LS L7C Fault Codes List

Troubleshoot your LS Electric L7C compact servo drive with our updated guide. Learn to interpret AL-xx alarm codes, use DriveView 9 for diagnostics, and resolve common motor trips.

L7C Fault Codes Reference Table

Below is the complete list of protective functions and alarm codes for the L7C series. Please refer to this table to match the code on your drive’s display with the specific hardware or tuning diagnostic.

LS L7C Fault Codes List

LS L7C Fault Codes List

Fault Code and Meaning Cause and Remedy
AL-10
IPM fault
(Overcurrent H/W)		 Cause:
  • Motor cable abnormality.
  • Encoder cable abnormality.
  • Parameter setting abnormality (Motor ID, Encoder type).

Remedy:
  • Check for abnormal wiring and short circuits; replace motor/encoder cables.
  • Make sure parameter settings [0x2000], [0x2001], [0x2002] match the motor label.
  • Modify parameters to match the motor label.
AL-14
Over current
(Overcurrent S/W)		 Cause:
  • Motor phase resistance inspection (U-V, V-W, W-U).
  • Apparatus abnormality (conflicts or binding).
  • Drive abnormality.
  • Noise-related abnormalities.

Remedy:
  • Inspect resistance between motor lines; replace motor if below several Ω.
  • Inspect apparatuses for binding.
  • If alarms occur continually after power re-input, replace the drive.
  • Inspect PE wiring and match wire sizes.
AL-11
IPM temperature
(IPM overheat)		 Cause:
  • Ambient temperature exceeds 50°C.
  • Continual overload alarm (Load > 100%).
  • Highly frequent or continual regenerative operation.
  • Drive installation direction/status.

Remedy:
  • Lower the ambient temperature.
  • Check accumulated operation overload ratio [0x2603]; Change drive/motor capacity or adjust gain.
  • Adjust regenerative resistance setting [0x2009] or use external regenerative resistance.
  • Verify wiring and connection installation status.
  • Replace the drive if alarms occur continually.
AL-15
Current offset		 Cause:
  • Excessive setting of the motor's U and V Phase current offset.
  • Drive abnormality.

Remedy:
  • Check if offsets [0x2015] - [0x2017] are 5% of rated current or higher; Re-adjust phase current offset.
  • If alarms occur continually after adjustment, replace the drive.
AL-21
Continuous overload		 Cause:
  • Continuous operation with a load exceeding the rated value.
  • Motor brake abnormality (opening of brake).
  • Parameter setting abnormality (Motor ID/Encoder info).
  • Apparatus abnormality.
  • Motor or Encoder cable wiring/short circuit.

Remedy:
  • Check accumulated overload ratio [0x2603]; Change capacity of motor/drive or adjust gain.
  • Supply power to the motor brake during SVON.
  • Modify parameters to match motor label; set appropriate basic load ratio [0x200F].
  • Inspect apparatuses and cables; replace if necessary.
AL-22
Drive temperature 1
(Drive overheat 1)		 Cause:
  • Ambient temperature exceeds 50°C.
  • Drive abnormality (Sensor reading vs Ambient).

Remedy:
  • Lower the ambient temperature.
  • Check displayed temp [0x260B]; if highly different from ambient, replace the drive.
AL-23
Regenerative overload		 Cause:
  • Capacity exceeded due to high frequency or continual regenerative operation.
  • Parameter setting abnormality ([0x2009]~[0x200E]).
  • Main power input voltage abnormality (> AC253V).
  • Drive abnormality (Heat in regenerative resistance).

Remedy:
  • Check accumulated regenerative overload ratio [0x2606]; Use external regenerative resistance.
  • Set appropriate parameter values.
  • Re-inspect the main power source.
  • Replace the drive if resistance heats up when not operating.
AL-24
Motor cable open		 Cause:
  • Motor cable abnormality (disconnection).
  • Motor abnormality (internal short circuit).
  • Drive abnormality.

Remedy:
  • Check for disconnection; replace motor cable.
  • Check for U, V, W short inside motor; replace the motor.
  • If alarms occur continually while SVON is on, replace the drive.
AL-25
Drive temperature 2
(Drive overheat 2)		 Cause:
  • Ambient temperature exceeds 50°C.
  • Drive abnormality (Heat leakage).

Remedy:
  • Lower the ambient temperature.
  • Check if temp [0x260C] differs significantly from ambient; Replace the drive.
AL-30
Encoder communication
(Serial encoder error)		 Cause:
  • Encoder cable abnormality (disconnection/short).

Remedy:
  • Check for disconnection or abnormal connection; Replace the encoder cable.
AL-31
Encoder cable open		 Cause:
  • Parameter setting abnormality (Motor ID/Encoder ID).
  • Encoder abnormality.
  • Drive abnormality.

