What the 12005 alarm means

The temperature sensor circuit of the regenerative ballast (braking) resistor reads open, so the controller cannot verify braking resistor health and may limit or stop motion. 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

  • Sensor wire disconnected at the CCU or at the resistor
  • Broken temperature sensor
  • Wrong plug position on the CCU
  • Genuine resistor overheat after a high-duty cycle
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. Let the resistor cool, then check the sensor connector at the CCU and at the resistor
  2. Reseat or repair the sensor wiring
  3. Measure the sensor resistance and replace it if open
  4. Verify the cell duty cycle is not forcing continuous regeneration
Safety first: For KUKA 12005, 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. What you can check yourself first is Let the resistor cool, then check the sensor connector at the CCU and at the resistor; the DC bus and power stage handling is not a DIY job. On KUKA 12005: 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 12005 belongs to the drive & power stage family. On KUKA 12005 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 12005 at the smartPAD message window (KSS message numbers: 1xxx operator, 2xxxx drive) with KPP/KSP module LEDs.

The chain involved in KUKA 12005 runs: three-phase mains -> rectifier -> DC bus (bus capacitors) -> brake chopper / braking resistor -> inverter (IGBT) -> motor.

Sensor wire disconnected at the CCU or at the resistor is common on KUKA 12005, but look at the duty cycle: Cells with high-inertia loads or frequent start-stop cycles return far more regenerative energy than a plain transfer cell, and the braking resistor lives in a hot cycle that shortens its life. When we suspect this family we ask what changed: if the takt was raised recently or a heavier fixture went on, the alarm cluster usually lines up with that process change. Replacing the resistor alone will not fix it - the chopper rating and resistor wattage have to be re-checked against the new duty.

Field notes on this page cover KUKA 12005 (Ballast Resistor Temperature Sensor — Wire Disconnection); written by the Henghuan repair team, updated 2026-10-01.

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Related Drive & Power Stage alarms

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) 26111 — KSP Device Overtemperature (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 12005 alarm mean?

The temperature sensor circuit of the regenerative ballast (braking) resistor reads open, so the controller cannot verify braking resistor health and may limit or stop motion. 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 12005 sits in the drive & power stage family; on our work orders the highest-frequency trigger for this code is "Sensor wire disconnected at the CCU or at the resistor".

QCan I clear a KUKA 12005 alarm myself?

Whether KUKA 12005 clears on its own depends on the outcome of "Let the resistor cool, then check the sensor connector at the CCU and at the resistor". Finish the flow with "Verify the cell duty cycle is not forcing continuous regeneration" to confirm KUKA 12005 - do not skip it. If that step is clean, the second most frequent cause on KUKA 12005 is "Broken temperature sensor". Do not chase takt through a repeating KUKA 12005. Left alone, drive & power stage faults tend to graduate from repairable to must-replace.

QFor drive/power alarms like KUKA 12005, what spares do you bring on site?

The commonest causes we see on KUKA 12005 are "Sensor wire disconnected at the CCU or at the resistor, Broken temperature sensor, Wrong plug position on the CCU", so we stock the van against those. For KUKA 12005 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 12005, drive alarms usually stop the whole line, so they sit at the front of our dispatch queue. Before we roll, tell us what KUKA 12005 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 12005 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.