18 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Pick the one you have. The fault codes, GC numbers and manual differ by type.
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 →
Tap any card for details
Your boiler is temporarily pausing because it cannot properly read the water temperature, or water is not flowing through it correctly.
Your boiler has detected that the water inside it is getting too hot, too quickly, or is unable to circulate properly, so it has shut down to prevent damage.
Your boiler is struggling to accurately measure the temperature of the water flowing through it, so it has shut down to prevent overheating.
Your boiler has temporarily shut down because it has become too hot, usually due to a lack of water flow or a blocked circulation path.
Your boiler has received a signal from an external control, such as a smart thermostat or a safety device, telling it to turn off.
Your boiler has detected that it is running much too hot and has automatically shut itself down to prevent damage or overheating.
Your boiler is trying to start up, but it is failing to detect a flame and light properly.
Your boiler has stopped because the flame inside has gone out and it cannot get it to stay lit.
Your boiler is failing to light or stay lit, which means it has stopped producing heat and hot water as a safety precaution.
Your boiler has stopped working because it cannot safely test or run the internal fan that expels combustion gases.
Your boiler's internal computer is struggling to communicate with its own parts, meaning it has safely shut down until it can 'talk' to itself properly again.
Your boiler is unable to safely move air through its system, so it has shut down to prevent any risk of incomplete combustion.
Your boiler has lost its memory or cannot communicate with its internal computer, meaning it has completely stopped working for your safety.
Your boiler's internal computer is experiencing a software or communication error and has stopped working to prevent any potential damage.
Your boiler's internal computer has encountered a memory error or a communication issue with its control system, preventing it from starting up correctly.
Your boiler is temporarily locked out because it is having trouble reading its internal settings or communicating properly with its internal parts.
Your boiler has detected an internal electronic error within its main control system that is preventing it from starting safely.
Your boiler has stopped working because its internal components are struggling to talk to each other or have detected a sequence error.
Monthly cover means no unexpected bills when your boiler breaks down.
Affiliate links. We may earn a commission at no extra cost to you.
BoilerFaultCodes