Why Your Aircon Is Making Noise

Why Your Aircon Is Making Noise (Types of Sounds & What They Mean)

November 22, 2025

Air conditioners are designed to run quietly. So when your unit begins producing unusual sounds — whether it’s knocking, buzzing, hissing, or grinding — it’s usually an early warning sign that something inside is not functioning correctly.

In Singapore’s hot and humid climate, your aircon works harder than most countries, making noise issues more common in HDB, condo and landed homes.

This guide explains the most common aircon noises, what each sound means, and when you should call for professional aircon servicing or troubleshooting.

🔊 Why Does an Aircon Make Noise?

Your aircon has moving components such as fan blades, blower motors, pipes, and compressor parts. When these parts become loose, dirty, blocked, worn out, or misaligned, the system starts producing noise.

Understanding each sound can help you decide whether it requires simple servicing or urgent aircon troubleshooting.

1. Banging or Knocking Sounds

1. HDB Homes

A loud banging or knocking noise is one of the clearest signs that a mechanical component is loose.

Common causes:

• Loose or misaligned fan blades
• Blower wheel imbalance
• Fan hitting internal obstruction
• Loose compressor mount

If ignored, these parts may break and damage other components.

Recommendation: Book a troubleshooting inspection immediately.

2. Clicking Sounds When Turning the Aircon On

Soft clicking during startup is normal.

But continuous clicking indicates electrical issues.

Possible reasons:

• Faulty relay switch
• Faulty thermostat
• Loose electrical wiring
• Control board malfunction

Electrical faults should NEVER be ignored because they can cause short circuits.

Recommendation: Schedule aircon servicing.

3. Buzzing or Humming Noise

A persistent buzzing sound usually points to strain inside the system.

Likely causes:

• Fan blades hitting casing
• Loose panels vibrating
• Frozen evaporator coil
• Clogged air filter causing airflow resistance
• Faulty electrical capacitor
• Outdoor compressor struggling

If buzzing is paired with weak cooling, dirt buildup may be the cause.

Recommendation: Consider a chemical wash.

4. Whistling or Hissing Noise

A high-pitched whistling or hissing sound typically means an air pressure or gas leak issue.

Possible causes:

• Leakage in refrigerant line
• Air escaping through gaps in the ducting
• Blocked or restricted airflow
• Leaking valve or coil

Refrigerant (gas) leaks reduce cooling efficiency and can damage the compressor.

Recommendation: Stop using the unit and book aircon gas top-up + leak check

5. Grinding or Screeching Noise

This is a serious noise that indicates internal wear or metal friction.

Common causes:

• Worn-out motor bearings
• Faulty blower motor
• Lack of lubrication
• Fan motor misalignment

Grinding noises often lead to motor failure if not fixed early.

Recommendation: Urgent troubleshooting required.

6. Dripping or Water-Running Noise

Soft water sounds are normal due to condensation.

But loud dripping indicates:

• Blocked drainage pipe
• Overflowing drain pan
• Backflow caused by poor installation levels
• Dirty evaporator coil

A normal aircon servicing usually clears this problem.

⚠️ When Should You Be Concerned About Aircon Noise?

You should act quickly if:

These signs indicate internal failure that can damage the entire system if left untreated.

How to Prevent Aircon Noise Issues

Good maintenance habits can significantly reduce noise issues:

• Clean filters every 2–4 weeks
• Service your aircon every 2–3 months
• Perform chemical wash every 6–12 months
• Avoid running at 16°C for long duration
• Don’t block airflow with curtains or furniture
• Fix minor noises early before they worsen

Proper care ensures your system operates smoothly, efficiently, and quietly.