151 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Replaced by: Greenstar 30i
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 experienced a serious internal communication error or hardware failure that has caused it to shut down for safety.
Your boiler is accidentally stuck in a technician's testing mode and needs to be switched back to its normal operating setting.
Your boiler is currently stuck in a manual testing mode normally used by engineers during a service.
Your boiler's internal computer parts do not recognise each other because an incorrect or incompatible control module has been installed.
Your boiler’s internal computer chip is incompatible or has been incorrectly identified, causing the system to shut down for safety.
Your boiler's main internal computer has lost communication with its identification chip, meaning the system cannot safely operate or provide heating and hot water.
Your boiler is operating normally and is currently providing heat for your radiators.
Your boiler is currently working correctly and is simply letting you know that it is in central heating mode.
Your boiler is simply indicating that it is currently busy heating your water and there is no actual fault to worry about.
Your boiler is currently working to provide hot water to your taps and this code is simply a status update rather than a fault.
Your boiler is currently taking a brief pause and is waiting for the heating or hot water signals to communicate properly before it starts up.
Your boiler has temporarily paused its burner to prevent it from switching on and off too frequently, which helps protect the system from unnecessary wear.
Your boiler is currently in standby mode and waiting for a signal from your thermostat or programmer to start heating.
Your boiler is working perfectly fine and is simply waiting for a signal from your thermostat to start heating.
Your boiler is currently taking a temporary break because the water inside it is already hotter than the temperature you have requested.
Your boiler has paused because it detects that the water inside is currently hotter than the temperature you have requested.
Your boiler is currently running at full power for a manual testing sequence and will not respond to your normal thermostat settings until this mode is turned off.
Your boiler is currently stuck in a professional test mode used by engineers to check emissions, often caused by a button being held too long or a recessed switch becoming stuck.
Your boiler is overheating because the water inside is heating up faster than the system can move it away.
Your boiler has switched itself off because it has detected an unsafe rise in temperature, usually caused by low water pressure or a blockage in the system.
Your boiler has recorded that a physical diagnostic tool was plugged into it to view the internal error history.
Your boiler is trying to light but cannot establish a flame, meaning your heating and hot water will not work.
Your boiler thinks there is a flame burning even though the gas should be off, causing it to shut down for safety.
Your boiler's internal computer chips are not communicating correctly because they have mismatched software versions.
Your boiler has detected that the water isn't heating up or circulating properly after the burner has ignited.
Your boiler is temporarily limiting its power output to prevent overheating because it is struggling to move heat away from the unit quickly enough.
Your boiler is currently running a self-diagnostic check, which usually happens briefly after a reset or power cut.
Your boiler is noting that the temperature is rising too quickly during its normal operation, which often suggests the water isn't moving through the system fast enough.
Your boiler is currently behaving as normal and is simply going through its standard sequence to light the burner.
Your boiler has stopped working because the flame has failed to light, likely due to a problem with the internal gas control system.
Your boiler is confused and thinks you are still running a hot tap elsewhere in the house, preventing it from switching back to heating mode.
Your boiler is temporarily pausing the hot water production to prevent itself from overheating or cycling too frequently.
Your boiler is still detecting a flame even after it has been told to shut off the gas, which is a safety concern that requires a professional inspection.
Your boiler has detected an issue with the electrical power supply coming into your home, meaning the internal computer cannot function correctly.
Your boiler has detected that the electrical supply coming into your home is too weak or unstable for it to operate safely.
Your boiler's internal computer brain cannot communicate properly with its main control unit, preventing the heating and hot water from starting up.
Your boiler's internal computer chip is giving the wrong signal to the main control board, which has caused the system to stop working for safety.
Your boiler has detected a problem with a temperature sensor that monitors how heat is moving through your system, which may prevent your heating from working correctly.
Your boiler has lost its internal connection to the smart controls or sensors, meaning different parts of the system are no longer talking to each other.
Your boiler has detected that the water pressure is too low for it to run safely and simply needs more water added to the system.
Your boiler is unable to provide hot water because the internal sensor responsible for monitoring its temperature has stopped communicating with the system.
Your boiler is struggling to accurately measure the temperature of your hot water, which usually means the internal sensor is either loose or has failed.
Your boiler is having trouble reading the temperature outside, which means it might not adjust its heating levels correctly for the weather.
Your boiler's internal sensor can no longer tell if there is enough water pressure to run safely, so the system has shut itself down as a precaution.
Your boiler is struggling to know how cold it is outside, which can prevent it from heating your home efficiently or at all.
Your boiler has stopped working because an internal sensor that monitors water temperature has developed an electrical fault.
Your boiler has lost communication with the internal thermometer that monitors water temperature, causing the system to shut down for safety.
Your boiler has detected an electrical fault with an internal thermometer, causing the system to shut down for safety.
Your boiler has lost communication with a vital heat sensor, meaning it won't fire up because it cannot safely monitor its internal temperature.
Your boiler has stopped working because it cannot confirm that the flame is burning safely, so it has shut down as a precaution.
