121 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 lost its connection to the control key or internal system, causing it to flash red and stop working.
Your boiler has temporarily stopped working because the water pressure inside the system has dropped too low.
Your boiler is shutting down because it is heating up much faster than it can circulate the water, which often points to a blockage or a pump issue.
Your boiler has stopped working because it detected a problem with the internal fan that pushes exhaust gases out of your home.
Your boiler has detected that the internal fan responsible for venting exhaust gases failed to start properly during its initial safety check.
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 is trying to start, but it cannot detect a flame, so it has safely shut itself down to prevent gas from building up.
Your boiler has detected a signal that suggests a flame is present when it should not be, leading the system to shut down for safety reasons.
Your boiler has stopped heating because the flame inside went out while it was trying to run.
Your boiler has been told to stop running by an external device, such as a smart thermostat or a frost protection controller.
Your boiler has lost communication with its internal computer, meaning it cannot safely operate or control your heating and hot water.
Your boiler has detected an issue with the control system that manages the gas supply, so it has safely shut down to prevent any risk.
Your boiler's internal computer is confused because its internal identification settings do not match the specific components installed, causing it to lock itself to prevent incorrect operation.
Your boiler has detected an internal communication error and has safely shut down to prevent potential damage.
Your boiler's internal computer is experiencing a major communication error and is unable to safely control the system.
Your boiler's main control unit is experiencing a communication error or electrical glitch that is preventing it from operating correctly.
Your boiler's main control computer is experiencing a temporary glitch or internal error, which has caused it to stop working for safety reasons.
Your boiler has detected an internal communication error and has safely shut down to prevent potential damage.
Your boiler's internal computer is experiencing a communication error and cannot safely manage the heating or hot water systems.
Your boiler's internal computer is experiencing a communication error or technical failure, preventing it from operating correctly.
Your boiler's computer is experiencing a temporary processing error and needs to be reset to clear the glitch.
Your boiler's computer system has encountered an internal error and cannot operate correctly.
Your boiler's computer is having a internal communication error and cannot safely start up.
Your boiler's computer system has encountered a critical internal processing error and needs to be restarted to restore normal operation.
Your boiler's internal computer is experiencing a critical error while trying to run its own memory check, causing the system to lock up for safety.
Your boiler's computer memory has detected an internal data error, meaning the control system is confused and cannot safely operate the boiler.
Your boiler's internal computer is experiencing a communication error and has decided to shut down to prevent potential damage.
Your boiler's main control computer is experiencing a temporary glitch or internal error, which has caused it to pause its normal operation as a safety precaution.
Your boiler's internal computer has encountered a software glitch and has shut itself down as a safety precaution.
Your boiler's computer is having trouble reading its own internal electronic signals, which is preventing it from starting up correctly.
Your boiler's computer system has encountered a software glitch and needs to be restarted to clear the error.
Your boiler's computer is experiencing a temporary software confusion which is preventing it from starting up correctly.
Your boiler is struggling to breathe properly, meaning it cannot safely clear exhaust gases and has shut down to protect your home.
Your boiler is currently heating the water faster than your radiators or taps can use it, causing it to throttle down or pause to prevent overheating.
Your boiler is failing to detect a flame, which means it has safely shut itself down to prevent gas from building up inside the unit.
Your boiler has stopped working because it cannot safely start the internal fire that heats your water.
Your boiler is struggling to push water through your heating system because the water pressure inside is too low.
Your boiler has detected that the flame is still burning even though it has told the gas supply to shut off.
Your boiler's internal computer is failing to communicate correctly with its external controls, preventing your heating or hot water from turning on.
Your boiler has briefly lost power, likely due to a minor power cut or a loose plug connection.
Your boiler is heating up much faster than it should, which has caused it to automatically shut down to prevent potential damage from overheating.
Your boiler is heating the water much faster than it is able to move it away, causing the system to stop as a safety precaution to prevent overheating.
Your boiler has lost its ability to accurately measure the temperature of the water flowing through the heating system because one of its internal sensors is sending a faulty electrical signal.
