F.29Vaillant
Vaillant F.29: the flame went out during use and the boiler could not relight
Checked against Vaillant's own documentation: Vaillant: boiler fault codes list and 3 more sources. Last reviewed October 2026. How we check
Check these first, then call an engineer
The boiler was running, lost its flame, and failed to relight. Vaillant's current ecoTEC plus fault table lists a temporary break in the gas supply and a blocked condensate duct among the causes, along with earthing and ignition faults.
What you can safely do
- Check your gas supply: does your hob work, and does your prepayment meter have credit?
- In freezing weather, check the condensate pipe outside. If it is frozen, pour warm (not boiling) water along it, as Vaillant advises.
- Reset only if your user manual tells you to for this code.
Call a Gas Safe engineer if
- Your gas supply is fine and the code comes back.
- You smell gas at any point. Leave the property and call 0800 111 999.
Find a Gas Safe engineer near you
Opens the official Gas Safe Register search.
Applies to ecoTEC plus. Codes can differ between models, so check your manual.