20 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Replaced by: Greenstar Si Compact
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 failed to ignite properly, meaning it cannot create the flame needed to heat your home or water.
Your boiler has detected a general internal fault that requires a system reset or power cycle to clear.
Your boiler has detected a safety-related issue and has locked itself out to prevent further damage, requiring a manual reset to restart.
Your boiler's internal settings dial has been accidentally moved into an active testing mode instead of its normal operating position.
Your boiler has lost power because it is switched off at the front, there is no electricity reaching the unit, or an internal fuse has blown.
Your boiler has suffered an electrical failure that has caused it to lose power and stop providing heating and hot water.
Your boiler’s internal control system has suffered an electrical component failure and can no longer manage the heating process.
Your boiler is not receiving a signal from your thermostat or internal timer telling it to turn on.
Your boiler has detected a problem with the internal sensor that tells it when to provide hot water, meaning you currently have no hot water when you turn your taps on.
Your boiler has likely detected that it is too cold to operate safely or that moisture has affected its internal electronics.
Your boiler has shut down because it has reached a temperature that is too high, often due to a lack of water or a circulation issue.
Your boiler has detected that it is getting dangerously hot and has shut itself down to prevent damage.
Your boiler has stopped working because it cannot light the flame, which means you currently have no heating or hot water.
Your boiler has stopped working because it cannot ignite the flame needed to heat your water and radiators, possibly due to a gas supply problem or an issue with the internal ignition system.
Your boiler has detected an electrical issue with one of its internal sensors or the gas valve, causing the system to shut down for safety.
Your boiler has lost the ability to read the temperature correctly, which is preventing it from heating your water or home safely.
Your boiler has detected a problem with how air and waste gases are moving through the system, causing it to shut down for safety.
Your boiler's main internal computer has developed a serious communication error and cannot operate, often because it has been exposed to water or has suffered an electrical failure.
Your boiler has likely been left in a testing mode during a service, or it is struggling to control the temperature of your hot water properly.
Your boiler has stopped working because it cannot detect a flame, likely due to a gas supply interruption.
BoilerFaultCodes