F.68
Unstable flame fault
The boiler has detected an unstable flame or implausible analogue flame signal.
What this code means
The boiler has detected an unstable flame or implausible analogue flame signal.
Possible causes
- Air in gas supply
- Gas flow pressure too low
- Incorrect air/gas ratio
- Incorrect gas restrictor
- Ionisation cable or electrode fault
Common symptoms
- F.68 displayed
- Boiler may repeatedly lose flame or lock out
Checks to make
- Do not repeatedly reset
- Arrange qualified combustion and flame-sensing diagnosis
Safety
- Do not remove the boiler casing or work on gas, combustion, flue or internal electrical components unless appropriately qualified. If gas is suspected, follow the national gas-emergency procedure.
Model notes
Vaillant notes that not every fault code is visible on every product model.