BoilerFaultCodesThe 6 most common faults
01
1 (Group 1) High Engineer
Your boiler is trying to start up and even lighting the gas, but it fails to recognise that the flame has actually caught, so it safely shuts down again.
Full guide for 1 (Group 1)02
2 (Group 1) High Engineer
Your boiler has temporarily stopped because it cannot detect the flame needed to keep it running safely.
Full guide for 2 (Group 1)03
4 (Group 1) High Engineer
Your boiler has failed to light properly on its first attempt and safely shut down to prevent gas from building up.
Full guide for 4 (Group 1)04
7 High Engineer
Your boiler has automatically shut down because the internal water temperature reached an unsafe level.
Full guide for 705
11 High Engineer
Your boiler's main electronic control brain has suffered an internal fault and has safely shut down to prevent damage.
Full guide for 1106
12 High Engineer
Your boiler has temporarily stopped working because it cannot detect the correct airflow through the internal fan.
Full guide for 12on the Worcester Bosch Greenstar Ri
ElectrodesLeadPrinted Circuit Board (PCB)Flame sensing electrodeIgnition leadGas valve
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
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