BoilerFaultCodesThe 6 most common faults
01
A7 High Engineer
Your boiler is currently struggling to measure the temperature of the water it is heating, which means it will stop providing you with hot water.
Full guide for A702
B1 High Engineer
Your boiler's internal computer is struggling to identify the specific settings it needs to operate, so it has safely shut down to prevent incorrect functioning.
Full guide for B103
d1 High Engineer
Your boiler is struggling to accurately measure its own temperature, so it has safely shut itself down to prevent potential damage.
Full guide for d104
E2 High Engineer
Your boiler has lost the ability to measure the temperature of the water used for your radiators, so it has safely shut down to prevent overheating.
Full guide for E205
EA High Engineer
Your boiler is trying to start up but cannot light the internal flame, so it has shut itself down as a safety precaution.
Full guide for EA06
LOCKOUT High Engineer
Your boiler has failed to light the flame after several attempts and has shut itself down as a safety precaution.
Full guide for LOCKOUTon the Worcester Bosch Greenstar 30si
Domestic Hot Water NTC SensorCoding plugPrinted Circuit Board (PCB)NTC Temperature SensorWiring harnessIgnition electrode
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