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ErrorLib — Industrial Fault Code Library

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OH4

Heatsink overtemperature (C0122)

Lenze · 9300 Series

What does OH4 mean?

The heatsink temperature has exceeded the threshold set in C0122. Causes include ambient temperatures above +40°C or +50°C, a dirty heatsink, an incorrect mounting position, or the value specified under C0122 being set too low.

Common Causes

  • Heatsink temperature (C0122) has exceeded its critical limit, potentially leading to power module failure.
  • Inadequate airflow or blocked heatsink fins on the drive's power module.
  • High ambient temperature combined with heavy drive load.
  • Cooling fan for the heatsink is not functioning.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Allow the module to cool and ensure better ventilation within the control cabinet.

  2. 2

    Check the ambient temperature in the control cabinet.

  3. 3

    Clean the heatsink if it is very dirty to improve heat dissipation.

  4. 4

    Change the mounting position if it is hindering airflow.

  5. 5

    Enter a higher value under C0122 if the threshold is set too low.

  6. 6

    Switch off monitoring by setting C0582 = 3.

Browse all codes in this manual (145)
Verified technical data. Last updated: April 2026

Related Faults

0011OC1 Overcurrent in motor cable0012OC2 Motor cable earth fault0013OC3 Overload during acceleration
Source: Lenze 9300 Series
Open Manual (Page 327)Search more codes in this manual