J
Over-heat of Resistor Module (ECM)
Fanuc · Alpha i Series AC Servo Motor and Spindle
What does J mean?
The Resistor Module has detected an abnormal temperature, indicating overheating. This is typically detected by a built-in thermostat.
Common Causes
- The temperature of the braking resistor module has exceeded its safe operating limit.
- Braking resistor is continuously subjected to high power dissipation.
- Inadequate cooling or ventilation of the braking resistor assembly.
- Faulty temperature sensor within the braking resistor module.
- Overload condition causing excessive regenerative energy.
Repair Steps & Checklist
Click steps to track your progress.
- 1
Check for blockages to airflow around the Resistor Module.
- 2
Verify the operation of any cooling fans associated with the Resistor Module.
- 3
Ensure the discharge duty cycle is within specifications; excessive regeneration can cause overheating.
Verified technical data. Last updated: March 2026
Related Faults
Source: Fanuc Alpha i Series AC Servo Motor and Spindle