BoilerFaultCodesWorcester Bosch 8.F Fault Code
Also written as 8F — same fault.
The Worcester Bosch 8.F fault code means: your boiler has detected a flame when there shouldn't be one, which usually means a internal component is stuck or damaged.. It appears on 1 Worcester Bosch model in our database.
Technical description: Permanent ignition
What causes the Worcester Bosch 8.F fault?
This fault occurs when the boiler's sensors detect a flame still burning even after the heating or hot water has been turned off. The most common reason is an internal component like the gas valve becoming stuck open or an electrical failure on the main control board that keeps the ignition system active. Because this involves gas flow that isn't being controlled properly, the boiler shuts down immediately as a safety precaution.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Worcester Bosch models that show the 8.F fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch 8.F 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 27 April 2026