144 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
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Your boiler's internal computer brain is unable to talk to the front display panel, meaning the system cannot receive instructions to provide heating or hot water.
Your boiler has lost its connection to an internal temperature sensor, meaning it cannot accurately read how hot it is.
Your boiler has lost the connection to the temperature sensor that tracks the flow of water, causing it to stop heating as a safety precaution.
Your boiler has lost the temperature reading from one of its internal sensors, meaning it cannot safely regulate heat and has temporarily shut down.
Your boiler has stopped working because it has lost its connection to a sensor that measures the temperature of the water returning to the system.
Your boiler has temporarily stopped working because it has detected a faulty temperature sensor connection linked to its internal hot water storage cylinder.
Your boiler has lost the ability to read the temperature of your hot water supply, which means it has stopped providing hot water to your taps.
Your boiler has detected a faulty temperature sensor connection, which usually stops it from working safely.
Your boiler has lost communication with the temperature sensor in your hot water tank, meaning it cannot accurately detect when your water is hot enough.
Your boiler has detected a faulty temperature sensor or a wiring problem, meaning it cannot accurately measure how hot the water is.
Your boiler has stopped working because it thinks the main water temperature sensor is broken or there is a problem with its internal wiring.
Your boiler has detected a faulty temperature sensor or a wiring issue, which means it cannot accurately measure how hot the water is and has stopped working for your safety.
Your boiler has stopped working because it cannot correctly read the temperature of the water returning to the unit due to an electrical connection issue.
Your boiler has detected a faulty temperature sensor and a possible wiring issue, which will cause it to shut down to prevent damage.
Your boiler has detected a faulty electrical signal related to the sensor that monitors your hot water temperature.
Your boiler has detected a sensor wiring fault relating to its hot water temperature monitoring.
Your boiler has detected an electrical fault with the internal sensor that monitors the temperature of its hot water storage tank.
Your boiler has safely shut down because it has detected an electrical safety issue or a faulty temperature sensor inside the unit.
Your boiler has shut down because it has detected an unsafe increase in internal temperature, likely caused by a sensor fault or an issue with water flow.
Your boiler has temporarily stopped working because the water pressure inside the system has dropped too low.
Your boiler has stopped working because the water pressure is too low for it to operate safely.
Your boiler has stopped working because water is not flowing properly through it, which is usually caused by trapped air, a stuck pump, or incorrect pipe connections.
Your boiler has detected that water isn't moving through the system fast enough, causing a large temperature difference that has triggered a safety shutdown.
Your boiler has stopped working because water is not flowing properly through it, usually due to trapped air or low system pressure.
Your boiler is overheating too quickly because water isn't flowing through the system correctly, often due to low pressure or trapped air.
Your boiler has temporarily stopped working because it has detected a loose electrical connection or safety sensor issue related to the exhaust flue.
Your boiler has detected an internal electrical connection issue that is preventing it from running safely.
Your boiler has detected an issue with the valve that controls the gas supply, meaning it cannot safely ignite to provide heating or hot water.
Your boiler has detected an issue with the valve that controls the gas supply, meaning it cannot safely start up to provide heating or hot water.
Your boiler has detected moisture or a false flame signal inside the unit and has safely locked itself out to prevent unsafe operation.
Your boiler has detected a flame when there shouldn't be one, which has caused the system to shut down for safety.
Your boiler is failing to light because it cannot detect a successful flame or is not receiving enough gas to start up.
Your boiler is failing to light the gas flame, meaning it cannot provide heat or hot water.
Your boiler has tried to start up several times but failed to ignite, usually because the gas supply has been temporarily interrupted or the system cannot clear exhaust gases properly.
Your boiler has lost its flame while running and cannot manage to restart itself, likely due to a temporary interruption in the gas supply or a component failure.
Your boiler has detected an issue with the internal fan that safely removes combustion gases, causing it to lock out for safety.
Your boiler has detected a problem with the fan that safely pushes waste gases out of your home, causing the system to shut down for safety.
Your boiler has detected an issue with the airflow or flue system, meaning it cannot safely remove combustion gases and has temporarily stopped working.
Your boiler has detected an issue with the airflow system, which means it cannot safely vent exhaust gases, so it has shut down to prevent any risk.
Your boiler has detected a blockage or restriction in the pipe that brings in fresh air and removes exhaust gases.
Your boiler is having trouble breathing because there may be a blockage, damage, or an obstruction in the pipework that vents exhaust gases outside.
Your boiler has detected an internal configuration issue with the fuel type settings on its main computer board, which requires professional calibration.
Your boiler has lost the digital instructions telling it which type of gas it should be using, causing it to stop working for your safety.
Your boiler has detected an electrical communication problem in its internal wiring control system, causing it to shut down to protect its internal electronics.
There is a communication error between your boiler and its controls, often caused by an electrical wiring fault or a heavy load on the internal data connection.
Your boiler has detected an issue with its internal gas sensor or combustion system and has temporarily locked itself out to keep your home safe.
Your boiler has detected an issue with the sensor that monitors combustion, meaning it has shut down to keep your home safe.
