Loud rattling or vibrating noise during operation.

Safety: Unplug the unit before tightening screws or touching internal parts.

Steps:

• Check installation: Ensure the unit is on a solid, level surface. For window units, verify that side panels and mounting brackets are secure.
• Tighten hardware: Remove the outer shell and tighten all accessible screws on the blower housing, fan motor brackets, and compressor mounting plate.
• Inspect blower wheel: Check that the blower wheel is firmly attached to the motor shaft and not cracked. Replace if damaged.
• Compressor mounts: Inspect the rubber compressor mounting grommets. Replace if deteriorated or missing.
• Panel damping: If thin metal panels vibrate, apply foam tape or pads at contact points to reduce noise.