Your boiler has lost its ability to measure the temperature of the water flowing through the system, so it has purposefully stopped working to prevent overheating.
Your boiler is struggling because the electricity supply it is receiving is weaker than it needs to operate reliably.
Your boiler's internal computer is struggling to recognise the electronic identification chip that stores its specific settings.
Your boiler's computer is having trouble recognising its own internal settings and requires a professional to reset or replace the electronic control unit.
Your boiler is struggling to confirm that the burner flame has safely extinguished before attempting to restart.
Your boiler has detected that an internal valve responsible for controlling gas flow is not sealing properly, meaning it cannot operate safely.
Your boiler has detected an internal issue where a component responsible for controlling the fuel supply is failing to shut properly, preventing the system from operating safely.
Your boiler's electronic brain is having trouble communicating with the burner, meaning your heating and hot water have stopped working for safety reasons.
Your boiler is failing to detect or trigger the heating process required to provide you with hot water.
Your boiler is struggling to read the temperature accurately from an optional heating component called a low loss header, which may temporarily affect how efficiently your system distributes warmth.
Your boiler has stopped working because the water pressure inside the heating system has dropped below the required level.
Your boiler is having trouble 'talking' to your hot water tank or internal sensor, which means it cannot accurately tell if your water is hot enough.
Your boiler is struggling to accurately measure your hot water temperature because a sensor has stopped working properly.
Your boiler's brain is struggling to measure the internal water pressure because a sensor has failed or become unplugged, which usually stops the heating from working.
Your boiler's computer has detected a serious internal processing error that is preventing it from operating safely.
Your boiler has detected an internal software or communication error that is preventing it from operating correctly.
Your boiler's internal computer is experiencing a communication error, meaning it has safely shut itself down to prevent potential issues.
Your boiler's internal computer is experiencing a communication error and has shut down for safety to prevent incorrect operation.
Your boiler is having trouble breathing, meaning it cannot properly clear exhaust gases or draw in fresh air due to a possible blockage or a fan issue.
Your boiler's internal computer has failed to automatically adjust its settings to ensure it burns gas safely and efficiently.
Your boiler is struggling to start the internal fire necessary to produce heat, meaning it has safely shut itself down to prevent gas from building up.
Your boiler is struggling to detect the flame accurately while it tries to set itself up, meaning it cannot safely start your heating or hot water.
Your boiler's internal computer is failing to talk to the part that creates heat, meaning it cannot start up.
Your boiler's air extraction fan is staying on longer than it should after finishing its work, which often points to an electronic communication error inside the unit.
Your boiler has detected a potential issue with the gas flow control system after it has finished running, which may indicate a safety concern.
Your boiler is failing to light the internal flame needed to heat your home's water.
Your boiler has detected an issue with the way it is burning gas and has shut itself down to ensure your safety.
Your boiler is failing to detect a flame, so it has safely shut itself down to prevent gas from escaping.
Your boiler is currently stuck in a diagnostic testing mode used by engineers rather than operating in its normal heating mode.
Your boiler has encountered an internal electronic error that is preventing it from operating correctly.
Your boiler has detected an issue with how the gas supply is being controlled, so it has safely shut itself down to prevent any risk.
Your boiler has detected that it cannot safely communicate with the part that controls the gas flow, so it has shut itself down to keep your home safe.
Your boiler is struggling to control the gas flow needed to heat your home, so it has safely shut itself down to prevent any issues.
Your boiler has detected an issue with the fuel supply control system and has deliberately shut down to stay safe.
Your boiler has stopped working because the flame inside went out while it was trying to heat your water or home.
Your boiler's computer is experiencing a software or internal communication error, meaning it has safely shut down to prevent incorrect operation.
Your boiler's internal computer is experiencing a temporary communication error which has caused the system to stop working as a safety precaution.
Your boiler's internal computer has experienced a temporary glitch or memory error, causing it to stop operating to protect the system.
Your boiler's internal computer is experiencing a communication error, meaning it has safely shut down to prevent incorrect operation.
