Glow-worm CXi Fault codes & diagnostics

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

Combi Natural Gas 24-30 kW 2005-2010 Discontinued

Replaced by: Flexicom

The fault code is already on your display

Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Fault codes

All 1 documented codes

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12

Your boiler is performing a routine self-test of the fan speed and it is not necessarily a permanent error code.

Low DIY-safe £0-220

What to check first

  1. Wait for the boiler to complete its internal test sequence
  2. If the '12' remains or repeats indefinitely, try resetting the boiler
  3. Check for any visible obstructions at the external flue terminal

Parts commonly replaced

  • Fan
  • Printed Circuit Board (PCB)
Full explanation for 12