27 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
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Your boiler has temporarily stopped working because it cannot properly read the temperature of the water flowing through its system.
Your boiler has temporarily stopped working because it cannot properly read the temperature of the water returning from your radiators.
Your boiler has detected a temperature reading that is unusually low, though this specific sensor fault usually applies to combination boilers rather than your system boiler model.
Your boiler has stopped working because a temperature sensor on the main water pipe has developed an electrical fault.
Your boiler has detected an electrical fault with one of its internal temperature sensors, which stops it from working safely.
Your boiler has detected a faulty connection or wiring issue with the hot water temperature sensor inside your water cylinder.
Your boiler has temporarily shut down because the internal temperature got too hot, which is a built-in safety feature to prevent damage.
Your boiler has temporarily stopped working because the water pressure inside your heating system has dropped too low.
Your boiler has temporarily stopped working because there is either too little water inside or the water cannot circulate properly.
Your boiler is locking out because the water inside is heating up much too quickly, usually due to low water pressure or a blocked circulation path.
Your boiler has detected a false flame signal inside, meaning it thinks a fire is burning when the gas valve is actually closed.
Your boiler is trying to start up, but it is failing to ignite the gas safely.
Your boiler has lost its flame during operation and failed to restart, usually because the gas supply has been briefly interrupted or the ignition system cannot spark properly.
Your boiler has detected that its internal air fan is spinning much faster than it should be when trying to start up.
Your boiler has detected an internal electrical safety fault within the gas control system, so it has safely shut down to prevent any hazard.
Your boiler has detected an electrical fault with the valve that controls the gas supply, meaning it has safely shut down to prevent any risk.
Your boiler has detected an issue with the internal gas valve failing to shut off correctly when required, which poses a safety risk.
Your boiler has suffered an internal computer memory error, meaning the main control board has failed and cannot save its settings.
Your boiler has detected an issue with its internal temperature sensors or main electronics, meaning it cannot accurately measure how hot the water is.
Your boiler has temporarily stopped working because the main computer board inside has become too hot.
Your boiler has lost its identity programming after a replacement part was fitted incorrectly, meaning it doesn't know how to run properly.
Your boiler has temporarily stopped working because the sensor that measures the water temperature inside has stopped updating correctly.
Your boiler is temporarily locked out because it has detected a disagreement or fault between the temperature sensors on its main pipes.
Your boiler has lost its reading on the water pressure inside the system because the sensor or its wiring is faulty.
Your boiler has detected an electrical fault with its internal water pressure sensor, meaning it cannot correctly read the pressure inside the system.
Your boiler has noticed that the water pressure doesn't jump up when the internal pump turns on, which usually means there is either not enough water in the system or the pressure sensor is struggling to read it correctly.
Your boiler has detected dangerously high temperatures inside its main heating unit, triggering an emergency safety lock-out.
Not faults — these are normal operating states. Tap to expand.
BoilerFaultCodes