BoilerFaultCodesThe 6 most common faults
Your boiler has shut down because it thinks the water inside is getting too hot or is not moving through the system properly.
Why it happens: This fault occurs when the water inside the boiler exceeds a safe temperature limit or isn't circulating correctly. The most common reasons are a failed pump that can't move the water, a blockage caused by sludge in the system, or a faulty sensor giving an incorrect temperature reading.
Check that your radiator valves and any isolation valves are fully openEnsure your system pressure is topped up to between 1 and 1.5 barBleed your radiators to remove any trapped air and then reset the boiler
Your boiler has failed to light several times and has shut down for safety, meaning you currently have no heating or hot water.
Why it happens: This fault occurs when the boiler tries to ignite three times but fails to detect a stable flame, leading the system to shut down for safety. The most common reasons include a lack of gas supply to the unit, a blocked flue, or components inside the burner being too dirty or worn out to create a spark.
Check if your gas supply is active by testing another gas appliance like a hob.Check if your condensate pipe (the white plastic pipe outside) is frozen or blocked.Reset the boiler by turning the control knob to 'Reset' and holding for two seconds.
Your boiler has tried to start five times in a row but failed to keep the flame alight, causing it to shut down as a safety precaution.
Why it happens: This fault occurs when the boiler's internal computer detects that the flame has gone out or failed to light properly five times in quick succession. It is usually caused by a problem with the gas supply reaching the burner or a worn-out ignition component that can no longer create a reliable spark. To prevent a build-up of unburnt gas, the boiler permanently shuts down until the underlying mechanical issue is fixed.
Check if other gas appliances in your home, like a hob, are working to ensure gas is reaching the propertyCheck if your gas meter has creditPress the 'Reset' button and wait for the boiler to restart
Your boiler has detected that water is heating up too quickly or not circulating properly, which usually means something is blocking the flow of water through the system.
Why it happens: This fault occurs when the boiler detects a rapid rise in temperature because heated water isn't moving away from the burner fast enough. The most common reasons are a pump failure, a blockage in the pipework, or an internal part that has become restricted with sludge and debris.
Check that all blue-handled isolation valves underneath the boiler are fully turned to the open positionEnsure all radiator valves (TRVs) are turned up to a high settingCheck your central heating filter for any obvious blockages if you have one installed
Your boiler thinks a flame is burning even though it shouldn't be, causing the system to shut down for safety.
Why it happens: This fault occurs when the boiler's internal sensors detect a flame after the burner has been told to switch off, or before it has even started. It is usually caused by a faulty sensing probe sending an incorrect signal to the main control board, or a leak inside the unit that has allowed moisture to interfere with the electrical components.
Full guide for L6Your boiler has detected that the water is flowing in the wrong direction through the pipes or that the temperature sensors have been installed on the wrong pipes.
Why it happens: This fault occurs when the boiler detects that the return pipe is hotter than the flow pipe, suggesting the water is moving backwards through the unit. It is often caused by a failing internal pump that cannot push water in the right direction, or by the temperature sensors becoming faulty and sending incorrect readings to the control board.
Full guide for FAon the Ideal i Combi 2
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
Avoid the next call-out bill
Monthly cover means no unexpected bills when your boiler breaks down.
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