BoilerFaultCodesKeston C13 Fault Code
The Keston C13 fault code means: your boiler is struggling to breathe properly because the pipework that brings in fresh air and pushes out exhaust fumes is blocked, damaged, or incorrectly installed.. It appears on 2 Keston models in our database.
Technical description: A room sealed appliance designed for connection via ducts to a horizontal or vertical terminal, which admits fresh air to the burner and discharges the products of combustion to the outside through orifices which, in this case, are concentric.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Keston models that show the C13 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Keston C13 fault code information on this page is sourced and cross-checked against the official Keston service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026