Yaskawa A1000 oL5 Fault — What It Means
The oL5 fault on a Yaskawa A1000 VFD is identified as Mechanical Weakening Detection 1. It trips when the drive detects an overtorque condition that matches the threshold and timing defined in parameter L6-08. In plain terms, the motor or load exceeded the configured torque-monitoring limit long enough to activate the protection logic.
This fault is primarily a mechanical or process signal, not a drive component failure. The VFD is telling you that something in the driven machine increased torque demand beyond the normal operating envelope set in the drive’s configuration.
Before You Replace Anything
Technicians sometimes replace the VFD itself without inspecting the mechanical load. Always inspect the motor, coupling, gearbox, bearings, and driven machine for binding or damage before assuming a drive electronics problem.
Common Causes
- Mechanical binding or seized components (~50%) Seized bearings, jammed gearbox, tight couplings, stuck conveyor, or any mechanical obstruction raises torque demand and triggers the overtorque detection.
- Incorrect torque-monitoring parameter (~25%) Parameter L6-08 may be set too sensitively for the application, causing nuisance trips during normal operation.
- Process conditions raising torque (~15%) High acceleration demand, frequent starts and stops, or abnormal load cycles can push torque high enough to exceed the detection threshold.
- Motor or coupling train mechanical damage (~10%) Worn motor bearings, misaligned coupling, or abnormal drag in the mechanical train increases the torque required to turn the load.
Quick Diagnosis
Answer these to narrow it down fast.
Does the driven machine turn freely by hand when the motor is disconnected?
No: You have a mechanical problem. Inspect bearings, couplings, gearbox, and the driven load for binding, jamming, or seized components before clearing the fault.
Does the fault trip during the same part of the machine cycle every time?
No: The fault may be random or tied to process variation. Review load size, cycle timing, and parameter L6-08 for proper tuning.
Has the machine or process recently changed (new product, faster cycle, heavier load)?
No: The fault is likely due to new mechanical wear or failure. Inspect motor, coupling, bearings, and driven equipment for wear or damage.
Step-by-Step Fix
- Record the fault and operating conditions. Note what the machine was doing when oL5 tripped, including load state, speed, acceleration, and whether the fault repeats at the same point in the cycle.
- Inspect the driven machine mechanically. Check for binding, jammed product, seized bearings, gearbox problems, misaligned couplings, and excessive friction in the load train.
- Review parameter L6-08. Access the drive parameters via the keypad or programming software and verify that the overtorque detection threshold and timing are appropriate for normal machine operation and not set too low.
- Check the load profile and motion settings. Review acceleration and deceleration times, load size, and cycle timing to confirm the machine is not demanding excessive torque during normal operation.
- Verify motor and mechanical health. If the mechanical load appears normal but trips persist, inspect the motor for abnormal drag, check coupling alignment, and test motor bearings for wear or noise.
- Clear the fault and retest. After correcting the mechanical issue or adjusting L6-08, reset the fault from the drive keypad and run the machine through a normal cycle to confirm the repair.
- Monitor for recurrence. If the fault returns, the mechanical repair was incomplete or the parameter setting still does not match the real load demand. Repeat inspection and consider a load study or torque measurement.
Parts Often Needed
| Part | Notes |
|---|---|
| Motor bearings | Amazon | Replace if seized, noisy, or dragging during manual rotation. |
| Coupling | Amazon | Replace if misaligned, worn, or damaged. Match type and size to your motor and load shaft. |
| Gearbox or reducer | Amazon | Repair or replace if internal gears are jammed, worn, or binding. |
When to Call a Pro
Call a qualified electrician or automation technician if you are not trained to work with VFD parameters, motor circuits, or mechanical drive systems. Adjusting L6-08 incorrectly can disable important protection or cause repeated nuisance faults. Mechanical inspection of gearboxes, bearings, and couplings often requires lockout/tagout, alignment tools, and experience with rotating equipment. If the fault persists after basic mechanical checks and you lack the tools or training to measure torque, inspect internal drive components, or tune advanced motor-control parameters, professional diagnostics are the safest and most cost-effective path.
Rough cost: A pro service call runs about $200-800.