Indoor unit shows F4; compressor may not start; sometimes accompanied by outdoor fan running without cooling.

Safety: This fault involves high-voltage inverter electronics. Only basic visual checks should be done by non-professionals. Always turn off power at the breaker.

Steps:

• 1. Allow cool-down: Turn off power for at least 30 minutes to allow the compressor and inverter to cool and internal overloads to reset.
• 2. Restore power and test: Turn power back on and start the unit. If F4 reappears immediately, do not keep resetting; further damage may occur.
• 3. Visual inspection: With power OFF, remove the outdoor panel and inspect the PCB for burnt components, cracked modules, or strong burnt smell.
• 4. Check wiring: Ensure compressor terminals and harnesses are firmly connected and not burnt.
• 5. Professional diagnosis: Overcurrent and inverter faults require specialized tools to measure compressor winding resistance, insulation, and inverter output. Contact an authorized Airwell technician.

Do not attempt to bypass protections or repeatedly reset the system; this can cause catastrophic compressor or PCB failure.