BoilerFaultCodesThe 6 most common faults
01
lock-out High Engineer
Your boiler is failing to light the flame, so it has safely shut itself down to prevent a gas leak.
Full guide for lock-out02
LOCKOUT High Engineer
Your boiler has stopped working because it cannot light its internal flame, which means your heating and hot water have switched off for safety.
Full guide for LOCKOUT03
Fan does not run High Engineer
Your boiler has stopped working because it cannot properly move the air and fumes required for safe operation.
Full guide for Fan does not run04
Ignition lockout High Engineer
Your boiler is failing to light the flame needed to heat your home, so it has locked itself for safety and requires a manual reset.
Full guide for Ignition lockout05
Flue overheat High Engineer
Your boiler has detected that it is getting dangerously hot and has shut itself down to prevent damage or fire risks.
Full guide for Flue overheat06
Volatile lockout High Engineer
Your boiler has detected an internal error and has safely shut itself down to prevent damage, meaning your heating and hot water will not work until it is reset or repaired.
Full guide for Volatile lockouton the Worcester Bosch Greenstar 15i System
Ignition electrodeGas valveIgnition leadPrinted Circuit BoardFlame rectification probeFan
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