Error code
Vaillant Boiler Fault Code F29
Quick answer
F29
Flame detection has been lost during operation
First safe action
Check the boiler manual for any user-level checks allowed for this code.
Meaning
Vaillant boiler fault code F29 usually means the boiler lit initially or tried to run, but then lost flame detection and shut down for safety.
Likely causes
- Intermittent gas supply issue
- Flame sensing fault
- Combustion or control issue
Safe first checks
- Check the boiler manual for any user-level checks allowed for this code.
- Try the standard reset once if permitted by the manufacturer.
- Stop using the boiler if the fault returns repeatedly.
How to reset
- Use only the standard user reset process if the manual allows it.
- Arrange professional diagnosis if the flame fault returns.
When to call an engineer
Repeated flame-loss faults should be assessed promptly by a Gas Safe registered engineer.
Safety warning
Do not attempt internal gas or combustion repairs. Persistent flame faults are not a DIY job.
Useful hub links
Related fault codes
F27 for Vaillant Boiler
Flame detection has been lost during operation
F28 for Vaillant Boiler
The boiler has failed to ignite properly
F32 for Vaillant Boiler
Fan, flue, or air pressure sensing problem
F54 for Vaillant Boiler
Gas supply control or gas valve issue
F24 for Vaillant Boiler
Water circulation or pump performance issue
F61 for Vaillant Boiler
Gas supply control or gas valve issue
Relevant guides
Frequently asked questions
Can I keep resetting a Vaillant boiler with F29?+
No. If F29 returns after one standard user reset, stop there and arrange a qualified engineer if the manual gives no safe next step.
Is F29 something I can repair myself?+
Boiler faults should be treated cautiously. Stay within the user checks in the manual, and leave gas, combustion, and internal boiler repairs to a qualified professional.