Technical description
Check gas supply, check flue system, check polarity
What causes this fault?
This fault occurs when the boiler's control system attempts to start a flame but fails to detect one after several attempts. The most common reasons include a lack of gas reaching the unit, a worn-out ignition spark, or a blockage in the pipes that carry exhaust fumes away from your home.
This issue is more frequent during extremely cold spells, as external gas meters or regulator components can sometimes struggle with freezing temperatures or high demand.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.