Keystone air conditioner makes loud rattling or buzzing noises during operation.

Safety: Unplug the unit before tightening or removing parts. Keep fingers away from fan blades.

Steps:

• Inspect front and rear panels: Tighten any loose screws on the front grille, side curtains, and rear cover.
• Check blower wheel: Remove the front cover and inspect the indoor blower for cracks or missing fins. Replace if damaged.
• Look for debris: On the outdoor side, remove the case and clear any leaves, plastic, or other debris from the condenser fan.
• Compressor mounts: Verify the compressor mounting bolts and rubber grommets are intact. Replace worn grommets to reduce vibration.
• Re-test: Reassemble and run the unit. If noise persists and seems internal to the compressor, professional evaluation is recommended.