BoilerFaultCodesIdeal 918 Fault Code
The Ideal 918 fault code means: your boiler has shut down because it has detected that the water inside is getting too hot, which is often caused by a blockage or a pump failure.. It appears on 2 Ideal models in our database.
Technical description: Maximum temperature - Flow temperature T1 too high
What causes the Ideal 918 fault?
This fault occurs when the water leaving the boiler exceeds its safe temperature limit, causing the system to shut down to prevent damage. It is usually caused by a failure in the circulation pump or a physical blockage within the internal pipework that stops heat from moving away from the burner. In some cases, a faulty sensor may also be incorrectly reporting that the water is overheating.
This issue is frequently seen when the heating is first turned on after summer, as the circulation pump can seize up after long periods of inactivity.
DIY fix possible
Check that all radiator valves are fully openCheck that the boiler pressure is between 1.0 and 1.5 barReset the boiler by turning the mode dial to the 'RESET' position for two seconds
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Gas Safe Register →Ideal models that show the 918 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal 918 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