BoilerFaultCodesThe 6 most common faults
Your boiler has become too hot and has automatically shut itself down to prevent damage and ensure safety.
Why it happens: This fault occurs when the water temperature inside the boiler exceeds a safe limit, causing the safety sensors to cut the power. The most common reasons are a pump failure that stops water from moving or a blockage in the system that prevents heat from being carried away from the boiler.
Check that your radiator valves are openEnsure there is enough water pressure in the system (usually between 1 and 1.5 bar on the gauge)Once the boiler has cooled down, press the reset button on the front control panel
Your boiler has failed to light or maintain a flame, meaning your heating and hot water have stopped working.
Why it happens: This fault occurs when the boiler's control system attempts to start the burner but cannot detect a stable flame. The most common reasons are a lack of gas supply to the unit, a worn-out ignition component that fails to create a spark, or a dirty internal sensor that cannot 'see' the flame once it has lit.
Check if other gas appliances, like a hob, are working to ensure gas is reaching your homeCheck if your gas meter has creditPress the 'Reset' button on the boiler control panel
Your boiler's internal computer has encountered a critical electronic failure and can no longer control the heating process safely.
Why it happens: This fault occurs when the boiler's main control board suffers an internal electronic failure or loses communication with its sensors. The most common reason is age-related wear on the electrical components or a sudden power surge that has damaged the delicate circuitry. Because the board can no longer safely monitor the flame or water temperature, it shuts the system down as a safety precaution.
Full guide for HEYour boiler has sensed that the exhaust gases are getting too hot and has shut down as a safety precaution to prevent internal damage.
Why it happens: This fault occurs when the internal temperature of the exhaust fumes exceeds a safe limit, triggering an emergency shutdown to protect the boiler's components. The most common reason is a build-up of limescale or debris inside the heat exchanger, which prevents heat from being transferred to your water and instead sends it out through the flue. It can also be caused by a faulty sensor giving an incorrect reading or a blockage in the system's circulation.
Full guide for H9Your boiler has shut down because the internal gases have reached a temperature that is dangerously high for the system.
Why it happens: This fault occurs when the gases produced by the burner become too hot, triggering a safety sensor to prevent damage to the boiler or flue. The most common reasons are a build-up of debris or limescale inside the main heat exchanger or a failing pump that isn't moving water through the system fast enough to carry the heat away.
Full guide for L9Your boiler has switched off because water produced during the heating process cannot drain away properly, likely due to a blockage in the pipe leading outside.
Full guide for Automatic Shutdownon the Ideal Mexico HE
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