F1
Saunier Duval Ignition Failure / Flame Detection Fault

Boiler shows F1 and will not ignite, no flame established

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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.

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Possible Causes

Faulty ignition electrode, Faulty flame detection electrode (ionisation probe), Incorrect electrode gap or contamination, Damaged ignition cable or poor earth connection

How to Fix / Troubleshooting

Safety first: Isolate electrical power and gas supply before removing the boiler cover. Risk of electric shock and gas leak.

Steps to check:

  • Remove the front panel to access the burner and ignition assembly.
  • Locate the ignition and ionisation electrodes on the burner front plate.
  • Inspect the ceramic insulators for cracks and the metal tips for heavy soot or oxidation. Clean gently with fine emery cloth if dirty.
  • Check the electrode gap and position relative to the burner as per the Saunier Duval service manual.
  • Inspect the ignition cable and earth wire for damage, loose connections, or signs of arcing. Reseat connectors firmly.
  • Restore power and gas, then attempt a reset. Observe through the sight glass: if there is no spark or flame, the electrode assembly may need replacement.

Warning: Burner and gas valve adjustments must only be carried out by a Gas Safe / qualified technician. If F1 persists after basic cleaning and checking connections, call a professional.

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Repair Difficulty

Hard 4/5

Required Part

Ignition / Ionisation Electrode Assembly
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