129 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 reached the correct temperature and is simply taking a normal break from firing until the heat is needed again.
Your boiler has detected that it is getting too hot or that water is not moving through the system correctly, causing it to shut down for safety.
Your boiler has switched itself off because it got too hot, which is a safety measure to prevent damage to the system.
Your boiler has lost its flame briefly and is trying to restart itself, which could indicate a temporary issue with your fuel supply or a dirty sensor.
Your boiler has tried to light several times but cannot start, usually because of an empty fuel tank or a blocked oil line.
Your boiler is having a temporary 'conversation' issue between its internal electronics which should resolve itself automatically.
Your boiler's internal safety system has detected that the fan, which clears exhaust gases, is not spinning correctly or has lost power.
Your boiler has experienced a brief internal memory glitch and is currently trying to restart itself.
Your boiler's internal memory chip has developed a communication fault, meaning the control system can no longer read the settings it needs to operate safely.
Your boiler has encountered a minor temporary glitch and is currently trying to restart itself automatically.
Your boiler has detected an internal communication error or a generic failure that is preventing it from running safely.
Your boiler's internal fan, which safely exhausts fumes, is not starting or is being blocked, causing the system to shut down for safety.
Your boiler has detected that the electrical supply coming into the property is too weak for it to run safely.
Your boiler has become too hot and has shut itself down as a safety precaution to prevent damage.
Your boiler's main control computer has developed an internal electronic fault and can no longer manage the system safely.
Your boiler's internal computer has likely developed a fault and can no longer control the heating system safely.
Your boiler has detected that water isn't moving through the system properly or there isn't enough water inside the unit to operate safely.
Your boiler's temperature sensor has failed or is disconnected, meaning the system cannot safely tell how hot the water is and has shut down as a precaution.
Your boiler has detected an electrical wiring issue where the power supply wires are connected in the wrong order.
Your boiler's internal computer has encountered a critical error and can no longer control the heating system safely.
Your boiler has become too hot and has shut itself down as a safety precaution to prevent damage.
Your boiler has too much water inside its system, which is causing it to shut down to prevent damage from the excess pressure.
Your boiler has detected that there is not enough water in the system to operate safely, causing it to shut down temporarily.
Your boiler has stopped working because the water pressure in the central heating system has dropped too low.
Your boiler is struggling to move water through the system, which causes it to shut down to prevent overheating.
Your boiler has failed to heat the water to a high enough temperature to kill off any potentially harmful bacteria in the system.
Your boiler started to heat up but the flame went out unexpectedly while it was running.
Your boiler has tried to light several times but has been unable to create a steady flame, causing it to shut down for safety.
Your boiler has experienced a lockout and needs to be manually cleared to restart the system.
Your boiler has detected a problem with the fan that safely removes exhaust gases, meaning the system has shut down as a safety precaution.
Your boiler has detected an issue with how air is moving through the system, preventing it from lighting safely.
Your boiler has detected a problem with how water is flowing or being measured, causing it to stop running as a safety precaution.
Your boiler has stopped working because it cannot confirm that the fan is blowing safely and the chimney is clear.
Your boiler has detected that it is firing without enough water inside it, which could cause the unit to overhead rapidly.
Your boiler has detected an electrical grounding issue which is preventing it from running safely for your protection.
Your boiler has shut down because the internal water has reached a dangerously high temperature and is overheating.
Your boiler has lost connection with its internal temperature sensor, meaning it cannot monitor water temperature correctly and has shut down as a precaution.
Your boiler's internal thermometer that monitors water returning to the unit is either broken or not plugged in correctly.
Your boiler has detected that the water coming back from your radiators is hotter than the water going out, which usually means water is flowing in the wrong direction or a sensor is faulty.
Your boiler is struggling to keep its flame lit and has stopped working after failing to stay ignited several times within a day.
Your boiler's fan isn't spinning at the right speed, often because strong winds are blowing into the flue pipe or a component has failed.
Your boiler has stopped working because it believes the water returning to the unit is hotter than the water leaving it, which usually indicates a circulation problem or a sensor error.
Your boiler has stopped working because water is not moving through the system properly or a vital internal sensor has lost its connection.
