Flame not detected. High

Worcester Bosch Flame not detected. Fault Code

Also written as FLAMENOTDETECTED — same fault.

The Worcester Bosch Flame not detected. fault code means: your boiler is unable to light the burner, meaning it cannot produce heat or hot water because it does not detect a flame.. It appears on 3 Worcester Bosch models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Is gas cock turned on? Check gas supply pressure, power supply, igniter electrode and lead, ionisation sensing electrode and lead, flue duct and COo level.
Typical repair cost £120-250 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Worcester Bosch models that show the Flame not detected. fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Worcester Bosch Flame not detected. fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026