BoilerFaultCodesIdeal F2, FN or LN Fault Code
Also written as F2FNORLN — same fault.
The Ideal F2, FN or LN fault code means: your boiler has lit correctly but the flame has gone out unexpectedly, meaning the system has shut down for safety.. It appears on 10 Ideal models in our database.
Technical description: Flame loss
What causes the Ideal F2, FN or LN fault?
This fault occurs when the boiler's internal sensor can no longer detect a steady flame after the burner has ignited. The most common reasons include a buildup of carbon on the sensing probe, an inconsistent gas supply, or a component failure that prevents the system from confirming the fire is safely lit.
This fault is more common during extreme cold spells, as freezing temperatures can affect gas pressure or cause the condensate pipe to backup, both of which can extinguish the flame.
DIY fix possible
Check if other gas appliances, like a cooker, are working to ensure gas is reaching the propertyCheck if your gas meter has credit (if using a prepay meter)Press the Reset button on the front of the boiler
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Ideal models that show the F2, FN or LN fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal F2, FN or LN fault code information on this page is sourced and cross-checked against the official Ideal service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026