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Vaillant Boiler F.68 Error Code
Unstable flame on Vaillant boilers.
VaillantAll Vaillant boiler codes
The flame signal is wavering during operation. The manual lists air in the gas, low gas pressure, the wrong air ratio, the wrong injector or a break in the ionization circuit.
Compatible models
The ecoTEC plus VU 126 to 356/6-5 OVZ manual is the source for this one. Check your own manual for other models.
Also shown as
No other codes are listed for this fault.
Difficulty
Try the basic checks, but the usual fix is a technician's job.
Not sure you are reading the code right? See how to read Vaillant boiler codes.
How to fix Vaillant F.68
See if other gas appliances behave
A hob that lights poorly or a weak flame elsewhere suggests a supply problem, which the gas supplier or an engineer needs to sort out.
Reset once
Hold reset for more than 3 seconds and watch whether the code returns.
When to call a technician
Gas pressure and combustion settings are checked with an analyzer by a Gas Safe engineer. Book one if F.68 repeats.
Parts linked to F.68
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.68 code?
The ecoTEC plus VU 126 to 356/6-5 OVZ manual is the source for this one. Check your own manual for other models.
Can I fix Vaillant F.68 myself?
Only the outside checks. The steps above are the ones Vaillant's user instructions allow; if they don't clear F.68, the fix is inside the boiler and needs a Gas Safe registered engineer (RGII in Ireland).
Other Vaillant boiler codes
- F.22Water pressure in the heating system is too low
- F.28Boiler failed to light
- F.29Flame went out and the boiler couldn't relight
- F.20Overheat safety cut-out has tripped
- F.23Too big a gap between flow and return temperature
- F.24Temperature rising too fast
- F.25Flue gas temperature too high
- F.27Flame detected with the burner off
- F.75No pressure rise when the pump starts
- F.00Flow or return temperature sensor not reading
- F.10Temperature sensor short circuit
- F.13Hot water cylinder sensor short circuit
- F.32Fan speed out of range
- F.61Gas valve control fault
- F.62Flame took too long to go out
- F.70Invalid device code after a repair
- F.83Dry fire: no temperature change when the burner lit
Last reviewed 2026-10-21. Codes and steps can vary by model; check your owner's manual.