High
AL 96 on Sime Murelle Pro HE R MkII System

Your boiler has shut down because it cannot safely expel exhaust fumes, usually due to a blockage in the chimney or pipe leading outside.

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

Lockout due to flue (exhaust) blockage / smoke outlet clogged — inspect and clear flue system

From this model's manual
Verified against the Sime Murelle Pro He R Mkii System installation & service manual, page 40.
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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