14 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Replaced by: Logic Heat
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 |
|---|---|---|
| 41-415-20 | Mexico HE 36 | 2005–present |
| 41-429-39 | Mexico HE15 | 2005–present |
| 41-429-65 | Mexico HE18 | 2005–present |
| 41-429-98 | Mexico HE 24 | 2005–present |
| 41-429-99 | Mexico HE 30 | 2005–present |
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Your boiler has detected a faulty temperature sensor reading, causing it to shut down for safety to prevent overheating.
Your boiler has detected that the electrical supply connections to the unit have been installed the wrong way around.
Your boiler has lost its ability to measure the temperature of the water leaving the unit, meaning it cannot operate safely and has shut itself down.
Your boiler has detected that the pipes carrying water in and out of the unit have been installed or connected the wrong way around.
Your boiler has detected that it is running at a dangerously high temperature and has automatically shut itself down to prevent damage.
Your boiler has detected that the gases venting out of your flue are getting dangerously hot, so it has safely turned itself off to prevent damage.
Your boiler's internal computer is experiencing a communication or processing error, which has caused it to stop working for your own safety.
Your boiler has detected that it is running much hotter than it should be and has switched itself off to prevent permanent damage or a safety hazard.
Your boiler has detected that it is running much hotter than it should be and has switched itself off to prevent permanent damage or a fire risk.
Your boiler's electronic brain is unable to communicate correctly, which has caused the system to shut down for safety reasons.
Your boiler has shut down because it has detected it is getting too hot or that water is not moving through the system properly.
Your boiler has failed to light because it cannot detect a flame, causing the system to lock itself for safety.
Your boiler has detected that it is running much hotter than it should be and has automatically switched itself off to prevent damage.
Your boiler has stopped working because the water pressure in the pipes has become too low for it to operate safely.
BoilerFaultCodes