BoilerFaultCodesThe 6 most common faults
01
Burner Lock-out High DIY-safe
Your boiler has stopped working for safety reasons and requires a manual reset to attempt to start again.
What to try first
Locate the temperature control knob on the front of the boiler.Turn the knob fully anticlockwise to the 'O' (reset) position and hold for a few seconds.Turn the knob back clockwise to your desired temperature setting to see if the burner ignites.
02
lock-out High Engineer
Your boiler has stopped working because it cannot detect a flame, so it has purposefully shut down to prevent gas from building up inside your home.
Full guide for lock-out03
NO LIGHTS AT ALL High Engineer
Your boiler has lost all power and is completely unresponsive, meaning it cannot provide heating or hot water until the electrical supply is restored.
Full guide for NO LIGHTS AT ALL04
LOCKOUT LIGHT ON CONSTANTLY High Engineer
Your boiler has detected that it is running too hot and has automatically shut itself down to prevent damage.
Full guide for LOCKOUT LIGHT ON CONSTANTLY05
LOCKOUT LIGHT FLASHING High Engineer
Your boiler has stopped working because it failed to light or stay lit, so it has purposefully shut itself down for safety.
Full guide for LOCKOUT LIGHT FLASHING06
OTHER FAULTS High Engineer
Your boiler is struggling to control its internal temperature correctly, causing it to shut down to prevent overheating or inefficient operation.
Full guide for OTHER FAULTSon the Worcester Bosch 24i/28i Junior
Ignition electrodeGas valvePrinted Circuit Board (PCB)Control board fuseMains isolator switchPump
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 Worcester Bosch 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