When a VFD Error Means Hardware Service Is Required

Most VFD errors are protective and recoverable. They exist to stop damage before it happens.

However, a small number of errors indicate that the VFD itself may have experienced an internal fault. When this happens, further troubleshooting or repeated resets can make the situation worse.

This article explains how to recognize those cases early and what to do next.

Two Categories of VFD Errors

All VFD errors fall into one of two categories:

1. User-Fixable / Configuration-Related

These are caused by:

Power quality issues
Aggressive acceleration settings
Load conditions
Wiring mistakes external to the VFD

These errors usually clear once the underlying cause is corrected.

2. Internal Hardware-Related

These indicate a failure or abnormal condition inside the VFD.

When these occur, continued operation or repeated resets can:

Damage internal components
Cause cascading failures
Turn a recoverable issue into a permanent one

Errors That Require Hardware-Level Attention

If you encounter any of the following errors, stop troubleshooting and contact support.

ERR31 – Current Detection Fault

What it means:
The VFD’s internal current-sensing circuitry is reporting abnormal behavior.

Why this matters:
Current detection is a core safety system. When it fails, the VFD can no longer reliably monitor motor load.

Do not:

Repeatedly reset and retry
Continue running under load

ERR33 – Abnormal Current Detection

What it means:
The VFD is receiving invalid or inconsistent current feedback from its sensing hardware.

Common causes:

Internal driver board issues
Hall sensor malfunction

Important:
This is not caused by spindle load or cutting parameters.

ERR37 – Driving Power Supply Fault

What it means:
The internal power supply that drives the VFD’s control electronics is unstable or failed.

Why this is serious:
The VFD cannot safely control output power when its internal supply is compromised.

ERR26 – Parameter Read-Write Abnormality

What it means:
The VFD’s non-volatile memory (EEPROM) cannot reliably store or retrieve parameters.

Symptoms may include:

Parameters not saving
Random resets
Inconsistent behavior after power cycling

This is an internal memory fault.

Why Continued Troubleshooting Can Make Things Worse

When hardware-level faults occur:

The VFD may no longer correctly protect itself
Repeated resets can stress damaged components
Running under load can cause permanent failure

At this point, more testing is not safer testing.

Stopping early preserves the best chance of recovery.

What You Should Do Instead

If you encounter ERR31, ERR33, ERR37, or ERR26:

Power the system down
Do not continue cutting or jogging
Do not repeatedly reset the fault
Contact support with the error code and context

📩 [email protected]

Include:

Error code shown
When it occurred
Whether it repeats immediately
Any recent wiring or power changes

What This Article Is Not Saying

This does not mean:

You caused the failure
Your spindle is bad
Your setup was careless

Electronic components can fail, and protective systems exist to limit damage when they do.

Recognizing when an error crosses from “configuration issue” into “service required” is part of using industrial electronics responsibly.

Key Takeaway

Some errors are warnings.
Some errors are boundaries.

Knowing the difference protects your equipment — and your time.

If an error indicates internal hardware failure, stopping early is the correct decision.