BoilerFaultCodesIdeal 408 Fault Code
The Ideal 408 fault code means: your boiler has detected a problem with how air or water is flowing through the system and has shut down as a safety precaution.. It appears on 1 Ideal model in our database.
Technical description: Pressure differential switch failure (not applicable)
What causes the Ideal 408 fault?
This fault occurs when the boiler's internal components detect that the airflow required for safe combustion is not being properly maintained. The system relies on a pressure switch to confirm the fan is moving air correctly, so a blockage in the flue or a failing fan motor will trigger this safety shutdown. In many cases, it is simply caused by debris or moisture preventing the pressure sensors from giving a clear reading.
This fault is more frequent during periods of heavy wind or extreme cold, as external debris can blow into the flue and ice can restrict the airflow necessary for the pressure switch to activate.
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 408 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal 408 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