H4 appears; unit may not cool or heat and may shut down shortly after startup.

Safety first: Unplug the unit. Inverter circuits involve high voltage and should generally be serviced by qualified technicians.

Steps to address H4:

• 1. Visual inspection only: Remove covers to access the inverter module (often a separate board near the compressor). Look for burned components or melted connectors.
• 2. Check wiring: Ensure all high-voltage connectors between the main PCB, inverter board, and compressor are fully seated and not discolored.
• 3. Do not bypass protections: Never attempt to bypass fuses or jump out safety circuits on the inverter.
• 4. Professional diagnosis: H4 typically requires specialized tools to test the inverter and compressor. Contact an authorized Insignia service provider for repair or board/compressor replacement.