Alarm guide · Delta · Updated October 2026
Delta AL011 alarm: CN2 communication failed
Delta ASDA AL011 means the drive lost communication with the motor encoder on the CN2 connector. Causes include incorrect or loose CN2 wiring, a damaged encoder cable, interference, a faulty encoder, or a motor not supported by the drive series.
By Suresh Sankaran, founder of Star Automations, servo motor repair since 1998.
What the alarm means
Delta ASDA AL011 means the drive lost communication with the motor encoder on the CN2 connector. Causes include incorrect or loose CN2 wiring, a damaged encoder cable, interference, a faulty encoder, or a motor not supported by the drive series.
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 check the CN2 wiring against the manual.
- Reseat the CN2 connector and the motor-side connector.
- Inspect the cable and connectors for damage.
- Check the motor earth and keep the encoder cable away from power cables.
- Confirm the motor model is supported by the drive.
When to send it for repair
Send the motor when a new cable does not clear the alarm or it follows the motor. The encoder is tested, repaired or replaced and aligned.
See Delta servo motor repair, encoder repair and servo drive repair.
Questions
Can I clear the AL011 alarm and keep running?
A reset may clear it for a while, but a feedback alarm usually comes back until the cable, connector or encoder is fixed. Running with an intermittent feedback fault can stop the axis without warning, so find the cause first.
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.