F.67
Vaillant Flame Signal Processing Fault

F.67 flame signal error; appliance locks out after failed ignition attempts

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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

Defective ionisation electrode, Poor earth or neutral connection, Electrical noise on flame signal, Faulty PCB flame detection circuit

How to Fix / Troubleshooting

Safety: Isolate power and gas. Combustion diagnostics should be performed by a qualified engineer.

  • Check earthing: Ensure the appliance is correctly earthed and that earth connections are tight and corrosion-free.
  • Inspect ionisation electrode: Clean or replace the electrode and ensure correct positioning in the flame.
  • Check wiring routing: Ensure ionisation cable is routed away from high-voltage ignition leads and mains cables to reduce interference.
  • Test PCB: If the flame is clearly present but not detected, the PCB flame circuit may be faulty. Replace the PCB after confirming other components are sound.
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Repair Difficulty

Professional Required 5/5

Required Part

Main Control PCB
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