Furnace shows F0, no heating or hot water, display may be blank or frozen

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

Loose communication cable between display and main PCB, Faulty user interface board, Defective main PCB communication port

Safety first: Isolate power before removing the front panel or display module.

Remove the front cover to access the user interface module.
Check the low-voltage communication cable between the display and the main PCB. Unplug and firmly reseat both ends.
Inspect the cable for damage or pinched sections where it passes through the casing.
Restore power and see if the display returns to normal operation.
If F0 persists, either the display module or main PCB is faulty. Replacement and re-commissioning should be done by an ATAG-trained technician.

Hard 4/5

ATAG user interface board

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