Mitsubishi MR-JE Servo Alarm Codes Troubleshooting Guide

AL.32 Overcurrent

AL.32 means current above the permissible level flowed through the amplifier. The detail number identifies whether it happened during operation or while stopped.

With qualified personnel and the system safely isolated, Mitsubishi’s troubleshooting sequence separates the amplifier, power cable, and motor:

1. Disconnect U/V/W and check whether the alarm remains.
2. Check the motor power cable for a short or ground fault.
3. Check motor insulation using the approved procedure.
4. Verify the encoder cable is connected to the correct motor.
5. Inspect environmental conditions such as noise and temperature.

If the alarm remains with the motor power cable disconnected, the amplifier is a strong suspect. If it disappears, continue testing the cable and motor rather than replacing the drive immediately.

AL.33 Overvoltage

AL.33 means the DC bus exceeded the alarm level. The MR-JE troubleshooting manual identifies AL.33.1 as a main circuit voltage error.

If it occurs during deceleration, check:

• Regenerative option selection
• Pr. PA02
• Regenerative resistor wiring and resistance
• Deceleration time
• Load inertia
• Frequency of positioning cycles

Also measure the incoming supply. A supply that is already near the upper limit leaves less margin for regenerative energy.

AL.E0 Excessive regeneration warning is an early warning that regenerative power is approaching the permissible level. Investigating it early can prevent AL.30 or AL.33.

AL.37 Parameter Error

AL.37 means a parameter is outside its permitted range, conflicts with another parameter, or a point-table setting is invalid.

The principal details are:

• AL.37.1: Parameter setting range error
• AL.37.2: Parameter combination error
• AL.37.3: Point table setting error

Check the parameter error number and compare the current file with a known machine backup. This alarm often appears after replacing a drive or loading parameters from a different model.

Mitsubishi notes that AL.37 is not stored in alarm history, so record it while it is displayed.

AL.45, AL.46, and AL.47 Temperature-Related Alarms

AL.45 means the inside of the amplifier overheated. Check cabinet temperature, mounting clearances, ventilation, dust buildup, and whether nearby components are heating the drive.

The official troubleshooting manual lists an ambient temperature above 55°C as one possible cause for the covered MR-JE models.

AL.46 means the servo motor overheated. Check effective load ratio, motor surface temperature, duty cycle, brake release, acceleration frequency, and mechanical resistance.

AL.47 indicates a cooling fan problem. Remove foreign material if the fan is obstructed. If the fan has reached the end of its service life, the amplifier may need replacement or authorized repair.

AL.50 Overload 1

AL.50 means the load exceeded the amplifier’s overload protection characteristic.

Before increasing motor capacity, check:

• Motor power cable continuity
• U/V/W phase connection
• Electromagnetic brake release
• Mechanical binding
• Effective and peak load ratios
• Acceleration and deceleration times
• Motor-amplifier combination
• Encoder feedback

A brake that remains applied can produce an overload even when the machine has no obvious mechanical jam.

AL.51 Overload 2

AL.51 is more severe. Mitsubishi defines it as maximum output current flowing continuously due to a machine collision or similar condition.

Stop and inspect the mechanics before resetting. Look for a hard stop, jammed slide, seized bearing, locked brake, damaged gearbox, or command that drives the axis past its travel.

If peak torque remains saturated during normal operation, reduce the load, revise the motion profile, or select a correctly sized motor and amplifier.

AL.52 Error Excessive

AL.52 means droop pulses exceeded the alarm level. The commanded position and actual feedback position separated farther than permitted.

Typical causes include:

• Mechanical jam
• Brake not released
• Insufficient torque
• Excessive acceleration
• Incorrect electronic gear
• Incorrect U/V/W connection
• Torque limit set to zero
• External force moving the axis during servo-off

Do not simply increase the error threshold. First determine why the axis cannot follow its command.

AL.8A and AL.8E Communication Alarms

AL.8A is a communication timeout. Depending on the MR-JE model and configuration, it may refer to USB, serial, or Modbus RTU communication.

Check timeout settings, cable continuity, controller state, station address, baud rate, and whether the controller stopped transmitting.

AL.8E indicates a communication receive, checksum, character, command, message-frame, or Modbus CRC error. Intermittent errors usually justify checking shielding, grounding, termination, cable routing, and communication settings before replacing hardware.

MR-JE-B systems may additionally report SSCNET receive alarms such as AL.34 and AL.36, while MR-JE-C systems can report network-related alarms. Diagnose these with the interface-specific manual.

A Reliable MR-JE Troubleshooting Sequence

Use the same sequence each time:

1. Record the complete alarm and detail number.
2. Save alarm history and MR Configurator2 data.
3. Identify whether the fault occurred at power-up, servo-on, acceleration, steady speed, deceleration, or stop.
4. Switch off power and follow the discharge waiting procedure.
5. Inspect the circuit associated with the alarm.
6. Check recent wiring, parameter, motor, controller, and mechanical changes.
7. Correct the cause before resetting.
8. Test at low speed with personnel clear of the machine.
9. Monitor load ratio, bus voltage, speed, current, and feedback during the test.

This sequence prevents a wiring or mechanical problem from being mistaken for a failed amplifier.