BoilerFaultCodesThe 6 most common faults
01
H A (flashing) High DIY-safe
Your boiler has stopped working because the water pressure inside the heating system has dropped too low to operate safely.
What to try first
Locate the filling loop, which is a silver braided hose under your boiler.Open the valves at both ends of the hose to let water into the system.Watch the pressure gauge on the front of the boiler until the needle reaches 1.5 bar, then turn the valves off securely.
02
HE High Engineer
Your boiler's computer system is experiencing a major internal processing error and cannot safely manage the heating process.
Full guide for HE03
L9 High Engineer
Your boiler has detected that the gases leaving through the flue are getting too hot, so it has automatically shut itself down to prevent damage.
Full guide for L904
H9/L9 High Engineer
Your boiler has shut down because the internal gases have become too hot, causing the system to lock out for safety until it cools down.
Full guide for H9/L905
L-F High Engineer
Your boiler is failing to light the internal flame or keep it burning, which means your heating and hot water have stopped working.
Full guide for L-F06
H-E High Engineer
Your boiler’s internal computer has encountered a critical communication error and can no longer control the heating or hot water functions.
Full guide for H-Eon the Ideal Icos
Filling loopPressure relief valvePrinted Circuit Board (PCB)Heat exchangerNTC thermistorFlue gas sensor
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