Key Takeaways
A soft running-water sound and short cracks at start-up, shut-down or as the room cools are normal and need no fix.
Clicking that repeats in a rhythm while the fan runs, a scraping sound, or loud air with weak airflow usually comes from dust or a loose part.
If you hear grinding or banging, or smell burning, switch the aircon off at the breaker and call a technician.
Most noise after a clean goes away once the technician re-seats the parts.
Table of Contents
What causes a noisy aircon: normal sounds vs warning signs
How to fix a clicking aircon
Aircon fan blade noise: dust, debris or a cracked blade
Aircon compressor noise: is it normal?
Why is my aircon noisy after cleaning?
When to switch off and call a technician
Book an aircon clean on gigit
1. What causes a noisy aircon: normal sounds vs warning signs
The quickest way to narrow it down is to listen for the type of sound and whether it comes from the indoor unit or the outdoor unit. Manufacturers say several sounds are perfectly normal. Panasonic Thailand explains that a sound like running water is refrigerant circulating inside the unit, and that an occasional crack comes from the plastic casing contracting and expanding as the temperature changes.
Use this table to work out what to do next.
What you hear | Where it comes from | Normal? | What to do |
|---|---|---|---|
Soft running water while it runs | Refrigerant moving through the pipes | Normal | Nothing |
Short cracks or clicks at start-up, shut-down or as the room cools | Plastic casing contracting and expanding, the refrigerant valve, or the louvre | Normal | Nothing |
A short sound from the outdoor unit at start-up, about 2 seconds | Compressor starting | Normal | Nothing |
Loud air but weak airflow | Dirty filter or indoor unit | Not normal | Clean the filter, or book a clean |
Clicking that repeats in a rhythm, or scraping, while the fan runs | Dust, debris or a loose part around the fan | Not normal | Clean the filter; if it continues, book a clean |
Humming, vibration or repeated pops from the outdoor unit | Loose parts or pipes, or the unit's electrics | Not normal | A technician checks it (see the compressor section) |
Hissing or whistling | Refrigerant pipes | Not normal | A technician checks it |
Grinding, banging or a burning smell | Motor or compressor | Not normal | Switch off at the breaker and call a technician |
If your aircon hasn't been cleaned in a while and has started making noise, download the gigit mobile app and post an aircon cleaning task. It only takes 2 minutes, and you'll receive offers from verified 5-star professionals in your local area. The technician will clean the filter, the evaporator coil, the fan and the outdoor unit's condenser coil, which is where dust causes most noise.
2. How to fix a clicking aircon
If the click is short and only happens when the unit starts, stops or the temperature changes, there's nothing to fix. Daikin notes that a clicking sound can come from the refrigerant control valve or electrical components operating, and that it is not a malfunction.
Clicking that repeats in a rhythm the whole time the fan is running is a different story. The usual causes are a clump of dust or debris hitting the fan, a filter or front panel that hasn't clipped in fully and rattles in the airflow, or screws that have worked loose in an older unit.
The only safe fix you can do yourself is cleaning the filter.
Switch the aircon off and unplug it or turn off its breaker.
Lift the front panel, slide the filter out, rinse it under plain water and let it dry.
Slide the filter back until it clicks into its slot, then press the front panel fully closed.
Turn the aircon back on and listen again.
If it still clicks, the cause is deeper inside, usually the fan or an internal part. A technician will take those parts out, clean them and tighten them. For which cleaning jobs are safe to do yourself and which aren't, see how to clean your aircon at home.
3. Aircon fan blade noise: dust, debris or a cracked blade
Most fan blade noise comes from dust. In a wall-mounted aircon the fan is a long cylinder that spins behind the evaporator coil (the thin metal fins sitting behind the filter). Carrier Thailand explains that dust or debris such as leaves or insects caught in the fan causes a scraping sound, because the fan can no longer spin smoothly.
The fan sits too deep inside the unit to clean safely yourself. If dust is the cause, a clean fixes it: the technician will cover the unit with a drainage sheet, wash the fan and evaporator coil, then reassemble it and run a test.
