Disconnect the power at the main isolator switch or unplug the unit. Wait at least 5–10 minutes to allow the capacitors to discharge fully. Restore power and check if the code persists. Check Remote Wiring
: Loose or damaged wires connecting the indoor and outdoor units can sometimes mimic a board mismatch. Ensure all terminal connections are tight and there are no breaks in the signal wire. Professional Maintenance o general ac error code 9c