BoilerFaultCodesThe 6 most common faults
Your boiler has become too hot or water is not moving through the system properly, causing the unit to shut down for safety.
Why it happens: This fault occurs when the water inside your boiler reaches a temperature that is too high for safe operation. It is usually caused by a blockage in the pipework or a mechanical failure in the pump, which prevents water from moving away from the heat source quickly enough. In some cases, a buildup of debris or sludge in the system can restrict flow and trigger this safety shutdown.
Check that your radiator valves are fully openEnsure your boiler pressure is between 1.0 and 1.5 barBleed your radiators to remove any trapped air
Your boiler’s internal computer brain hasn't been programmed correctly, meaning it doesn't know which model it is and cannot start up.
Why it happens: This fault occurs when the boiler's main control board has lost its identity or was never properly told which model it is installed in. It usually happens after a power surge scrambles the memory or if a new part was installed without the specific configuration chip being inserted. Without this digital profile, the boiler cannot safely coordinate the fan and gas valve, so it shuts down as a precaution.
Full guide for F9Your boiler has detected that it is running too hot and has automatically turned itself off to prevent damage.
Full guide for L 01Your boiler is failing to light the flame needed to generate heat and has safely shut down to prevent gas buildup.
Full guide for L 02Your boiler has stopped heating because the flame inside has gone out unexpectedly, preventing it from producing heat.
Full guide for F 02 or FN or LNYour boiler has detected that the internal fan is not working correctly, which prevents it from safely venting gases, so it has shut down to protect your home.
Full guide for F 03on the Ideal Logic+ Heat
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
Avoid the next call-out bill
Monthly cover means no unexpected bills when your boiler breaks down.
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