BoilerFaultCodesThe 6 most common faults
01
F 01 High DIY-safe
Your boiler has stopped working because the water pressure inside the heating system has dropped below the required level.
What to try first
Locate the filling loop (a silver flexible hose) underneath your boiler or near your airing cupboard.Open the valves on both ends of the hose to allow water into the system.Watch the pressure gauge on the front of the boiler until the needle reaches the green zone (usually between 1.0 and 1.5 bar).Close both valves tightly and remove the hose if required by your specific setup.
02
L 01 High Engineer
Your boiler has detected that it is getting too hot and has automatically switched itself off to prevent any damage.
Full guide for L 0103
L 02 High Engineer
Your boiler has failed to light the flame, so it has safely shut itself down to prevent any unburned gas from building up.
Full guide for L 0204
F 02 or FN or LN High Engineer
Your boiler is failing to stay lit, which means it has safely shut down because it cannot maintain a stable flame to provide your heating and hot water.
Full guide for F 02 or FN or LN05
F 03 High Engineer
Your boiler has detected an issue with its internal air extraction system, which is preventing it from safely lighting and operating.
Full guide for F 0306
F 04 or L 04 High Engineer
Your boiler has stopped working because a sensor that measures the water temperature is failing to send a signal, meaning the system cannot safely regulate your heating.
Full guide for F 04 or L 04on the Ideal LOGIC SYSTEM2
Filling loopPressure gaugePressure relief valvePumpHeat exchangerNTC 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
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