14 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Replaced by: Greenstar i
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 |
|---|---|---|
| 47-311-73 | Greenstar ZWB 7-25 HE Combi | 2003–2003 |
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Your boiler is struggling to accurately measure the temperature of the water used for your taps and shower, which will likely prevent you from getting hot water.
Your boiler's computer is having trouble communicating with one of its internal control parts, causing the system to stop working as a safety precaution.
Your boiler's internal control computer has lost its connection to a secondary plug, which acts like a security key to tell the system which specific version of the boiler it is working with.
Your boiler is struggling to push air through its system correctly, so it has stopped working as a safety precaution to ensure it burns fuel properly.
Your boiler has lost the signal from the external control or bridge connection that tells it to start running, preventing the system from heating up.
Your boiler has stopped working because a sensor that measures the water temperature is providing an incorrect reading, causing the system to shut down as a safety precaution.
Your boiler has automatically turned itself off because it detected that the water inside has become dangerously hot, likely to prevent damage to the system.
Your boiler has failed to light its burner, which means it cannot produce any heating or hot water until the issue is resolved.
Your boiler has detected a flame inside even though it believes it should be switched off, which suggests a potential safety issue with the internal gas valve or sensor.
Your boiler is detecting a flame even though it has commanded the gas supply to turn off, which means it is preventing itself from running to ensure your safety.
You have accidentally triggered the system's reset feature, effectively telling the boiler to restart its startup sequence.
Your boiler is currently just running a routine internal safety check as it starts up, so please wait a few moments for it to finish.
Your boiler is currently going through its internal start-up process, so please wait a few moments for it to finish booting up.
Your boiler is simply performing its routine internal startup check and should start working normally after a few moments.
BoilerFaultCodes