What the E0042 alarm means

The motor temperature sensor reports an over-temperature condition. This is one of the most common faults in our repair logs for the Nachi AW / FD series platform, and the first inspection typically locates the cause.

Most common causes

  • Sustained overload
  • Poor cooling/ventilation
  • High ambient temperature
  • Faulty temperature sensor
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. Reduce the duty and load
  2. Improve ventilation
  3. Check ambient temperature
  4. Verify the temperature sensor reading
  5. Let the motor cool before restarting
Safety first: For NACHI e0042, 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 Reduce the duty and load; the DC bus and power stage handling is not a DIY job. On NACHI e0042: 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

NACHI e0042 belongs to the drive & power stage family. On NACHI e0042 the failing stage is servo amplifier modules in the cabinet, assigned per axis on the AX-series / FD-series controllers - the fault sits on the energy chain: mains input, rectification, DC bus, braking resistor, inverter power devices and the drive board. We start reading NACHI e0042 at the pendant error-code screen (E-series codes) with amplifier panel indicators.

The chain involved in NACHI e0042 runs: three-phase mains -> rectifier -> DC bus (bus capacitors) -> brake chopper / braking resistor -> inverter (IGBT) -> motor.

Bottom line up front: Sustained overload is the first suspect for NACHI e0042, 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 NACHI e0042 (Motor Temperature Rise Abnormal); written by the Henghuan repair team, updated 2026-10-01.

Can't clear it yourself? Contact us for remote diagnosis

Just tell us the alarm code, the robot model and which program was running, and our engineers will help you narrow it down — phone and video remote diagnosis are both free.

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Related Drive & Power Stage alarms

E0028 — Motor Power Voltage Drop E0032 — Overcurrent E0038 — Overload E0044 — Motor Power Overvoltage
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 Omron · ESTUN · INOVANCE and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the NACHI e0042 alarm mean?

The motor temperature sensor reports an over-temperature condition. This is one of the most common faults in our repair logs for the Nachi AW / FD series platform, and the first inspection typically locates the cause. NACHI e0042 sits in the drive & power stage family; on our work orders the highest-frequency trigger for this code is "Sustained overload".

QCan I clear a NACHI e0042 alarm myself?

Whether NACHI e0042 clears on its own depends on the outcome of "Reduce the duty and load". Finish the flow with "Let the motor cool before restarting" to confirm NACHI e0042 - do not skip it. If that step is clean, the second most frequent cause on NACHI e0042 is "Poor cooling/ventilation". When NACHI e0042 keeps coming back it is not a one-off trigger - especially if Let the motor cool before restarting is where you get stuck. Do not keep producing through NACHI e0042.

QFor drive/power alarms like NACHI e0042, what spares do you bring on site?

The commonest causes we see on NACHI e0042 are "Sustained overload, Poor cooling/ventilation, High ambient temperature", so we stock the van against those. For NACHI e0042 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 NACHI e0042, drive alarms usually stop the whole line, so they sit at the front of our dispatch queue. Before we roll, tell us what NACHI e0042 shows on the pendant error-code screen (E-series codes) with amplifier panel indicators and what the machine was doing - phone or video triage is free.

The content on NACHI e0042 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 Nachi documentation, or contact us to confirm. Henghuan is an independent service provider with no affiliation or endorsement by Nachi.