IndustrialDriveDataDrive Board & Diagnostic Database
Danfoss fault record

Alarm 29: Heatsink Temperature Fault

The VLT trips on alarm 29 during load, in high ambient temperature, or after cooling airflow has degraded.

Meaning of the indication

The drive heatsink temperature has exceeded the allowed limit or the temperature feedback/cooling path is not credible.

Checking order

  1. Inspect fan operation, airflow direction and blocked filters.
  2. Check heatsink contamination and cabinet ventilation.
  3. Compare load current with drive rating and derating conditions.
  4. Record ambient temperature and enclosure condition.
  5. If cold-start alarm 29 appears, consider sensor feedback or control-board evidence after safe isolation.

Suspect areas

Cooling fanBlocked heatsinkCabinet ventilationOverloadTemperature sensorControl electronics
Fault-specific caution

Do not bypass thermal protection; repeated overheating shortens capacitor, module and board life.

Diagnostic workflow

Workflow
Danfoss VLT Alarm 29 Heatsink Temperature Workflow

Danfoss VLT reports alarm 29 during operation or immediately after power-up.

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