Your boiler is struggling because it is not receiving the correct amount of electrical power, which is likely due to a poor connection or a minor electrical fault.
Your boiler is struggling to pump enough water through the system, meaning it cannot heat your home or provide hot water effectively.
Your boiler has stopped working because it cannot detect that the internal fan, which is essential for safely venting exhaust gases, is spinning correctly.
Your boiler is struggling to work because the electricity supply it is receiving from your home's wall socket is weaker than it needs to be.
Your boiler is rapidly cycling on and off because it cannot efficiently release the heat it is generating, which often points to a blockage or a bottleneck in your heating system.
Your boiler's internal computer chip has identified that the electronic component containing its specific configuration settings is either incorrect or not properly connected.
Your boiler has attempted to ignite but failed to keep its flame burning at the required low intensity, so it has shut down as a safety precaution.
Your boiler is trying to start but the flame is failing to establish, so it has safely shut itself down to prevent gas from building up.
Your boiler has failed to light the flame, which means it cannot produce any heating or hot water for your home.
Your boiler is trying to stay lit but keeps failing, which means it has automatically shut down to keep your home safe.
Your boiler is having trouble confirming that the gas flame is lit properly and has stopped working as a safety precaution.
Your boiler has attempted to start but failed to detect a flame, meaning it cannot produce heat or hot water.
Your boiler has attempted to ignite several times but is failing to stay lit, meaning you currently have no heating or hot water.
Your boiler has detected that its internal settings do not match the way your heating system is physically set up, meaning it cannot safely start until these are corrected.
Your boiler has detected an internal fault within its computer brain that prevents it from safely lighting the flame.
Your boiler's main control computer is experiencing a temporary brain freeze and cannot communicate properly with the rest of the unit.
Your boiler's main control computer is experiencing a software or internal communication error, meaning the system has safely shut itself down to prevent further issues.
Your boiler's main computer is having an internal communication error and cannot operate safely.
Your boiler has stopped working because it cannot confirm that the internal fan, which safely clears exhaust gases, is spinning correctly.
Your boiler has stopped working because it cannot move the air and exhaust gases through the system properly.
Your boiler has detected an incorrect temperature reading, which has caused it to shut down for safety reasons to prevent overheating.
Your boiler has detected that water is not flowing through it fast enough to keep it cool, so it has stopped working as a safety precaution.
Your boiler has detected that the water inside the unit is getting too hot and has automatically shut down to prevent damage.
Your boiler has detected that the water inside it is heating up much faster than it safely should, causing the system to shut down to prevent damage.
Your boiler has detected that the water is not heating up evenly, which means it will stop working to protect itself from internal damage.
Your boiler is currently refilling or pressurising itself automatically.
Your boiler's automatic filling system has topped up the water pressure too many times in a short period, suggesting there may be a leak in your heating system.
Your boiler has stopped working because the water pressure inside your heating system has dropped below the required level.
Your boiler has detected that the electricity supply coming from your mains is weaker than required to operate safely.
Your boiler's internal computer is experiencing a communication error, meaning the system cannot safely operate your heating or hot water.
Your boiler has detected an internal software or processing error that is preventing it from operating correctly.
Your boiler's computer is struggling to read its internal configuration settings, which is preventing it from starting up correctly.
Your boiler's internal air blower is struggling to run at the correct speed, which is preventing the system from safely igniting your heating and hot water.
Your boiler is struggling to shut down its internal ventilation system properly, which means it cannot safely restart or regulate itself.
Your boiler has detected that the internal ventilation fan is spinning faster than it should, which has caused it to shut down for safety reasons.
Your boiler has paused temporarily to protect itself, but it usually recovers automatically once conditions return to normal.
Your boiler is struggling to accurately measure the temperature of the water returning to it, which causes it to stop working to protect the system from overheating.
Your boiler is failing to detect a request for heat from your thermostat or internal timer, likely due to a loose wire or a disconnected control link.
Your boiler has lost its ability to accurately measure the water temperature, so it has safely shut itself down to prevent overheating.
Not faults — these are normal operating states. Tap to expand.
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BoilerFaultCodes