How much does it cost to fix Sime error code 59?

Typical repair cost for the Sime 59 fault is £120-200 including labour.

59 Medium

Sime 59 Fault Code

Q: What does the Sime 59 fault code mean?

Your boiler is struggling to heat your radiators at the expected speed, likely due to a poor connection or an internal sensor reading that something is wrong with the heat flow.

The Sime 59 fault code means: your boiler is struggling to heat your radiators at the expected speed, likely due to a poor connection or an internal sensor reading that something is wrong with the heat flow.. It appears on 4 Sime models in our database.

Technical description: Heating gradient

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 59 fault code

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

Source

Sime 59 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