40 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 |
|---|---|---|
| 47-044-73 | ecoFIT sustain 835 VUW 356/6-3 (H-GB) | 2016–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.
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Your boiler has lost its ability to talk to its display panel, meaning it doesn't know what you are asking it to do.
Your boiler has temporarily stopped working because it cannot accurately measure the temperature of the water leaving the system.
Your boiler has temporarily stopped working because it cannot accurately measure the temperature of the water returning from your radiators.
Your boiler has temporarily stopped working because it has detected an electrical fault with one of its internal temperature sensors.
Your boiler has temporarily stopped working because it has detected an electrical fault with one of its internal temperature sensors.
Your boiler has detected a faulty electrical signal from the hot water temperature sensor, meaning it cannot properly monitor the temperature of your hot water.
Your boiler has temporarily shut down because the internal water temperature got too high.
Your boiler has temporarily stopped working because it has detected a dangerously low level of water pressure inside the system.
Your boiler has shut down because there is a dangerous difference in temperature between its internal sensors, usually caused by a restriction in water flow.
Your boiler is temporarily shutting down because the water inside is heating up much faster than normal, usually due to poor water flow.
Your boiler has temporarily shut itself down because the exhaust gas coming out of the flue is getting dangerously hot.
Your boiler has temporarily shut down because it cannot reliably detect the flame inside, meaning it is currently unsafe for it to keep running.
Your boiler is failing to light the flame needed to produce heat or hot water.
Your boiler is failing to stay lit, which means it has safely shut itself down because it cannot consistently produce or hold a flame.
Your boiler has detected that the fan, which pushes waste gases outside, isn't spinning at the correct speed to ensure safe operation.
Your boiler's communication system is experiencing a power supply issue, causing it to lose its ability to talk to your thermostat or internal components.
Your boiler has detected an issue with the control system that regulates the flow of gas into the unit.
Your boiler has detected an issue with the internal safety mechanism that controls the gas flow, so it has safely shut itself down to prevent operation.
Your boiler's internal computer has encountered a memory error and cannot read the essential configuration data required to operate safely.
Your boiler's main computer control panel is failing to process signals from its sensors, meaning it cannot safely operate the system.
Your boiler has detected that its internal control brain is overheating and has shut itself down to prevent damage.
Your boiler's computer is struggling to safely detect or manage the flame, so it has shut itself down to prevent any unsafe operation.
Your boiler is struggling to keep a steady flame, causing it to shut down for safety reasons.
Your boiler has lost its unique digital identity, meaning the internal computer no longer knows how to correctly control your specific heating system.
Your boiler is struggling to accurately measure the temperature of the water flowing through the system, so it has safely shut itself down to prevent overheating.
Your boiler has detected that the sensors measuring water temperature going in and out are giving conflicting readings, so it has shut down as a safety precaution.
Your boiler has lost the signal from its water pressure sensor, meaning it cannot accurately read the internal water level.
Your boiler has detected an electrical fault with its water pressure sensor, which usually prevents it from safely measuring the system pressure.
Your boiler is struggling to accurately read its internal water pressure, so it has locked out to keep itself safe.
Your boiler has detected a critical safety disagreement between its internal components and has safely shut itself down to prevent any risk.
Your boiler has detected a potential blockage or mechanical issue with the system that manages exhaust gases, which has triggered a safety shutdown to prevent harmful gases from entering your home.
Your boiler is having trouble communicating with an external hot water control component, meaning it doesn't know the temperature of the water heading to your taps.
Your boiler is not detecting enough water circulating inside the system to safely turn on the burner.
Your boiler has detected a mix-up with its internal temperature sensors, usually meaning they are reading the wrong pipes or have been incorrectly installed.
Your boiler has stopped working because its internal thermometers are giving conflicting readings and believe they have been fitted to the wrong pipes.
Your boiler has stopped providing heat because a safety limit switch for your underfloor heating has been triggered or disconnected.
Your boiler is failing to light the flame properly because there is a communication issue with the part responsible for ignition.
Your boiler has detected an electrical connection issue with the gas valve, meaning it cannot safely ignite to provide heating or hot water.
Your boiler has detected an issue with the water pump's wiring or connection, meaning it cannot circulate water properly to provide heating or hot water.
Your boiler has detected an internal computer system failure and has safely shut down.
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BoilerFaultCodes