Your boiler has shut down because it has become too hot internally, likely due to a lack of water flow or a sensor malfunction.
Your boiler is simply acknowledging that the reset button has been pressed and is now attempting to restart its normal operation.
Your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.
Your boiler's main internal computer has suffered a serious electronic failure and can no longer communicate with the system.
Your boiler has stopped working because the internal control board and the fuel delivery system are no longer talking to each other correctly.
Your boiler's internal computer settings have been altered or are not being read correctly, meaning the control board doesn't know which model it is operating.
Your boiler's internal control settings have been disrupted, likely due to a configuration error on the main circuit board.
Your boiler's internal computer settings have been altered or detected an error in its configuration chips.
Your boiler has lost communication with an external control, such as your thermostat or programmer, due to a wiring issue.
Your boiler is having trouble communicating with your external thermostat or smart controller, meaning it cannot receive instructions to turn the heating on.
Your boiler has lost its connection to the fuel control system and cannot safely light the flame to provide heat or hot water.
Your boiler has detected a electrical fault with the sensor that measures water temperature, meaning it cannot safely determine how hot the water is and has shut down as a precaution.
Your boiler has stopped working because it cannot accurately measure the temperature of the water moving through the system.
Your boiler has shut down because the water inside is getting too hot too quickly, usually because it isn't moving through the system properly.
Your boiler has detected a problem with the sensor that monitors exhaust gases, and it has shut down as a safety precaution.
Your boiler has detected an issue with the sensor that monitors exhaust gases, causing it to shut down for safety.
Your boiler has shut down because it has detected dangerously high internal temperatures or a lack of water movement, and it requires a professional reset and inspection.
Your boiler has locked itself out because it has reached a dangerously high temperature or detected a lack of water circulation.
Your boiler is failing to ignite a flame, meaning you will not have any heating or hot water at the moment.
Your boiler thinks a flame is burning when it shouldn't be, which is a safety lock-out caused by a sensor issue or electrical glitch.
Your boiler has detected that the internal fan, which safely clears exhaust fumes and brings in fresh air, has stopped spinning correctly.
Your boiler has detected a serious internal fault with the fuel control system and has shut down for safety.
Your boiler has detected an issue with the sensor that monitors internal heat levels, causing the system to shut down as a safety precaution.
Your boiler has become too hot and has automatically shut down for safety, often because air is trapped in the heating system or water isn't circulating properly.
Your boiler is struggling to move water through the system, which is usually caused by trapped air blocking the pipes.
Your boiler's internal computer has developed a fault and can no longer control the system safely.
Your boiler has failed to light, which may be caused by excess air in your heating system preventing proper operation.
Your boiler has detected a communication problem between its main control board and the internal gas valve, causing it to shut down for safety.
Your boiler is having trouble reading the outside temperature, which may cause it to run less efficiently or at the wrong temperature.
Your boiler has stopped working because it cannot detect water moving through the system to safely carry heat away.
Your boiler has detected that a internal water safety switch is stuck in the 'on' position, preventing the system from starting up safely.
Your boiler has detected an internal communication error with the gas control system and has shut down as a safety precaution.
Your boiler has lost its connection to the sensor that monitors the temperature of the water for your radiators.
Your boiler has detected a problem releasing waste gases safely, which could be due to a sensor fault or a physical blockage.
Your boiler has detected an issue with the sensor that monitors the temperature of the water returning from your radiators.
Your boiler's hot water sensor has detected a fault, meaning the system cannot accurately measure or control the temperature of your hot water.
Your boiler is struggling to breathe properly because something is likely blocking the exhaust pipe where it exits your house.
Your boiler is struggling to detect when you turn on a hot tap, meaning you might have inconsistent or no hot water.
Your boiler has lost its settings and needs to be professionally synchronised to ensure it burns fuel correctly and safely.
Your boiler has lost track of the system's water pressure because a sensor has stopped reporting correctly.
Your boiler's internal computer has lost its connection with the control panel or sensors, preventing it from functioning correctly.
Your boiler has detected an issue with the air and fuel mixture while trying to automatically adjust its settings for efficient burning.
Your boiler's computer board has lost track of the current time, which can disrupt your scheduled heating periods.
