20 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
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Your boiler has stopped working because the internal computer has lost contact with the unit that controls the gas supply.
Your boiler has stopped working because it cannot properly control the flow of gas needed to light the flame.
Your boiler's temperature sensor for the heating system has developed a fault, preventing the unit from knowing how hot the water is.
Your boiler has detected a sensor problem that prevents it from monitoring the temperature of the exhaust gases, causing it to shut down for safety.
Your boiler has detected a problem with a sensor that monitors the temperature of the water returning from your radiators.
Your boiler is struggling to move water around the system properly before it starts the main heating process, usually due to a blockage or a pump issue.
Your boiler has switched itself off because it has detected that the water inside the system has become too hot to operate safely.
Your boiler has detected that it is running too hot and has automatically shut itself down to prevent any damage or safety issues.
Your boiler has detected that the water pressure inside the system is currently too high, which has caused it to shut down to prevent damage.
Your boiler has detected that the water pressure is too low for it to operate safely, which is why it has stopped working.
Your boiler has detected that water is not moving through the system properly, which is causing it to shut down to prevent overheating.
Your boiler has lost its flame while it was running, meaning it cannot stay alight to provide heating or hot water.
Your boiler has sensed that the exhaust gases are getting too hot and has shut down as a safety precaution to prevent internal damage.
Your boiler has failed to light because it cannot get enough gas or cannot detect the flame used to heat your water.
Your boiler has lost its connection to the gas supply due to an internal technical fault and cannot stay lit.
Your boiler has stopped working because it cannot light the internal flame or keep it burning reliably.
Your boiler has detected that the internal fan, which safely removes waste gases from the system, is not spinning correctly or has lost power.
Your boiler is struggling to accurately measure the temperature of your hot water, which usually means it can't heat your taps and showers properly.
Your boiler thinks a flame is present when it should be off, which is a safety conflict that has caused the system to lock out.
Your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.
Not faults — these are normal operating states. Tap to expand.
BoilerFaultCodes