Slow flash High

Worcester Bosch Slow flash Fault Code

Also written as SLOWFLASH — same fault.

The Worcester Bosch Slow flash fault code means: your boiler has detected a safety concern or internal fault and has automatically shut down to protect itself, requiring you to attempt a manual reset.. It appears on 3 Worcester Bosch models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Once per second. Can only be cleared by using the facia reset button (press for at least one second).
Typical repair cost £120-250 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Worcester Bosch models that show the Slow flash fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Worcester Bosch Slow flash 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 31 August 2026