BoilerFaultCodesWorcester Bosch E1 Fault Code
The Worcester Bosch E1 fault code means: your boiler has detected an issue with how it clears exhaust fumes, causing it to stop running for safety.. It appears on 2 Worcester Bosch models in our database.
Technical description: Flue pressure switch failure
What causes the Worcester Bosch E1 fault?
This fault occurs when the boiler's safety sensors detect that exhaust fumes are not being cleared safely through the outdoor flue pipe. It is typically caused by a blockage in the air pressure tubes, a build-up of debris in the fan, or a mechanical failure in the switch that monitors airflow.
This issue is more frequent during periods of high winds or extreme cold, which can cause pressure fluctuations or ice blockages in the external flue terminal.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Search the official register for a qualified engineer in your area.
Gas Safe Register →Worcester Bosch models that show the E1 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch E1 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