Why Is My Aircon So Noisy?
Is your aircon keeping you up at night with a rattle you can’t place?
Every aircon noise has a cause. A rattling cover, a buzzing outdoor unit, clicking at start-up, a grinding fan or loud vibration on the aircon ledge each point to a different fault.
Brian started Cool Earth Aircon in 2007 as a one-man workshop, and our Serangoon team still diagnoses noisy aircon repair jobs the same way. The technician listens first, then checks the indoor and outdoor units. You get the cause and a quote before we fix anything.
Repairs start from S$60, with any parts quoted upfront, and carry our 90-day workmanship warranty.
Some noises are urgent. Switch the unit off at once and keep it off until we check it if you hear or smell any of these:
- Grinding or scraping
- Loud banging
- A burning smell
Noise to Cause: What You Hear and What It Usually Means
Here’s a quick cheat sheet. Match the sound to the table, and you’ll often know what we’re likely to find before we arrive.
| Noise | Where | Usual cause |
|---|---|---|
| Rattling | Indoor unit | Loose front cover, panel or louvre clip |
| Rattling or vibration | Outdoor unit | Loose mounting bracket, worn vibration pads |
| Buzzing or humming | Outdoor unit | Weak capacitor, contactor or wiring fault |
| Clicking at start-up | Indoor or outdoor | Relay or electrical fault |
| Grinding or scraping | Either | Worn fan motor bearing, blower wheel rubbing |
| Whooshing or wobble hum | Indoor unit | Dirty, unbalanced blower wheel |
| Rising hum after start-up | Outdoor unit | Normal inverter ramp-up, unless it rattles |
Take a short video with sound before you WhatsApp us. It helps the technician come prepared with the right parts.
Common Problems We Solve
Most of the calls we get from Serangoon Central and Serangoon North flats fall into five groups. Two to four wall-mounted units means a few more places for a noise to start, so it helps to know which one is yours.
A rattling indoor unit at night
Night is when you notice it most. Often the front cover or a louvre clip has loosened after cleaning. It’s a small fix, done in minutes.
An outdoor unit shaking on the ledge
HDB aircon ledges are concrete, so a loose unit shakes loudly against them. We tighten the bracket and fit new vibration pads so the condenser fan runs quietly.
Rubber pads harden with age, and hardened pads stop absorbing vibration. Other Singapore aircon firms, such as Uncle 7 Aircon, list this as a common cause of heavy outdoor humming on HDB ledges.
Grinding from the fan
A worn bearing in the fan motor grinds before it fails. Replacing the motor early stops a breakdown on a hot night. We quote the part before we replace it.
A hum from a dirty blower wheel
When mould and dust build up unevenly on the blower wheel, it spins off balance and hums. Cleaning it in a chemical overhaul brings it back into balance.
A buzzing compressor
Buzzing from the outdoor unit when the compressor tries to start can mean a weak capacitor. Snowflake Aircon describes a classic pattern: a buzz, then a click, then silence.
Left alone, it can stop the unit from starting. Please don’t open the outdoor casing yourself, as the capacitor holds a charge. See aircon repair for other electrical faults.
Noise Normal vs Noise Not Normal
Some sounds are part of normal running. Here’s what we’d happily leave alone:
- A soft click as plastic warms up
- A gentle hum from the fan
- The rise in sound as an inverter speeds up after start-up
- A single click when the unit starts or stops
For a rough guide, Xool Aircon Experts puts a healthy outdoor unit at about 45 to 55 dB, similar to a moderate conversation. Continuous clicking is different. A 2026 guide from Aircons.sg says it points to an electrical fault rather than normal relay action.
New noises, louder noises and noises that change pitch are the ones to get checked early, while they are still cheap to fix. Send us a short video on WhatsApp, and we’ll tell you what we think it is and book a technician for your Serangoon flat.