What the 26111 alarm means

The KSP heat-sink temperature exceeded its limit; the drive derates or stops to protect the power stage. Our engineers run into this alarm every week on KUKA KRC2 / KRC4 / KRC5 (KSS) controllers, and a single on-site inspection usually identifies the problem.

Most common causes

  • Cabinet cooling fan failure or clogged filters
  • High ambient temperature
  • Sustained overloading of the axis
  • Degraded thermal interface or fan inside the KSP
Field note: In our repair stats the first cause has the highest hit rate, so confirm it first before digging further.

Step-by-step field fix

  1. Check cabinet fans and clean or replace the filters
  2. Verify cabinet cooling or ventilation is working
  3. Review the program for sustained peak loads on the axis
  4. Let the drive cool and retry; replace the KSP if overtemp recurs in normal duty
Safety first: For KUKA 26111, 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: Check cabinet fans and clean or replace the filters. Beyond that it is the DC bus and power stage work - leave it to a professional. On KUKA 26111: 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

KUKA 26111 belongs to the drive & power stage family. On KUKA 26111 the failing stage is KPP power packs and KSP servo packs (next-generation drive modules on KRC5) on the KRC2 / KRC4 / KRC5 - the fault sits on the energy chain: mains input, rectification, DC bus, braking resistor, inverter power devices and the drive board. We start reading KUKA 26111 at the smartPAD message window (KSS message numbers: 1xxx operator, 2xxxx drive) with KPP/KSP module LEDs.

The chain involved in KUKA 26111 runs: three-phase mains -> rectifier -> DC bus (bus capacitors) -> brake chopper / braking resistor -> inverter (IGBT) -> motor.

Bottom line up front: Cabinet cooling fan failure or clogged filters is the first suspect for KUKA 26111, but read it along the energy chain: Any link on this chain dropping voltage shows up at the end as a drive alarm, so order matters. We measure the mains first: more than 3% phase imbalance is enough to sag the bus under load, and plenty of bus over/under-voltage alarms are actually a grid problem wearing a robot costume. Mains fine, then the bus capacitors - bulged cases, weeping electrolyte or a lifted vent mean replacement; capacitance down 20% or more cannot hold the bus during braking. Last, the braking resistor: healthy values sit in the tens of ohms depending on rating, and an open or drifted resistor trips regenerative overvoltage directly.

Field notes on this page cover KUKA 26111 (KSP Device Overtemperature (Axis N)); written by the Henghuan repair team, updated 2026-10-01.

Stalled on the diagnosis? Let an engineer help remotely

Share the alarm code, machine model and the operating condition at the moment of the alarm. Our engineers are highly experienced with KUKA 26111, and remote diagnosis (phone/video) is completely free.

Get a Free Remote Diagnosis See Repair Services

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

Related Drive & Power Stage alarms

12005 — Ballast Resistor Temperature Sensor — Wire Disconnection 26012 — General Servo Error (Drive N) 26013 — General Inverter Failure (Drive N) 26107 — KSP DC Link Overvoltage (Axis N) 26108 — KSP DC Link Undervoltage (Axis N) 26122 — KSP Braking Resistor Fault (Axis N)
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 ABB · Yaskawa · Universal Robots and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the KUKA 26111 alarm mean?

The KSP heat-sink temperature exceeded its limit; the drive derates or stops to protect the power stage. Our engineers run into this alarm every week on KUKA KRC2 / KRC4 / KRC5 (KSS) controllers, and a single on-site inspection usually identifies the problem. KUKA 26111 sits in the drive & power stage family; on our work orders the highest-frequency trigger for this code is "Cabinet cooling fan failure or clogged filters".

QCan I clear a KUKA 26111 alarm myself?

Whether KUKA 26111 clears on its own depends on the outcome of "Check cabinet fans and clean or replace the filters". Finish the flow with "Let the drive cool and retry; replace the KSP if overtemp recurs in normal duty" to confirm KUKA 26111 - do not skip it. If that step is clean, the second most frequent cause on KUKA 26111 is "High ambient temperature". When KUKA 26111 keeps coming back it is not a one-off trigger - especially if Let the drive cool and retry; replace the KSP if overtemp recurs in normal duty is where you get stuck. Do not keep producing through KUKA 26111.

QFor drive/power alarms like KUKA 26111, what spares do you bring on site?

The commonest causes we see on KUKA 26111 are "Cabinet cooling fan failure or clogged filters, High ambient temperature, Sustained overloading of the axis", so we stock the van against those. For KUKA 26111 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 KUKA 26111, drive alarms usually stop the whole line, so they sit at the front of our dispatch queue. Before we roll, tell us what KUKA 26111 shows on the smartPAD message window (KSS message numbers: 1xxx operator, 2xxxx drive) with KPP/KSP module LEDs and what the machine was doing - phone or video triage is free.

This page on KUKA 26111 is based on the field experience of the Henghuan Robotics repair team. Alarm explanations are our own summary for troubleshooting reference and may differ across controller and software versions — if unsure, verify against KUKA documentation or reach out to us. Henghuan is an independent service provider with no affiliation or endorsement by KUKA.