# Why Is My Aircon Making Noise? | Aircon Expert

> Rattling, buzzing, clicking, hissing or squealing: what each aircon noise means, which need immediate shutdown, and repair next steps.

URL: https://www.airconexpert.com.my/guide/aircon-making-strange-noise/
Last-Modified: 2026-10-05
Tags: aircon making noise, aircon rattling noise, loud air conditioner

Aircon Guide

# Why Is My Aircon Making a Strange Noise?

Rattling, buzzing, clicking, hissing or squealing: what each aircon noise means, which need an immediate shutdown, and repair next steps.

Updated 5 October 2026 6 min read Reviewed by our lead technician

![Technician listening closely to an outdoor aircon unit on a terrace house wall](/images/featured/technician-with-ear-near-outdoor-aircon-unit-on-te.webp)

## What’s Normal and What Isn’t

As a professional service team, we field calls every single day from Klang Valley homeowners frustrated by an aircon making noise.

A soft whoosh of air from the indoor blower or a low hum from the outdoor compressor is perfectly normal. The occasional click as the thermostat engages is also standard operation.

Our primary concern is always a completely new sound, or a familiar hum that is steadily getting louder. Ignoring these changes often turns a simple, cheap fix into a massive replacement bill.

Here are the normal sounds you do not need to worry about:

-   A quiet hum from the outdoor box.
-   A soft blowing sound from the indoor unit.
-   A single click when the room reaches the target temperature.
-   A faint hiss right after turning the power off.

Our 

aircon repair

[/aircon-repair/ →](/aircon-repair/)

 technicians read new, unfamiliar sounds like a diagnostic code. Let us look at the data, what it is actually telling us, and explore a few practical ways to respond.

## Noise Guide: What Each Sound Means

| Noise | Where | Likely cause | Urgency |
| --- | --- | --- | --- |
| Rattling | Indoor or outdoor | Loose panel, screw or debris, worn mounts | Book soon |
| Buzzing | Outdoor, sometimes indoor | Failing capacitor, contactor or loose wiring | Switch off, book now |
| Repeated clicking | Outdoor | Contactor or start-up electrical fault | Switch off, book now |
| Hissing or bubbling | Piping, indoor unit | Refrigerant leak, or normal pressure equalising | Book soon |
| Squealing or screeching | Indoor or outdoor fan | Worn fan motor bearings | Book soon |
| Thumping or wobbling | Indoor | Unbalanced blower wheel from buildup | Book soon |
| Loud bang or grinding | Outdoor | Compressor or fan damage | Switch off, book now |

## Rattling

An aircon rattling noise is the most common complaint, and it usually signals the least serious type of problem. The sound typically comes from something physically loose vibrating against another part, like a front panel that is not clipped in properly. We often find that a single loose screw on the casing causes a huge racket, or a dried leaf is simply caught inside the outdoor fan grille.

On older split units, the rubber isolation mounts sitting under the outdoor compressor eventually degrade in the hot Malaysian sun. Our technicians replace these perished rubber mounts daily because they allow the heavy metal box to vibrate violently against its wall bracket.

![Loose outdoor fan blade and worn rubber mounts](/images/content/loose-outdoor-aircon-fan-blade-and-worn-cracked-ru.webp)

Check that your indoor plastic panel is firmly snapped shut, and look for any visible debris outside. We recommend booking a professional check if the rattling continues after these quick visual inspections.

## Buzzing

A loud electrical buzz coming from the outdoor unit is a serious warning sign. A failing run capacitor will buzz loudly as the compressor tries, and fails, to draw enough power to start. A worn-out contactor relay can also produce a harsh, chattering vibration.

We frequently discover a very specific local problem causing this issue. House geckos, or cicaks, love to crawl into the warm outdoor circuit boards and short out the electrical contactor. Loose high-voltage wiring will also create a continuous, aggressive humming sound.

Our strict advice is to switch off the power at the wall switch immediately. Electrical faults force components to overheat rapidly and can cause electrical burning. A trained technician must inspect the system to:

-   Test the dual run capacitor with a multimeter.
-   Inspect the contactor for burnt insects or melted wires.
-   Check the compressor current draw.

## Clicking

A single, quiet click when the unit starts or stops is just the internal relay doing its normal job. Rapid, repeated clicking from the outdoor unit usually points directly to a failing electrical component. This means the system is desperately trying to pull power but failing to engage the compressor.

