What the A.71 alarm means

The motor delivered torque far above rating for several seconds; the ESTUN drive treats this as a stall and trips. We have built up many handled cases of this ESTUN ERC / ED3L controller + ESTUN servo alarm, and usually the first on-site inspection tells us what is wrong.

Most common causes

  • Robot collided with a fixture or workpiece
  • Mechanical binding: damaged reducer, seized bearing
  • Axis brake not releasing
  • Motor or encoder wiring fault making the drive fight itself
Field note: Confirm or rule out the first cause first — it is the situation we encounter most.

Step-by-step field fix

  1. Jog the robot off the interference in teach mode and inspect the mechanical path
  2. Verify the holding brake releases when the axis is enabled
  3. Check motor and encoder cable continuity
  4. Confirm payload and speed are within the robot's rated envelope
  5. Swap-test motor and drive if mechanical causes are ruled out
Safety first: For ESTUN a-71, 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. On site you may not carry out the first step yourself: Jog the robot off the interference in teach mode and inspect the mechanical path. Beyond that it is the DC bus and power stage work - leave it to a professional. On ESTUN a-71: 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

ESTUN a-71 belongs to the drive & power stage family. On ESTUN a-71 the failing stage is matched servo drives (in-house / Inovance-class servos) on the ESTUN robot controllers (motion-control-platform based) - the fault sits on the energy chain: mains input, rectification, DC bus, braking resistor, inverter power devices and the drive board. We start reading ESTUN a-71 at the pendant alarm list (A.xxx / E.xxx segments) and the servo panel display code.

The chain involved in ESTUN a-71 runs: three-phase mains -> rectifier -> DC bus (bus capacitors) -> brake chopper / braking resistor -> inverter (IGBT) -> motor.

When ESTUN a-71 fires, the site usually reports Robot collided with a fixture or workpiece 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 ESTUN a-71 (Overload — Instantaneous High Load); written by the Henghuan repair team, updated 2026-10-01.

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Related Drive & Power Stage alarms

A.02 — Parameter Setting Error A.10 — Overcurrent A.30 — Regeneration Error / Regenerative Overload A.40 — Main Circuit Overvoltage A.41 — Main Circuit Undervoltage A.72 — Overload — Continuous Over-torque
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 INOVANCE · EFORT · JAKA and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the ESTUN a-71 alarm mean?

The motor delivered torque far above rating for several seconds; the ESTUN drive treats this as a stall and trips. We have built up many handled cases of this ESTUN ERC / ED3L controller + ESTUN servo alarm, and usually the first on-site inspection tells us what is wrong. ESTUN a-71 sits in the drive & power stage family; on our work orders the highest-frequency trigger for this code is "Robot collided with a fixture or workpiece".

QCan I clear a ESTUN a-71 alarm myself?

Whether ESTUN a-71 clears on its own depends on the outcome of "Jog the robot off the interference in teach mode and inspect the mechanical path". Finish the flow with "Swap-test motor and drive if mechanical causes are ruled out" to confirm ESTUN a-71 - do not skip it. If that step is clean, the second most frequent cause on ESTUN a-71 is "Mechanical binding: damaged reducer, seized bearing". When ESTUN a-71 keeps coming back it is not a one-off trigger - especially if Swap-test motor and drive if mechanical causes are ruled out is where you get stuck. Do not keep producing through ESTUN a-71.

QFor drive/power alarms like ESTUN a-71, what spares do you bring on site?

The commonest causes we see on ESTUN a-71 are "Robot collided with a fixture or workpiece, Mechanical binding: damaged reducer, seized bearing, Axis brake not releasing", so we stock the van against those. For ESTUN a-71 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 ESTUN a-71, drive alarms usually stop the whole line, so they sit at the front of our dispatch queue. Before we roll, tell us what ESTUN a-71 shows on the pendant alarm list (A.xxx / E.xxx segments) and the servo panel display code and what the machine was doing - phone or video triage is free.

The notes on ESTUN a-71 were summarized by the Henghuan Robotics repair team from on-site service. The alarm interpretation is our empirical summary for troubleshooting reference and may vary by controller and software version — please check ESTUN documentation or contact us with questions. Henghuan is an independent service provider, not affiliated with or endorsed by ESTUN.