Vaillant F29 Fault Code Explained
Hertfordshire, Bedfordshire & Cambridgeshire
An F29 fault on a Vaillant boiler means the boiler lit successfully but then lost the flame while it was running, so it has shut down for safety.
It is closely related to F28, which is failure to light in the first place. The checks start the same way, but F29 more often ends with an engineer.
What F29 actually means
The boiler has a flame sensor that confirms combustion is happening. If that signal disappears mid-cycle, the gas valve closes immediately and the boiler locks out. That is the appliance doing exactly what it should.
A flame that starts and then dies usually points to something interrupting the gas supply, the combustion air, or the flue.
What you can safely check yourself
Check whether other gas appliances in the house are working. If the hob will not light either, the supply is the problem rather than the boiler.
If you are on a prepayment meter, check the credit.
After that, one reset. If it lights and dies again, stop.
When to stop, and why
What causes it beyond the simple checks
A dirty or failed flame sensing electrode, a gas valve not holding a steady supply, low incoming gas pressure, a blocked or partially restricted flue, or condensate backing up. Every one of these is Gas Safe work.
How Vantage can help
We are Gas Safe registered and cover Hertfordshire, Bedfordshire and Cambridgeshire, with an emergency line answered 24 hours a day.
Call us on 01462 506374. See also boiler repair and Vaillant boiler installation.
Frequently asked questions
Is F29 the same as F28?
No. F28 is failure to light at all. F29 is lighting and then losing the flame. The causes overlap.
Can I keep resetting it?
One or two attempts at most. After that it needs an engineer.
Could it be a frozen condensate pipe?
In cold weather, yes, and it often comes with a gurgling noise from the boiler.
Related fault codes
Other Vaillant codes: Vaillant F22 · Vaillant F75 · Vaillant F28 · Vaillant F27 · Vaillant F20 · Vaillant F23 · Vaillant F83 · Vaillant F32 · Vaillant F62 · Vaillant F61 · Vaillant F72
The same problem on other makes (ignition and flame faults): Ideal L2 · Ideal F2 · Baxi E133 · Glow-worm F28 · Viessmann F4
See also our guide to boiler not firing up, the full boiler advice section, and boiler repair.
In Vaillant’s own words
Vaillant describes F29 as the ignition following a flame loss during operation being unsuccessful.
So the boiler did light, lost the flame partway through, tried to relight and could not. That sequence points somewhere different from a boiler that never lit at all.
When to call an engineer
If the fault keeps returning after a reset, it is telling you something is degrading rather than broken. Call 01462 506374 and we will diagnose it properly rather than swapping parts and hoping. Gas Safe registered 956889, 12 months on our own labour.
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