Why is my aircon making a clicking noise?
A single click at startup or shutdown is normal switching. Repeated clicking during a run is not. The two faults that cause it sound almost identical from across the room: a louvre stalling on its travel path, or a relay contact chattering inside the unit. They trace to different parts.
By Team Snowflake | Reviewed 30 May 2026
1. Normal startup or shutdown click
You hear one brief click as the unit starts, switches mode, or shuts down, then nothing. A relay inside the indoor or outdoor unit closes to power the compressor or fan, and that contact closing is the click. It happens once at a predictable point in the sequence, not on a loop, and cooling carries on as normal.
How to tell
This path is one click at a predictable moment. Unlike louvre noise, it is not tied to swing movement. Unlike relay chatter, it does not repeat mid-run. The unit cools normally after the click, so the relay is switching as designed.
- Click is brief and happens once, not constantly during the run.
- Cooling and airflow stay normal throughout.
- No vibration, smell, or surging operation comes with the click.
How we confirm it
We listen through a full run cycle and time the click against normal relay and mode-switching behaviour before treating anything as a fault.
Do not let anyone replace a relay, contactor, or control board off a single startup click. That one click is the relay working as designed, not a part on its way out.
2. Louvre stall on travel path
You hear the click return through the run, often in time with the swing flap as it sweeps up and down. The swing louvres are driven by a small motor through a plastic linkage. When that linkage wears or something blocks the travel path, the motor stalls for an instant and recovers, and that stall is the click.
How to tell
This path follows the swing flap. Unlike relay chatter, it repeats at the same point in the louvre sweep. Unlike a normal startup click, it returns during movement. Stop the swing command; if the click stops too, the linkage or louvre motor is the source.
- Clicking repeats at the same point in each swing cycle.
- The flap direction or movement also looks off or jerky.
- The click starts the moment a swing command is triggered.
How we confirm it
We inspect the louvre linkage, swing motor, and fan barrel. Then we hold the swing command still to confirm the click before naming any part.
If someone reaches for the relay or contactor before testing the swing command, push back. A mechanical louvre click gets misread as an electrical fault whenever that simple hold-the-swing step is skipped.
3. Relay chatter with unstable operation
You hear rapid, uneven clicking while the unit surges on and off, and cooling drops at the same time. A worn relay contact no longer closes cleanly. Instead of one decisive click it bounces open and shut before settling, or drops out mid-cycle. Because that relay carries compressor or fan power, the stutter shows up as surging operation, not just sound.
How to tell
This path is rapid and uneven. Unlike a louvre stall, holding the swing still changes nothing. Unlike a normal startup click, it keeps firing while cooling drops, fan behaviour shifts, or buzzing appears. The fault is in switching, not the flap.
- Clicking is rapid and uneven during on-off surging.
- Cooling drops or operation turns erratic at the same time.
- Buzzing or breaker trips appear alongside the click pattern.
How we confirm it
Stop running the unit. We check the relay and contactor for contact bounce and measure board output to isolate the switching fault before more damage builds.
Stop forcing restarts the moment clicking comes with erratic operation. Each restart drives a high-current spike through already-pitted contacts and pushes a switching fault toward a compressor or board failure.
Related reading
Ready to get started?
Tell us what’s going on. Symptoms, setup, photos, anything we should know. We’ll assess and come back with the right next step.