ALL 26 Low

Sime ALL 26 Fault Code

Also written as ALL26 — same fault.

The Sime ALL 26 fault code means: your boiler's temperature sensor responsible for reading your solar water heating system is not working correctly, which may prevent your solar panels from contributing to your hot water supply.. It appears on 3 Sime models in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: S3 SOLAR PROBE FAILURE
Typical repair cost £120-200 (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 ALL 26 fault code

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

Source

Sime ALL 26 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