AL High

Sime AL Fault Code

The Sime AL fault code means: your boiler has detected a general problem and is waiting for a specific sub-code to appear to tell you exactly what is wrong.. It appears on 1 Sime model in our database.

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.

Technical description: Generic fault/malfunction indicator followed by a specific fault code
Typical repair cost £100-350 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Sime models that show the AL fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Sime AL 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