F.68
FAULT CODE
Vaillant
Unstable Flame / Air in Gas
High Severity
Engineer Required
The boiler flame is unstable, often caused by air in the gas supply, a partially blocked burner, or incorrect gas/air ratio settings.
Step-by-Step Fix Guide
-
Step 1 Engineer only
Call a Gas Safe engineer — this requires a full combustion analysis and gas pressure test
Gas Safe Reminder
Work on gas appliances must be carried out by a Gas Safe registered engineer. The steps above cover safe checks a homeowner can perform - any internal component replacement requires a qualified professional. If in doubt, always call an engineer.