Indoor unit does not operate, display shows E0 shortly after power on

Safety first: Turn off the AC using the remote, then switch OFF the circuit breaker and unplug (if plug type) before opening any covers.

Steps to try:

• Power reset: Turn off power at the breaker for 5–10 minutes to discharge the control board, then restore power and test. Sometimes transient EEPROM errors clear after a full reset.
• Check indoor unit front panel: Open the front cover and verify that no moisture or insect infestation is present on the control PCB area. Dry any visible moisture with a clean, dry cloth (do not use heat guns).
• Inspect wiring harness: With power OFF, remove the indoor unit front cover and carefully check the multi-pin connectors going to the main PCB and display PCB. Reseat each connector firmly; look for bent pins, corrosion, or burnt marks.
• Check for aftermarket devices: If a third‑party Wi‑Fi module or timer is connected to the indoor PCB, disconnect it and test again. Some non‑Hitachi modules can corrupt communication.
• If E0 persists: The indoor main PCB or EEPROM is likely faulty. Replacement requires correct model‑specific board and anti‑static handling. This is typically a technician‑level repair.

Do NOT: Attempt to reprogram or solder the EEPROM yourself unless you are trained and have the correct Hitachi firmware and tools.