22 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Replaced by: Greenstar i Junior
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Your boiler is signalling that the water inside your heating system is contaminated with sludge or debris, which can damage the system over time.
Your boiler has detected that it is getting too hot and has automatically switched itself off to prevent any damage or danger.
Your boiler is failing to detect the incoming electrical signal it needs to start or continue its heating cycle.
Your boiler is failing to light the flame needed to produce heat or hot water and has automatically shut down for your safety.
Your boiler has reached an unsafe temperature and has shut itself down to prevent damage to the internal components.
Your boiler is attempting to start but is unable to detect a steady flame, so it has safely shut itself down to prevent gas from building up.
Your boiler has detected that it is running too hot and has automatically shut itself down to prevent damage.
Your boiler is struggling to detect or control the flow of gas required to ignite the flame, meaning it cannot currently produce hot water or heating.
Your boiler is struggling to detect the flame needed to heat your water, which is causing it to shut down for safety reasons.
Your boiler has detected a dangerous problem with the flue or ventilation system, preventing it from safely removing exhaust gases.
Your boiler has stopped working because it cannot safely clear waste gases through the flue pipe.
Your boiler has detected that a internal sensor responsible for measuring water temperature has stopped working correctly.
Your boiler has detected an electrical communication problem with its internal control system which is preventing it from firing up.
Your boiler has lost communication between its internal computer and a key electrical sensor or motor, meaning it cannot operate safely.
Your boiler is having trouble communicating with the sensor that monitors the temperature of your hot water cylinder.
Your boiler is failing to light the burner, meaning it cannot provide you with any hot water or heating.
Your boiler is struggling to light smoothly, causing it to build up a small amount of gas before igniting with a loud bang.
Your boiler has detected that the burner flame is still lit even after it has tried to turn the gas supply off, which indicates a serious safety malfunction.
Your boiler is struggling to detect the flow of water needed to heat your taps, usually because the incoming water supply is restricted or a internal sensor is stuck.
Your boiler is struggling to control the temperature of the water, which means it cannot reliably provide hot water or heating.
Your boiler is failing to ignite the flame needed to heat your water, which could be caused by blocked gas flow or a worn internal component.
Your boiler is struggling to pass water through its heating system, which is causing it to make loud, rumbling, or banging noises.
Not faults — these are normal operating states. Tap to expand.
BoilerFaultCodes