68 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Replaced by: Greenstar Highflow
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 a critical internal error with its electronic brain or air flow system and has locked itself for safety.
Your boiler's internal computer module does not match the main control board, preventing the system from starting up.
Your boiler has lost its connection to its internal memory chip, meaning it cannot properly identify itself or control the heating process.
Your boiler is working correctly and is simply waiting for a signal from your thermostat to start heating up.
Your boiler is taking a short, temporary break to prevent the burner from turning on and off too frequently, which protects the internal components and saves energy.
Your boiler is temporarily pausing because the water inside it is currently hotter than the temperature you have requested.
Your boiler is overheating because the water inside is heating up too fast, often due to a pump failure or a blockage preventing water from moving through the system.
Your boiler has switched itself off because it has detected it is getting too hot, likely due to low water pressure in the system.
Your boiler is failing to light properly even though it is trying to ignite, which means it cannot provide any heating or hot water until it is repaired.
Your boiler thinks a flame is burning even though it hasn't actually started, which is preventing it from running for safety reasons.
Your boiler's internal computer parts are talking to each other using different languages and need a software update or a compatible replacement part to work together properly.
Your boiler has fired up, but it cannot detect the water getting any warmer, so it has shut down to prevent overheating.
Your boiler has temporarily reduced its power output because it has reached the required temperature and is waiting for the heating system to catch up.
Your boiler is busy prioritising your hot water and is waiting for that cycle to finish before it can provide heating for your radiators.
Your boiler is taking a short, programmed break to prevent it from switching on and off too frequently while heating your water.
Your boiler is still detecting a flame even after it has been told to shut off the gas, which is a safety conflict requiring professional attention.
Your boiler has detected an unstable electrical supply or an internal fault with its control board, meaning it cannot operate safely.
Your boiler is not receiving a steady or strong enough supply of electricity from your home to operate safely.
Your boiler's internal computer chips are not communicating correctly because the replacement part fitted is incompatible with the main control board.
Your boiler’s internal computer chip is not communicating correctly with the main control board, meaning the system cannot identify which model it is meant to be.
Your boiler's internal computer system has lost communication with its smart controls or sensors due to a wiring issue or a blown fuse.
Your boiler has detected that the water pressure is too low for it to operate safely and simply needs more water added to the system.
Your boiler's hot water sensor isn't communicating with the system, which means it cannot safely or accurately heat your water.
Your boiler has lost connection with the sensor that monitors your hot water tank, meaning it cannot tell how hot your water is.
Your boiler is having trouble reading the temperature outside, which means it might not adjust its heating levels correctly to match the weather.
Your boiler's internal computer has lost contact with the sensor that monitors water pressure, meaning it cannot safely tell if there is enough water in the system to operate.
Your boiler's outdoor thermometer is not communicating properly, which may cause the heating to run at the wrong temperature for the current weather.
Your boiler has detected an electrical fault with the internal sensor that monitors water temperature, causing the system to shut down as a safety precaution.
Your boiler has lost communication with its internal thermometer, meaning it cannot safely tell how hot the water is getting and has shut down as a precaution.
Your boiler has detected an electrical fault with its main temperature sensor, which has caused the system to shut down for safety.
Your boiler has lost communication with its internal temperature sensor, preventing it from knowing how hot it is and causing the system to shut down for safety.
Your boiler has detected an issue where it cannot confirm if the gas flame is burning correctly, causing the system to shut down for safety.
Your boiler has stopped working because its internal computer has lost communication with the valve that controls the gas supply.
Your boiler has stopped working because the internal control board has lost communication with the gas valve that manages the flame.
Your boiler was running but the flame went out unexpectedly, causing the system to shut down for safety.
Your boiler's internal computer memory chip is missing, broken, or doesn't match the model, preventing the system from starting up.
Your boiler is struggling to light or maintain its burner flame and may require an internal adjustment to the gas mixture.
Your boiler is failing to detect a flame when it tries to start, which is preventing it from heating your home safely.
Your boiler has detected an unusual temperature reading because a sensor wire is faulty or has come loose, causing the system to shut down for safety.
Your boiler is struggling to push water through the heating system quickly enough to prevent it from overheating.
Your boiler has shut down because the water inside has become too hot, which is usually caused by a blockage or a pump failure preventing heat from moving away from the unit.
Your boiler's water is getting too hot too quickly, causing the system to shut down to prevent damage.
Your boiler has sensed an unusual temperature difference between internal sensors, suggesting that water isn't flowing through the system correctly.
Your boiler has detected that the water pressure in your pipes is dropping much faster than it should, often because of a leak or an issue with the expansion tank.
Your heating system has lost water pressure and likely needs to be topped up to continue working.
Your boiler has detected that there is not enough water circulating, which could be due to a leak or a mechanical issue with the pump.
Your boiler is struggling to accurately measure the temperature of your hot water, which usually means it can't provide reliable heat for your taps and showers.
Your boiler has lost its connection to the external heating controls, meaning it cannot receive the signal to turn on properly.
Your boiler's internal computer chip is missing or has lost its connection, meaning the system doesn't know which model it is and cannot operate.
Your boiler has shut down because a built-in safety fan is not spinning fast enough to clear away exhaust fumes.
Your boiler has lost communication with the outdoor temperature sensor, which means the system cannot automatically adjust its efficiency based on the weather outside.
Your boiler has detected a fault with the sensor that monitors the temperature of the water leaving the unit, meaning it cannot safely regulate heat.
Your boiler has sensed that it is becoming dangerously hot and has shut itself down for safety.
Your boiler has tried to light several times but has failed to detect a flame, meaning it has locked itself out for safety.
Your boiler is failing to light or is losing its flame while running, which means your heating and hot water have stopped working.
Your boiler was running but the flame went out unexpectedly, causing the system to shut down for safety.
Your boiler's computer module has encountered an internal error and has stopped the heating to protect the system.
Your boiler is struggling to move water through the system efficiently, causing it to slow down to prevent overheating.
Your boiler's internal computer or control unit has suffered an electrical failure and can no longer manage the heating process.
Your boiler's internal computer is having trouble communicating with its electrical components, meaning it cannot safely start the ignition process.
Your boiler thinks it sees a flame even though it should be turned off, which is a safety conflict that prevents it from starting up.
Your boiler is still detecting a flame even though it has tried to turn the gas off, which is a serious safety concern.
Your boiler thinks it still sees a flame even though it has commanded the burner to turn off.
Your boiler has detected a potential internal gas leak or a fault with the safety valve that controls the fuel supply.
Your boiler has detected a potential internal gas leak during its safety startup checks and has shut down to keep you safe.
Your boiler has stopped because the reset button was pressed accidentally or for too long, and it just needs a quick restart to clear the error.
Your boiler has experienced a sudden loss of electrical power or a significant voltage drop, causing it to shut down for safety.
Your boiler appears to have no electrical power, meaning it won't respond or show any signs of life.
Not faults — these are normal operating states. Tap to expand.
BoilerFaultCodes