Your boiler has detected high levels of carbon monoxide inside its casing and has safely shut itself down to protect your home.
Your boiler has detected an issue with the fuel-to-air balance that could affect safe operation, so it has safely shut itself down to prevent any risk.
Your boiler has detected that an internal component used for safe ignition has become worn or corroded over time.
Your boiler has detected that a key ignition component is wearing out, meaning it is struggling to reliably start the flame needed to heat your home.
Your boiler has detected an issue with the internal valve that controls the gas supply, meaning it cannot safely ignite.
Your boiler has detected a technical communication error between the main control board and the gas valve, preventing it from lighting safely.
Your boiler has detected an issue with the gas valve not shutting off properly when it should, which requires a Gas Safe registered engineer to inspect for safety.
Your boiler has detected a potential internal gas leak or an electrical failure that stops the gas supply from closing correctly, so it has shut down for safety.
Your boiler's main computer control panel has suffered a critical internal memory failure and can no longer process instructions to run your heating system.
Your boiler's internal computer brain has developed a memory error and can no longer process instructions correctly.
Your boiler has detected a sudden reading error from one of its internal temperature sensors, causing it to lock out for safety.
Your boiler has detected an electrical fault within its internal sensors or control board, which has caused the system to shut down for safety.
Your boiler has detected that its internal computer is running too hot and has safely shut down to prevent permanent damage.
Your boiler’s internal computer brain is overheating, which has caused the system to shut down for safety.
Your boiler has temporarily stopped working because the internal computer is receiving a confusing signal from the flame sensor.
Your boiler's main control board is receiving an incorrect electrical signal from the flame sensor, meaning the system cannot safely confirm if the burner is lit.
Your boiler is locking out because the flame inside is flickering or going out unexpectedly, which usually points to an issue with the gas supply, air flow, or waste pipe blockage.
Your boiler is struggling to keep its internal flame lit steadily, which has caused it to shut down for safety reasons.
Your boiler's computer system is confused because internal identification numbers were not properly set up after a recent repair.
Your boiler’s internal computer boards are having trouble communicating because they haven't been properly synced or configured to recognize each other.
Your boiler has temporarily stopped working because a sensor that measures water temperature is giving a faulty reading.
Your boiler has detected that a temperature sensor is sending a stuck or frozen reading, preventing it from heating your home or water safely.
Your boiler has detected an unusual temperature difference between the water leaving it and the water returning to it, usually due to a faulty reading from the internal sensors.
Your boiler has detected that its temperature sensors are giving conflicting or incorrect readings, causing it to shut down for safety.
Your boiler's water pressure sensor is failing to communicate properly, which usually means the sensor itself is faulty or has a loose wire.
Your boiler's internal sensor that monitors water pressure has lost electrical contact or has failed, causing the system to stop working for safety.
Your boiler has detected an electrical fault with the internal water pressure sensor, which means it cannot accurately read the system pressure and has stopped working as a safety precaution.
Your boiler has detected an electrical issue with its internal water pressure sensor, meaning it cannot accurately tell if there is enough water in the system to run safely.
Your boiler has detected low water pressure or a circulation issue, meaning it cannot safely run the heating or hot water.
Your boiler has stopped working because it cannot detect the necessary change in pressure when the pump starts up.
Your boiler has detected an issue with the system that safely removes waste gases or water, meaning it has temporarily stopped working for your safety.
Your boiler is struggling to remove excess water or is experiencing a communication error with an external safety part, causing it to shut down to prevent damage.
Your boiler has registered a wiring configuration error related to the hot water sensor when an external control or link box is fitted.
Your boiler is struggling because it has detected an external control unit connected for hot water, but the required safety link or sensor connection is missing.
Your boiler has detected a faulty temperature sensor inside its hot water storage cylinder, meaning it may struggle to provide reliable hot water.
Your boiler is having trouble communicating with the temperature sensor in your hot water storage unit, meaning your water might not heat up correctly.
Your boiler is struggling to pump hot water to your cylinder, which means your stored hot water is not heating up properly.
Your boiler is struggling to heat your hot water tank effectively, causing it to time out before the water reaches the requested temperature.
Your boiler has detected an electrical fault with a special component inside the hot water cylinder that prevents corrosion, meaning it is either unplugged or damaged.
Your boiler has detected a communication issue with the safety component that prevents internal corrosion, meaning it cannot confirm the tank is protected.
Your boiler has detected that the water inside is not heating up as quickly as expected when the burner tries to start.
Your boiler is failing to detect a change in temperature when it tries to fire up, which usually means there is either not enough water circulating inside the system or a sensor isn't reading correctly.
Your boiler has detected an unexpected difference in temperature between its internal pipes, usually because the main sensors are misread, incorrectly installed, or mixed up.
Your boiler is confused because its temperature sensors are detecting heat patterns that do not match the expected flow of water, often caused by the sensors being swapped or losing contact with the pipes.
Your boiler has detected an internal sensor installation error, meaning the temperature monitoring components are incorrectly positioned or wired.
Your boiler is confused because its temperature sensors have likely been swapped or placed on the wrong pipes during installation or a recent repair.
