40 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
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Your boiler's internal computer parts are struggling to talk to each other, which means the system cannot receive the signals it needs to turn on.
Your boiler has stopped working because it cannot communicate with the sensor that monitors the temperature of the water leaving the unit.
Your boiler has stopped working because it can no longer monitor the temperature of the water coming back from your radiators.
Your boiler has detected an electrical fault with the sensor that monitors water temperature, causing it to stop heating for safety.
Your boiler has detected an electrical fault with the sensor that monitors water returning from your radiators, causing the system to stop working for safety.
Your boiler has lost communication with the hot water cylinder temperature sensor because of an electrical fault, meaning it cannot safely tell if your water is hot enough.
Your boiler has shut itself down because it has become too hot to operate safely.
Your boiler has stopped working because there is not enough water pressure in the system to operate safely.
Your boiler has shut down because the internal water temperature is rising too quickly or unevenly, usually due to a circulation blockage.
Your boiler is overheating too quickly because water isn't moving through the system properly, causing it to shut down for safety.
Your boiler has shut down because the exhaust gases have become too hot, which is a safety mechanism to prevent internal damage.
Your boiler has detected a flame when there shouldn't be one, so it has shut down as a safety precaution.
Your boiler has tried to light several times but has been unable to establish a flame, meaning you have no heating or hot water.
Your boiler has lost its flame while it was running and cannot manage to light itself back up.
Your boiler has detected a problem with the fan that safely removes exhaust gases, meaning it has shut down as a safety precaution.
Your boiler has identified a problem with how it moves air and fumes through the system, preventing it from starting safely.
Your boiler's internal communication system has lost power or experienced a short circuit, preventing the controls from talking to the main unit.
Your boiler has detected a communication error with the gas valve, preventing it from safely lighting the burner for heating and hot water.
Your boiler has detected that the gas valve is not closing as quickly as it should, which is preventing the unit from operating safely for your protection.
Your boiler's internal computer brain is struggling to process its saved memory, which has caused the system to stop working for safety.
Your boiler has detected an internal electrical communication error or a faulty sensor that is preventing it from running safely.
Your boiler's internal control board has become too hot and has shut itself down to prevent any damage to the electronics.
Your boiler’s control board is receiving an incorrect electrical signal from the flame sensor, meaning it cannot safely confirm if the burner is lit.
Your boiler is struggling to keep a steady flame lit, which is causing the system to shut down for safety.
Your boiler’s control board has forgotten which model it is supposed to be, usually after a part has been replaced or due to a memory error.
Your boiler has detected that one of its internal thermometers has stopped responding or is stuck on a single temperature reading, preventing it from heating safely.
Your boiler has detected that the sensors measuring water temperature are giving conflicting readings or have failed, preventing the system from heating safely.
Your boiler is unable to accurately measure the water pressure because the internal sensor is sending an incorrect or missing signal.
Your boiler has detected that the water pressure is too high, or the internal sensor that monitors pressure has developed a fault.
Your boiler is unable to sense a change in water pressure when the pump starts up, preventing it from firing for safety.
Your boiler is having trouble clearing away excess water or exhaust gases, causing it to shut down for safety.
Your boiler is having trouble communicating with the hot water sensor in your external control box, meaning your hot water may not reach the desired temperature.
Your boiler has detected that its temperature sensors aren't registering a change in heat when the burner is on, which is often caused by a lack of water or a sensing error.
Your boiler is confused because its internal thermometers are giving conflicting readings, causing it to shut down to prevent overheating.
Your boiler has detected that a temperature sensor is either loose or has been fitted to the wrong pipe, preventing it from reading the heat levels correctly.
Your boiler has detected an issue with the electrical connection to your underfloor heating system, preventing that part of your home from warming up properly.
Your boiler is struggling to spark correctly to light the gas, meaning it cannot provide heating or hot water until the ignition system is fixed.
Your boiler has detected a problem with how it controls the gas supply, meaning it cannot safely light the flame to provide heating or hot water.
Your boiler has stopped working because the internal pump that moves water around your heating system has failed or is struggling to turn.
Your boiler has stopped working because the water pressure is too low for it to operate safely.
Not faults — these are normal operating states. Tap to expand.
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BoilerFaultCodes