7 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 |
|---|---|---|
| 41-047-53 | Protherm 40-50 CI | 2001–present |
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Your boiler has stopped working because it is not receiving the necessary electrical power or an internal electrical safety fuse has blown.
Your boiler has detected that it is getting too hot and has automatically switched itself off to prevent any damage or safety issues.
Your boiler has detected a communication failure between its main computer and the firing controls, causing all the lights to stay on and the heating to stop working.
Your boiler is not receiving any electrical power, which could be due to a tripped switch or an internal fuse failure.
Your boiler has shut down because it has detected it is getting too hot, likely triggered by a safety switch to prevent damage.
Your boiler has detected an issue with how it moves air and exhaust gases, which has caused it to stop running for safety.
Your boiler has failed to light the gas flame or cannot detect that it is lit, so it has shut down as a safety precaution.
Not faults — these are normal operating states. Tap to expand.
BoilerFaultCodes