit, especially with the fan or compressor struggling to start, is usually electrical — a failing capacitor or a contactor. Repeated clicking indoors with nothing happening is often the swing flap motor or the control board. Neither is something to poke at with the power on.
The fix: A diagnostic visit. A capacitor is a cheap part and a quick job; a control board on an older unit sometimes is not worth it, and we will say so. Aircon repair in Singapore
Gurgling, bubbling or dripping
Water in the drain line, and by itself it is normal. It only matters when the gurgling comes with water marks on the wall, damp on the front cover, or actual dripping — that means the drain is silting up and backing water into the tray.
The fix: A drain vacuum, which is part of a general service. If it is already leaking, treat it as a repair rather than waiting for the next clean. Aircon general servicing in Singapore

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

What you can check yourself

Press the front cover shut and check the filter: Push gently along both bottom corners of the cover until it clicks, and check the filters are pushed fully in behind it. A cover left slightly open buzzes against the bracket. No tools, nothing to open.
Clear the top of the unit: Anything resting on the indoor unit — a picture frame, a bag hooked on the corner, a curtain rail touching it — will pick up the vibration and tap. Same outside: a pot, a pole or a plank leaning on the outdoor box.
Change the fan speed and listen: Run it on low, then on high. A noise that rises and falls with the fan is coming from the fan or the casing. A noise that stays the same whatever the speed is more likely the compressor or something electrical.
Work out which unit it is coming from: Listen in the room, then from a safe spot near the outdoor box. Indoor or outdoor changes the job and the price, and it is the first thing we will ask. Do not open any casing and do not put your hands near a fan.

When to call someone

Grinding, screeching or a metallic scraping that has lasted more than a day
A burning or hot electrical smell along with the noise
The breaker trips when the unit runs
A loud buzz outside with the fan or compressor not starting properly
Banging or clattering that started suddenly rather than creeping up
The noise is still there after a service, or came back within days

What it costs

Most noisy units end up as a cleaning job, which 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 one visit. No GST, and 90 days of workmanship warranty. If the blower wheel is too caked to clean on the wall, a chemical overhaul is $130 for the first unit and $88 after.

A fan motor, a bearing or a capacitor is a repair, not a clean, and no amount of washing will quiet it. We diagnose it on site and give you one number covering parts and labour before any work starts. If a unit is old enough that the repair is not worth the money, we will say so instead of taking it.

If you do not know which of these you have, the call-out to find out is $50, or $120 for VRV and VRF systems, and it is free if we go on to do the work.

See the full price list