8

Low-voltage of Capacitor Module (ECM)

Fanuc · Macro B CNC Programming

What does 8 mean?

A low-voltage condition has occurred in the Energy Charge Module's Capacitor Modules. This indicates that the capacitor bank is not sufficiently charged or is discharging too rapidly, potentially due to a power supply issue, excessive load on the ECM, or a faulty capacitor module.

Common Causes

  • Low voltage detected on the capacitor module (ECM) below P1-75 threshold.
  • Inadequate power supply to the ECM.
  • Capacitor module (ECM) internal fault causing voltage drop.
  • External load drawing excessive current, reducing ECM voltage.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Immediately stop the machine using the emergency stop button and open the external Main Circuit Contactor (MCC) of the Power supply.

  2. 2

    Measure the voltage across the Capacitor Modules (A06B-6158-H020) to confirm the low-voltage condition.

  3. 3

    Verify the input power supply to the ECM for stable voltage and adequate current to properly charge the capacitors.

  4. 4

    Check for any abnormal load connected to the ECM that could cause rapid discharge of the Capacitor Modules.

  5. 5

    Inspect the Capacitor Modules (A06B-6158-H020) for internal faults, such as leakage or degradation, that prevent them from holding charge.

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Verified technical data. Last updated: March 2026

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Source: Fanuc Macro B CNC Programming