Boiler shows F9 and will not operate, sometimes after power surge or wiring work
Safety Warning
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
How to Fix / Troubleshooting
Safety first: Turn off the boiler at the isolator and verify power is off before removing the control panel.
Steps to check:
- Inspect the mains supply to the boiler: ensure live, neutral, and earth are correctly connected and secure.
- Remove the front cover and carefully access the main PCB compartment.
- Check all plug-in connectors to the PCB (sensors, fan, pump, gas valve) are fully seated.
- Look for visible damage on the PCB such as burnt components or corrosion.
- Restore power and attempt a reset. If F9 persists and wiring is correct, the PCB will likely need replacement.
Warning: PCB replacement and configuration (parameter setting) must be done by a qualified engineer familiar with Saunier Duval boilers.
Repair Difficulty
Required Part
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