What the 4152 alarm means

The main-circuit power relay was detected welded (contacts stuck closed) after a power system overcurrent event; the controller cannot safely disconnect motor power. This is one of the faults our repair team handles on Epson RC90 / RC700 (EPSON RC+) systems — the cause is usually identifiable within the first on-site inspection.

Most common causes

  • Overcurrent event welded the relay contacts
  • Repeated e-stop under heavy load
  • Aging relay
  • Short downstream that the relay interrupted
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. Power down completely and verify with a meter that motor power is actually off
  2. Find and clear the overcurrent cause (short, seized motor, drive fault)
  3. The controller must be replaced (main-circuit relay is internal) — do not keep running with a welded power relay
  4. Inspect downstream wiring for damage from the overcurrent
  5. After replacement, run a full E-stop functional test
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.

Get a Free Remote Diagnosis See Repair Services

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

Related Drive & Power Stage alarms

4154 — Regeneration Resistor Overtemperature 5040 — Motor Torque Output Failure — High Power State 5048 — Overvoltage of Main Power Circuit 5049 — Overcurrent of Motor Driver 5054 — Motor Overload (Duty)
Other brands: we also keep field-fix libraries for Nachi · Omron · ESTUN and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the Epson 4152 alarm mean?

The main-circuit power relay was detected welded (contacts stuck closed) after a power system overcurrent event; the controller cannot safely disconnect motor power. In field practice it belongs to the drive & power stage family of faults.

QCan I clear a Epson 4152 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 Epson documentation or contact us. Henghuan is an independent service provider, not affiliated with or endorsed by Epson.