6 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Replaced by: Mexico HE or Mexico Slimline
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 |
|---|---|---|
| 41-392-89 | Mexico Slimline CF 440 | 2001–2006 |
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Your boiler is unable to start the small pilot flame needed to ignite the main heating system.
Your boiler is failing to keep the pilot light burning after you let go of the ignition button, meaning the heating cannot start.
Your boiler has successfully lit its pilot light, but the main burner is failing to ignite because it is not receiving the main supply of gas.
Your boiler's pilot light is failing to stay ignited after you try to light it, meaning the main burner cannot start to provide heat.
Your boiler has managed to start the small pilot flame, but the main burner fails to ignite to provide full heating.
Your boiler is losing the water it needs to heat your home, which is likely caused by a slow leak somewhere in your radiators or pipework.
Not faults — these are normal operating states. Tap to expand.
BoilerFaultCodes