43 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
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Your boiler has lost connection with its internal thermometer, meaning it cannot safely tell how hot the water is and has shut down as a precaution.
Your boiler has stopped working because it cannot communicate with the sensor that monitors the temperature of the water returning from your radiators.
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 internal sensor that monitors the temperature of the water returning to the unit has developed an electrical fault.
Your boiler has shut itself down because it has detected that it is getting far too hot, usually due to a lack of water flow or a circulation blockage.
Your boiler has switched itself off because the water pressure has dropped too low to operate safely.
Your boiler has shut down because water isn't moving through the system quickly enough, causing it to overheat too rapidly.
Your boiler has shut down because it is heating up much faster than it can circulate the water, usually due to a blockage or a pump issue.
Your boiler has shut down automatically because it detected that the exhaust gases are getting too hot, which is a safety feature to prevent damage to the internal components.
Your boiler is unable to release gas into the burner because the internal electronic valve is not operating correctly, meaning it cannot ignite to provide heat or hot water.
Your boiler has detected a flame when there shouldn't be one, which has caused it to shut down for safety purposes.
Your boiler is unable to light the gas to produce heat, meaning your heating and hot water will not work.
Your boiler has lost its flame while running and is unable to automatically restart, likely because the gas flow is being interrupted.
Your boiler has detected an issue with the fan that helps clear exhaust gases, causing the system to shut down for safety.
Your boiler is struggling to send signals between its internal components because the communication line has a low electrical voltage.
Your boiler is unable to send gas to the burner because of a communication failure between the main control board and the gas valve.
Your boiler is failing to shut off the gas properly at the end of a heating cycle, which is a safety issue requiring professional inspection.
Your boiler’s internal computer chip has suffered a memory error, preventing it from processing the instructions needed to run your heating.
Your boiler's computer has detected a conflict between its internal sensors or a wiring fault, causing it to shut down for safety.
Your boiler's internal control board has overheated or suffered an electrical failure, causing the system to shut down to prevent damage.
Your boiler's computer has detected a flame when it shouldn't be there, or is confused by an electrical signal from the burner area.
Your boiler is struggling to keep its flame steady, which is preventing it from staying on and heating your home.
Your boiler's main control board has lost its identity or is communicating incorrectly with the display unit, often following a part replacement.
Your boiler's internal thermometer is reporting a temperature that doesn't make sense, causing the system to shut down for safety.
Your boiler has detected that the two pipes measuring temperature are giving very different readings, which usually means a sensor is failing or there is a blockage in the system.
Your boiler's internal sensor is struggling to detect the correct water pressure levels, which is preventing the system from running safely.
Your boiler has detected that the water pressure is too high, which has caused it to stop working to protect the internal components.
Your boiler is struggling to detect a rise in water pressure when the pump starts up, which is preventing it from firing for your heating or hot water.
Your boiler has stopped working because it cannot properly drain away waste water or there is a blockage in the ventilation system.
Your boiler is confused because it is looking for a hot water sensor that is either missing or has a broken connection, preventing it from heating your water correctly.
Your boiler is struggling to detect a proper temperature change between the pipes, which usually means there is not enough water moving through the system to heat your home properly.
Your boiler is confused because the temperature sensors measuring water going out and coming back are giving contradictory or swapped readings.
Your boiler has detected that the temperature sensors are giving unusual readings, likely because they are loose or have been installed on the wrong pipes.
Your boiler has detected that the fuel type it is being supplied with does not match its internal settings, causing it to shut down for safety.
Your boiler is temporarily pausing because the fan is having trouble reaching or maintaining the correct speed to start the ignition process safely.
Your boiler has shut down because it has detected an issue with a safety sensor or the pump that removes excess water from the system.
Your boiler has detected that there is too much water in the system, causing the internal pressure to rise above safe operating levels.
Your boiler has stopped working because it has detected a blockage in the exhaust system or a failure in the pump that removes waste water.
Your boiler has temporarily paused because water is not moving through the system fast enough to take the heat away safely.
Your boiler has paused operation because it has detected a lack of water flow or pressure, preventing the system from heating up safely.
Your boiler has detected that its internal safety settings don't match the type of gas being supplied to the property, causing it to stop running for safety.
Your boiler has detected a potential blockage or issue with the gas supply or internal gas valve, causing it to shut down for safety.
Your boiler is struggling to accurately check the quality of its exhaust gases, which is preventing it from completing its ignition cycle safely.
Not faults — these are normal operating states. Tap to expand.
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BoilerFaultCodes