BoilerFaultCodesThe 6 most common faults
Your boiler has shut down because it has detected it is getting too hot or there isn't enough water moving through the system to keep it cool.
Why it happens: This fault occurs when the water inside the boiler exceeds a safe temperature limit or stops moving entirely, triggering a safety shutdown to prevent damage. The most common reasons include a seized pump that isn't circulating the water, a blockage in the pipework caused by sludge, or a faulty sensor that is incorrectly reporting the temperature.
Check that your radiator valves are fully openEnsure your boiler pressure is between 1.0 and 1.5 barCheck for any visible leaks in the pipeworkPress the Reset button on the front of the control panel
Your boiler has tried to light several times but cannot establish a flame, meaning your heating and hot water will not work until it is reset or repaired.
Why it happens: This fault occurs when the boiler's internal computer senses that a flame has not been successfully lit after several attempts. The most common reasons include a lack of gas reaching the burner, a dirty or worn spark plug that can't create a flame, or an issue with the gas valve not opening correctly.
Check if your gas supply is turned on at the meter or if other gas appliances are working.If you have a prepaid gas meter, ensure it has sufficient credit.Press and hold the 'Reset' button for five seconds to see if the boiler restarts.Check that the white plastic condensate pipe outside hasn't frozen during cold weather.
Your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.
Why it happens: This fault occurs when the water pressure inside your heating system drops below the minimum level required for the boiler to fire up. The most common reasons are a slow leak from a radiator valve or pipework, or the pressure being manually reduced after bleeding your radiators. In some cases, it may be caused by a faulty internal component like the expansion vessel losing its charge.
Locate the filling loop (usually two blue-handled taps or a braided hose) underneath the boiler.Slowly open both taps until you hear water flowing and the needle on the pressure gauge reaches 1.5 bar (the green zone).Close both taps tightly and press the 'Reset' button on the boiler control panel.
Your boiler has stopped working because the electricity supply coming into your home is currently too weak to power the internal electronics safely.
Why it happens: This fault occurs when the electrical voltage reaching the boiler drops below the minimum level required for its sensitive electronic components to function. While it can occasionally be caused by a failing internal control board, it is most often the result of an external issue with the local power grid or a temporary 'brownout' in your area. The boiler shuts down as a safety precaution because it cannot guarantee the correct operation of the gas valve and fan at such low power levels.
Check if other appliances or lights in your home are flickering or dimmingSwitch the boiler off and back on at the fused spur switch to see if the error clearsContact your regional electricity distribution network operator (DNO) to report a local supply issue
Your boiler has detected that heat is not moving away from the unit quickly enough, often because water flow is being blocked or restricted.
Why it happens: This fault occurs when there is a massive temperature gap between the water entering and leaving the boiler, suggesting the heat has nowhere to go. It is usually caused by a physical blockage in the pipework, such as a buildup of sludge, or a mechanical failure in the pump that prevents water from circulating. The boiler shuts down immediately to protect the internal components from overheating and potential heat stress damage.
Check that the blue and red lever valves underneath the boiler are turned fully to the open positionEnsure all radiator valves (TRVs) are turned up to a high settingCheck your central heating filter (if fitted) to see if it is blocked or needs cleaning
Your boiler thinks it sees a flame even though it isn't currently firing, causing it to shut down as a safety precaution.
Why it happens: This fault occurs when the boiler's internal sensor detects a flame signal at a time when the burner should be off. The most common reason is a faulty sensing electrode that is sending an incorrect electrical signal to the main control board, or moisture buildup on the electrical components causing a short circuit.
Full guide for L6on the Ideal Logic+ System
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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