Alarm guide · Yaskawa · Updated October 2026
Yaskawa A.810 alarm: Encoder Backup Error
Yaskawa A.810 means the absolute encoder lost its backup data. It appears at first power-up, after the encoder cable was disconnected, or when the backup battery or its supply failed. After a battery check and an encoder reset, the axis needs its reference set again.
By Suresh Sankaran, founder of Star Automations, servo motor repair since 1998.
What the alarm means
Yaskawa A.810 means the absolute encoder lost its backup data. It appears at first power-up, after the encoder cable was disconnected, or when the backup battery or its supply failed. After a battery check and an encoder reset, the axis needs its reference set again.
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.
- Check the backup battery voltage and its cable and connector.
- Replace the battery with power on if the manual for your series allows it.
- Reset the absolute encoder as the SERVOPACK manual describes.
- Set the axis reference position again before running the machine.
When to send it for repair
Send the motor when the alarm comes back after a new battery and a reset, or appears without any cable change. The encoder may have an internal fault and is tested, repaired or replaced, then aligned.
See Yaskawa servo motor repair, encoder repair and servo drive repair.
Questions
Can I clear the A.810 alarm and keep running?
You can clear it after a battery check and an encoder reset, but the axis reference must be set again before running. If the alarm returns without a cable change, the encoder may be faulty and the motor should be checked.
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.