BoilerFaultCodesWorcester Bosch 660 Fault Code
The Worcester Bosch 660 fault code means: your boiler has detected an electrical fault within its internal wiring or a control component, causing it to shut down for safety.. It appears on 1 Worcester Bosch model in our database.
Technical description: Short circuiting
What causes the Worcester Bosch 660 fault?
This fault occurs when an electrical current follows an unintended path within the boiler's circuitry, often due to a component failure or damaged insulation. The most common reasons are water leaking onto internal electrical parts or a critical failure within the main control board's surface components.
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 660 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch 660 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