BoilerFaultCodesThe 6 most common faults
01
L F High Engineer
Your boiler is struggling to keep its flame lit or cannot detect the flame, so it has safely shut itself down to prevent gas from building up.
Full guide for L F02
L E High Engineer
Your boiler has detected a communication error between its internal electronic brains, causing it to stop functioning for safety reasons.
Full guide for L E03
L A High Engineer
Your boiler has detected a critical internal error that prevents it from starting, and it requires a professional safety check.
Full guide for L A04
L 8 High Engineer
Your boiler has detected an issue with the heat exchanger or its temperature control, and it has stopped working to prevent potential damage.
Full guide for L 805
H 1 High Engineer
Your boiler has detected an issue with the water flow or temperature readings and has safely shut down to prevent damage.
Full guide for H 106
H 4 High Engineer
Your boiler has detected that the water temperature inside the system has risen too high, causing it to shut down for safety.
Full guide for H 4on the Ideal Icos System
Ignition electrodeFlame rectification probeGas valvePCBMain printed circuit boardWiring harness
Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.
Call a Gas Safe engineer if…
- You can smell gas or see signs of a leak
- The Ideal shows an Emergency or High severity code
- The boiler keeps locking out after repeated resets
- You've tried the DIY checks and the fault hasn't cleared
- There's visible water leaking from the boiler
- The flame is yellow or orange instead of blue