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 |
|---|---|---|
| 41-397-96 | HE 12 HE 12 | 2004–present |
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Your boiler has detected an internal communication error between its electronic control boards or an incorrect configuration.
Your boiler is displaying an 'H' and 'E' sequence to indicate its current operating status or a diagnostic mode, often triggered by a system reset or power-up.
Your boiler is displaying a service notification or a specific lockout state that requires a professional to check the internal sequence and settings.
Your boiler has shut down because the exhaust gases have reached a temperature that is too high, which is a safety feature to prevent damage to the system.
Your boiler's internal computer has encountered a critical communication error and can no longer control the heating system safely.
Your boiler has overheated, causing it to shut down automatically for safety.
Your boiler has sensed that the exhaust gases are getting too hot and has shut down as a safety precaution to prevent internal damage.
BoilerFaultCodes