Vaillant fault guide
Vaillant F28 and F29: ignition failure and flame loss
On Vaillant ecoTEC boilers, F28 means the boiler failed to light on start-up and F29 means the flame went out while it was running. F22 is different: it means the system pressure is too low.
Phones answered 7am–8pm, 7 days a week. Gas Safe registered 943380.
Further work and parts are always priced and agreed before we carry on.
What it means
The boiler has tried to ignite (F28) or keep a flame going (F29) and failed, so it has locked out for safety.
Common causes
- Gas supply problem or prepayment meter out of credit
- Frozen or blocked condensate pipe
- Ignition or flame-sensing electrode wear
- Gas valve fault
- Flue blockage or air-supply problem
Safe checks you can do
- Check your gas supply. Do your hob or gas fire work? If you have a prepayment meter, check it has credit and the emergency credit hasn’t run out.
- In freezing weather, check the white or grey plastic condensate pipe that runs outside to a drain. If it is frozen, pour warm (not boiling) water along it, then reset the boiler.
- Reset the boiler once using the reset button or dial (check your user manual). If the code comes straight back, stop resetting. Repeated resets won’t fix it and can make the fault harder to diagnose.
- If the display shows F22 instead, the pressure is too low. See our guide to a boiler losing pressure.
When to call an engineer
If the checks above don’t clear it, or the fault keeps coming back, the boiler needs a Gas Safe engineer to diagnose it. Our diagnostic visit is £144 including VAT, covering attendance and up to the first hour. We tell you the repair price before doing any further work.
When you call, tell us the boiler make and model, the exact code on the display and what you have already tried.
Other guides
Need a repair? Boiler repair in Portsmouth · Southampton · Guildford