Delta VFD-L Series Drive Fault Codes List (2026) – Access the complete 2026 reference guide for Delta VFD-L nano drive fault codes. Learn to interpret basic error codes, troubleshoot the onboard potentiometer, and reset faults.
The Delta VFD-L Series is a “Sub-Micro” or “Nano” AC drive, designed for low-power applications like small conveyors, packing machines, and DIY projects. It is instantly recognizable by its compact white casing and the built-in speed potentiometer on the front panel. Because it is designed for simplicity, it lacks complex communication ports, meaning troubleshooting relies entirely on the digital display and manual settings.
This guide provides the most updated reference for 2026 to help you interpret the basic codes on this compact drive.
Delta VFD-L Fault Codes Reference Table
Use the search bar below or browse the table to identify your specific error code.
| Fault Code | Cause & Solution |
|---|---|
| EF External fault | Cause: The external terminal EF-GND goes from OFF to ON. Soultion: 1. When external terminal EF-GND is closed, the output will be turned off. (Under N.O. E.F.) 2. Press RESET after fault has been cleared. |
| bb External Base Block | Cause: This fault comes when drive received this command. Soultion: 1. When the external input terminal (B.B) is active, the AC drive output will be turned off. 2. Disable this connection and the AC drive will begin to work again. |
| oc Overcurrent | Cause: Output current of the AC drive exceeds the OC level Soultion: – Extend the accel/decel time – Check whether the motor rating and the AC drive rating match up with each other – Check whether there is short-circuit among U-V-W of the AC drive – Check whether the wiring to the motor is short-circuited or grounded – Check whether the screw between the AC drive and the motor is tightened or not – Check whether the motor is over loaded |
| ov/ou overvoltage | Cause: DC voltage of the main circuit exceeds the over-voltage detection level – The DC bus voltage has exceeded its maximum allowable value. Soultion: – Check whether the input voltage is within the scope of the rated input voltage of the AC drive, and monitor whether there is any occurrence of the voltage transients – If it is of the motor inertia uprising voltage that caused the exceeding voltage on the DC high-voltage side within the AC drive, the solution is to extend the accel/decel time or install the braking resistor (optional) |
| oH Overheating | Cause: Overheating- Heat sink temperature too high Soultion: 1. Ensure that the ambient temperature falls within the specified temperature range. 2. Make sure that the ventilation holes are not obstructed. 3. Remove any foreign objects from the heatsinks and check for possible dirty heat sink fins. 4. Check the fan and clean it. 5. Provide enough spacing for adequate ventilation |
| Lu/Lv Low Voltage | Cause: DC high-voltage side is exceedingly low within the AC drive Soultion: – Check whether the input power voltage is normal – Check whether the loading will be put on another unexpected heavy loading – Whether the 3-phase model is of the single-phase power input or the phase-lacking |
| oL overload | Cause: AC drive overload- Output current exceeds the AC drive-bearable current; e.g. could sustain for 60 seconds if the output is 150% of the AC drive rated current. Soultion: – Decrease the loading and extend the acceleration time – Check whether the motor is overloaded – Reduce torque compensation setting as set in Pr.7-02. – Increase the AC drive output capacity |
| oL1 Overload 1 | Cause: Overload 1- Internal electronic overload trip Soultion: 1. Check for possible motor overload. 2. Check electronic thermal overload setting. 3. Use a higher power motor. 4. Reduce the current level so that the drive output current does not exceed the value set by the Motor Rated Current Pr.7-00. |
| oL2 Motor overload | Cause: OL2- motor overload Motor with exceedingly great loading Soultion: – Check whether the loading of the motor is too great – Adjust the over-torque detection setting to an appropriate setting (Pr.06-03 to Pr.06-05). |
| cE1 Communication Error | Cause: Communication Error. Soultion: 1. Check the connection between the AC drive and computer for loose wires. 2. Check if the communication protocol is properly set. |
| ocA Over-current during acceleration | Cause: Over-current during acceleration (Output current exceeds triple rated current during acceleration.). Soultion: 1. Short-circuit at motor output: Check for possible poor insulation at the output lines. 2. Acceleration Time too short: Increase the Acceleration Time. 3. AC motor drive output power is too small: Replace the AC motor drive with the next higher power model. |
