VFD Fault Codes: What You Need to Know Right Away
A fault code on a variable frequency drive display is not a breakdown — it is a protection signal that triggered before something actually failed. Most faults can be resolved without replacing the drive. You just need to know what the code means and where to look.
ABB VFD Fault Codes — ACS355, ACS550, ACS580, ACS880
ABB uses F-XXXX (Fault — stops the drive) and A-XXXX (Alarm — warning without stopping). ACS880 uses a different numeric format (e.g., 2310 instead of F-0001), but causes and responses are the same.
| Code | Name | Cause | Solution |
|---|---|---|---|
| F-0001 | OVERCURR | Output overcurrent: motor overload, too-short acceleration time, cable short circuit | Increase acceleration time (Acc1), check load, measure cable insulation |
| F-0002 | OVERVOLT | DC bus overvoltage: rapid deceleration or excessive supply voltage | Increase deceleration time, install braking resistor, check supply voltage |
| F-0003 | UNDERVOLT | Undervoltage: supply voltage drop, faulty circuit breaker or contactor | Check voltage on all three phases, circuit breaker and contactor condition |
| F-0004 | OVERTEMP | Drive heatsink overtemperature: clogged fan, high ambient temperature | Clean ventilation channels and filters, check cooling fan |
| F-0006 | MOTOR TEMP | Motor overtemperature by thermal model or thermistor signal | Check motor load, configure thermal model (Pn, In), check thermistor |
| F-0009 | UNDERCURR | Undercurrent: broken belt, dry pump, mechanical decoupling from load | Check mechanical coupling, liquid level in pump, belt condition |
| F-0011 | OUTPUT PH | Output phase imbalance or phase loss | Check motor cable, U/V/W terminals at drive output and motor terminal box |
| F-0012 | INPUT PH | Input phase loss or significant supply imbalance | Check voltage on all three supply phases, fuses, and supply cable |
| F-0014 | EARTH FLT | Ground fault: damaged cable or motor winding insulation | Disconnect motor, measure insulation resistance (min 1 MOhm at 500V) |
| F-0016 | MOTOR STALL | Motor stall: mechanical jam or severe overload | Check mechanical equipment, remove load, review stall protection settings |
To reset a fault on ABB: press RESET on the operator panel or trigger a digital input configured as Fault Reset. Trip Locked faults require full power removal for 5–10 seconds.
Browse our ABB frequency converter catalogue.
Danfoss VLT Fault Codes — FC51, FC101, FC202, FC301, FC302
Danfoss distinguishes three protection responses: Warning (alert, no stop), Alarm (trip with stop), and Trip Locked (requires manual reset). AL codes apply across the entire VLT product family.
| Code | Type | Cause | Solution |
|---|---|---|---|
| AL 4 | Alarm | Input phase loss | Check supply voltage on all three phases, circuit breaker, and supply cable |
| AL 7 | Alarm | DC bus overvoltage: high-inertia load or rapid deceleration | Increase deceleration time (par. 3-42), install braking resistor or enable Kinetic Backup |
| AL 8 | Warning/Alarm | DC bus undervoltage: supply drops below minimum threshold | Check supply quality, configure Mains Failure function (par. 14-10) |
| AL 9 | Alarm | Inverter overloaded: sustained overcurrent beyond rating | Reduce load or select a higher-rated drive |
| AL 10 | Alarm | Motor ETR overtemperature (Electronic Thermal Relay) | Configure ETR parameters (1-24, 1-25), check motor cooling and load |
| AL 13 | Alarm | Overcurrent: motor cable fault or sudden load surge | Check motor cable and winding insulation, increase acceleration time |
| AL 14 | Trip Lock | Ground fault — current leakage exceeded threshold | Measure cable and motor insulation with megohmmeter; check EMC filter for capacitive leakage |
| AL 15 | Trip Lock | Short circuit in output circuit | Check motor cable for phase-to-phase or phase-to-ground short |
| AL 29 | Alarm | Drive overtemperature: clogged heatsink, fan failure | Clean heatsink fins and ventilation paths, check cooling fan |
| AL 30-32 | Alarm | Motor phase loss (AL30=U, AL31=V, AL32=W) | Check motor cable connections and winding continuity |
| AL 36 | Alarm | Mains Failure: unstable or lost supply | Check supply stability, configure Mains Failure and Kinetic Backup |
AL 14 and AL 15 do not auto-reset. After fixing the cause, send a Reset signal via terminal 27 or the LCP button. If Trip Lock returns immediately — the root cause is still present.
Browse our Danfoss VLT frequency converter catalogue.
INVT VFD Fault Codes — GD10, GD100, GD200, GD300
INVT uses the E0XX fault format. Codes E001–E007 specify both the fault type and the operating mode when it occurred.
- E001 — IGBT module protection (output overcurrent): cable or motor short circuit
- E002 — Overcurrent during acceleration: too-short Acc time or excessive starting load
- E003 — Overcurrent during deceleration: too-short Dec time, high-inertia load
- E004 — Overcurrent at constant speed: sudden load spike
- E005 — Overvoltage during acceleration
- E006 — Overvoltage during deceleration: increase Dec time or install braking resistor
- E007 — Overvoltage at constant speed
- E009 — Undervoltage: supply below minimum for the series
- E010 — Drive overload: load exceeds 150% for more than 1 minute
- E011 — Motor overload (thermal model)
- E012 — Input phase loss
- E013 — Output phase loss: motor cable break or open winding
- E014 — IGBT module or heatsink overtemperature
- E015 — External fault (EXT FAULT input activated)
- E016 — Communication error (Modbus, CANopen, PROFIBUS)
- E018 — Current detection fault: current sensor or board failure
- E019 — Motor autotuning fault
- E021 — EEPROM fault: parameter memory corruption
- E022 — PID feedback loss
- E023 — Braking unit or resistor fault
- E040 — Speed deviation: actual speed differs from setpoint beyond limit
- E041 — Overspeed (above configured maximum)
In the field, E014 and E002/E003 are most frequent. E014 — clean the ventilation. E002/E003 — increase Acc/Dec times (parameters F0-17, F0-18) or switch from V/F to vector control.
