BoilerFaultCodesThe 6 most common faults
01
LED 1 High DIY-safe
Your boiler is currently completely unresponsive because it is not receiving any power, which might be due to a tripped switch, a disconnected plug, or a blown internal fuse.
What to try first
Check your home's central fuse box to ensure the boiler circuit breaker hasn't tripped.Verify the fused spur switch located near the boiler is turned to the ON position.Inspect the plug or connection point to ensure it is secure and the external fuse has not blown.
02
LED 3 (B) High DIY-safe
Your boiler is currently idle because it is not receiving a signal from your thermostat or timer to start heating.
What to try first
Check that your wall thermostat is set to a temperature higher than the current room temperature.Ensure your timer or programmer is set to an 'ON' period.Replace the batteries in your wireless room thermostat if it uses them.Check if any smart heating app linked to your boiler says the system is in 'Off' or 'Away' mode.
03
LED 4 (A) High Engineer
Your boiler has stopped providing hot water because it is struggling to read or regulate the temperature from its water heating sensor.
Full guide for LED 4 (A)04
LED 5 (A) High Engineer
Your boiler's electronic brain is malfunctioning and cannot correctly process its startup sequence, meaning it will currently fail to provide heating or hot water.
Full guide for LED 5 (A)05
LED 6 (A) High Engineer
Your boiler has stopped working because it is unable to accurately detect the water pressure or temperature, preventing it from safely heating your home or water.
Full guide for LED 6 (A)06
LED 4 (B) High Engineer
Your boiler has stopped working because it cannot properly read the water temperature or it has detected that it is running too hot.
Full guide for LED 4 (B)on the Ferroli Hawk II
Main printed circuit board (PCB)Internal fusePower supply cableExternal room thermostatProgrammer/TimerWiring centre
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