High
855 on Worcester Bosch Greenstar Heatslave II

Your boiler has stopped working because the burner failed to ignite or stay lit, meaning you currently have no heating or hot water.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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.

What the manual says

Manufacturer manual

9F Burner lock out

From this model's manual
Verified against the Worcester Bosch Greenstar Heatslave Ii installation & service manual, page 43.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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