What is an Error / Alarm Code?
Hitachi air conditioners use error or alarm codes to indicate when something is out of spec—sensor failure, communication faults, safety devices tripped, overheat, etc. These codes may display on:
- The indoor unit’s display
- The remote control (wired/wireless)
- Blinking LED(s) on indoor or outdoor PCBs
- Via the controller interface on commercial/VRF systems.
Known Hitachi AC Error / Alarm Codes & What They Mean
Here’s a consolidated list of Hitachi AC error/alarm codes based on multiple manuals, support documents, and user-reports. Many are widely used; some may not apply to your model.
Hitachi Room Air Conditioner (RAC) — Indoor Unit Alarm Codes
(from Hitachi “Room Air Conditioner range” quick reference)
- 01 – Indoor coil too warm in cooling / too cold in heating → Reversing valve or coil thermistor fault.
- 02 – Forced operation from outdoor unit (not an error).
- 03 – Communication error (wiring/indoor or outdoor PCB).
- 04 – Outdoor unit fault (confirm exact problem on outdoor PCB LEDs).
- 06 – Float switch activated (check pump & drain).
- 07 – Drain pump forced operation (test switch left on, or PCB fault).
- 08 – Louvre not opening (louvre motor/microswitch/PCB) — RAF only.
- 09 – Indoor thermistor fault (air inlet/coil thermistor open/short, or PCB).
- 10 – Indoor fan motor over-current or abnormal RPM (motor/PCB).
- 13 – EEPROM data error (PCB).
Notes: If the timer lamp flashes 1s on / 1s off that’s pre-heating (not an error). If it flashes in a pattern, match the count to the table above.
Hitachi Room Air Conditioner (RAC) — Outdoor Unit Indicators
(interpreted via outdoor PCB LEDs)
- 1 – Normal, power on.
- 2 – Compressor over-current (PCB or locked compressor).
- 2 (with LED302 lit) – Compressor over-current (SPM/PCB failure).
- 3 – Low compressor speed / abnormal rotor position (SPM/compressor/PCB).
- 4 – Compressor switching failure (SPM/compressor/PCB).
- 5 – Low compressor speed with over-current (often high pressure / fan fault / low mains).
- 6 – Discharge thermistor temperature rising (short of refrigerant, thermistor/compressor/fan/main PCB).
- 7 – Thermistor faulty (Summit & Monozone).
- 8 – Compressor not accelerating above minimum (short of refrigerant or compressor fault).
- 9 – Communication error (C/D not connected, cable/PCB).
- 10 – Abnormal voltage (mains/reactor).
- 12 – Fan rotation abnormal (fan/PCB/fuse).
- 13 – EEPROM error (main PCB).
- 14 – Over-voltage detected by SPM.
- LD302 blink map (thermistors):
1=Compressor OH, 2=Defrost, 3=Ambient, 4=Expansion (circ 1), 5=Suction (circ 1), 6=Expansion (circ 2), 7=Suction (circ 2), 8=Expansion (circ 3), 9=Suction (circ 3).
Hitachi Set Free IVX Systems & Utopia ES — Alarm Codes (shared table)
(official quick-reference alarm table; where ranges differ, both wordings shown)
01 – Indoor unit: Float switch / fan / drain protection activated (fan overload or float; check drain, fan).
02 – Outdoor unit: High-pressure trip (41.3 bar) or phase reversal (Utopia ES also lists phase reversal).
03 – Communication error: Indoor ↔ outdoor comms (cable / power / DIP settings / PCB).
04 – Comms (outdoor): Main PCB ↔ inverter PCB (or on some ES, main ↔ fan PCB) wiring/power/PCB fault.
05 – Power supply: Phase failure / phase reversal (not used on all ranges).
06 – Voltage drop (inverter): To compressor inverter (or condenser fan inverter on ES). Check mains, capacitors, inverter electronics.
07 – Refrigerant cycle: Discharge superheat decrease (overcharge; indoor EEV stuck open in cool / outdoor EEV stuck open in heat; short-cycling air to indoor).
08 – Refrigerant cycle: Compressor temperature increase (short of charge, blockage, EEV locked closed, etc.).
09 – Outdoor unit (ES text): Thermal overload of fixed-speed fan motor / locked fan (N/A on some IVX).
11 – Indoor: Inlet-air thermistor alarm (wiring open/short/PCB).
12 – Indoor: Outlet-air thermistor alarm (wiring open/short/PCB).
13 – Indoor: Freeze-protection (liquid line) thermistor alarm (wiring open/short/PCB).
14 – Indoor: Gas pipe (suction) thermistor alarm (wiring open/short/PCB).
19 – Indoor: Fan motor alarm (AC fan thermal, or DC fan over/under-current/RPM).
