What the EStopChain alarm means

The CS8/CS9 safety chain (category-1 stop loop) is open, so drive power is blocked. On CS9 the DC bus pre-charge will not complete while the chain is open. This is one of the faults our repair team handles on Staubli CS8 / CS9 (VAL3) systems — the cause is usually identifiable within the first on-site inspection.

Most common causes

  • E-stop button pressed (pendant, cabinet or cell)
  • Safety gate switch open
  • Jumper plug missing from the safety chain after maintenance
  • Faulty safety relay output
Field note: the first item on this list is what we find most often on real machines. Check it before you go deeper.

Step-by-step field fix

  1. Release all E-stops and close all gates
  2. Trace the safety loop with the wiring diagram, including external devices
  3. Verify the maintenance plug / jumpers are seated
  4. Check safety relay LEDs
  5. Power-cycle after closing the chain and retry enabling power
Safety first: never bypass safety circuits or force contactors closed. If the alarm involves E-stop chains, brakes or drive power, and you are not a trained robot technician, contact a professional — wrong moves here can cost you a robot or an injury.

Still stuck? Get an engineer on the phone — right now

Tell us the alarm code, the robot model and what was happening when the alarm came up. Our engineers run these diagnostics every day, and remote diagnosis by phone or video call is free.

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Hotline: +86-20-39029800 · WhatsApp: +86-188-1886-2860

Related Safety Chain & E-Stop alarms

ArmPowerRefused — Arm Power Enable Request Refused
Other brands: we also keep field-fix libraries for Epson · Nachi · Omron and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the Staubli EStopChain alarm mean?

The CS8/CS9 safety chain (category-1 stop loop) is open, so drive power is blocked. On CS9 the DC bus pre-charge will not complete while the chain is open. In field practice it belongs to the safety chain & e-stop family of faults.

QCan I clear a Staubli EStopChain alarm myself?

Sometimes. Work through the step-by-step checks on this page — the first listed cause is what we find most often in the field. If the alarm returns after two attempts, or the fault involves power, brakes or safety circuits, stop and call a qualified robot service engineer.

QHow fast can a Henghuan engineer help?

On-site response in the Pearl River Delta within 30 minutes to 3 hours, across mainland China in 1-3 business days, and worldwide within 2-5 business days. Remote diagnosis by phone/WhatsApp/video is available immediately.

Written by the Henghuan Robotics repair team from field service experience. Alarm descriptions are our own summary for troubleshooting reference and may vary by controller and software version — when in doubt, check your Staubli documentation or contact us. Henghuan is an independent service provider, not affiliated with or endorsed by Staubli.