Vaillant Boiler F.29 Error Code

Flame went out and the boiler couldn't relight on Vaillant boilers.

F.29

Moderate DIY

The burner was lit and running, lost its flame, and the attempt to relight it failed. A short break in the gas supply is the classic cause (a prepayment meter running dry mid-evening, for example). Flue gases being drawn back in, a blocked condensate pipe, earthing faults and ignition parts are the other suspects.

Compatible models

Vaillant's UK fault list includes F.29 with no model list, and so does the manual for the ecoTEC plus VU ..6/6-5 OVZ boilers.

Also shown as

No other codes are listed for this fault.

Difficulty

Start with the safe checks below; a worn part may need replacing.

How to fix
When to call a pro
Parts
FAQ

Not sure you are reading the code right? See how to read Vaillant boiler codes.

Safety first: never take the casing off a gas boiler. If you smell gas, open windows, don't use light switches, turn the gas off at the meter if you can and call your gas emergency number from outside. A carbon monoxide alarm going off means the same: switch the boiler off, get fresh air and call.

How to fix Vaillant F.29

Confirm gas is still on
Light the hob or another gas appliance. If nothing works, the problem is the supply or the meter (check for credit on a prepayment meter) and the boiler itself may be fine.
Check the condensate pipe outside
In freezing weather, look at the plastic condensate pipe where it runs outside. Vaillant links F.29 to a frozen pipe, so thaw it with a watering can of warm water, never boiling, before you reset.
Reset
Hold reset for over 3 seconds. One or two clean restarts after a supply hiccup is normal; repeat lockouts aren't.

When to call a technician

When F.29 comes back with gas available and the condensate pipe clear, the cause is inside the boiler or the flue and needs a Gas Safe engineer. Any gas smell means leaving the house and phoning the gas emergency line.

Parts linked to F.29

These are the parts an engineer usually checks for this code. They sit inside the sealed casing, so leave them to a Gas Safe registered engineer.

Frequently asked questions

Which Vaillant models show the F.29 code?

Vaillant's UK fault list includes F.29 with no model list, and so does the manual for the ecoTEC plus VU ..6/6-5 OVZ boilers.

Can I fix Vaillant F.29 myself?

Only the outside checks. The steps above are the ones Vaillant's user instructions allow; if they don't clear F.29, the fix is inside the boiler and needs a Gas Safe registered engineer (RGII in Ireland).

Other Vaillant boiler codes

Last reviewed 2026-10-21. Codes and steps can vary by model; check your owner's manual.

Sources we checked