F.68 — Unstable flame signal fault

What does F.68 mean?

The boiler has detected an unstable flame signal, indicating that the flame is not burning consistently or reliably. This can lead to inefficient operation or safety shutdowns.

• Air mixed in with the gas supply.
• Gas flow pressure is too low.
• Incorrect air-to-gas ratio for combustion.
• Condensate route is blocked.
• Interruption in the ionisation current (cables, electrodes) or flue gas recirculation.

Click steps to track your progress.

1. 1

   Check that your gas supply to the property is active and stable.

2. 2

   Inspect the condensate pipe for any blockages, especially during cold weather.

3. 3

   Press the fault clearance key on the boiler to reset it. If the fault persists, contact Vaillant Service Solutions.