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.
Huawei SUN2000 all models and generations
LUNA2000 battery fault codes included
Sourced from Huawei technical documentation
Jump to category
Huawei fault you can't resolve?
If your Huawei inverter is showing a fault code and you need expert diagnosis, a remote diagnostic identifies the cause and recommends the fix — usually within 30 minutes.
Book Huawei diagnosis — £75 → How diagnostics work
ℹ
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 2001
Grid 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 2002
Grid undervoltage
AC grid voltage has dropped below the lower safety limit (typically below 216V). Inverter has disconnected. This often occurs during high-load periods. Wait for grid voltage to recover — the inverter will reconnect automatically.
Fault 2003
Grid 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 2004
Grid 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 2006
Grid 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 3001
PV 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 4001
Battery 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 4002
Battery 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 4003
Battery 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 4004
Battery 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 4005
BMS 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 1001
DSP 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 1002
Inverter 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.
Frequently asked questions
How do I access FusionSolar to see my alarm history? ↓
Download the FusionSolar mobile app or visit the web portal at https://global.fusionsolar.huawei.com. Log in with your account credentials. Select your device, then go to Alarm History or Device Events to view all fault codes with timestamps and descriptions.
Why does Fault 2001 (grid overvoltage) appear during sunny afternoons? ↓
During peak solar generation in the afternoon, many solar systems in your area are exporting power to the grid simultaneously. This can cause grid voltage to spike. If Fault 2001 appears frequently during peak hours, it indicates a grid quality issue. Contact your DNO to investigate.
What's the difference between temporary faults and persistent faults? ↓
Transient faults appear once or occasionally — usually grid disturbances or brief communication glitches. These often clear automatically. Persistent faults return repeatedly after power cycles and require diagnosis. Check your alarm history to see if the fault is trending or one-off.
Should I be worried if I see battery faults in the alarm history? ↓
Many battery faults are protective events that trigger when limits are approached — not catastrophic failures. Fault 4004 (SOC low) is common if your battery has fully discharged. Fault 4003 (overtemperature) can occur in hot weather. If the same fault repeats after proper charging/cooling, then diagnosis is needed.
Book
Can't find your Huawei fault code?
Our remote diagnostics service can pull and interpret your full Huawei SUN2000 event log, identify the root cause, and provide a clear repair plan — without needing a site visit first.
Independent — not affiliated with any manufacturer
Full Huawei event log analysis
Remote diagnosis before any site visit