We see this issue constantly, and it is closely related to the fan-only fault covered in our guide on an 

outdoor unit that isn’t running

[/guide/aircon-outdoor-unit-not-running/ →](/guide/aircon-outdoor-unit-not-running/)

. The control board, or PCB, might be sending erratic signals to the contactor switch. A weak capacitor can also cause this repetitive clicking loop.

Our team advises shutting the system down completely at the breaker to protect the motor. Book a full diagnostic inspection so a professional can trace the exact electrical fault.

## Hissing or Bubbling

Hearing a brief, quiet hiss right when the aircon switches off is entirely normal. This is just the highly pressurized refrigerant gas equalizing inside the copper pipes. A continuous hiss or a wet bubbling sound means something is wrong.

We usually trace this constant noise to refrigerant escaping through a tiny leak in the system. These leaks happen most frequently at the copper flare joints connecting the indoor and outdoor piping. You will likely notice much weaker cooling power or visible white frost forming on the copper pipes outside.

Our standard procedure is to perform a proper pressure test to locate the exact leak. We strongly advise against simply topping up the R32 gas without a full inspection for a few key reasons:

-   The new gas will simply hiss out again within weeks.
-   Running a system low on refrigerant permanently damages the compressor.
-   Leaking refrigerant reduces cooling power and inflates your electricity bill.

## Squealing or Screeching

A sharp, high-pitched squeal almost always comes from metal rubbing on metal. The fan motor bearings in either the indoor blower or the outdoor exhaust fan eventually dry out. The factory lubrication evaporates over months of running in our tropical heat.

We notice this specific sound frequently on older wall-mounted models from major brands like Daikin and Panasonic. It usually starts as a faint chirp and grows into a deafening screech as the friction increases.

Our technicians can sometimes save the motor if we catch the problem early. Applying specialized electric motor oil to the bearings often stops the noise completely, but ignoring the screeching will cause the bearings to seize and force a costly motor replacement.

## Thumping or Wobbling

A rhythmic thump that rises and falls with the fan speed indicates a severe balance problem. High indoor humidity mixes with household dust to create a heavy, jelly-like mould on the indoor blower wheel. This buildup rarely happens evenly across the plastic blades.

We find that this uneven weight makes the entire cylindrical fan heavier on one side. The wheel wobbles aggressively as it spins fast, creating a loud thumping vibration against the plastic casing.

![Blower wheel with uneven buildup seen through the louvre](/images/content/indoor-aircon-blower-wheel-with-uneven-dust-buildu.webp)

Our deep 

chemical wash service

[/aircon-chemical-wash/ →](/aircon-chemical-wash/)

 easily dissolves this stubborn mould and restores the balance. A massive buildup might require a 

complete overhaul

[/aircon-overhaul/ →](/aircon-overhaul/)

, where we dismantle the entire indoor unit to scrub and manually balance the fan blades.

> **When to switch off immediately**
> 
> Buzzing, repeated clicking, grinding, a loud bang, or any noise with a burning smell. Switch off at the remote and the wall switch, and do not switch it back on to test it.

## What Happens on a Repair Visit

A professional technician will first listen to the loud air conditioner running to isolate the specific noise. They then open the casing to check all the usual mechanical and electrical suspects. A standard diagnostic check involves:

-   Inspecting fan blades and rubber mounts.
-   Testing the capacitor with a multimeter.
-   Measuring compressor current with a clamp meter.
-   Checking the copper pipes for pressure leaks.

We always provide a clear explanation of the faulty part and a final price before any wrench is turned. Basic repair labour in the Klang Valley for 2026 ranges from RM85 to RM200, depending on the complexity of the fault. Replacement parts like a new capacitor or a fresh PCB are quoted separately.

Our team responds within 24 hours to get your home cool again quickly. Recording a short video of the aircon making noise on your phone and sending it to us on WhatsApp is incredibly helpful. The audio often tells us exactly which spare parts to load into the van before we even arrive.

FAQ

## Quick Answers

Is a buzzing aircon dangerous?

It can be. Buzzing often points to an electrical fault such as a failing capacitor or contactor. Switch it off and book a check.

Why does my aircon hiss?

A short hiss when it switches off can be normal pressure equalising. A constant hiss or bubbling sound can mean a refrigerant leak.

Can a dirty blower cause noise?

Yes. Uneven dust and mould buildup throws the blower wheel out of balance, causing a wobble, hum or rhythmic thump.

Is a clicking sound normal?

A single click when the aircon starts or stops is normal. Repeated clicking without the compressor starting usually points to an electrical problem.

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## Learn more about Aircon Repair

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