| ocd Over-current during deceleration | Cause: Over-current during deceleration (Output current exceeds triple rated current during deceleration.) Soultion: 1. Short-circuit at motor output: Check for possible poor insulation at the output line. 2. Deceleration Time too short: Increase the Deceleration Time. 3. AC motor drive output power is too small: Replace the AC motor drive with the next higher power model. |
| ocn Over-current during steady state operation | Cause: Over-current during steady state operation (Output current exceeds triple rated current during constant speed.) Soultion: 1. Short-circuit at motor output: Check for possible poor insulation at the output line. 2. Sudden increase in motor loading: Check for possible motor stall. 3. AC motor drive output power is too small: Replace the AC motor drive with the next higher power model. |
| cF1 Internal EEPROM can not be programmed | Cause: Internal EEPROM can not be programmed. Soultion: 1. Press “RESET” key to the factory setting 2. After this same fault comes then there is an hardware issue in drive need to repair or replace drive. |
| cF2 Internal EEPROM can not be read | Cause: Internal EEPROM can not be read. Soultion: 1. Press “RESET” key to the factory setting 2. After this same fault comes then there is an hardware issue in drive need to repair or replace drive. |
| EF External fault | Cause: The external terminal EF-GND goes from OFF to ON. Soultion: 1. When external terminal EF-GND is closed, the output will be turned off. (Under N.O. E.F.) 2. Press RESET after fault has been cleared. |
| cF3 Drive’s internal circuitry abnormal | Cause: Drive’s internal circuitry abnormal. Soultion: There is an hardware or software issue in drive. Need to repair or replace drive. |
| HPF | Cause: Hardware protection failure. Soultion: There is an hardware or software issue in drive. Need to repair or replace drive. |
| CodE Software protection failure | Cause: Software protection failure. Soultion: There is an hardware or software issue in drive. Need to repair or replace drive. |
| cFA Auto accel/decel failure | Cause: Auto accel/decel failure. Soultion: 1. Check if the motor is suitable for operation by AC motor drive. 2. Check if the regenerative energy is too large. 3. Load may have changed suddenly. |
| bb External Base Block | Cause: This fault comes when drive received this command. Soultion: 1. When the external input terminal (B.B) is active, the AC drive output will be turned off. 2. Disable this connection and the AC drive will begin to work again. |
How to Read VFD-L Faults (Manual Diagnostics)
Unlike the high-performance C2000 series, the VFD-L typically does not connect to VFDSoft or DIAStudio (unless using a specific RS-485 model). In 2026, diagnostics are performed using “Screwdriver logic”:
- The Onboard Potentiometer: A common issue with the VFD-L isn’t a “Fault Code” but a “No Run” condition.
- If the drive says “Run” but the motor won’t turn, check the knob on the front. It is often the frequency reference source. If the potentiometer is damaged or loose, the drive will sit at 0.0Hz.
- 7-Segment Display: The display is small and basic.
- “oc” (Overcurrent): If this happens immediately at start, the acceleration time (Parameter 1-09) is likely too short for the motor inertia.
- “Lv” (Low Voltage): Since these are often powered by 110V/220V single-phase, a slight dip in line voltage (e.g., sharing a circuit with a welder) will trip the drive instantly.
- Parameter Reset: Since there is no PC backup, if the drive behaves erratically, a Factory Reset is the quickest fix. Set Parameter 00-02 to 9 or 10 (50Hz/60Hz reset).
Frequently Asked Questions (FAQ)
Q: What does the “Lu” or “Lv” code mean?
A: This stands for Low Voltage on the DC Bus.
- Check your input power. If you are using a long extension cord to power the machine, the voltage drop might be starving the drive.
- If the fault persists even with good power, the internal charging resistor or capacitor bank has likely failed (common in older VFD-L units).
Q: How do I reset a Delta VFD-L fault?
A:
- Press the STOP/RESET button on the front panel.
- Power cycle the drive (unplug it, wait for the screen to go dark, plug it back in).
- Note: The VFD-L generally does not have external terminals dedicated to reset unless configured specifically in software.
Q: Can I replace the VFD-L with a VFD-EL or MS300?
A: Yes, and it is recommended in 2026. The VFD-L is a legacy nano drive. If it fails, upgrading to a Delta VFD-EL or MS300 provides better protection, a removable keypad (on some models), and PC connectivity for easier setup.