Emergency
AL 96 on Sime Brava Slim HE System

Your boiler has switched itself off because it has detected an obstruction in the exhaust pipe that prevents waste gases from leaving the building safely.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

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 Brava Slim He installation & service manual, page 34.
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 emergency severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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