17 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's temperature sensor for hot water is faulty, meaning your system cannot accurately gauge or control the temperature of the water coming out of your taps.
Your boiler's internal components are having trouble talking to each other, meaning the main control board has lost connection with a key part.
Your boiler's main control board has lost communication with an internal plug-in component or accessory, preventing the system from operating correctly.
Your boiler's internal memory chip is not being recognized, meaning it has forgotten how to operate correctly.
Your boiler has stopped working because the fan that removes waste gases is not spinning fast enough to operate safely.
Your boiler's internal fan is running constantly and won't shut down, preventing the system from starting its normal ignition sequence.
Your boiler has lost its connection to an essential safety link or external control component, causing it to stop running for protection.
Your boiler has lost its ability to measure the temperature of the water leaving the unit, causing it to shut down to prevent overheating.
Your boiler has switched itself off because it has detected that the internal water or exhaust gases have reached a dangerously high temperature.
Your boiler has tried to light several times but has failed to detect a flame, causing the system to shut down for safety.
Your boiler thinks it can see a flame even though it should be turned off, so it has shut down for safety.
Your boiler is still detecting a flame even though it has tried to turn the gas supply off, which is a safety concern that requires professional attention.
Your boiler has been placed into a temporary lock mode because the reset button was held down for too long.
Your boiler has stopped working because it failed to light or stay lit, causing it to shut down for safety reasons.
Your boiler is struggling to start up because a small internal fuse has blown, meaning the main control board cannot send power to the parts it needs to run.
Your boiler is struggling to start up because a small internal fuse has likely blown, preventing the electronics from working correctly.
Your boiler is failing to start up because a small internal fuse has blown, meaning the electronics lack the power they need to run.
Not faults — these are normal operating states. Tap to expand.
BoilerFaultCodes