12 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 →
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 |
|---|---|---|
| 47-830-09 | KESTON COMBI2 C30 | 2022–present |
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Your boiler's temperature sensor for hot water is giving an incorrect reading, meaning you may have inconsistent or no hot water at your taps.
Your boiler has stopped working because the fan that removes waste gases is not spinning correctly, meaning the system has shut down for safety.
Your boiler is starting up but cannot keep the flame lit, which means it will stop providing heating and hot water to your home.
Your boiler's safety sensor thinks a flame is already burning before it has even turned the gas on, causing the system to shut down for safety.
Your boiler has detected a problem with the sensor that measures the temperature of the water leaving the unit, which is preventing it from heating up correctly.
Your boiler has tried to light several times without success, so it has shut itself down for safety.
Your boiler has stopped working because the water level inside the system has dropped too low and needs topping up.
Your boiler’s control panel has no power, meaning the system is completely unresponsive and cannot provide heating or hot water.
Your boiler has lost communication with the outdoor temperature sensor, which helps it adjust its settings based on the weather outside.
Your boiler has switched itself off because it has become too hot internally and needs to cool down for safety.
Your boiler has detected a problem with the sensor that monitors the temperature of the water coming back from your radiators, preventing it from heating correctly.
Your boiler is repeatedly trying and failing to stay alight, causing it to lock itself out for safety after five unsuccessful attempts.
Not faults — these are normal operating states. Tap to expand.
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BoilerFaultCodes