97 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
The fault code is already on your display
Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →
Tap any card for details
Your boiler's internal computer system is having trouble talking to its main control unit, meaning the appliance cannot tell itself to heat your home or water.
Your boiler has lost the ability to 'talk' to its display, meaning it cannot receive commands or show you what it is doing.
This is a settings menu adjustment that controls the maximum heat output of your boiler rather than a mechanical breakdown.
Your boiler is continuing to run its internal pump after the heating has switched off to safely cool down the heat exchanger.
Your boiler is taking a short, programmed energy-saving break to prevent the burner from turning on and off too frequently.
Your boiler is currently in a brief, automatic resting period between heating cycles to prevent excessive wear on the system.
Your boiler is displaying the current temperature of the water inside your hot water storage cylinder; this is a status information code rather than a system failure.
This is a normal status message showing the temperature your boiler is currently aiming to reach for your heating, rather than a fault code.
Your boiler is displaying the current temperature setting for your hot water tank rather than a fault code.
Your boiler is waiting for a signal from your thermostat to tell it to turn on, which means the heating is currently switched off or the room has reached the desired temperature.
Your boiler is simply displaying the target temperature being requested by your external room thermostat or smart control system, rather than indicating a breakdown.
Your boiler is displaying a status message to show that the internal pump responsible for circulating heat is currently active.
Your boiler is checking or operating an external pump that helps circulate water through your heating system.
Your boiler is providing an update on whether the pump responsible for moving hot water around your system is currently running or stopped.
Your boiler is currently set to a configuration mode that requires an adjustment to how water is circulated through your heating system.
This is a normal status screen showing whether your thermostat is currently telling the boiler to turn the heating on or off.
Your boiler is currently set to measure the temperature of the water returning to the unit rather than the water flowing out to your radiators.
This is a settings status showing whether your pump stays on longer for extra comfort or switches off sooner to save energy, rather than an actual fault code.
Your boiler is displaying the current maximum limit it is allowed to reach when heating your hot water, rather than being a breakdown fault.
This is a normal status code indicating whether your central heating is currently requested to be on or off.
Your boiler is checking whether there is enough water pressure to run safely, but it hasn't yet reached the point of locking out with a permanent error.
Your boiler is currently being told by your thermostat to heat your hot water tank or maintain a pilot of pre-warmed water.
Your boiler's internal computer is having trouble communicating with an add-on control module, meaning some of its extra functions aren't working correctly.
Your boiler is notifying you of an issue with how an optional internal or external control module is communicating with the main system.
Your boiler is displaying a configuration setting rather than a fault, indicating how the system is set to top up its water pressure.
Your boiler's fan is struggling to reach the speed required to safely clear exhaust gases, which is preventing the boiler from firing up.
Your boiler is displaying a technical information readout regarding the current fan speed rather than an actual fault code.
Your boiler is measuring the temperature of the water leaving the unit to heat your radiators.
Your boiler is displaying the current temperature of the water returning from your radiators rather than showing an error; this is an informational status code and not a fault.
Your boiler's energy-saving settings for heating your radiators are not correctly configured to match the outside temperature.
This is a settings menu adjustment rather than a fault, showing the starting temperature point for your heating system's energy efficiency curve.
Your boiler is struggling to accurately measure the weather outside, which may cause it to heat your home less efficiently.
Your boiler is notifying you that it has automatically adjusted the fan's minimum power level to ensure the system continues to run reliably.
Your boiler is struggling to automatically adjust its internal fan speed to ensure it burns gas safely and efficiently.
Your boiler is currently set up to allow an external solar heating system to pre-heat your water, which is a status message rather than a breakdown.
Your boiler has paused heating because it detects a sudden temperature imbalance, likely caused by trapped air or a blockage in the pipes.
This is a diagnostic information code showing the total count of times your boiler has successfully lit its flame, rather than an active fault preventing operation.
Your boiler is currently running at a lower temperature during the night to save energy, which is a normal setting and not an error.
Your boiler is taking longer than expected to light the flame, which could lead to an intermittent loss of heating and hot water if the issue worsens.
Your boiler is struggling to light the flame correctly or is taking too long to detect that the burner has started.
Your boiler is notifying you that the 'warm start' feature is active, which keeps a small amount of water pre-heated so it reaches your taps faster.
Your boiler is taking a planned temporary break to prevent the burner from turning on and off too frequently, which helps save energy and protect internal parts.
Your boiler is struggling to light the flame on the first try, though it may eventually start after multiple attempts.
Your boiler is struggling to light its flame and is failing on the second try, which usually indicates an issue with the fuel supply or the ignition components.
Your boiler is notifying you that it has reached the maximum temperature limit set for your central heating water.
Your boiler has taken longer than it should to heat up your hot water cylinder, which usually means the heat isn't being transferred efficiently from the boiler to the tank.
Your boiler is notifying you that it is currently prioritising reheating your hot water cylinder at its maximum power setting.
Your boiler's memory of past errors has been successfully cleared and it is now operating normally.
Your boiler is currently reverting its internal settings back to the manufacturer's original state.
