Why is my air conditioner making a strange noise?

Match the sound to the problem

• Rattling or clicking: note whether it is at the indoor unit, an outlet, the outdoor unit or only at startup. A loose external panel or debris is possible, but a fan or other moving part can also contact its housing.
• Buzzing or humming: note whether either fan actually starts and whether cooling continues. A panel can vibrate, while a stalled fan or electrical component also requires testing; do not keep trying to start a system that only buzzes.
• Hissing or bubbling: can be normal refrigerant movement on some systems, but persistent hissing with poor cooling or oily residue needs professional assessment.
• Grinding or screeching: suggests friction around a fan or motor assembly and warrants switching the system off.

These are diagnostic clues, not a remote diagnosis. The same sound can have different causes across brands and system types.

Checks you can make safely

Turn the system off before checking anything around it. Clean only the filters and user-accessible parts described in the owner’s manual. Check that furniture is not touching the indoor unit and that leaves or loose items are not sitting against the outdoor unit. Do not remove a cover, reach through a grille, or try to tighten an internal part.

What to record

Record where and when the sound occurs: indoor unit, duct outlet or outdoor unit; at startup, continuously, only in one mode, or while a fan slows down. Note whether airflow and cooling continue, whether the outdoor unit starts, and whether a code, smell or breaker trip accompanies it. A short video can help a technician prepare, although electrical measurements and inspection are still required to confirm the cause.

If you’re in the Perth metro area, see our air-conditioning repairs and maintenance service. We diagnose split-system and ducted units and explain the repair options before work starts.