Hitachi Aircon Error Codes

Indoor safety device activated

Drain protection or float-switch trigger · Indoor fan or airflow-related protection trip · Indoor control circuit fault

Outdoor safety/high-pressure device activated

Outdoor high-pressure switch trip · Condenser airflow restriction · Outdoor protection circuit activation

Abnormal transmission between indoor and outdoor units

Interconnection wiring fault or poor contact · Communication PCB fault at indoor or outdoor unit · Power disturbance affecting serial communication

Phase signal detection abnormal

Phase pickup/synchronization circuit fault · Inverter board signal processing issue · Power supply waveform abnormality

Inverter voltage abnormal (too low/high)

Undervoltage or overvoltage at outdoor inverter · DC bus voltage instability · Inverter PCB power-stage fault

Discharge superheat control abnormal

Refrigerant flow instability · Expansion control issue · Compressor loading outside normal envelope

Compressor discharge temperature too high

Compressor thermal overload · Poor heat rejection at condenser · Sensor/control drift causing overheating protection

Indoor heat-exchanger liquid-pipe thermistor abnormal

Liquid-pipe thermistor open or short circuit · Loose sensor connector · Indoor PCB input channel fault

Indoor heat-exchanger gas-pipe thermistor abnormal

Gas-pipe thermistor open or short circuit · Sensor harness damage or poor contact · Control PCB thermistor sensing fault

Fresh-air/air-temperature thermistor abnormal

Outdoor/fresh-air thermistor failure · Sensor wiring disconnection · PCB thermistor read error

Indoor fan motor protection activated

Indoor fan motor lock or overload · Fan drive circuit issue on indoor PCB · Wiring/connector fault to fan motor

Compressor discharge thermistor abnormal

Discharge thermistor open or short · Loose thermistor connector · Outdoor control board sensing fault

Outdoor ambient thermistor abnormal

Outdoor ambient thermistor open/short · Sensor connector corrosion or looseness · Outdoor PCB sensor input issue

Evaporating-temperature thermistor abnormal in heating

Evaporating thermistor open or short · Sensor installation or contact issue · Heating-cycle control board sensor error

Incorrect indoor unit number/capacity setting

Indoor-outdoor addressing mismatch · Incorrect combined indoor capacity setup · Installation/configuration error after replacement

Outdoor protective circuit abnormal

Outdoor protection circuit component fault · Inverter board fault · Protection logic triggered by abnormal electrical load

Cooling overload with high-pressure protection

Condenser airflow restriction · Outdoor fan underperformance · System high-pressure condition during cooling

Heating overload with high-pressure protection

High refrigerant pressure during heating · Outdoor heat-exchanger airflow limitation · Outdoor fan or control fault

High-pressure increase protection activated

Rapid pressure rise in refrigerant circuit · Condenser heat rejection problem · Outdoor control/protection trip

Low-suction-pressure protection active

Very low suction pressure in refrigerant circuit · Refrigerant shortage or restriction · Protection logic activation to prevent damage

Instantaneous overcurrent protection (inverter)

Inverter current spike beyond threshold · Compressor electrical stress · Power module or drive-circuit fault

Current sensor circuit abnormal

Faulty current sensor · Sensor circuit wiring fault · Outdoor PCB current-measurement fault

IPM/transistor module protection activated

Inverter transistor module fault · IPM protection triggered by abnormal load · Outdoor drive circuit abnormality

Outdoor DC fan motor protection abnormal

Outdoor fan motor output drop or lock · Fan driver fault on outdoor board · Mechanical resistance at fan assembly

Incorrect unit and refrigerant-cycle number setting

Wrong unit addressing setup · Refrigerant cycle number mismatch · Configuration error after installation or PCB replacement

EEPROM or indoor control memory error

Corrupted indoor control memory data · Indoor PCB failure · Power interruption during control write cycle

High-pressure protection activated

Blocked condenser airflow at outdoor unit · Outdoor fan underperforming or stalled · High refrigerant pressure from overcharge or restriction

Indoor coil freeze protection active

Restricted indoor airflow from dirty filter or coil · Low refrigerant condition · Indoor fan or thermistor control issue

Low-pressure protection activated

Refrigerant leak or undercharge · Refrigeration circuit restriction · Pressure sensor or control fault

Compressor overheating protection

High compressor thermal load · Poor condenser heat rejection · Compressor or inverter drive abnormality

Overcurrent protection active

Compressor current draw above limit · Inverter power module stress · Power supply instability

Indoor-outdoor communication error

Loose or damaged interconnection cable · Terminal contact corrosion or loose connection · Indoor or outdoor PCB communication circuit fault

Indoor temperature sensor fault

Room thermistor open or short circuit · Loose sensor harness connection · Indoor PCB sensor input fault

Evaporator coil sensor fault

Evaporator thermistor open or short circuit · Sensor wire damage or connector looseness · Indoor PCB sensing circuit issue