Hitachi Aircon Error Codes

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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

Typical causes

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