48 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
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Your boiler has failed to ignite or detect a flame, meaning it has safely shut down to stop gas from flowing without a fire.
Your boiler has logged a previous system fault that requires attention from a qualified heating engineer.
Your boiler has shut down because it detected that exhaust gases are not escaping correctly through the flue, which is a safety risk.
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 is too high, which can cause the system to stop working to prevent damage.
Your boiler has detected a problem with the temperature sensor that controls your hot water, meaning you may experience cold or inconsistently heated water.
Your boiler has detected a fault with the sensor that monitors the temperature of the water leaving the unit, meaning it cannot operate safely or effectively.
Your boiler is failing to light properly, which means you currently have no heating or hot water.
Your boiler has switched itself off to prevent overheating, usually because the water isn't moving through the system correctly or there is trapped air.
Your boiler is struggling to detect a flame, which means it cannot stay lit to provide heating or hot water.
Your boiler has stopped working because water is not moving around the system correctly, which could be due to a blockage or a stuck pump.
Your boiler has stopped working because its internal computer is confused about its settings or a sensor has developed an electrical fault.
Your boiler has detected a communication error with the component that controls the gas supply, preventng it from firing up safely.
Your boiler's computer has been set to the wrong internal configuration, causing it to shut down for safety because it doesn't recognize how it is built.
Your boiler has shut down because it detected that the exhaust gases are getting too hot or the sensor that monitors them has failed.
Your boiler has detected an issue with the sensor that monitors exhaust gases, meaning it has shut down as a safety precaution.
Your boiler has detected a communication problem with its internal fan, which is preventing it from starting up safely for heating and hot water.
Your boiler has detected that the water drain for condensation is backed up or blocked, which has caused the system to shut down for safety.
Your boiler has been manually reset too many times in a short period and has temporarily locked itself for safety reasons.
Your boiler has detected a problem with the sensor that monitors water temperature returning from your radiators, and it has stopped working for safety.
Your boiler has stopped working because the electricity supply coming into your home is currently too weak or unstable to power the unit safely.
Your boiler has detected an issue with the electrical power supply coming into your home, meaning the frequency of the electricity does not match what the boiler needs to operate safely.
Your boiler has failed to stay lit after six attempts and has shut down to prevent damage, possibly due to a fuel supply issue or a faulty internal sensor.
Your boiler's controls have detected a stuck or malfunctioning button on the front panel, preventing it from processing your commands.
Your boiler is struggling to talk to your smart thermostat or wall controller, preventing the system from following your heating instructions.
Your boiler is failing to light because its internal computer and gas valve are not communicating correctly.
Your boiler has shut down because the water is not flowing through the system quickly enough, causing the temperature difference between the pipes to become too large.
Your boiler has temporarily locked itself because it has detected an unusual temperature reading and needs to recalibrate its internal sensors to work correctly again.
Your boiler has detected that a temperature sensor is not sitting correctly on its pipe, preventing the system from accurately monitoring the heat of your water.
Your boiler has detected an issue with a temperature sensor that monitors the water being sent to your taps or radiators, meaning it cannot accurately gauge the water heat.
Your boiler has detected an electrical issue with the internal gas valve, which is preventing it from lighting the burner safely.
Your boiler has detected an internal electrical fault with the gas control valve, preventing it from firing safely.
Your boiler has detected an internal electrical fault with the gas control valve or the main control board, preventing it from firing up safely.
Your boiler has detected an internal communication failure between the main control board and the gas valve, meaning it cannot safely manage the fuel supply.
Your boiler has detected an issue with the air or gas mixture during ignition, often caused by a blocked vent or a sensor problem, and has locked itself out for safety.
Your boiler has shut down because it has struggled to start or maintain a steady flame several times in a row.
Your boiler is struggling to burn gas correctly, often because of air in the pipes or a blockage in the chimney.
Your boiler has detected that the gas supply pressure coming into the unit is too low to operate correctly.
Your boiler's internal computer has detected a serious electronic failure and has shut down to protect its circuits.
Your boiler is struggling to maintain a steady flame and has shut down as a safety precaution to ensure gas is burning correctly.
Your boiler is struggling to manage the correct balance of gas and air needed for a safe flame, causing it to shut down for safety.
Your boiler's internal sensor has detected an issue with the air and gas mixture, causing the system to stop for safety.
Your boiler is struggling to burn gas correctly and is failing to reach its required performance levels, causing the system to shut down for safety.
Your boiler is struggling to maintain a steady flame, causing it to shut down to prevent damage or unsafe operation.
Your boiler has shut down because it cannot safely expel exhaust fumes, meaning the vent to the outside may be blocked.
Your boiler's internal computer has encountered a software glitch while trying to start up.
Your boiler's internal computer has suffered a total failure and can no longer control the heating system.
Your boiler is displaying a service reminder indicating that it has reached its scheduled time for an annual check-up.
Not faults — these are normal operating states. Tap to expand.
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BoilerFaultCodes