BoilerFaultCodesIdeal SL Fault Code
The Ideal SL fault code means: your boiler is not actually broken; it is currently in a manual service mode used by engineers to test the system or displays a history of recent issues.. It appears on 5 Ideal models in our database.
Technical description: Service Mode / Sequence indicator following the last 3 faults
What causes the Ideal SL fault?
This code appears when the boiler has been manually put into a specialized mode for testing or when the system is displaying a history of its most recent operations. It is physically triggered by an engineer interacting with the control buttons to check how the boiler is firing or to diagnose previous issues. Because this is a manual override state rather than a mechanical failure, it does not indicate that any internal parts have broken.
DIY fix possible
Check if the function knob is set to 'Reset' or a specific service position.Turn the selector knob back to the 'on' or 'standby' position.Press the reset button briefly to return the boiler to normal operation mode.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Ideal models that show the SL fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal SL 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