Your boiler is struggling to move water through the system effectively, which is causing it to stop running to prevent overheating.
Your boiler has switched itself off because it has reached a temperature that is too high, often caused by a blockage or a pump issue.
Your boiler has detected that there is too much water pressure in the system, which can prevent it from running safely.
Your boiler has stopped working because the water pressure in the central heating system has dropped too low.
Your boiler has stopped working because the water pressure inside the system has dropped too low.
Your boiler is overheating because the water is not moving around the system properly.
Your boiler is repeatedly losing its flame during operation, causing it to shut down to prevent damage or unsafe running.
Your boiler is struggling to keep a steady flame while trying to set itself up, causing it to shut down for safety.
Your boiler has shut down because a sensor has detected that the exhaust gases are getting too hot, which can be a sign of a serious internal blockage or overheating.
Your boiler has shut itself down because it detected that the exhaust gases have become dangerously hot, which could indicate a blockage or a serious internal circulation issue.
Your boiler has failed to light because it either cannot get enough gas or the flame has gone out unexpectedly.
Your boiler is trying to light but cannot find a steady supply of fuel, causing it to shut down for safety.
Your boiler has lost its connection to the gas supply or is experiencing an internal electronic failure preventing it from lighting.
Your boiler has noticed that water isn't moving through the system correctly, which is causing its internal sensors to record conflicting temperatures.
Your boiler has detected a problem with the fan that safely removes exhaust gases, meaning it has shut down as a safety precaution.
Your boiler has detected a problem with the fan that clears away waste gases, causing the system to shut down for safety.
Your boiler's hot water sensor has failed or has a wiring issue, meaning it cannot accurately measure how hot the water is or provide it to your taps.
Your boiler has stopped working because it cannot correctly detect the water pressure, often caused by a faulty internal sensor or a wiring issue.
Your boiler's internal computer has encountered a communication fault and can no longer control the heating system safely.
Your boiler's internal computer is experiencing a communication error or has detected an internal fault, causing it to shut down for safety.
Your boiler is struggling to move water through the system properly before it starts the heating process, often due to a blockage or a pump issue.
Your boiler has detected that it is overheating because there is not enough water moving through the system to keep things cool.
Your boiler has detected an issue with the electrical power timing coming into the unit, which is preventing it from running safely.
Your boiler's temperature sensor for hot water has stopped working correctly, meaning your taps may only provide cold or lukewarm water.
Your boiler thinks it is firing up when it shouldn't be, causing the system to lock out for safety.
Your boiler is not receiving the correct amount of electricity from the mains supply to operate safely.
Your boiler is performing a temporary check to ensure there is enough water pressure in the system to operate safely.
Your boiler has stopped working because its internal computer has lost contact with the control system that manages the gas flow.
Your boiler is getting too hot because water isn't moving through the system quickly enough or a sensor is misreading the temperature.
Your boiler is heating up too quickly or water isn't moving through the system properly, causing the unit to shut down to prevent overheating.
Your boiler has detected that the water is getting too hot too quickly, usually because it isn't moving through the system properly.
Your boiler has stopped working because water is not moving through the system correctly or a temperature sensor has detected a problem.
Your boiler is heating up too quickly because water isn't moving through the system properly or a sensor is misreading the temperature.
Your boiler’s internal computer has forgotten its identity and needs to be told which model it is before it can start up again.
Your boiler's computer is confused because its internal settings do not match the specific model requirements, often following a power cut or a part being replaced.
Your boiler's internal computer is temporarily confused by its own settings and cannot operate correctly.
Your boiler has detected that the water pressure is either too low or there is a leak somewhere in the heating system causing the unit to stop working.
Your boiler has stopped working because its internal computer has lost contact with one of its temperature sensors.
Your boiler's main internal computer is having trouble communicating with the rest of the unit, preventing it from starting up correctly.
Your boiler has unexpectedly lost its flame while it was running, meaning it can no longer heat your water or radiators.
Your boiler has no electricity and is completely powered down, which could be due to a simple tripped switch or a blown fuse.
Your boiler has failed to ignite several times and has locked itself out for safety reasons.
Your boiler has detected a communication problem between its electronic internal components, meaning it cannot operate safely.
BoilerFaultCodes