IndustrialDriveDataDrive Board & Diagnostic Database
Danfoss VLT FC-series field-service reference

Danfoss VLT FC 102 / FC 202 / FC 302 service platform

A family-level diagnostic record for common VLT FC-series alarm cases, emphasizing phase-loss evidence, earth-fault isolation, output short-circuit checks, heatsink cooling evidence and overvoltage during deceleration.

Record facts

Common service pathAlarm number plus symptom, often without a full model code
First diagnostic boundaryInput phase/DC link, output earth/short path, cooling/heatsink, or braking/deceleration path
Database roleConvert alarm cases into support-ready evidence requests

Service notes

  • Ask for the full type code, frame size, alarm number and trip condition before giving component advice.
  • Alarm 14 and alarm 16 require motor/cable isolation discipline before a power-stage conclusion.
  • Alarm 4 should be proven at the drive input terminals rather than assumed from upstream voltage only.
  • Alarm 29 usually needs fan, heatsink, dust, ambient and load-current evidence before board replacement is considered.

Related technical records

Alarm 14
Earth Fault / Ground Fault

The Danfoss VLT reports alarm 14, trips on start or trips when the motor cable is connected.

Open →Alarm 16
Short Circuit

The VLT reports alarm 16 or trips instantly when the inverter output is enabled.

Open →Alarm 4
Mains Phase Loss

The VLT reports mains phase loss, trips at power-up, or loses ready state when plant load changes.

Open →Alarm 29
Heatsink Temperature Fault

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

Open →Circuit
Danfoss VLT Input Phase, DC-Link and Brake Energy Path

Routes Alarm 4, undervoltage and deceleration overvoltage through the same energy path: L1/L2/L3 input, fuses, contactor, rectifier, DC-link capacitors, brake chopper, braking resistor and DC-link voltage feedback.

Open →Circuit
Danfoss VLT Input Phase and DC-Link Path

Routes alarm 4 and deceleration overvoltage through line phases, fuses, contactor, rectifier, DC-link ripple, high line voltage and braking energy paths.

Open →Circuit
Danfoss VLT Output Earth-Fault and Short-Circuit Path

Routes alarm 14 and alarm 16 through output insulation, terminal contamination, motor cable damage, IGBT module, gate driver and current-feedback path.

Open →Circuit
Danfoss VLT Cooling and Heatsink Temperature Path

Routes alarm 29 through cooling fans, heatsink contamination, airflow, cabinet ventilation, ambient temperature, load current and temperature feedback.

Open →Workflow
Danfoss VLT Alarm 14 / Alarm 16 Earth and Short Diagnostic Workflow

Danfoss VLT reports alarm 14 earth fault or alarm 16 short circuit.

Open →Workflow
Danfoss VLT Alarm 4 Mains Phase Loss Workflow

Danfoss VLT reports alarm 4 or shows input phase instability.

Open →Workflow
Danfoss VLT Alarm 29 Heatsink Temperature Workflow

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

Open →
Evidence intake

Turn this record into a qualified service request

A repair decision is much more reliable when the request includes the exact identity of the drive, the first fault evidence and the machine condition when the symptom appeared.

  • Complete drive type code / MLFB or nameplate model
  • Fault code, fault value and first event before reset
  • When the event appears: power-up, enable, ramp, run, decel or stop
  • Motor/cable connected or isolated during the symptom
  • Visible board, option-card, module and connector identifiers
  • Previous repair history, replacement parts and repeat-failure pattern
Prepare request →