39 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
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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 |
|---|---|---|
| 41-583-20 | Activ A Plus 16S | 2011–present |
| 41-583-21 | Activ A Plus 25S | 2011–present |
| 41-583-14 | Activ A 12OV | 2010–present |
| 41-583-15 | Activ A 15OV | 2010–present |
| 41-583-16 | Activ A 20OV | 2010–present |
| 41-583-17 | Activ A 25OV | 2010–present |
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Your boiler is trying to start but cannot sense the flame, so it has shut itself down as a safety precaution.
Your boiler is having trouble detecting flow around your radiators, which means it cannot heat your home or provide hot water.
Your boiler has failed to light the gas flame, meaning it has shut itself down for safety and cannot provide heating or hot water.
Your boiler has switched itself off because it has detected that it is getting too hot inside.
Your boiler has stopped working as a safety precaution because it is not successfully venting waste gases or detecting the airflow correctly.
Your boiler has stopped working because the water pressure inside the heating system has dropped too low.
Your boiler has stopped working because the internal water pressure has dropped too low for it to operate safely.
Your boiler has detected an issue with the air flow or pressure inside the unit, causing it to shut down to stay safe.
Your boiler is struggling to confirm that the internal fan is exhausting fumes correctly, so it has safely shut down to prevent unsafe operation.
Your boiler is struggling to accurately measure the temperature of the water inside the system, which is preventing it from heating up correctly.
Your boiler has stopped working because it cannot correctly read the temperature of the water inside the heating system.
Your boiler is struggling to accurately measure the temperature of the water coming out of your taps, which usually means your hot water will be inconsistent or not work at all.
Your boiler is struggling to accurately measure the temperature of your hot water, which means the system may stop producing hot water to prevent it from overheating.
Your boiler's outside temperature sensor is sending an incorrect signal or has lost connection, meaning the system may not know how hard it needs to work to heat your home.
Your boiler is struggling to detect the outside temperature, so it has stopped heating to prevent it from working incorrectly.
Your boiler has detected a communication issue with the sensor that monitors the temperature of the exhaust fumes, causing the system to stop working as a precaution.
Your boiler has stopped working because a sensor that monitors the temperature of the exhaust gases is not sending the correct signal, causing the system to shut down for safety.
Your boiler has switched itself off because it has detected an issue with the sensor that monitors the temperature of the exhaust gases.
Your boiler is failing to light the flame or keep it running, which means it cannot provide you with heating or hot water.
Your boiler has stopped working because it is unable to accurately measure the temperature of the water returning to it from your radiators.
Your boiler has stopped working because it cannot correctly detect the temperature of the water returning to it from your radiators.
Your boiler is struggling to move heat around because the temperature difference between the water leaving and returning to the boiler is too high, often caused by a blockage or a faulty circulating pump.
Your boiler has detected that the water leaving the unit is significantly hotter than the water returning, suggesting a restricted flow through your heating system.
Your boiler is failing to recognise that the flame has lit correctly, causing the system to shut down for safety.
Your boiler has stopped working because it is either overheating or the internal water pump has failed to circulate water properly.
Your boiler has lost the ability to read the temperature of the water circulating back from your radiators, so it has shut down to prevent potential overheating.
Your boiler has detected a problem with the gas valve and has safely locked itself out to prevent unsafe operation.
Your boiler has detected an issue with the internal gas valve, causing it to shut down for safety reasons.
Your boiler has detected an issue with the gas valve or ignition sequence, causing it to shut down for safety reasons.
Your boiler has stopped working because it cannot detect that the gas valve is opening correctly, meaning it is preventing itself from igniting for safety reasons.
Your boiler has failed to light the flame properly and has locked itself out for safety reasons, meaning you currently have no heating or hot water.
Your boiler has detected that it cannot burn gas correctly and has safely shut itself down to prevent a potential hazard.
Your boiler has detected a communication or connection issue within its internal wiring system and has safely shut itself down to prevent damage.
Your boiler has detected an issue with its internal electrical connections, triggering a safety shutdown to prevent any potential damage.
Your boiler's internal computer has lost its settings or has not been properly programmed, meaning it does not know how to operate your heating system correctly.
The internal computer of your boiler has lost its settings and doesn't know how to operate the system correctly.
Your boiler has lost its configuration settings or isn't receiving power correctly, meaning it doesn't know which specific model it is supposed to be.
Your boiler has detected that the water inside the unit is getting too hot while it is trying to heat your tap water, so it has shut down to prevent damage.
Your boiler has switched itself off because it has detected that it is getting too hot or there is a problem with the exhaust temperature.
Not faults — these are normal operating states. Tap to expand.
BoilerFaultCodes