What the 4154 alarm means

The temperature of the regeneration (braking) resistor exceeded its limit; the controller limits or stops motion to prevent the resistor from burning out. This is one of the most common faults in our repair logs for the Epson RC90 / RC700 (EPSON RC+) platform, and the first inspection typically locates the cause.

Most common causes

  • Robot duty cycle too high for the installed resistor
  • Acceleration/deceleration too aggressive
  • Aging or degraded resistor
  • High ambient temperature around the DPB board
Field note: Field experience says the first cause is the most likely — verify it before moving on to the rest.

Step-by-step field fix

  1. Let the resistor cool and retry
  2. Lengthen waiting time or reduce acceleration values
  3. Lower the overall motion duty
  4. If the alarm persists at normal duty, replace the DPB board/resistor
  5. Check ventilation around the controller
Safety first: For EPSON 4154, this alarm family involves the DC bus, which sits at several hundred volts and stays charged for minutes after power-off - touching terminals is a shock hazard. The self-serviceable action is Let the resistor cool and retry; anything past that falls under the DC bus and power stage and needs a certified engineer. On EPSON 4154: checking incoming voltage at the disconnect and looking at breakers and fuses is fine to do yourself; opening the cabinet to touch bus terminals or pulling power modules needs a qualified electrician.

How we diagnose drive alarms on site

EPSON 4154 belongs to the drive & power stage family. On EPSON 4154 the failing stage is drive units integrated in the controller cabinet, per axis on the RC700-A / RC90-B and the RC series - the fault sits on the energy chain: mains input, rectification, DC bus, braking resistor, inverter power devices and the drive board. We start reading EPSON 4154 at the EPSON RC+ error list and controller front-panel indicators; codes segment as 4xxx / 5xxx / 9xxx.

The chain involved in EPSON 4154 runs: three-phase mains -> rectifier -> DC bus (bus capacitors) -> brake chopper / braking resistor -> inverter (IGBT) -> motor.

When EPSON 4154 fires, the site usually reports Robot duty cycle too high for the installed resistor first, but the real cause is often cooling: More than half of power-stage alarms are not a dead device but a device cooked by failed cooling. A stopped cabinet fan, a packed filter mat or a dusted air duct keeps IGBT junction temperature high: intermittent over-temperature first, hard fault days later. On these alarms we open the power module and look for cracked thermal paste and felted dust in the duct, then measure phase-to-phase output and insulation to frame. Swapping the module without cleaning the duct just buys the same failure again.

Field notes on this page cover EPSON 4154 (Regeneration Resistor Overtemperature); written by the Henghuan repair team, updated 2026-10-01.

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Related Drive & Power Stage alarms

4152 — Relay Welding Error of Main Circuit 5040 — Motor Torque Output Failure — High Power State 5048 — Overvoltage of Main Power Circuit 5049 — Overcurrent of Motor Driver 5054 — Motor Overload (Duty)
Same family: this code belongs to the Drive & power stage alarms family - the page collects all Drive & power stage-family codes we have handled, with the common inspection order and spares.
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 4154 alarm mean?

The temperature of the regeneration (braking) resistor exceeded its limit; the controller limits or stops motion to prevent the resistor from burning out. This is one of the most common faults in our repair logs for the Epson RC90 / RC700 (EPSON RC+) platform, and the first inspection typically locates the cause. EPSON 4154 sits in the drive & power stage family; on our work orders the highest-frequency trigger for this code is "Robot duty cycle too high for the installed resistor".

QCan I clear a EPSON 4154 alarm myself?

Whether EPSON 4154 clears on its own depends on the outcome of "Let the resistor cool and retry". Finish the flow with "Check ventilation around the controller" to confirm EPSON 4154 - do not skip it. If that step is clean, the second most frequent cause on EPSON 4154 is "Acceleration/deceleration too aggressive". Do not chase takt through a repeating EPSON 4154. Left alone, drive & power stage faults tend to graduate from repairable to must-replace.

QFor drive/power alarms like EPSON 4154, what spares do you bring on site?

The commonest causes we see on EPSON 4154 are "Robot duty cycle too high for the installed resistor, Acceleration/deceleration too aggressive, Aging or degraded resistor", so we stock the van against those. For EPSON 4154 specifically, we stock the van along the energy chain: braking resistors, bus capacitors, input fuses, drive-board supply parts and the common power modules for the brand. For EPSON 4154, drive alarms usually stop the whole line, so they sit at the front of our dispatch queue. Before we roll, tell us what EPSON 4154 shows on the EPSON RC+ error list and controller front-panel indicators; codes segment as 4xxx / 5xxx / 9xxx and what the machine was doing - phone or video triage is free.

The content on EPSON 4154 was written by Henghuan Robotics service engineers from hands-on repair experience. Alarm descriptions are our own reference summary and may differ by controller or software version — defer to Epson documentation, or contact us to confirm. Henghuan is an independent service provider with no affiliation or endorsement by Epson.