F04
Ferroli Flame Detection Fault

Boiler displays F04 and locks out; may be related to flame detection issues.

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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

Dirty or damaged flame sensor, Poor earth connection, Incorrect gas/air ratio, PCB flame circuit fault

How to Fix / Troubleshooting

Safety first: Isolate gas and power. Flame sensing is part of the combustion safety system and must be handled by a Gas Safe engineer.

  • Reset once: If F04 reappears, do not continue resetting.
  • Engineer checks:
    • Clean or replace the flame sensing electrode.
    • Check boiler earth continuity and bonding.
    • Verify combustion settings with a flue gas analyser.
    • Test PCB flame detection circuitry and replace PCB if necessary.
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Repair Difficulty

Professional Required 5/5

Required Part

Flame Sensing Electrode
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