BoilerFaultCodes A
The flue or flue terminal is blocked or obstructed in some way, or there is an internal fault.
Main Combi 24 Fault codes & diagnostics
5 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Combi Natural Gas 24 kW 2005-2012 Discontinued
GC Number 47-474-02
Replaced by: Main Combi Eco
Download the Main Combi 24 manual
PDF
Versions & GC numbers
The fault code is already on your display
Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →
Which version do you have?
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 |
|---|---|---|
| 47-474-02 | Combi 24 HE | 2005–2012 |
Appliance names and production years are taken from the UK Product Characteristics Database (the SAP/SEDBUK register). Where a GC number is also printed in this model's own manufacturer manual, both sources were checked to agree.
Just want the most common Main Combi 24 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 5 documented codes
Tap any card for details
Status & diagnostic codes 5 operating states & engineer diagnostics
Not faults — these are normal operating states. Tap to expand.
5 operating states & engineer diagnostics
Not faults — these are normal operating states. Tap to expand.
2A Diagnostic Your boiler has stopped working because an internal safety fuse has blown, cutting off the power to its main control systems. 3A Diagnostic Your boiler has detected an issue with the power supply fuse, which prevents it from operating safely. 170W Diagnostic Your boiler is experiencing a problem with its internal electrical supply or energy usage, which is preventing it from running safely. G20 Status Your boiler is signalling that it is unable to detect or receive a steady supply of natural gas to ignite the flame. IPX4D Status This code indicates that your boiler has detected a potential issue with its weatherproofing or electrical integrity, meaning it has automatically shut down to prevent a short circuit or damage.