Remedy:
  • Modify parameters [0x2001]/[0x2002] to match motor label.
  • If parameters are correct but alarm persists, replace the motor.
  • If alarms occur continually after power re-input, replace the drive.
AL-32
Encoder data error		 Cause:
  • Drive abnormality.

Remedy:
  • If alarms occur continually after power re-input, replace the drive.
AL-33
Motor setting error		 Cause:
  • Motor ID setting mismatch.
  • Drive abnormality.

Remedy:
  • Modify [0x2000] to match the information on the motor label.
  • If alarms occur continually after power re-input, replace the drive.
AL-34
Z Phase open		 Cause:
  • Encoder cable abnormality.
  • Encoder abnormality.
  • Drive abnormality.

Remedy:
  • Check wiring/short circuit; replace encoder cable.
  • If alarms occur continually, replace the motor.
  • If alarms occur continually after motor checks, replace the drive.
AL-35
Low battery		 Cause:
  • Parameter setting abnormality (Incremental vs Absolute).
  • Defective battery connection.
  • Low battery voltage (< 3.3V).

Remedy:
  • To use incremental encoder, set [0x2005] to 1 to disable alarms.
  • Connect the battery accurately.
  • Replace the battery.
AL-36
Preset Error
(Encoder initialize)		 Cause:
  • Parameter setting error (Absolute/Incremental).
  • Poor battery contact or disconnected.
  • When initial encoder power is turned on.

Remedy:
  • To use as incremental, set [0x2005] to 1.
  • Connect battery, reset alarm, re-apply power. Reset mechanical origin.
  • Reconnect power and reset mechanical origin.
AL-40
Under voltage		 Cause:
  • Main power input voltage abnormality (Single phase < AC170V).
  • Drive abnormality (Input normal but value incorrect).
  • Lowered power voltage during operation.

Remedy:
  • Re-inspect the main power source.
  • Check value of [0x2605]; replace drive if input is normal but reading is wrong.
  • Use a 3-phase voltage supply.
AL-41
Over voltage		 Cause:
  • Main power input voltage abnormality (AC253V or higher).
  • High external regenerative resistance.
  • Highly frequent acceleration/deceleration.
  • Drive abnormality.

Remedy:
  • Re-inspect main power source.
  • Review regenerative resistance value and operation conditions.
  • Set a high value for acceleration/deceleration time.
  • Replace the drive if alarms occur continually.
AL-42
Main power fail		 Cause:
  • Main power input voltage abnormality (L1-L2 AC200-230V).
  • Parameter setting abnormality [0x2006].
  • Momentary power outage.
  • Drive abnormality.

Remedy:
  • Re-inspect the main power source.
  • For a warning instead of alarm, modify [0x2006].
  • Lower setting of [0x2007] or inspect power source.
  • Replace the drive if alarms occur continually.
AL-50
Over speed limit		 Cause:
  • Motor or Encoder cable abnormality.
  • Parameter setting abnormality (Motor ID, Gear Ratio).
  • Encoder or Drive abnormality.

Remedy:
  • Replace motor/encoder cables.
  • Modify parameters to match motor label. Set electric gear ratio to a low value.
  • Re-adjust gain according to operation conditions.
  • Replace motor or drive if abnormalities persist.
AL-51
POS following error		 Cause:
  • Parameter setting abnormality (Gain, Gear Ratio, Error Range).
  • Apparatus abnormality (binding).
  • Drive abnormality.

Remedy:
  • Readjust parameters and gain according to operation condition.
  • Set electric gear ratio to a low value.
  • Inspect apparatuses.
  • Replace drive if alarms occur continually.
AL-53
Excessive SPD deviation		 Cause:
  • Motor or Encoder cable abnormality.
  • Parameter setting abnormality.

Remedy:
  • Replace motor or encoder cables.
  • Modify parameters to match motor label.
  • Set electric gear ratio to a low value.
AL-63
Parameter checksum		 Cause:
  • O/S replacement (Software update).
  • Drive abnormality.

Remedy:
  • Perform restoration of initial parameters and re-set parameters before operation.
  • Replace drive if alarms occur continually.
AL-71
Factory setting error		 Cause:
  • Drive abnormality.

Remedy:
  • Contact service center.
  • Replace drive if alarms occur continually.
W01
PWR_FAIL
(Main power phase loss)		 Cause:
  • Main power input voltage abnormality.
  • Parameter setting abnormality.
  • Momentary power outage.

