BoilerFaultCodesWorcester Bosch Flue blockage Fault Code
Also written as FLUEBLOCKAGE — same fault.
The Worcester Bosch Flue blockage fault code means: your boiler has detected that waste gases cannot safely leave the property through the flue pipe, causing the system to shut down for safety.. It appears on 1 Worcester Bosch model in our database.
Technical description: Fault indication / Lockout reset button
What causes the Worcester Bosch Flue blockage fault?
This fault occurs when the boiler's internal sensors detect that the exhaust gases are not being cleared from the system effectively. The most common reasons include a physical obstruction in the external flue pipe, such as a bird's nest or debris, or a mechanical failure of the fan that pushes these gases out. Because these gases are dangerous, the boiler will immediately stop working as a safety precaution.
This issue is slightly more frequent in winter as high winds can cause pressure fluctuations in the flue, or heavy snowfall can physically block the external terminal.
DIY fix possible
Check the external flue pipe for any visible obstructions like bird nests, debris, or leavesIn freezing weather, check the end of the flue for ice buildup and carefully clear itPress and hold the blue reset button for 3 to 5 seconds to see if the boiler restarts
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Gas Safe Register →Worcester Bosch models that show the Flue blockage fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch Flue blockage 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