BoilerFaultCodesThe 6 most common faults
Your boiler’s internal computer brain has developed a critical electronic fault and can no longer communicate with the rest of the system.
Why it happens: This fault occurs when the boiler's main control board suffers a hardware failure, meaning it can no longer send or receive the signals needed to manage the heating process safely. The most common reason is age-related wear to the delicate electrical circuits on the board, though it can also be triggered by a sudden power surge or moisture getting into the control box.
Full guide for 410Your boiler has detected that the internal temperature sensors have been wired or installed in the wrong positions, preventing it from heating safely.
Why it happens: This fault occurs when the boiler's control board detects that the water temperature readings are backwards, usually following a recent repair or component replacement. It is physically caused by the flow and return temperature sensors being plugged into the wrong ports on the main circuit board or clipped onto the incorrect internal pipes. Because the boiler cannot accurately track how heat is moving through the system, it shuts down to prevent overheating.
Full guide for 424Your boiler's internal computer has encountered a critical error and can no longer communicate with the rest of the system.
Why it happens: This fault occurs when the boiler's main control board suffers a hardware failure, meaning it can no longer send or receive instructions to vital components like the pump or gas valve. The most common reason is an electrical short-circuit or component degradation on the circuit board itself, which prevents the 'brain' of the boiler from functioning correctly.
Full guide for 460Your boiler's main control computer has encountered an internal error and can no longer safely manage the heating system.
Full guide for 00Your boiler's main control computer has encountered a serious internal error and has shut down to prevent further damage.
Full guide for 01Your boiler's main brain has detected a critical internal error, which means it has safely shut itself down to prevent further damage.
Full guide for 03on the Ideal Classic SE15P FF
Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.
Call a Gas Safe engineer if…
- You can smell gas or see signs of a leak
- The Ideal shows an Emergency or High severity code
- The boiler keeps locking out after repeated resets
- You've tried the DIY checks and the fault hasn't cleared
- There's visible water leaking from the boiler
- The flame is yellow or orange instead of blue