Remedy:
  • Re-inspect the main power source (L1-L2 AC200-230V).
  • Modify [0x2006] to set an alarm instead of a warning.
  • Lower setting of [0x2007] or inspect power source.
W02
LOW_BATT
(Low encoder battery)		 Cause:
  • Parameter setting abnormality.
  • Defective battery connection.
  • Low battery voltage.

Remedy:
  • To use incremental type absolute encoder, set [0x2005] to 1.
  • Connect the battery accurately.
  • Replace the battery (if below 3.3V).
W04
SW_POS_LMT
(Software position limit)		 Cause:
  • Position command value larger than software limit input.

Remedy:
  • Ensure command values stay within limits.
W08
OV_DB_CUR
(DB overcurrent)		 Cause:
  • Motor operation by external power source.
  • DB resistance capacity exceeded.
  • Drive abnormality.

Remedy:
  • Do not operate motor using external power.
  • Lower command speed, moment of inertia, or frequency of DB stop.
  • Replace the drive.
W10
OV_LOAD
(Operation overload)		 Cause:
  • Continuous operation with load exceeding rated value.
  • Motor brake abnormality.
  • Parameter setting abnormality.
  • Apparatus or cable abnormality.

Remedy:
  • Change capacity of motor/drive or adjust gain.
  • Supply power to the motor brake.
  • Modify parameters to match motor label.
  • Inspect apparatuses and cables.
W20
SETUP
(Abnormal combination)		 Cause:
  • Applied motor capacity exceeds that of the drive.
  • IO setting abnormality (repeated signal assignments).

Remedy:
  • Lower torque limit value or replace motor/drive to match capacity.
  • Set the parameters appropriately for the operation conditions.
W40
UD_VTG
(Low voltage)		 Cause:
  • Main power input voltage abnormality.
  • Lowered power voltage during operation.

Remedy:
  • Re-inspect main power source.
  • Check wiring status of main power.
  • Replace drive if input is normal but alarm persists.
W80
EMG
(Emergency signal input)		 Cause:
  • Emergency pause by EMG contacts.
  • EMG contact abnormality.

Remedy:
  • Check wiring and drive parameter settings [0x211F], [0x2200]~.
  • Set parameters appropriately.
  • Replace drive if alarm persists continuously.
 

How to Read L7C Faults via DriveView 9

While the front-panel LED is useful for immediate identification, connecting your PC to the L7C’s USB port using DriveView 9 software offers professional-grade diagnostic data for 2026 maintenance standards.

  • Alarm History: The L7C drive records the last 16 alarms. DriveView 9 displays these with the total power-on time at which they occurred, making it easier to correlate trips with power surges or mechanical wear.
  • Real-Time Monitor: You can monitor motor speed, torque, and position error in real-time. If a trip like AL-40 (Overload) occurs, you can see if the torque was spiking due to mechanical friction.
  • Status Dashboard: The software clearly shows the status of digital I/O terminals. This helps verify if an external safety signal or a limit switch is triggering a stop.

General Troubleshooting Steps for L7C Servos

Before performing a reset, verify these three critical areas of the L7C servo system:

  1. Power Supply Check: Ensure the control power (L1C, L2C) and main power (L1, L2, L3) are stable. Many AL-41 (Undervoltage) trips are caused by temporary power sags in the factory.
  2. Encoder Integrity (AL-21): For encoder communication errors, check the feedback cable connectors. Ensure the cables are high-flex type if the motor is on a moving axis, as broken internal wires are a common cause of 2026 maintenance calls.
  3. Regeneration (AL-14/15): If the drive trips on Overvoltage during rapid stops, check the internal regenerative resistor or ensure an external resistor is correctly wired to the B and B+ terminals.

Frequently Asked Questions (FAQ)

Q: What is the difference between an Alarm and a Warning?

A: An Alarm (e.g., AL-10) is a critical fault that stops the motor immediately to prevent damage. A Warning (indicated by a specific code or a flashing display) notifies you of a non-critical issue, like a low absolute encoder battery, allowing the drive to continue running for a limited time.

Q: How do I reset a fault on the LS L7C?

A: Once the cause of the trip has been resolved, you can reset the drive by:

  • Pressing the [SET/RESET] key on the front panel operator.
  • Sending a Reset signal through the digital input (if configured).
  • Performing a power cycle (Wait for the display to turn off completely before turning it back on).

Q: Why does my drive show “bb” on the display?

A: bb stands for Base Block. This is not a fault; it indicates the drive is in a standby state and the motor is currently de-energized because the “Servo-ON” signal is not active.

Q: What does “AL-24” (Absolute Position Lost) mean?

A: This occurs if you are using an absolute encoder and the backup battery has died or been disconnected. You must replace the battery and perform the Absolute Encoder Reset procedure to re-establish the machine’s home position.

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