Liebherr Fault Code
Free · no signupSPN 520840 FMI 00
Hydraulics Derated / Inverter Thermal Alarm
System
Inverter / Thermal
Symptom
Hydraulics Derated / Inverter Thermal Alarm
Diagnosis & fix steps
LOGIC: Traction/Implement Inverter IGBT Junction Temp Exceeds Safety Limit.
ACTION: Verify electric coolant circulation pump runs under command. Bleed air from the low-temperature inverter cooling loop; check for blocked heat exchanger plates or dried thermal interface paste beneath the IGBT power modules.
Red Seal field insights
Silicon Thermal Runaway: Insulated Gate Bipolar Transistors (IGBTs) generate intense localized heat under heavy digging and slewing loads; trapped air pockets in cooling plates boil instantly, destroying power modules.
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