151 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Replaced by: Heatslave II
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 communication or sensing error and has shut down as a safety precaution.
Your boiler has been left in a maintenance setting intended only for testing, which prevents it from operating normally.
Your boiler has been left in a manual testing mode after a recent service or inspection, which is preventing it from running normally.
Your boiler's internal computer parts do not recognise each other and are unable to communicate, preventing the system from starting up.
Your boiler's internal computer chip is either incorrect for this model or has not been properly communicated to the main control board.
Your boiler has lost its internal identity or configuration details due to a component recognition error, which has caused the system to stop working entirely.
Your boiler is operating normally and is currently providing heat to your radiators.
Your boiler is working normally and is currently providing heat to your radiators.
Your boiler is currently focused on heating your taps rather than your radiators, which is often a normal part of its operation.
Your boiler is simply letting you know it is currently working to heat up your hot water.
Your boiler is working normally and is simply waiting for a signal from your thermostat to start heating up.
Your boiler is taking a short, programmed break to prevent itself from turning on and off too frequently, which protects the internal components from unnecessary wear.
Your boiler is currently in standby mode and waiting for a signal from your thermostat or timer to begin heating.
Your boiler is working correctly and is simply waiting for you to turn up your thermostat or programmer to request heat.
Your boiler has temporarily stopped firing because it is currently hotter than it needs to be to meet your heating or hot water settings.
Your boiler has stopped running because the water inside the main tank has become hotter than it is supposed to be.
Your boiler has been manually set to a testing mode used by engineers to check its performance, which overrides your normal thermostat settings.
Your boiler is currently set to a manual testing mode used by engineers and is not following its normal heating schedule.
Your boiler is heating up much faster than it should and has shut down to prevent the system from overheating.
Your boiler has shut down because the internal water pressure is too low for it to operate safely.
Your boiler has recorded that a service tool was plugged in while checking the history of past errors, which is usually just an advisory note for an engineer.
Your boiler is trying to start up but cannot detect a flame, meaning it won't be able to provide any heating or hot water until the issue is resolved.
Your boiler thinks it can see a flame even though none should be present, which is causing it to shut down for safety.
Your boiler's internal computer system is having a communication error because its software components are not speaking the same language.
Your boiler has fired up but cannot detect the water getting any hotter, causing it to shut down for safety.
Your boiler is temporarily reducing its power because it is producing heat faster than your home can take it away.
Your boiler is currently running a self-diagnostic check of its internal parts, which usually happens during startup or after a reset.
Your boiler is operating normally and is simply bumping up its power output to meet a high demand for heating or hot water.
Your boiler is currently going through its normal startup routine and is preparing to light the burner.
Your boiler has stopped working because its internal control system has detected an electrical issue with the valve that controls the fuel flow.
Your boiler is currently focused on providing hot water and will resume central heating once the hot water demand is finished.
Your boiler is temporarily pausing the hot water heating cycle to prevent the system from overheating or overworking.
Your boiler is still detecting a flame even after it has tried to shut off the fuel supply, which is a safety conflict preventing the system from running.
Your boiler is struggling with an unstable electrical supply from the house or the main grid, preventing it from running safely.
Your boiler is receiving an unstable or insufficient supply of electricity, which is preventing it from running safely.
Your boiler's internal computer chips are not communicating correctly or don't match, preventing the system from starting up.
Your boiler's internal computer chips are not communicating properly because they don't recognise each other.
Your boiler's temperature sensors are detecting an inconsistency, usually meaning a sensor has failed or has been knocked out of place.
Your boiler has lost its internal communication link, meaning the control system cannot send instructions to the heating components.
Your boiler has detected that the water pressure is too low for it to operate safely and it needs filling back up.
Your boiler is unable to tell how hot your water is because a internal sensor is either unplugged or has failed, meaning you likely have no hot water.
Your boiler has lost track of how hot the stored water is, meaning you likely have no hot water or the temperature is inconsistent.
Your boiler is having trouble communicating with the outdoor sensor that monitors the weather, which may affect how efficiently it balances your heating.
Your boiler has lost the ability to monitor its own water pressure, which means it has shut down to prevent any internal damage.
Your boiler is struggling to detect the temperature outside, which means it might not adjust your heating levels correctly for the weather.
Your boiler's internal thermometer has developed an electrical fault and can no longer accurately measure the temperature of the water inside.
Your boiler has lost communication with its internal thermometer, meaning it cannot tell how hot the water is and has stopped running as a safety precaution.
Your boiler's internal temperature sensor has stopped working correctly because of an electrical short, meaning the system can no longer safely monitor how hot it is getting.
Your boiler has lost communication with a central temperature sensor, which means it cannot monitor the internal heat and has shut down as a safety precaution.
Your boiler is having trouble detecting its own flame, which means it has stopped running as a safety precaution.
Your boiler has stopped working because its internal control system isn't communicating correctly with the gas valve that fuels the burner.
Your boiler has lost its connection with the internal gas control valve, preventing it from lighting safely.
