What causes FANUC alarm 429?

Continuous heavy cutting or sustained high axis load without adequate thermal recovery time. Servo motor cooling fan failure — motor not dissipating heat adequately. Mechanical axis binding causing above-rated current and heat generation in the motor. Ambient temperature in the machine enclosure above the rated limit for the servo motor. Motor thermistor or temperature sensor fault triggering a false overheat reading. Servo drive current limits set too high allowing sustained overcurrent and motor heating.

How do I fix FANUC alarm 429?

1. Allow the servo motor to cool for at least 30 minutes before clearing the alarm. 2. Check the motor body for abnormal heat and listen for unusual bearing noise. 3. Check the servo motor cooling fan if the motor has a dedicated external fan. 4. Manually move the axis with servo power off to check for mechanical binding. 5. Monitor servo load percentage during a light-duty cycle after cooldown — sustained high load indicates overloading. 6. If the alarm triggers without load on a cold motor, suspect the motor thermistor.

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FANUC Controller

Overheat/Thermal · Intermediate · 30-60 minutes

Alarm 429

Fanuc Alarm 429 - SERVO ALARM: n AXIS SERVO MOTOR OVERHEAT

Fanuc Alarm 429 indicates the servo motor temperature has exceeded the thermal threshold monitored by the thermistor embedded in the motor windings. The amplifier receives temperature feedback through the motor power cable and triggers this alarm when parameter-defined limits are exceeded, protecting the motor from thermal damage.

FANUCOverheat/ThermalIntermediate30-60 minutes

429

Fanuc Alarm 429 - SERVO ALARM: n AXIS SERVO MOTOR OVERHEAT

SERVO ALARM: n AXIS SERVO MOTOR OVERHEAT

Root Cause Summary

Fanuc Alarm 429 indicates the servo motor temperature has exceeded the thermal threshold monitored by the thermistor embedded in the motor windings. The amplifier receives temperature feedback through the motor power cable and triggers this alarm when parameter-defined limits are exceeded, protecting the motor from thermal damage.

Causes and Fixes

1
Navigate to DIAGNOSIS > SERVO > SERVO MONITOR and observe parameter 300 (current load meter) for the affected axis during operation. Values consistently above 80% indicate overload conditions.
2
Check servo parameters 2020-2023 (position loop gain), 2034-2037 (velocity loop gain), and 2041-2044 (current limit) for the affected axis. Compare against Fanuc recommended values in the servo motor specification manual for your motor model.
3
Review part program for excessive rapid traverse rates (G00) or feed rates (G01) causing continuous high current demand. Reduce acceleration parameter 1620-1623 (rapid traverse acceleration) by 20-30% and retest.
Reducing acceleration will increase cycle time but may be necessary for thermal management
4
Verify motor specification matches application requirements using MAINTENANCE > SERVO > SERVO SPEC screen. Check rated torque vs actual load using diagnostic 300 and consider motor upgrade if undersized.

DIY Feasiblehigh confidence

Call a technician if:

·Motor thermistor replacement required
·Servo amplifier internal failure suspected
·Repeated alarms after cooling system repair

Prevention

Implement regular cooling system maintenance schedule
Monitor servo load percentages during program optimization
Install temperature monitoring in electrical cabinet
Use appropriate acceleration parameters for application

Common Mistakes

Ignoring gradual temperature increase before alarm
Cleaning motor while hot causing thermal shock
Adjusting parameter 2024 instead of fixing root cause
Operating with blocked cooling assuming short-term use is acceptable

Related Alarms

414 415 430 431

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