20 – Outdoor: Compressor/discharge gas thermistor alarm (wiring open/short/PCB) — N/A on some IVX.
21 – Outdoor: Discharge pressure transducer alarm (wiring open/short/PCB) — N/A on some ES.
22 – Outdoor: Ambient air thermistor alarm (wiring open/short/PCB).
23 – Outdoor: Compressor/discharge gas thermistor alarm (alt. mapping on some ranges) — N/A on some ES.
24 – Outdoor: Evaporation (outdoor coil) thermistor alarm (wiring open/short/PCB).
26 – Outdoor (FSVNE): Suction gas thermistor alarm — N/A on ES.
29 – Outdoor: Suction pressure transducer alarm (wiring open/short/PCB) — N/A on ES.
30 – System: Incorrect H-LINK wiring (two CH boxes wired in series) — N/A on ES.
31 – System capacity: Indoor capacity >130% or <50% (or Indoor/Outdoor capacity mismatch on ES).
32 – System communication: Loss of other indoor on same refrigerant cycle (other unit off, wiring error, PCB on that indoor).
35 – System addressing: Duplicate indoor/outdoor unit address on same H-LINK.
36 – Combination error: Indoor/Outdoor unit combination not compatible.
38 – Outdoor protection circuit abnormal: Wrong connection to outdoor PCB or PCB failure.
39 – Outdoor: Fixed-speed compressor over/under-current — N/A on ES.
41 – Pressure/temperature: Outdoor pipe >55 °C and compressor temp >95 °C (cooling) — N/A on IVX.
42 – Indoor freeze protection (liquid) >55 °C with compressor >95 °C (cooling) — N/A on IVX.
43 – Protection (ratio falling): Discharge and suction pressures too close (charge/pressure transducer/compressor). — N/A on ES.
44 – High suction gas pressure protection — N/A on ES.
45 – High discharge gas pressure protection — N/A on ES.
47 – Low suction pressure protection / excessively low evaporating temperature (≈ −35 °C).
48 – Inverter: Over-current detected (IPM/PCB2, locked compressor, high discharge pressure).
51 – Inverter current sensor abnormal (sensor or inverter PCB; ES: Main PCB/IPM/PCB2).
52 – Inverter compressor over-current (electronics or seized compressor / thermistor plausibility).
53 – IPM protection: Over-current/low voltage/overheat (ES: IPM/PCB2 over-current/overheat).
54 – Inverter temperature rise protection (over-current or restricted airflow; ES notes outdoor fan abnormality possibility).
55 – Controller: Short on remote wiring / failed controller / indoor PCB fault.
56 – Outdoor fan: BLDC position/commutation abnormal (transmission failure) — N/A on ES.
57 – Outdoor fan controller protection: Abnormal fan speed (wiring between main & fan PCB or fan motor failure).
58 – Fan controller abnormal: Over-current or over-temperature of controller fins — N/A on ES.
61 – Central station: Loss of unit communication previously detected (power to indoor, wiring, PCB).
96 – KPI thermistor: Total heat exchanger room temp thermistor error (wiring open/short/PCB).
97 – KPI thermistor: Total heat exchanger outdoor temp thermistor error (wiring open/short/PCB).
dd – System wiring: Incorrect communication cable wiring (crossed with remote/CH box).
EE – Lockout: System locked out due to outdoor alarm reset 3× in 6 h.
Hitachi Wall Splits (RAK-PSE etc.) Additional code patterns
(some RAK/room models use a blink-count grid mapped to 000/001/003… plus remote “CHECK” read-out)
- 000 – Normal
- 001 – Refrigerant-cycle fault
- 003 / 012 – Communication error indoor↔outdoor
- 009 – Indoor thermistor fault
- 010 – Abnormal fan rotating numbers
- 013 – EEPROM read error
(These are read via blink counts; see the model’s service sheet for the full grid.)
Conclusion
Hitachi air conditioners are engineered with built-in safety and diagnostic systems that protect the unit and guide you to the source of a problem. Every error code—whether it’s a simple reminder like a sensor check or a more serious fault such as compressor overload or communication failure—is the unit’s way of signalling where to look.
By understanding these codes, you can:
- Carry out simple fixes yourself, such as cleaning filters, clearing a drain, or checking airflow.
- Provide technicians with precise fault information, saving both time and repair costs.
- Spot recurring issues early before they lead to costly breakdowns.
That said, many codes point to electrical, refrigerant, or PCB issues that should only be handled by a qualified engineer. Regular maintenance clean filters, clear coils, and professional servicing remains the best way to minimise errors and keep your system running smoothly.
In short: don’t ignore the error codes. Treat them as valuable clues that help keep your Hitachi AC safe, efficient, and reliable for years to come.
