Boiler displays F70 after PCB replacement or firmware update

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Incorrect control board type fitted, parameters not programmed, incompatible display unit, wrong coding plug

Safety: Configuration errors usually do not pose immediate physical danger but can prevent safe operation.

Check part numbers: Verify the installed PCB matches the exact Viessmann model and gas type.
Parameter setup: A technician must enter the service level and program boiler-specific parameters using Viessmann service codes.
Coding plug: Some models use a coding resistor/plug; ensure it is transferred from the old board or replaced correctly.
Reboot: After configuration, power-cycle the boiler and confirm F70 is cleared.

Hard 4/5

Main Control Board

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