If a blade is cracked or chipped, or the fan motor is wearing out, the noise stays after a clean. Carrier says worn motors and bearings (the parts that let the motor shaft spin freely) need replacing by a technician. That is a repair job, so book an aircon technician to replace the fan or motor.
4. Aircon compressor noise: is it normal?
The compressor is the motor inside the outdoor unit that pumps refrigerant round the system to make it cool. Some outdoor-unit noise is normal. Daikin Thailand says the outdoor unit makes a sound when it starts, but it is not loud and lasts only about 2 seconds (page in Thai), and Daikin Middle East and Africa describes a steady, low hum during operation as normal. A sound that is suddenly louder, sharper or different from usual is the cue to have a technician look.
If the outdoor unit's sound has changed, this table shows what each noise usually points to.
Outdoor-unit sound | Usually points to | What happens next |
|---|---|---|
Humming or buzzing louder than usual | Loose wiring, a failing capacitor (the part that helps the motor start), or debris inside the unit | A technician checks the electrics and clears any debris |
Rattling or vibrating the whole time it runs | Loose screws, panels or brackets, or refrigerant pipes shaking with the compressor | The technician tightens the parts and firms up the bracket and pipe clamps |
Loud pops that repeat several times | An outdoor unit that isn't sitting firmly, or pipes not clamped tightly to the wall | The technician adjusts the bracket, rubber pads and pipe clamps |
Heavy banging or clunking | Loose parts inside the compressor or fan assembly | Switch off at the breaker and have a technician check it |
Grinding, screeching or a burning smell | Worn motor bearings or a compressor problem | Switch off at the breaker and have a technician check it |
Repeated pops are the case Daikin Thailand covers directly: they usually come from the installation. Carrier Thailand adds that refrigerant pipes that are loose or over-tightened vibrate while the compressor runs (page in Thai). Both are adjustments a technician can make in one visit.
If dust or leaves are blocking the condenser coil (the heat-release fins at the back of the outdoor unit), the unit works harder and can get louder. A standard aircon clean already includes washing the condenser coil.
Don't open the outdoor unit yourself: there is live electricity and high-pressure refrigerant inside. An aircon technician will find the cause, tighten anything loose, and if the motor or compressor needs work, explain the repair options.
5. Why is my aircon noisy after cleaning?
A sound that is new after a clean usually means a part needs re-seating. Cleaning involves taking off the front panel and filter, and sometimes the drain pan or the fan. Once everything goes back, one piece may not be sitting quite right in its slot.
The usual spots after a clean:
The filter or front panel hasn't clipped in fully, so it vibrates in the airflow. Press the filter and panel back into place and the noise often stops.
The fan has shifted slightly on its shaft and is brushing the casing. The technician will reposition the fan and tighten it.
The outdoor unit or its pipes moved during washing. The technician will set the bracket and pipe clamps firm again.
Carrier advises that if a noise continues after cleaning or reassembly, a technician should take a look. Let the technician who did the clean know, and they will adjust the parts back into place.
6. When to switch off and call a technician
Switch the aircon off at the breaker straight away if you hear grinding or banging, or smell burning. Daikin advises stopping the unit and unplugging it or turning off the breaker when the indoor unit makes an abnormal noise, then calling for service. Running it longer can damage the motor or compressor further.
Apart from cleaning the filter, leave the rest to a technician: clicking that doesn't stop after a filter clean, scraping, hissing, and any noise from the outdoor unit.
Dust is behind many of the noises in the table above. Cleaning your aircon every 6 months keeps the fan and coils clean; see how often you should clean your aircon for more.
7. Book an aircon clean on gigit
An aircon cleaning technician will find what's causing the noise and fix it at the source: cleaning the fan and coils, re-seating loose parts and firming up the outdoor unit. Post an aircon cleaning task on gigit, set your budget (or leave it open to offers), and choose from the offers local gigit heroes send. Payment goes through gigit's Safe Payment System, backed by Kasikorn Bank.