26 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
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Your boiler has detected that the exhaust gases are too hot or are not escaping properly, causing it to shut down for safety.
Your boiler has stopped working because the water pressure is too low and needs to be topped up.
Your boiler has detected that the water pressure inside the system is too high, causing it to stop running for safety.
Your boiler has detected a problem with the temperature sensor that monitors your hot water, which may prevent it from heating water correctly.
Your boiler has stopped working because a sensor that monitors the temperature of the water leaving the unit has developed a fault.
Your boiler is failing to light properly, which means it will not be able to provide heating or hot water until the issue is resolved.
Your boiler has likely overheated or has an airlock, causing it to shut down as a safety precaution.
Your boiler is having trouble sensing the flame required to stay lit, which means it will stop working to ensure your safety.
Your boiler has detected that water is not moving around the system properly, which has caused it to shut down to prevent overheating.
Your boiler has detected an issue with an internal sensor or a setup error, meaning it cannot accurately monitor the water temperature.
Your boiler has lost communication with the part that controls the gas flow, meaning it cannot safely ignite to provide heating or hot water.
Your boiler's computer has been set up with the wrong internal settings, meaning it doesn't know which type of ventilation system it is connected to.
Your boiler has shut down because it detected that the waste gases are getting too hot or the flue sensor is faulty.
Your boiler has detected an issue with the sensor that monitors exhaust gases, which has caused the system to shut down for safety.
Your boiler has detected a communication problem with the internal fan, meaning it cannot safely clear waste gases to start the ignition process.
Your boiler has stopped working because the waste water pipe that carries moisture away from the unit is blocked or full.
Your boiler has been reset too many times in a short period and has temporarily locked itself for one hour as a safety precaution.
Your boiler has detected that the electricity supply from the mains is too weak to power the unit safely.
Your boiler has detected an issue with the electrical power supply coming into your home, meaning the electrical timing is not compatible with the boiler's sensitive electronics.
Your boiler has tried and failed to light the flame several times in a row, causing it to shut down for safety.
Your boiler has detected that one of its control buttons is stuck or faulty, which is preventing the control panel from working correctly.
Your boiler is having trouble communicating with your external thermostat or smart home controller.
Your boiler has detected that a temperature sensor is not sitting correctly on the main pipe, meaning it cannot accurately monitor the water leaving the unit.
Your boiler has detected an issue with the air or gas mixture during ignition, often caused by a blocked chimney or an internal sensor problem, and has shut down for safety.
Your boiler is struggling to burn gas correctly, often because air is trapped in the system or the burner is dirty.
Your boiler has shut down because the exhaust pipe is blocked or restricted, preventing harmful waste gases from leaving your home safely.
Not faults — these are normal operating states. Tap to expand.
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BoilerFaultCodes