Gas Safe: Gas work, flue work, and PCB replacement on a gas boiler must be carried out by a Gas Safe registered engineer. Homeowners can check obvious items such as heating pressure, condensate overflow, and whether a control is unplugged — then call an engineer.
Always confirm the part number against the boiler GC number and the installation manual before ordering.
Overview
F.67 is an implausible flame signal: the PCB thinks it sees flame when it should not, or the flame-sense circuit has failed. Related to F.27 (flame simulation).
Vaillant meaning: Electronics / flame fault
Possible causes
- Defective flame-monitoring electronics
- Damp PCB
- Electrode / ionisation lead issues that confuse the flame circuit
- Gas valve not shutting cleanly (also F.62)
Possible solutions
- Inspect for water on the PCB (leaking pump, pressure sensor, or case). Dry and find the leak before fitting a new board.
- Check electrode gap, insulation, and earth. Replace a tracked electrode and lead.
- If the flame signal is present with the gas valve unplugged (engineer test), the PCB or a leaking valve is at fault — see F.27 and F.62.
Possible parts needed
- Ignition / ionisation electrode 090709 or 0020133816 (by range)
- Ignition lead
- PCB
- Gas valve if it is not shutting
