21 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
This boiler uses LED flash patterns
Count the flashes in one repeating group before the pause. That number is your fault code. Do not reset until you have noted it. How to read fault codes →
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Your boiler has detected an internal error and has locked itself out for safety, requiring a professional inspection to identify the specific part that has failed.
Your boiler has stopped working because it cannot light the flame or the internal drainage pipe is backed up with water.
Your boiler has stopped heating because it is struggling to accurately read the temperature of the water circulating through your radiators.
Your boiler has stopped working because the fan isn't moving air through the system properly or there is a blockage in the exhaust pipe.
Your boiler has stopped working because the water pressure is too low or the pump that circulates water is struggling to move it through the system.
Your boiler has lost communication with the sensor that monitors your hot water temperature, meaning it cannot heat your water safely or accurately.
Your boiler has stopped working because it cannot correctly measure the temperature of the water used to heat your radiators.
Your boiler is struggling to detect water moving through the system, causing it to continuously turn itself on and off to protect against overheating.
Your boiler is not receiving any electrical power from the main supply or has a blown internal fuse, leaving the unit completely unresponsive.
Your boiler has lost electrical power to the pump, which means it cannot circulate water to your radiators or hot water tank.
Your boiler has detected low water pressure or a trapped air pocket, which is preventing it from circulating heat properly.
Your boiler has detected a failure in one of its internal safety sensors or the fan, meaning it cannot circulate water or vent gases safely and has stopped working.
Your boiler has detected an issue with how it extracts exhaust fumes, often caused by a blocked pipe or a sensor problem, and has shut down as a safety precaution.
Your boiler has tried to light but cannot find enough gas to start the heating process.
Your boiler is not controlling the gas flow to the burner correctly, which has caused it to shut down for safety.
Your boiler is struggling to light its flame, meaning it cannot heat your water or radiators until the ignition problem is fixed.
Your boiler is struggling to detect whether the gas has actually lit, causing it to shut down as a safety precaution.
Your boiler has got too hot and has automatically shut down to prevent damage to the internal components.
Your boiler's main control dial or internal computer has developed a fault, meaning the system cannot correctly process a reset command or switch between modes.
Your boiler has stopped working because the waste water pipe that drains excess liquid away is blocked or frozen.
Your boiler has switched itself off because the exhaust gases have become too hot, which is a safety measure to prevent damage to the system.
BoilerFaultCodes