20 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Replaced by: Greenstar 25i (2015-2021) / Greenstar 4000
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Your boiler is failing to detect the flame needed to heat your water because the internal sensor is dirty or worn out.
Your boiler has detected an internal communication error with its main control unit, which has caused it to stop working for safety reasons.
Your boiler's main computer control panel is failing to process instructions correctly, which has caused it to stop working for safety reasons.
Your boiler has detected that there is not enough water circulating inside the system to keep it running safely.
Your boiler is having trouble reading the temperature of the internal hot water store, so it has stopped producing hot water to prevent an error.
Your boiler is currently unable to detect the temperature of your hot water, which means it has stopped providing hot water to your taps and showers.
Your boiler has lost the digital connection between its internal components, meaning it has stopped working because it cannot properly coordinate its heating functions.
Your boiler has lost the connection to the sensor that measures the heat inside your hot water storage tank, so it cannot accurately tell when the water is hot.
Your boiler is struggling to recognise one of its internal electrical components, which is preventing it from starting up correctly.
Your boiler is struggling to push air through its system as required, which has caused it to switch itself off for safety.
Your boiler has lost communication with a key internal component that tells it how to regulate your heating and hot water, causing the system to stop working as a precaution.
Your boiler has lost the vital signal it needs from its internal control link, meaning it cannot safely start up your heating or hot water.
Your boiler has stopped working because it cannot correctly read the temperature of the water circulating through your radiators.
Your boiler has detected that it has become dangerously overheated and has automatically shut down to prevent damage.
Your boiler has detected a serious internal system error that prevents it from operating safely or correctly.
Your boiler has detected a flame inside the unit when it should be completely turned off, which indicates a potential safety sensor issue that requires professional attention.
Your boiler's electronic display panel is failing to communicate with the internal computer, which prevents the unit from operating normally.
Your boiler is struggling to power up correctly, likely because an internal electrical safety fuse has failed.
Your boiler is struggling to start up because a small internal fuse responsible for powering the electronic controls has stopped working.
Your boiler's electronic control system has failed to start up because a small internal protective fuse has blown.
Not faults — these are normal operating states. Tap to expand.
BoilerFaultCodes