Full catalogue of INVT GD-series drives.
Schneider Electric Altivar Fault Codes — ATV12, ATV320, ATV630
Altivar drives use letter codes. Three letters immediately signal the fault type: OCF = Overcurrent, OHF = Overheat, PHF = Phase Fault. Codes apply to ATV12, ATV320, ATV630, and ATV930.
| Code | Full Name | Cause | Solution |
|---|---|---|---|
| OCF | Overcurrent Fault | Overcurrent: cable short, too-short acceleration, sudden load | Check cable and motor insulation, increase acceleration time (ACC) |
| OHF | Drive Overheating | Heatsink overtemperature: clogged fan, high ambient temperature | Clean ventilation openings, check cooling fan |
| OLF | Motor Overload | Motor overload beyond configured protection threshold | Set nominal motor current (parameter ItH), reduce mechanical load |
| OBF | DC Bus Overvoltage | DC overvoltage: rapid braking or regenerative load | Increase deceleration time, install braking resistor |
| PHF | Input Phase Loss | Phase loss or significant supply imbalance | Check all three supply phases, circuit breaker, and supply cable |
| USF | Undervoltage | Supply voltage below minimum threshold | Check supply voltage, configure parameter UNS |
| SCF | Short Circuit | Short circuit between windings or to ground in motor or cable | Measure motor and cable insulation with megohmmeter |
| EPF | External Fault | External fault input activated by connected device or sensor | Check the external device generating the fault signal |
| SLF | Serial Link Fault | Modbus RTU communication loss: cable break, wrong address or baud rate | Check RS485 cable, device address, and baud rate settings |
| SOF | Output Overspeed | Motor speed exceeded maximum limit | Check maximum frequency setting (HSP) and speed setpoint |
| CFF | Configuration Fault | Incorrect configuration after parameter reset or macro change | Restore configuration settings to match load type |
| TNF | Autotuning Fault | Autotuning error: incorrect motor data or wiring issue | Verify nameplate data, check connections, run autotuning again |
| LFF | AI Loss (4-20 mA) | 4-20 mA signal lost on analog input | Check sensor, analog cable, and sensor power supply |
On the older ATV12, some codes display as Err with a number. From ATV320 onward, full letter codes appear in the drive menu. To reset: press STOP/RESET or trigger an input configured as Fault Reset.
Browse our Schneider Electric Altivar drive catalogue.
Common Fault Causes and Prevention
Five most common fault causes across all four brands:
- Overtemperature (OHF / F-0004 / AL 29 / E014) — dust clogs filters, cooling fan cannot keep up. Clean every 3–6 months, install a temperature sensor in the enclosure.
- Overcurrent on acceleration (F-0001 / AL 13 / E002 / OCF) — load inertia exceeds drive capability. Increase Acc time or switch to vector control.
- Ground fault (F-0014 / AL 14 / SCF) — insulation degradation from aging or moisture. Annual megohmmeter testing is the minimum.
- DC overvoltage on braking (F-0002 / AL 7 / E006 / OBF) — high-inertia load regenerates more energy than absorbed. Install a braking resistor.
- Phase loss (F-0012 / AL 4 / E012 / PHF) — worn contactor or loose terminal. Check at every scheduled maintenance.
For drives that keep tripping — read our guide on VFD breakdowns and repair.
Frequently Asked Questions
How do I reset a fault on an ABB VFD?
Press RESET on the operator panel or trigger the digital input configured as Fault Reset. Trip Locked faults (e.g., F-0014) require complete power removal for 5–10 seconds. If the root cause remains — the drive trips again immediately.
What does AL 14 mean on a Danfoss VLT?
AL 14 is Earth Fault — abnormal current leakage detected. Disconnect the motor, then measure insulation resistance on cable and motor windings (500V, min 1 MOhm). If insulation is fine, check the EMC filter — capacitive filters can produce leakage currents the drive reads as a ground fault.
Why does INVT show E014 when the heatsink is cold?
E014 fires from the temperature sensor on the IGBT module or heatsink. Cold heatsink with an active fault usually means a faulty sensor or control board. Reset all parameters to factory defaults (F0-02=1) and retry. If the fault persists, the control board or IGBT module needs professional diagnostics.
What does OCF mean on a Schneider Electric Altivar?
OCF is Overcurrent Fault. Instant OCF on RUN command usually means a short circuit in the cable or motor windings. OCF after a few seconds of running points to overload or too-aggressive acceleration. Check cable insulation and increase the ACC parameter.
Can I replace an ABB drive with an INVT without reprogramming?
Yes, but all parameters must be re-entered — ABB and INVT menu structures differ completely. Transfer at minimum: motor nameplate values, Acc/Dec times, protection thresholds, and control mode. If the drive is part of a Modbus system, verify register addresses. Always save the full parameter list before replacing any drive.
