BoilerFaultCodesThe 6 most common faults
01
4 green High Engineer
Your boiler's internal temperature sensors are stuck in a mode that is telling the system to stay on, which can lead to overheating or your heating staying on when it shouldn't.
Full guide for 4 green02
7 green High Engineer
Your boiler has detected an issue with the air flow or fan, meaning it has stopped working for safety reasons.
Full guide for 7 green03
LED1 High Engineer
Your boiler has detected that the internal air fan or pressure system is stuck in the 'on' position, preventing the boiler from starting its ignition sequence for safety.
Full guide for LED104
LED1 on High Engineer
Your boiler has detected a failure with the safety system that handles smoke and fumes, preventing it from firing up for your safety.
Full guide for LED1 on05
Relay 2 energised after 2 sec High Engineer
Your boiler has detected an internal electrical or sensor error that is preventing it from starting up safely.
Full guide for Relay 2 energised after 2 sec06
8 yellow Emergency Engineer
Your boiler has detected that the gas valve is opening at the wrong time or when it hasn't been told to, which is a safety concern that prevents the appliance from running.
Full guide for 8 yellowon the Ferroli Combi 77 FF Popular
NTC Temperature SensorCentral Heating SensorThermistorAir Pressure SwitchFan AssemblyVenting Venturi Tube
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