Your boiler has started to fire up but the flame has gone out unexpectedly, meaning the system has shut down for safety.
Your boiler's internal configuration hardware is either missing, faulty, or has been identified as the wrong version for this specific model.
Your boiler is struggling to keep its flame alight, meaning it may stop working or keep restarting to try and stay on.
Your boiler is failing to light properly and is struggling to detect a flame, causing the heating and hot water to stop working.
Your boiler has detected that a temperature sensor is not communicating properly, meaning the system cannot safely monitor how hot the water is getting.
Your boiler is struggling to push water through the heating system quickly enough, which is preventing it from running safely.
Your boiler has shut down because the internal water temperature has become too hot and reached a level that isn't safe for the system.
Your boiler is heating up much faster than it should, which usually means the water isn't moving through the system quickly enough to take the heat away.
Your boiler has detected that water is heating up too quickly or unevenly between different sensors, causing it to shut down to prevent overheating.
Your boiler has detected that the water pressure in your heating system is dropping too quickly, which usually means there is a leak somewhere or the system needs to be topped up.
Your boiler has detected that the water pressure in the pipes is too low for it to operate safely.
Your boiler has detected that there isn't enough water moving through the system, which is usually caused by a leak or a pump that has become stuck or worn out.
Your boiler's pump is unable to move water because it is either physically jammed or there is too much air trapped inside the system.
Your boiler has detected an electrical fault with the sensor that monitors exhaust gases and has stopped working to prevent potential damage.
Your boiler's temperature sensor for hot water is broken or has a loose connection, which means the system cannot correctly measure how hot your water is.
Your boiler has lost its connection to the external heating controls, meaning it cannot receive instructions on when to turn the heating or hot water on.
Your boiler is struggling to operate because the electrical power supply to it is unstable or too low, or there is a communication issue with its control chip.
Your boiler's internal computer chip is missing or not making a proper connection, which means the system doesn't know which model it is and has stopped working.
Your boiler's computer brain has encountered a serious internal error and can no longer communicate with the rest of the system.
Your boiler has shut down because the internal fan or air supply has stopped working while it was trying to run.
Your boiler's internal computer has suffered a critical electrical failure and can no longer control the heating process.
Your boiler's internal computer has noticed the air fan was spinning when it shouldn't have been, causing the system to stop for safety.
Your boiler has stopped working because the internal fan that clears out exhaust gases is spinning too slowly or is not communicating with the system.
Your boiler has detected that the internal fan is spinning at an incorrect speed, causing the system to shut down for safety.
Your boiler has stopped working because the internal fan that clears away waste fumes is not spinning fast enough.
Your boiler has stopped working because the internal fan, which safely exhausts waste gases, has failed to start or speed up.
Your boiler has stopped working because the fan that helps remove exhaust gases isn't spinning fast enough to operate safely.
Your boiler has shut down because a built-in safety sensor detected that the internal fan has suddenly stopped pushing out exhaust fumes.
Your boiler has lost communication with the sensor that monitors the temperature outside, which may cause your heating to run less efficiently.
Your boiler has stopped working because the water pressure inside the system has dropped below the minimum level required to run safely.
Your boiler has stopped working because the internal pump that moves hot water around your system has failed a self-test or is stuck.
Your boiler has lost track of the temperature of the water returning from your radiators, which usually means a internal sensor has failed or gotten wet.
Your boiler has stopped working because it has lost its connection to the internal sensor that monitors the temperature of the water returning to the unit.
Your boiler has stopped working because an external safety device or thermostat has disconnected the power supply to prevent damage.
Your boiler is overheating because the water inside is heating up faster than it can be moved away, leading to an automatic safety shutdown.
Your boiler has detected that the water is heating up too quickly or isn't circulating properly, causing it to shut down to prevent overheating.
Your boiler has shut down because it thinks the internal water temperature has become dangerously hot.
Your boiler is heating up too quickly and has shut down to prevent overheating, usually because water isn't moving through the system properly.
Your boiler's internal thermometer that monitors the temperature of the water heading to your radiators has broken or disconnected, causing the system to shut down for safety.
Your boiler has detected an electrical fault with the internal sensor that monitors water temperature, meaning it cannot safely heat your water or radiators.
Your boiler has lost its connection to the sensor that monitors water temperature, causing the system to shut down for safety.
Your boiler has lost communication with the sensor that monitors water temperature, causing the system to shut down as a safety precaution.
Your boiler has stopped working because a sensor that monitors water temperature has developed an electrical fault and can no longer read the heat levels correctly.
Your boiler has lost its connection to the component that monitors how hot the water is getting, meaning it cannot operate safely and has shut down.
Your boiler has shut down because the internal water temperature has become too hot for it to operate safely.
Your boiler has switched itself off because it has detected that the water inside has become dangerously hot or the system pressure is incorrect.
Your boiler has shut down because a safety sensor detected that the internal exhaust gases have reached a dangerously high temperature.
Your boiler has overheated or detected a serious sensor error and has shut down as a safety precaution.
