14 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Replaced by: Greenstar 24i / 28i Junior
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Your boiler is struggling to detect the flame needed to heat your home and has shut down as a safety precaution.
Your boiler is struggling to accurately measure the temperature of the water it is heating, which will likely prevent you from getting hot water through your taps.
Your boiler's internal control system has lost its connection, meaning it cannot properly talk to its own brain to coordinate heating or hot water.
Your boiler is failing to communicate with its primary control unit, meaning the system cannot start or maintain your heating and hot water.
Your boiler is struggling because a small internal identification chip that tells the system how to operate correctly has come loose or is not being recognised.
Your boiler has stopped heating because the internal mechanism that pushes air through the system is not spinning fast enough to allow for safe combustion.
Your boiler has detected that the internal exhaust fan is spinning faster than it should, so it has shut down as a safety precaution to prevent incorrect combustion.
Your boiler has detected an interruption in a safety circuit, usually meaning a wire or link is disconnected, which prevents the heating from turning on.
Your boiler has lost the ability to accurately measure the temperature of the water being sent to your radiators, so it has shut down to prevent overheating.
Your boiler has switched itself off because it has become dangerously hot and needs to cool down to prevent damage.
Your boiler has failed to light the flame needed to heat your water and home, so it has safely shut itself down.
Your boiler has detected a flame signal when it is supposed to be turned off, which suggests a potential fault in the burner control system.
Your boiler has detected that a flame is still burning inside the unit even though it should have turned off, which is a safety concern that requires an immediate professional check.
You have accidentally pressed the reset button on your boiler while it was already running normally, so it is just waiting for a few seconds to restart itself.
Not faults — these are normal operating states. Tap to expand.
BoilerFaultCodes