26 High

Main 26 Fault Code

The Main 26 fault code means: your boiler is struggling to clear air properly, meaning it has safely shut itself down to prevent any harmful combustion gases from lingering.. It appears on 2 Main models 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: Fault on Fan or Flue
Typical repair cost £150-350 (including labour)

Engineer required

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

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Main models that show the 26 fault code

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

Source

Main 26 fault code information on this page is sourced and cross-checked against the official Main service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026