BoilerFaultCodesThe 6 most common faults
01
Fault indication light (2) High DIY-safe
Your boiler has detected an internal error or has become too hot and has safely shut itself down as a precaution.
Why it happens: This fault occurs when the boiler's internal safety sensors detect that the water temperature has exceeded safe limits or if a component has failed. The most common reasons include a blockage in the system, a pump failure that prevents water from moving, or a build-up of limescale within the heat exchanger. Because the unit cannot safely cool itself down, it shuts off to prevent damage to the internal parts.
What to try first
Locate the reset knob on the front control panel.Turn the knob to the 'RESET' position and hold it for 2 seconds.Return the knob to its original setting and wait for the boiler to restart.
02
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 F03
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 E04
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 H905
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/L906
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 76on the Ideal Icos HE
Overheat ThermostatPCB (Printed Circuit Board)ThermistorIgnition electrodeGas valvePrinted circuit board (PCB)
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