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Fujitsu Minisplit Error Codes

All Fujitsu minisplit error codes with step-by-step troubleshooting, multimeter specs, and OEM part numbers.

4 error codes

CodeMeaning
A1A1 on a Fujitsu Halcyon mini-split means the indoor PCB has detected an internal fault it can't recover from on its own. That board controls everything: fan speed, temperature sensing, and the communication link to the outdoor unit. When it goes down, nothing works.
highadvanced
HUBFujitsu Halcyon units run constant self-checks on every sensor, motor, and communication line. When something reads outside of normal range, the control board trips a fault and stores it as a blink code or letter code. The unit shuts down or limits operation to protect the compressor and refrigerant circuit from getting fried.
lowbeginner
NOT-COOLINGThe system is running but failing to transfer heat from the indoor air to the refrigerant loop, resulting in supply air at or near room temperature. This can be caused by restricted airflow, an undercharged or overcharged refrigerant circuit, a failed compressor, a malfunctioning expansion valve, or sensor inputs that prevent the control board from engaging the compressor at full capacity.
moderateintermediate
NOT-HEATINGThe heat pump can't produce warm air. The reversing valve should be directing hot refrigerant to the indoor coil, but something's blocking that process, whether it's a sensor reporting the wrong temperature, a mode setting issue, or an actual mechanical failure in the refrigerant circuit.
moderateintermediate