Alarm guide · Yaskawa · Updated October 2026
Yaskawa A.100 alarm: Overcurrent or Heat Sink Overheated
Yaskawa A.100 means too much current flowed through the SERVOPACK output, or its heat sink overheated. Causes include a shorted or earthed motor or cable, wiring faults, regenerative resistor problems, heavy loads at low speed, or a failed power stage in the SERVOPACK.
By Suresh Sankaran, founder of Star Automations, servo motor repair since 1998.
What the alarm means
Yaskawa A.100 means too much current flowed through the SERVOPACK output, or its heat sink overheated. Causes include a shorted or earthed motor or cable, wiring faults, regenerative resistor problems, heavy loads at low speed, or a failed power stage in the SERVOPACK.
Safe first checks
General guidance only. Follow the drive manual and your site's electrical safety rules. Power off, and let the DC bus discharge, before touching connectors.
- Power off and wait for the charge lamp to go out.
- Disconnect the motor power cable and test the motor and cable insulation to earth.
- Check the motor phases for a phase-to-phase short.
- Check the cooling fan and heat sink for dust and blockage.
- Check the regenerative resistor wiring.
When to send it for repair
Send the SERVOPACK when the motor and cable test good and the alarm stays. Send the motor too if its insulation is low or a phase is shorted. Drives are repaired at component level and tested with a motor.
See Yaskawa servo motor repair, encoder repair and servo drive repair.
Questions
Can I clear the A.100 alarm and keep running?
Not safely until the cause is found. An overcurrent alarm that clears and returns can damage the drive further or burn the motor. Check the motor and cable first. If they test good and the alarm returns, the drive needs repair.
Is it the motor, the cable or the drive?
Swap with a known-good cable first, then swap the motor to another axis if you can. If the alarm follows the motor, send the motor. If it stays on the axis with a good motor and cable, send the drive. We test both when you are not sure.
How long does repair take?
Emergency repair is done the same day where the fault and parts allow, urgent in 3 working days and standard in 7 working days, counted from when the unit reaches our bench and the quote is approved. Every unit returns with a printed test report.
Can I get an exchange unit?
If we hold a matching unit, Servo Swap ships a tested exchange unit while yours is repaired. Mark "line down" on the request form and add the part number.
Brand names identify the units we repair. Star Automations is an independent multi-brand repair company and is not an OEM service centre.