BoilerFaultCodesThe 6 most common faults
01
L F High Engineer
Your boiler has stopped working because it failed to light correctly, causing it to lock itself down for safety.
Full guide for L F02
H E High Engineer
Your boiler's main computer control panel is experiencing a software or internal communication error and cannot operate the system.
Full guide for H E03
H9 High Engineer
Your boiler has detected that the gases it is producing are significantly hotter than they should be, so it has shut itself down to prevent damage or overheating.
Full guide for H904
H9/L9 High Engineer
Your boiler has detected that the gases moving through your flue are getting dangerously hot, so it has automatically shut itself down to prevent damage.
Full guide for H9/L905
76 High Engineer
Your boiler has detected that it is running without enough water and has shut itself down to prevent damage to its internal components.
Full guide for 7606
L9 Emergency Engineer
Your boiler has detected that the exhaust gases are becoming dangerously hot and has shut itself down to prevent damage or fire risk.
Full guide for L9on the Ideal Icos HE
Ignition electrodeGas valvePrinted circuit board (PCB)Main PCBWiring harnessFlue gas thermistor
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