Your boiler has stopped working because its internal control system is unable to communicate with the gas valve that fuels the burner.
Your boiler has stopped working because the internal control board is not receiving the correct electrical signal from the gas valve.
Your boiler has lost its flame while running and cannot stay lit, meaning it will likely shut down to prevent damage.
Your boiler's internal computer chip is faulty or has been identified incorrectly, meaning the system cannot communicate with itself to start up.
Your boiler is struggling to keep a flame alight, which is preventing it from providing you with consistent heating or hot water.
Your boiler is trying to light itself but cannot detect a flame, meaning your heating and hot water have likely stopped working.
Your boiler has detected that a temperature sensor is sending an unusual signal, likely due to a loose wire or a faulty connection internally.
Your boiler has detected that water isn't moving through the main heating unit quickly enough, often caused by a blockage or a pump issue.
Your boiler has become too hot and has shut itself down for safety to prevent damage to the internal components.
Your boiler is heating up too quickly and has shut itself down to prevent damage, which usually means the water isn't moving through the system properly.
Your boiler has detected that the water is heating up too quickly or unevenly, causing it to shut down to prevent overheating.
Your boiler has detected that the water pressure in your radiators or pipes is dropping much faster than it should, which usually indicates a significant leak or a fault with the pressure relief system.
Your boiler has detected that the water pressure is too low for it to run safely, likely due to a minor leak or air being trapped in the radiators.
Your boiler's pump is running without enough water, likely because the system has lost pressure or the pump itself has become stuck.
Your boiler's internal pump is either jammed or struggling to move water because there is air trapped inside the system.
Your boiler has detected an electrical fault with a sensor that monitors the safety of the exhaust gases, causing the system to shut down for protection.
Your boiler is struggling to accurately measure the temperature of your hot water, which usually means the hot water is either inconsistent or not heating up at all.
Your boiler has lost its connection with your external wireless temperature controls, meaning it cannot receive the correct signals to turn on or off.
Your boiler is struggling because it isn't receiving a steady supply of electricity from your home's mains power or a internal control module has failed.
Your boiler has lost its identity because a small internal computer chip is missing or not properly connected, causing the system to stop working for safety.
Your boiler's computer brain has encountered a serious internal error and can no longer control the heating system safely.
Your boiler has detected a problem with the fan or air supply and has shut down as a safety precaution while it was running.
Your boiler's internal computer has developed a fault and can no longer control the heating process safely.
Your boiler's fan was spinning when it was supposed to be stopped, often caused by strong winds or a sensing fault.
Your boiler has stopped working because the internal fan, which safely pushes exhaust fumes outside, is not spinning at the correct speed.
Your boiler has shut down because the internal fan is spinning faster than the system's safety limits allow.
Your boiler has stopped working because the fan that helps remove exhaust gases isn't spinning fast enough to operate safely.
Your boiler has stopped working because the internal fan, which safely exhausts gases, is not spinning or starting up.
Your boiler's fan is not spinning fast enough to clear out exhaust fumes safely, which has caused the system to shut down for your protection.
Your boiler has shut down because the internal fan, which safely clears exhaust gases, has suddenly stopped working while the heating was running.
Your boiler has lost communication with the outside temperature sensor, which means it cannot automatically adjust its performance based on the weather.
Your boiler has stopped working because there is not enough water in the system to operate safely.
Your boiler has stopped working because the internal pump that moves water around your pipes has failed its startup test.
Your boiler has detected a problem with the internal sensor that monitors the temperature of the water returning to the unit, causing it to stop heating for safety.
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 shut down because an external safety device, such as a thermostat or a condensate pump, has detected a problem and stopped the connection.
Your boiler is overheating because water is not flowing through the system quickly enough to carry the heat away.
Your boiler has identified that it is heating up too quickly or water isn't moving through the system properly, causing it to shut down to prevent overheating.
Your boiler has shut down because it has detected that the water flowing back into it is dangerously overheating.
Your boiler is overheating because the water inside it is getting too hot too quickly, usually because it isn't moving through the system properly.
Your boiler's temperature sensor has stopped communicating correctly, meaning the system cannot safely monitor how hot the water is and has shut down as a precaution.
Your boiler has stopped working because its internal temperature sensor is reporting a technical electrical fault.
Your boiler has stopped working because it has lost the connection to the internal sensor that monitors the temperature of the water.
Your boiler has lost its connection to the internal thermometer that measures the temperature of the water heading to your radiators, causing it to stop following your heating demands.
Your boiler has detected an electrical fault with the internal sensor that monitors water temperature, causing the system to shut down for safety.
Your boiler has lost its connection to the component that monitors water temperature, causing the system to stop working for safety.
Your boiler has sensed that the water inside IT is getting too hot too quickly, causing it to shut down for safety.
Your boiler has switched itself off because it has detected that the internal water temperature has become dangerously high.
Your boiler has shut down because it detected that the exhaust gases are getting too hot, which is a safety mechanism to prevent damage to the internal components.
