How do I clear or fix error 75?

Verify the communication cable (CAN/RS485/Modbus) is correctly seated and the right pinout is used. Check baud rate and protocol settings in both devices match.

Felicity inverter error 75 (F75)

MCU Communication Fault

Also displayed as F75 on some models.

Fault — the inverter cuts its output and the red LED stays solid until the fault is cleared.

T-REX-50KHP3G01

InverterFault

What it means

MCU Communication Fault — There is an error in the MCU communication, try to upgrade the software.

Cause: Communication has been lost between the inverter and a peripheral device — typically a battery BMS, smart meter, or external monitoring dongle.

How to fix it

Verify the communication cable (CAN/RS485/Modbus) is correctly seated and the right pinout is used.
Check baud rate and protocol settings in both devices match.
Reseat the dongle/comms module.
For BMS comms, confirm the battery is powered on and not in deep-discharge protection.

Source: t-rex-25-50khp3g01-user-guide-en.pdf, p.48

Frequently asked questions

What does error 75 mean on a Felicity inverter?: 75 means: MCU Communication Fault. Communication has been lost between the inverter and a peripheral device — typically a battery BMS, smart meter, or external monitoring dongle.
Is error 75 a fault or a warning?: 75 is a fault code: the inverter cuts its output and the red LED stays solid until it is cleared.
How do I clear or fix error 75?: Verify the communication cable (CAN/RS485/Modbus) is correctly seated and the right pinout is used. Check baud rate and protocol settings in both devices match.

Related error codes

Other codes on the T-REX-50KHP3G01

All T-REX-50KHP3G01 codes

Prefer the full written guide? Read the complete Felicity inverter error-code guide

Compiled from official Felicity user manuals. Always consult your device manual and a qualified technician before performing repairs.