Indoor unit vibrates excessively or makes knocking sounds, especially at high fan speed

Safety first: Turn off power before touching the indoor unit or fan.

Steps to try:

• Check mounting: Gently push on the indoor unit. Excessive movement suggests loose mounting screws or a bent wall bracket.
• Clean blower wheel: Remove the front cover and filters. Use a brush and vacuum to remove dust from the blower wheel blades.
• Tighten screws: Tighten accessible screws securing the indoor chassis to the wall bracket.
• Test at different speeds: After cleaning, run the unit and test vibration at low, medium, and high fan speeds.

When to call a pro: If vibration persists, the blower wheel may be warped or the refrigerant lines may be transmitting vibration and need adjustment.