Your boiler has switched itself off because it has detected an dangerously high internal temperature or a faulty internal sensor.
Your boiler has shut down because it has detected an dangerously high temperature or an electrical fault in its internal safety sensor.
Your boiler has shut down because it has detected internal temperatures that are too high, meaning it has effectively overheated to protect itself.
Your boiler has shut down because it has detected that the water inside is becoming dangerously hot.
Your boiler has shut down because it has detected its internal water temperature is getting dangerously hot.
Your boiler has sensed that the water inside is getting too hot and has shut itself down to prevent damage or overheating.
Your boiler has sensed that it is getting too hot and has shut itself down as a safety precaution to prevent damage.
Your boiler has stopped working because it cannot light the gas flame required to generate heat and hot water.
Your boiler has stopped working because it cannot light the gas or the flame has gone out unexpectedly.
Your boiler has lost its flame while it was running, which means it has stopped providing heating and hot water for safety.
Your boiler has stopped working because the internal control board has lost electrical communication with the gas valve.
Your boiler's internal computer has encountered a critical communication error and has stopped working for safety.
Your boiler is trying to light itself but the ignition process is taking longer than it should, often because it cannot detect a flame once it has sparked.
Your boiler's computer has detected an internal electronic failure and has stopped working to protect the system.
Your boiler is working harder than it should because water isn't moving through the system quickly enough to take away the heat.
Your boiler’s internal computer has developed a serious communication fault or hardware failure, meaning it can no longer control the heating process safely.
Your boiler has experienced an internal electrical communication error, meaning the control board cannot talk to the parts that start the burner.
Your boiler's internal computer has encountered a software glitch or a communication error that is preventing it from starting safely.
Your boiler has detected an internal electrical communication fault between the main control board and the gas valve, preventing it from lighting safely.
Your boiler's internal computer or control hub has developed a fault and is unable to manage the heating process.
Your boiler's internal computer has developed a logic error or electrical fault, which means it cannot tell the boiler how to operate safely.
Your boiler's electronic brains have encountered a critical internal error and can no longer communicate with the heating system.
Your boiler's internal computer has developed a communication fault or an electronic failure, meaning it cannot safely control the heating process.
Your boiler's internal computer brain is having trouble communicating or has failed, meaning the system cannot run safely.
Your boiler's internal computer is having trouble communicating with its temperature sensors, meaning it cannot safely monitor the water temperature to start up.
Your boiler’s internal computer has suffered a serious electronic failure and can no longer safely control the burner.
Your boiler's electronic command centre is having trouble communicating or has developed a fault, meaning it cannot process commands to heat your home.
Your boiler's internal computer has developed a communication fault and cannot safely tell the burner to fire up.
Your boiler’s internal computer has encountered a critical communication error and cannot operate the system.
Your boiler's internal computer brain or its memory chip has developed a fault and is struggling to communicate with the rest of the unit.
Your boiler's internal computer has encountered a critical communication error and can no longer control the heating process safely.
Your boiler thinks a flame is present even when it should be off, causing it to shut down for safety.
Your boiler thinks a flame is present even though it hasn't actually started the ignition process, causing it to shut down for safety.
Your boiler has experienced a temporary interruption in its electrical power supply, causing it to restart and stop working.
Your boiler is still detecting a flame even though it should have turned off, which is a safety concern that requires a professional inspection.
Your boiler is still detecting a flame even though it has been told to turn off, which is a safety precaution that stops the boiler from running.
Your boiler has detected a potential internal gas leak within its control valve, which is a critical safety issue that prevents it from starting up.
Your boiler has detected a potential internal gas leak and has shut down as a safety precaution.
Your boiler thinks the reset button was pressed by mistake or for too long and just needs a quick second tap to clear the error.
Your boiler has lost its connection to the electrical power supply or has experienced a sudden power cut.
Your boiler has detected that the water pressure is too low, which is preventing your heating and hot water from working properly.
Your boiler is experiencing a critical electronic failure that is causing it to repeatedly restart itself, meaning it cannot provide heating or hot water.
Your boiler is currently sitting in standby mode because it hasn't been told to turn on by your thermostat or timer.
Your boiler is operating normally and is currently heating your home or water exactly as requested.
Your boiler is overheating because the water inside it is getting too hot too quickly, causing it to shut down for safety.
Your boiler has lost power completely and is no longer responding, meaning it cannot provide heating or hot water.
Your boiler is undergoing a restart process after a fault has been cleared or because the reset button was pressed.
Your boiler is currently running a self-diagnostic test to check if the ignition system is working correctly.
Your boiler's fan is failing to start or communicate with the control board, preventing the system from heating up.
Your boiler is struggling to circulate water because the central pump is not functioning correctly.
Your boiler is having trouble switching between the heating and hot water functions because an internal valve is stuck or failing its startup check.
Your boiler has detected an internal electrical problem while checking the safety system that monitors the flame.
BoilerFaultCodes