High
9F on Worcester Bosch Greenstar Heatslave II

Your oil-fired boiler has stopped working because the burner failed to start, which can be caused by a fuel supply issue, a blocked filter, or the boiler needing a service.

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

Burner lock out. Check the burner and fuel supply.

From this model's manual
Verified against the Worcester Bosch Greenstar Heatslave Ii installation & service manual.
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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