35 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Replaced by: Heat 2
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Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →
The GC number on your boiler's data badge identifies the exact appliance and production years, as recorded in the UK Product Characteristics Database.
| GC number | Appliance (register name) | Produced |
|---|---|---|
| 41-930-40 | Heat 45 | 2013–present |
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Your boiler has failed to light the flame, so it has safely shut itself down to prevent a build-up of unburnt gas.
Your boiler has detected that it is running much hotter than it should be and has automatically switched itself off to prevent overheating damage.
Your boiler has failed to start up or stay burning, so it has purposefully shut down to prevent gas from building up in the system.
Your boiler has detected a flame when it shouldn't be there, so it has shut itself down to ensure your safety.
Your boiler was running but the flame went out unexpectedly, so it has safely shut itself down to prevent any gas issues.
Your boiler has detected that the internal fan is not working correctly, which prevents it from operating safely.
Your boiler has stopped working because it is unable to accurately read the temperature of the water or the exhaust gases, forcing it to shut down for safety.
Your boiler is unable to read the temperature of the water returning to it, so it has safely shut down to prevent overheating.
Your boiler is struggling to detect the outdoor temperature, so it is defaulting to a standard operation mode rather than adjusting based on the weather conditions.
Your boiler has detected that hot and cold water pipes have been incorrectly connected to the system, meaning it cannot circulate heat properly.
Your boiler has lost the signal from the sensor that monitors your hot water tank temperature, meaning it cannot accurately control your hot water heating.
Your boiler has stopped heating because a connected external safety device, such as a fire alarm or ventilation sensor, has signaled it to shut down.
Your boiler's computer memory card is not communicating correctly, preventing the heating system from operating safely.
Your boiler is providing hot water to your taps as normal, but it is refusing to activate the central heating for your radiators.
Your boiler has lost all power and the control screen is completely blank, meaning it is currently unable to provide heating or hot water.
Your boiler's internal memory chip is not communicating correctly with the main control board, which prevents the unit from starting or running reliably.
Your boiler has lost the signal from the sensor that monitors the temperature of your hot water cylinder, meaning it does not know when your water is hot enough.
Your boiler has detected that the water inside is getting too hot because it isn't moving through the system properly.
Your boiler has detected a flame when it shouldn't be there, so it has shut itself down to ensure your safety.
Your boiler has detected a flame when it should be turned off, so it has purposefully shut itself down to ensure your safety.
Your boiler has stopped working because it cannot properly clear exhaust gases, so it has shut down as a safety precaution to prevent dangerous fumes from building up.
Your boiler has stopped working because it cannot keep its internal flame lit, which means it is currently unable to heat your home or water.
Your boiler's temperature sensor is failing to send data, so the system has shut down to prevent overheating.
Your boiler has stopped working because it cannot correctly measure the temperature of the water flowing through it, likely due to a faulty sensor or a loose electrical connection.
Your boiler has detected that the water is circulating in the wrong direction, which usually means some pipes were connected incorrectly or there is a major issue with the water pump.
Your boiler has detected an issue with the sensor that monitors the temperature of the exhaust fumes leaving the unit, causing it to stop operating for safety reasons.
Your boiler has failed to light the flame properly and has safely shut itself down to prevent a gas build-up.
Your boiler has been manually reset too many times in a short period and has locked itself out as a safety precaution.
Your boiler is failing to operate because the electrical power it is receiving from your home is significantly lower than required.
Your boiler has stopped working because the water level inside the heating system has dropped too low.
Your boiler has lost the connection to the thermometer placed outside your home, so it can no longer automatically adjust its heating based on the outdoor temperature.
Your boiler has detected that it is running too hot and has automatically turned itself off to prevent damage.
Your boiler's central control computer is not communicating correctly, meaning the system cannot safely operate to provide your heating or hot water.
Your boiler's temperature sensor at the water return pipe is faulty or disconnected, causing the system to stop heating because it cannot accurately measure the water temperature.
Your boiler has been locked for safety because it has been manually reset too many times in a short period.
Not faults — these are normal operating states. Tap to expand.
BoilerFaultCodes