BoilerFaultCodesSime ALL09 Fault Code
The Sime ALL09 fault code means: your boiler has stopped working because water is not flowing through the system correctly.. It appears on 1 Sime model in our database.
Technical description: if the boiler detects inadequate system water circulation, the boiler will stop and display AL 09. Ensure that at least one radiator is turned on and that all isolation valves are open, if problem persists it could be due to a blocked filter within the boiler, seek help and advice from a qualified engineer.
DIY fix possible
Check that all radiator valves are fully openEnsure the blue handled isolation valves under the boiler are in the open positionCheck if the system pressure is too low and top up if necessary
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Sime models that show the ALL09 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Sime ALL09 fault code information on this page is sourced and cross-checked against the official Sime service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026