22 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 |
|---|---|---|
| 47-077-38 | 825 COMBI | 2019–present |
Appliance names and production years are taken from the UK Product Characteristics Database (the SAP/SEDBUK register). Where a GC number is also printed in this model's own manufacturer manual, both sources were checked to agree.
Tap any card for details
Your boiler's main internal computer has developed a communication fault and is unable to run the system safely.
Your boiler has detected a problem with the sensor that monitors the temperature of the exhaust gases, causing the system to shut down for safety.
Your boiler has detected an issue with the sensor that monitors the temperature of the water returning from your radiators.
Your boiler has switched itself off because it has detected an overheating issue to keep the system safe.
Your boiler has stopped working because the water pressure in the central heating system has dropped too low.
Your boiler has detected that water is not moving through the system properly, which is causing it to shut down to prevent overheating.
Your boiler's internal thermometer is sending incorrect or missing readings, causing the system to limit its performance to prevent overheating.
Your boiler has tried to light several times but cannot establish a flame, meaning you have no heating or hot water.
Your boiler is struggling to ignite or maintain a flame because it isn't getting the gas it needs to run safely.
Your boiler’s main control board has encountered an internal electronic error or a loose connection, preventing the system from running safely.
Your boiler's hot water sensor has developed a fault, meaning your taps and showers may not get as hot as they should or may stay cold.
Your boiler thinks there is a flame present when there shouldn't be, which is usually caused by an electrical fault or a sensor error.
Your boiler has detected an issue with its internal component that controls the fuel flow, causing the system to shut down for safety.
Your boiler's internal temperature sensor is reporting an error, which means the system cannot accurately monitor how hot the water for your radiators is getting.
Your boiler has detected a problem with the sensor that monitors the temperature of the exhaust gases, causing the system to shut down for safety.
Your boiler has shut itself down because it has detected that the water inside is getting too hot.
Your boiler has detected that the water pressure in the central heating system is too low to operate safely and has switched itself off.
Your boiler has detected that hot water isn't moving through the system properly, which usually means it is overheating and has shut down as a safety precaution.
Your boiler has lost its flame while it was running, which means it has stopped providing heating and hot water for safety reasons.
Your boiler has sensed that the exhaust gases are getting too hot and has shut down as a safety precaution to prevent damage.
Your boiler has failed to ignite or stay lit, which usually means the gas isn't reaching the burner or the system can't detect a flame.
Your boiler has stopped working because the fan that removes waste gases isn't spinning or communicating correctly with the main control board.
Not faults — these are normal operating states. Tap to expand.
Monthly cover means no unexpected bills when your boiler breaks down.
Affiliate links. We may earn a commission at no extra cost to you.
BoilerFaultCodes