Unit produces a high‑pitched whine or electrical buzzing during operation.

Safety first: Disconnect power before tightening any components.

• Check panels: Tighten all cabinet screws and ensure panels are firmly secured to reduce resonance.
• Inspect contactor: With power off, ensure the contactor is firmly mounted. A buzzing contactor may indicate low voltage or coil wear.
• Isolate source: Carefully listen (with covers in place) to locate the noise source. If it comes from the inverter PCB, this is often normal but can be reduced by ensuring the unit is firmly mounted.
• Professional evaluation: If the noise is new and accompanied by performance issues or error codes, have a technician inspect the inverter and contactor.