Fault diagnosis

What the flashing code on your panel means

5 codes the manufacturers actually document, each with its causes and its diagnostic procedure. We would rather have five sheets that help than forty that repeat "check the wiring".

F004

Allen-Bradley PowerFlex 525

The PowerFlex 525 drive shows F004 when the DC bus drops below its threshold. What causes it, how to tell a supply problem from a drive problem and what to measure.

oc

Delta MS300

The MS300 splits overcurrent by whether it happens during acceleration, deceleration or steady running. What each variant means and what to look for in motor, cable and load.

ERR/ALM

Omron CP1E

The CP1E lights ERR/ALM solid for a fatal error and flashing for a non-fatal one. How to separate the two, where to read the code and what to check in each case.

OBF

Schneider Electric Altivar ATV320

OBF on the ATV320 means DC bus overvoltage during deceleration. How it relates to the ramp, load inertia and the braking resistor, and how to correct it.

Red ERROR LED

Siemens S7-1200

The S7-1200 ERROR LED solid or flashing red. How to tell the two apart, how to read the diagnostic buffer and what to check before replacing the CPU.

Before you reset

Turn the code into a safe, repeatable check

A fault code identifies the condition the equipment detected; it does not replace lockout procedures, electrical inspection or the manufacturer manual. Use it to narrow the check, and record what changed before re-energizing.

If the alarm comes back, keep the code, the time, the affected unit and the process variables. That context separates an isolated fault from a pattern of supply, overload, communication or configuration problems.

  1. 1

    Make it safe

    Apply your plant safety procedure before working on the panel or the machine.

  2. 2

    Confirm the context

    Check the exact code, the model and the events right before the stop.

  3. 3

    Verify and document

    After fixing the cause, test operation and leave a record for the next shift.

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