Sime Format C Combi Fault codes & diagnostics

3 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Combi Natural Gas 1998-2008 Discontinued
GC Numbers 47-719-1247-719-1347-719-21
Download the Sime Format C Combi manualThe official installation and service manual (PDF), the document these fault codes were read from. PDF

This boiler uses LED flash patterns

Count the flashes in one repeating group before the pause. That number is your fault code. Do not reset until you have noted it. How to read fault codes →

Just want the most common Sime Format C Combi faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 3 documented codes

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LED / flash-pattern codes
Green led flashing

Your boiler has temporarily stopped working because it cannot safely clear its exhaust gases.

High Engineer only £150-300

Parts commonly replaced

  • Air pressure switch
  • Flue fan
  • Pressure switch silicone tubes
Full explanation for Green led flashing
Digital codes
Red led on

Your boiler has safely shut down because it failed to ignite or detected an issue with the exhaust gases.

High Engineer only £100-250

Parts commonly replaced

  • Ignition electrode
  • Flue/smoke thermostat
  • Gas valve
  • PCB

Related codes

Full explanation for Red led on