BoilerFaultCodesWorcester Bosch 75 Fault Code
The Worcester Bosch 75 fault code means: your boiler’s internal flame sensor is dirty and can no longer see the fire, causing the system to shut down for safety.. It appears on 1 Worcester Bosch model in our database.
Technical description: Photocell filmed over (dirty)
What causes the Worcester Bosch 75 fault?
This fault occurs when the photocell, which acts as the boiler's 'eye,' becomes coated in a thin layer of soot or oily film. Because the sensor can no longer detect the light from the flame, the boiler shuts down as a safety precaution to prevent unburnt fuel from building up. This is usually caused by natural wear over time or a slight change in the burner's combustion quality.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Worcester Bosch models that show the 75 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch 75 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