Your boiler has shut down because it has detected an dangerously high internal temperature or a faulty electrical connection in the safety sensor.
Your boiler has shut down because a safety sensor detected that the internal gases have become too hot.
Your boiler has shut down because the water inside it has become too hot and risked overheating.
Your boiler has shut itself down because it has detected that the water inside the unit is getting too hot and reaching unsafe temperatures.
Your boiler has sensed that the water coming back from your radiators or hot water tank is dangerously hot, causing it to shut down to prevent damage.
Your boiler has shut down because it can no longer safely monitor the temperature of the exhaust gases leaving the system.
Your boiler has stopped working because it cannot light the fuel required to provide heating and hot water.
Your boiler has tried to light several times but cannot establish a steady flame, meaning it has shut down for safety.
Your boiler has started to heat up but the flame has unexpectedly gone out, causing the system to stop working for safety.
Your boiler has stopped working because the internal control board has lost communication with the gas valve, meaning it cannot safely light the flame.
Your boiler's internal computer has encountered an error and cannot communicate properly, causing the system to stop working for safety.
Your boiler is trying to light itself but failing to sense a flame within the safe time limit, causing it to shut down for safety.
Your boiler's computer system has detected an internal electronic failure, meaning the burner cannot start and the system has shut down for safety.
Your boiler is working harder than it should because water isn't circulating properly through the system, causing the pipes leading out of the boiler to be much hotter than those coming back.
Your boiler’s internal computer system has detected a hardware failure or a loose connection, meaning it cannot communicate with the parts that manage heat.
Your boiler's internal computer is having trouble communicating with its electrical components, preventing it from starting up properly.
Your boiler has experienced an internal electronics crash or software glitch that is preventing it from starting up properly.
Your boiler has detected an electrical issue with the internal components that control the fuel flow, preventing it from firing up safely.
Your boiler's internal computer brain or control module has developed a fault and can no longer communicate with the rest of the system.
Your boiler's internal computer has encountered a critical communication error and cannot tell the system to heat your home or water.
Your boiler's internal computer or control unit has encountered a serious communication error and can no longer operate your heating or hot water safely.
Your boiler's internal computer brain or its connection chip has encountered a critical electrical failure and can no longer control the heating process.
Your boiler's internal computer has developed a critical electronic fault and cannot communicate with the system components.
Your boiler's internal computer has detected a problem with its electronic sensors or their wiring, preventing the system from starting up safely.
Your boiler's main internal computer has developed a serious communication error and can no longer safely control the burner.
Your boiler's electronic brains have developed a fault or aren't plugged in correctly, meaning the system cannot communicate or function.
Your boiler's internal computer has developed a communication fault, meaning it cannot safely control the burner to heat your home.
Your boiler's internal computer brain is either loose or has developed a fault, preventing the unit from starting up.
Your boiler's internal computer or its connection hub has developed a fault and cannot communicate correctly with the rest of the system.
Your boiler's internal computer has developed a fault and can no longer communicate with the main controls, meaning the unit cannot operate safely.
Your boiler thinks a flame is still burning even though it should be turned off, which is a safety error that prevents the system from starting.
Your boiler thinks it sees a flame even though the burner hasn't actually started yet, which is causing it to shut down for safety.
Your boiler has experienced a temporary interruption to its electrical power supply and needs to be restarted.
Your boiler is seeing a flame when it should be turned off, which means the fuel supply might not be closing properly.
Your boiler thinks a flame is still burning inside even though it has been told to turn off.
Your boiler has detected a potential internal gas leak within the control valve, which is a safety risk that prevents the appliance from firing.
Your boiler has detected a potential internal leak within the gas control valve and has shut down for safety.
Your boiler has gone into a temporary lockout because the reset button was pressed accidentally or for too long.
Your boiler has lost its electrical power supply or experienced a sudden interruption in the mains connection.
Your boiler has detected that the water pressure inside the system has dropped too low to operate effectively, meaning your heating and hot water may not work correctly.
Your boiler is experiencing a software or communication error that is causing it to constantly restart itself.
Your boiler is currently idle because it hasn't received a signal from your thermostat or timer to start heating your water.
Your boiler is currently working as expected and is responding to a request to provide heating for your home.
Your boiler is shutting down because it is heating up much faster than it can move the water around the system, often due to a blockage or a pump issue.
Your boiler has lost power completely and will not turn on because electricity is not reaching the main control unit.
Your boiler is currently attempting to restart itself multiple times due to an internal system error.
Your boiler is currently testing its ignition system to try and start the burner.
Your boiler's internal fan is failing to start correctly, meaning the system cannot safely clear exhaust fumes and will not fire up.
Your boiler is performing a routine check of its internal pump and has paused its normal operation to ensure everything is working correctly.
Your boiler's internal switching valve is stuck or having trouble moving between the heating and hot water settings.
Your boiler's control system has detected an internal electronic error during a safety check, preventing the unit from starting up.
BoilerFaultCodes