BoilerFaultCodesThe 6 most common faults
01
L1 High DIY-safe
Your boiler has switched itself off because the internal water temperature has become too hot, usually caused by a lack of water flow through the system.
What to try first
Check that your radiator valves are fully openEnsure your boiler pressure is between 1 and 1.5 bar on the gaugeReset the boiler by turning the control knob to 'RE' or pressing the reset button
02
F1 High DIY-safe
Your boiler has stopped working because the water pressure inside the heating system has dropped too low.
What to try first
Locate the internal filling loop, which is usually a small silver lever or a braided hose under the boiler.Open the filling valve slowly until the pressure gauge on the front of the boiler reads between 1.0 and 1.5 bar.Close the valve tightly and check that the fault code disappears.
03
L2 High Engineer
Your boiler has tried to start up several times but failed to ignite the gas burner.
Full guide for L204
LC High Engineer
Your boiler has temporarily locked itself out for safety after too many failed attempts to start up.
Full guide for LC05
L6 High Engineer
Your boiler thinks a flame is burning even though it shouldn't be, causing the system to shut down for safety.
Full guide for L606
F2 Or Fn Or Ln High Engineer
Your boiler is failing to stay lit, which means it has safely shut itself down because it cannot consistently produce or hold a flame.
Full guide for F2 Or Fn Or Lnon the Ideal CLASSIC2
Circulating pumpThermistor (NTC sensor)Main heat exchangerPressure sensorFilling loopPressure relief valve
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
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