BoilerFaultCodesIdeal 26 Fault Code
The Ideal 26 fault code means: your boiler has shut down because the mixture of gas and air required for a safe flame is incorrect, often due to a blockage or a dirty internal component.. It appears on 4 Ideal models in our database.
Technical description: Improper gas/air ratio. Check the air restriction and the gas injector for the correct diameter, mounting, and pollution.
What causes the Ideal 26 fault?
This fault happens because the boiler cannot achieve the precise balance of gas and oxygen needed for safe combustion. It is typically caused by a buildup of dust or debris in the air intake or a blockage in the internal nozzle that delivers gas to the burner. When the sensors detect that the mixture is unstable or inefficient, the boiler shuts down as a safety precaution.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Ideal models that show the 26 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal 26 fault code information on this page is sourced and cross-checked against the official Ideal service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026