35 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 has stopped working because it can no longer communicate with the internal sensor that monitors the temperature of the water leaving the unit.
Your boiler has stopped working because it cannot communicate with the sensor that monitors the temperature of the water returning to the unit.
Your boiler has detected an electrical fault with the internal sensor that monitors the temperature of the water leaving the unit, causing it to shut down for safety.
Your boiler has stopped working because a sensor that monitors the temperature of the water returning to the unit has developed an electrical fault.
Your boiler has shut down because it has detected it is getting too hot, usually caused by a lack of water flow or a blockage in the system.
Your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.
Your boiler has switched itself off because the water temperature inside it is rising much faster than the water temperature being sent to your radiators, usually due to a circulation blockage.
Your boiler has shut down because it is heating up much faster than it should, which usually means the water isn't moving through the system properly.
Your boiler has shut down because the exhaust fumes have become too hot, which is a safety measure to prevent damage to the internal components.
Your boiler has detected an electrical issue with the gas valve, meaning it cannot safely control the fuel needed to create a flame.
Your boiler has sensed a flame inside when there shouldn't be one, so it has shut down as a safety precaution.
Your boiler has failed to ignite and has locked itself out for safety, meaning you currently have no heating or hot water.
Your boiler was working but has suddenly turned off because the flame has gone out and it cannot manage to relight itself.
Your boiler has stopped working because the internal fan that safely removes exhaust gases is either stuck or not communicating correctly with the system.
Your boiler has lost communication between its internal computer and parts like the thermostat due to an electrical connection issue.
Your boiler is struggling to talk to the gas valve, which means it cannot safely control the fuel needed to create heat.
Your boiler has detected that the gas flame is not turning off when it should, which is preventing the system from running safely.
Your boiler's computer memory has suffered a technical glitch, meaning it can no longer remember its own settings and cannot operate.
Your boiler has detected a communication problem between its internal sensors or a fault in its main control board, causing the system to shut down for safety.
Your boiler's internal control board is getting too hot, usually because it is located too close to a heat source or there is a fault with the electronics.
Your boiler's internal computer is receiving a confusing signal regarding the flame, preventing the system from starting for safety reasons.
Your boiler is struggling to keep a steady flame alight because the gas supply is inconsistent or contains air pockets.
Your boiler's computer and internal display screen are no longer communicating correctly because they haven't been configured to recognize each other.
Your boiler has detected that a temperature sensor has stuck on a single reading, meaning it cannot accurately tell how hot the water is to safely heat your home.
Your boiler has detected that the temperature readings between two sensors don't match up, which prevents it from heating your water 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 a problem with the sensor that monitors water pressure, meaning it cannot accurately tell if there is enough water in the system to run safely.
Your boiler is unable to tell if its pump is running correctly, which means it has stopped working for your safety.
Your boiler has shut down because a safety sensor has detected that the main heat exchanger is getting too hot.
Your boiler has detected an issue with the drainage system that removes leftover liquid from the exhaust pipe or a fault with the safety flap inside the flue.
Your boiler is having trouble communicating with an external temperature sensor used for your hot water, meaning the system doesn't know how hot the water is.
Your boiler has detected that the temperature is not rising as expected when the burner is lit, which usually means there is a lack of water or a sensor issue.
Your boiler has noticed that its two internal temperature sensors are giving conflicting readings, suggesting they are either broken or have been installed incorrectly.
Your boiler has detected that its internal temperature sensors are either misaligned or not communicating correctly, preventing the system from heating safely.
Your boiler is struggling to light properly when you turn on your hot water taps.
Not faults — these are normal operating states. Tap to expand.
BoilerFaultCodes