Furnace shows F1 and will not start, often after a power surge or outage

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

Internal PCB failure, Power supply fault on PCB, Damage from voltage spike or incorrect polarity

Safety first: Disconnect power at the isolator before touching internal wiring.

Check the mains supply polarity and earth at the appliance terminals.
Inspect the PCB for visible damage (burn marks, cracked components).
Verify that all connectors are fully seated and that no moisture is present on the board.
Try a controlled power reset: leave the unit off for 5–10 minutes, then restore power.
If F1 reappears, the control board is likely defective and must be replaced and configured by a qualified technician.

Professional Required 5/5

ATAG main control PCB

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