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Fault code index · Huawei SUN2000 inverter & LUNA2000 battery

Huawei SUN2000 Fault Code Index

Every Huawei SUN2000 fault code from FusionSolar — what it means, the most likely cause, and what to do. Find your code in the index below or use the category sections to browse by system area.
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  • Huawei SUN2000 all models and generations
  • LUNA2000 battery fault codes included
  • Sourced from Huawei technical documentation
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How to find your fault code. Huawei fault codes appear in the FusionSolar mobile app and web portal. Log into FusionSolar → Device → Alarm History. The alarm history shows fault codes (e.g., Fault 2001, Fault 3004) with timestamps. Note the exact fault number — this will help you find the correct entry in this index to understand what it means and how to resolve it.

Grid faults

Fault codes generated in response to AC grid voltage or frequency being outside safe operating limits. These cause the inverter to disconnect from the grid.

Fault 2001Grid overvoltage
AC grid voltage has exceeded the upper safety limit (typically above 253V). Inverter has disconnected to protect itself and the grid. This is usually a temporary grid disturbance. Monitor the alarm history — if frequent, contact your DNO.
Fault 2002Grid undervoltage
AC grid voltage has dropped below the inverter's under-voltage limit (in the UK, below 184V for 2.5 seconds). Inverter has disconnected. This often occurs during high-load periods. Wait for grid voltage to recover — the inverter will reconnect automatically.
Fault 2003Grid overfrequency
Grid frequency has exceeded the upper safety limit. Inverter disconnected. Frequency events usually affect many users in your area. The inverter will reconnect when frequency normalizes.
Fault 2004Grid underfrequency
Grid frequency has dropped below the lower safety limit. Inverter disconnected. This indicates a significant grid disturbance — wait for frequency to recover and the inverter will reconnect automatically.
Fault 2006Grid frequency instability
Grid quality is poor — frequency is fluctuating rapidly. Inverter may disconnect and reconnect frequently. This is a grid quality issue affecting your area. Contact your DNO if the problem persists.

PV & DC faults

Fault codes related to DC string voltage, polarity, and insulation. These faults typically prevent the inverter from generating power.

Fault 3001PV overvoltage
PV string voltage is exceeding the MPPT input range. Check panel string configuration — may have too many panels in series. Do not touch DC cabling. Contact an engineer to review the string design.
Fault 3002 PV reverse connection
One or more PV strings have been connected with reversed polarity (positive and negative swapped). This is a critical safety issue. Isolate the system immediately. Do not touch any DC cabling. Contact a qualified engineer to identify which strings are reversed and reconnect them correctly.
Fault 3003 DC arc fault — URGENT
A DC arc has been detected in the PV string — this is a fire safety hazard. Isolate the system at the consumer unit immediately. Do not touch any DC cabling. Contact a qualified engineer to inspect string cabling and connectors for damage or loose connections.
Fault 3004 Insulation resistance fault — URGENT
Leakage current has been detected between the DC string and earth — a ground fault. This is a critical safety issue. Isolate at the consumer unit immediately. Do not touch any DC cabling. Check for water ingress at MC4 connectors, damaged insulation, or a faulty panel junction box. Contact a qualified engineer.

Battery & BMS faults

Fault codes from the LUNA2000 battery management system — communication failures, voltage protection, temperature, and state of charge events.

Fault 4001Battery comm fault
Communication lost between inverter and battery BMS. Check the SBU/BMU communication cable is connected securely at both ends. Verify polarity is correct. Try a full power cycle of the system.
Fault 4002Battery overcurrent
Discharge current from the battery has exceeded safe limits. BMS has activated protection. Check that no unusual loads are connected to the backup circuits. If using backup power, reduce load and try again. Contact Huawei support if persistent.
Fault 4003Battery overtemperature
Battery internal temperature has exceeded safe limits. Check that ventilation around the battery cabinet is clear and unobstructed. Ensure no heat sources are nearby. If ambient temperature is normal, the battery may have a thermal sensor issue — contact Huawei support.
Fault 4004Battery SOC too low
Battery state of charge has fallen below the safe minimum threshold. BMS has activated deep discharge protection. Allow the battery to charge fully during daylight. If persistent, check discharge cut-off SOC settings in battery options.
Fault 4005BMS protection active
Battery management system has activated a protection event. This typically means a specific cell voltage or temperature limit has been reached. Check FusionSolar for more details — a full power cycle may be needed.

Internal & thermal faults

Fault codes originating from inside the inverter — processor communication, temperature management, and control board issues.

Fault 1001DSP comm fault
Internal processor communication fault. Perform a full power cycle (AC isolator off, wait 60 seconds, back on). If the fault persists, the control board may require a firmware reflash — contact Huawei support or a qualified engineer.
Fault 1002Inverter overtemperature
Internal heatsink temperature has exceeded safe limits. Check ventilation — ensure minimum 20cm clearance on all sides, no direct sunlight, and no enclosed cabinets. Clear any dust from cooling vents. If ambient temperature is normal, the thermal sensor may be faulty.
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Fault code guides for the main UK solar inverter and battery brands: what each code means and what to do next. Find your brand and your code below.

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FAQ

Huawei SUN2000 fault code questions

Huawei fault codes appear in the FusionSolar app and web portal under Device → Alarm History, and as active alarms on the inverter's LCD display. Note the exact fault number (e.g. 2001, 3003) and the timestamp before searching this index. If FusionSolar itself is showing offline so you can't see the codes, see FusionSolar offline first.
Fault 3004 is an insulation resistance fault — leakage current detected between the DC string and earth. This is an urgent safety issue: isolate the system at the consumer unit immediately and do not touch any DC cabling. The usual causes are water ingress at MC4 connectors, damaged string-cable insulation, or a faulty panel junction box. Get a qualified engineer to inspect before any restart.
Many transient faults — brief grid-voltage events or comms glitches — clear automatically or after a power cycle — done in this order: AC isolator off first, then the DC string isolator, wait at least 2 minutes, then back on in reverse (DC, then AC). But if the same fault returns repeatedly, the cause is persistent and restarting won't fix it. A safety fault like 3004 or an AFCI arc fault must be diagnosed, not reset.
Fault 4004 means the LUNA2000 battery state of charge has fallen below the safe minimum and the BMS has activated deep-discharge protection. Let the battery charge fully during daylight. If it persists after a full charge, check the discharge cut-off SoC setting — if it's set too high the battery can stop discharging earlier than it should.
The remote diagnosis is free. We pull your full FusionSolar event log and string data to tell you what the code means and what's behind it. If it's something we can put right remotely — a setting or a comms reset — it's £125, and you only pay if we fix it. A physical fault — an insulation or arc fault, a failed board — is an on-site repair, quoted first, from £295.
Usually the same day. Send us the exact fault number and we read your FusionSolar history in a 30-minute remote session — you get a written summary of the cause and the recommended fix straight after.

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