Your boiler is temporarily confused and has lost internal communication with one of its connected water storage modules.
Your boiler has lost the digital connection to its hot water storage tank, preventing the two units from communicating properly.
Your boiler has detected a problem with water flow and pressure sensors, meaning it cannot circulate water safely and has shut down your heating and hot water.
Your boiler's internal water flow sensor is struggling to detect movement, which prevents the unit from starting safely.
Your boiler is currently running a routine diagnostic check to test its internal systems and settings.
Your boiler has successfully detected a request for hot water and is starting up normally.
Your boiler is currently preparing to fire up by starting its internal fan, which is a normal part of the ignition process.
Your boiler is struggling to light its flame, which means you may experience intermittent issues with your heating and hot water.
Your boiler is currently operating normally and is heating water for your taps or shower.
Your boiler is simply finishing a cooling cycle after you have used the hot water taps, which is a normal part of its operation.
Your boiler has detected an issue with the air fan system and has temporarily stopped heating to prevent further damage.
Your boiler is currently just running its internal pump to move residual heat away from the heat exchanger after a hot water cycle, which is a normal part of its operation.
Your boiler is currently running a brief internal testing sequence to check hot water settings and will return to normal operation by itself.
Your boiler is simply detecting that someone has turned on a hot tap and is preparing to heat the water for you.
Your boiler is currently going through its normal starting sequence to begin heating your water.
Your boiler is simply preparing the water pump before sending hot water to your taps, which is a normal part of its startup routine and not actually an error.
Your boiler is currently struggling to light the flame it needs to provide heating and hot water.
Your boiler is currently operating normally and is in the process of heating your radiators.
Your boiler is currently just finishing a routine cooling-down process after providing hot water and should return to normal operation shortly.
Your boiler's fan is attempting to spin, but the electronic control board isn't receiving the correct signal back to confirm it is working properly.
Your boiler is simply finishing its cooling cycle after providing hot water and is operating exactly as it should.
Your boiler is temporarily pausing between hot water cycles to protect itself from overheating and wear.
Your boiler is currently running an internal testing procedure for your hot water system and is not actually broken.
Your boiler is temporarily paused because your wall thermostat or heating controller is telling it not to send heat to your radiators.
Your boiler is simply resting because your heating controls are currently switched off or set to summer mode, meaning no heat is needed right now.
Your boiler is temporarily paused because the internal fan isn't spinning at the correct speed to safely clear exhaust fumes.
Your boiler is temporarily pausing its operation because it has detected a drop in the internal airflow pressure.
Your boiler has temporarily fired up its internal frost protection system to prevent the pipes from freezing during cold weather.
Your boiler has temporarily blocked heating mode because the room thermostat or smart controller is currently set to an invalidly low temperature.
Your boiler has temporarily paused because it detected a problem with the internal fan that safely pushes harmful gases out of your home.
Your boiler has temporarily paused heating because a safety switch, such as the one connected to your condensate drain pump, has triggered to prevent a water overflow.
Your boiler has detected a minor performance issue and is operating in a temporary energy-saving mode to ensure it keeps running safely while limiting output.
Your boiler has detected that the water pressure is too high, often caused by the filling loop being left open or a fault in the expansion system.
Your boiler has paused its heating because a safety sensor has detected a potential blockage in the waste water removal or the exhaust safety flap.
Your boiler has temporarily lowered its heating output to prevent the flame from going out completely, usually due to a minor combustion issue.
Your boiler has temporarily paused to protect itself because the water is not flowing properly between the pipes, usually due to low pressure or trapped air.
Your boiler has temporarily paused to protect itself because the water pressure inside is too low, or water isn't flowing properly through the system.
Your boiler is temporarily pausing its operation to allow its internal safety sensor to check the air quality before it starts up again.
Your boiler has temporarily paused its operation because it detected high levels of combustion byproducts, and it is waiting safely until it is clear to try again.
Your boiler has temporarily paused because an internal self-check didn't finish properly, but it has switched to a backup mode to keep you warm while it waits to try again.
Your boiler has temporarily reduced its power because it is detecting unusual air movement or wind pressure in the flue system, likely due to external weather conditions.
Your boiler has paused because the flow of water moving through the system has dropped too low to operate safely.
Your boiler has stopped working because the water pressure inside the heating system has dropped too low.
Your boiler is reminding you that its internal water flow sensor needs a routine check or service.
Your boiler is currently running an automatic program to clear air bubbles out of the internal pipework and does not require a repair.
Your boiler is currently running a routine check of the water flow inside the system to ensure it is operating safely and effectively.
Your boiler is temporarily running through a routine check of its exhaust gases, so you just need to wait a few moments for it to finish.
Your boiler is performing a routine diagnostic test on its internal temperature sensors, which temporarily pauses the heating.
Your boiler is currently running a brief self-test on its water pressure system and temporarily pausing heating until the check is complete.
Your boiler is temporarily running a self-test on its internal temperature sensors, which pauses your heating until the check is finished.
Your boiler is simply running through its routine internal system check and does not indicate a fault.
Not faults — these are normal operating states. Tap to expand.
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BoilerFaultCodes