Safety first: Turn off power before removing covers.

Tighten mounting: Check that the indoor unit is firmly attached to the wall bracket and that all screws are tight.
Inspect blower: Remove the front cover and look for debris in the blower wheel. Remove any foreign objects.
Check panel fit: Ensure the front panel clips are fully engaged and not vibrating.
If noise persists: The blower wheel may be warped or the motor bearings worn. Replace the blower wheel or fan motor as needed.

Loud rattling or buzzing noise from indoor unit during operation

Possible Causes