68 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’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 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 taking a temporary break because the water inside it is already hotter than the temperature you have requested.
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 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 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 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 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 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 has stopped working because the internal fan, which safely pushes exhaust fumes outside, is not spinning at the correct speed.
Your boiler has lost communication with the outside temperature sensor, which means it cannot automatically adjust its performance based on the weather.
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 switched itself off because it has detected that the internal water temperature has become dangerously high.
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's internal computer has encountered a critical communication error and has stopped working for safety.
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 thinks a flame is present even when it should be off, causing it to shut down for safety.
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 lost power completely and is no longer responding, meaning it cannot provide heating or hot water.
Not faults — these are normal operating states. Tap to expand.
BoilerFaultCodes