Your boiler has lost its connection to the sensor that measures how hot the water is inside it, preventing it from heating your home safely.
Your boiler has lost its connection to the sensor that monitors the water temperature returning to the unit, causing it to shut down for safety reasons.
Your boiler has stopped working because a sensor that monitors water temperature has developed a faulty faulty connection or failed completely, causing the system to shut down for safety.
Your boiler has stopped working because a sensor that measures the temperature of water returning to the system is providing an incorrect signal, causing a safety shutdown.
Your boiler is struggling to read the temperature of your hot water cylinder because a sensor or its connecting wire has developed a fault.
Your boiler is having trouble detecting the temperature of your hot water, which means it may struggle to provide a consistent hot shower or turn off the tap water heating properly.
Your boiler has detected that it is running too hot and has automatically shut itself down to prevent damage.
Your boiler has stopped working because the water pressure inside the heating system has dropped too low.
Your boiler has detected that the water is heating up significantly faster than it can move around the system, so it has safely turned itself off to prevent overheating.
Your boiler has detected that the water inside is heating up far too quickly for the system to handle, so it has shut down to prevent damage.
Your boiler has detected that the exhaust gases are becoming dangerously hot and has shut itself down to prevent overheating or fire risk.
Your boiler has detected an internal error where it mistakenly believes a flame is present when the burner is actually turned off, preventing it from starting safely.
Your boiler is trying to start up but cannot successfully light the flame needed to heat your water.
Your boiler has stopped because the flame inside has gone out and will not stay lit.
Your boiler has detected an issue with the internal ventilation system that helps move exhaust gases safely out of your home, so it has shut down to prevent unsafe operation.
Your boiler's internal communication system is failing to send signals correctly, which is preventing it from firing up.
Your boiler has detected an internal communication error with the gas control system, meaning it will not light because it cannot safely manage your fuel supply.
Your boiler has detected that the internal gas valve is not closing correctly when it should, which prevents the unit from starting safely.
Your boiler's computer memory has encountered an internal error, which prevents it from operating correctly and requires a specialist to reset or replace the main circuit board.
Your boiler's computer is struggling to read internal sensor signals, causing it to shut down to prevent incorrect operation.
Your boiler’s control brain is overheating, which has triggered a safety shutdown to protect the internal electronics from damage.
Your boiler has detected an internal communication error with its flame monitoring system and has shut down for your safety.
Your boiler is struggling to keep the flame lit reliably, causing it to shut down for safety reasons.
Your boiler's computer has lost its internal identification settings, essentially forgetting which specific model it is, which prevents it from operating correctly.
Your boiler is struggling to accurately measure the temperature of the water flowing into your heating system, so it has stopped working to prevent potential damage.
Your boiler has detected an inconsistent temperature reading between its internal pipes, meaning it cannot accurately measure how well it is heating your water.
Your boiler has detected that the internal sensor responsible for monitoring water pressure is sending an incorrect electrical signal, meaning the system may not be able to accurately tell how much water is inside.
Your boiler's internal water pressure gauge is sending a confused signal to the control panel, meaning the system cannot accurately read how much pressure is in the pipes.
Your boiler is not detecting the necessary water movement to safely ignite and provide heating or hot water, usually because the internal system pressure is too low or a sensor is blocked.
Your boiler has detected that it is getting too hot inside and has safely turned itself off to prevent damage.
Your boiler has detected a problem with the system that safely removes waste water or controls exhaust gases, causing it to shut down to prevent damage.
Your boiler has lost the connection to the temperature sensor that controls your hot water, meaning it cannot properly heat the water for your taps.
Your boiler is struggling to detect the expected temperature difference between the water leaving and returning to the system, causing it to shut down to prevent damage.
Your boiler is confused because the temperature readings between different parts of the system don't match, causing it to shut down to prevent damage.
Your boiler's internal temperature probe has been identified as being loose or incorrectly positioned, meaning it cannot accurately read the water temperature to heat your home safety.
Your boiler has lost the signal from the contact sensor that monitors your underfloor heating system, preventing it from heating that specific area.
Your boiler is failing to light the flame properly, meaning it cannot produce heat or hot water.
Your boiler is struggling to control its internal gas flow, which has triggered a safety shutdown to prevent the unit from operating incorrectly.
Your boiler's water circulation system is failing, which means the device cannot move heat around your home effectively.
Your boiler has lost the ability to read the temperature of your hot water cylinder, which means it cannot safely heat your tap water.
Your boiler has encountered a general system error that requires a specific diagnosis from the technical manual's fault table.
Your boiler is currently running a self-cleaning air removal cycle to clear trapped air from the system pipes.
Your boiler is currently running a professional diagnostic test to check its performance at full power, rather than showing a breakdown fault.
Your boiler is currently performing a routine automated safety check after starting up to ensure it is running efficiently.
Your boiler is currently running a specific commissioning test program rather than its normal heating mode.
Your boiler is currently in a manual filling or draining mode, which is why it is temporarily preventing the heating and hot water from working.
Your boiler is operating normally and is currently running to provide heating to your radiators.
Your boiler is currently working exactly as it should, warming up the water for your taps and shower.
BoilerFaultCodes