BoilerFaultCodesThe 6 most common faults
01
F37 High DIY-safe
Your boiler has stopped working because the water pressure inside the system is too low to operate safely.
What to try first
Locate the filling loop (a flexible silver hose connected to two valves under the boiler).Open the valves slowly to allow mains water into the system until the pressure gauge reads between 1 and 1.5 bar.Close both valves tightly and check the boiler display to see if the fault has cleared.
02
F41 High DIY-safe
Your boiler has switched itself off because the water inside it is heating up much faster than it is moving away, preventing it from working as intended.
What to try first
Check that all your radiator valves are fully openEnsure your central heating system is pressurized to the correct level (usually 1-1.5 bar)Turn the boiler off and back on again after waiting 10 minutes for the internal temperature to lower
03
F10 High Engineer
Your boiler has lost the ability to measure its own water temperature, so it has safely shut down to prevent overheating.
Full guide for F1004
A03 High Engineer
Your boiler has detected that it has become dangerously overheated and has automatically shut itself down to prevent damage.
Full guide for A0305
A06 High Engineer
Your boiler has detected that the water inside the heating system has become dangerously hot and has shut itself down to prevent damage or overheating.
Full guide for A0606
A08 High Engineer
Your boiler has stopped working because it cannot detect a rise in temperature when it tries to heat your water, suggesting a sensor is failing to report its readings correctly.
Full guide for A08on the Ferroli Leb TS
Pressure relief valveWater pressure switchExpansion vesselCirculating pumpFlow sensorMain heat exchanger
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 Ferroli 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