BoilerFaultCodesThe 6 most common faults
01
E00-730 High Engineer
Your boiler is not detecting the correct airflow needed to operate safely, so it has shut itself down to prevent any issues.
Full guide for E00-73002
E80-450 High Engineer
Your boiler is unable to regulate the gas supply correctly, which is preventing it from firing up to provide your heating and hot water.
Full guide for E80-45003
E00-720 High Engineer
Your boiler is failing to ignite the flame needed to produce heat and hot water.
Full guide for E00-72004
E00-711 High Engineer
Your boiler is struggling to transfer heat between its internal systems, which means it cannot reliably provide hot water or heating.
Full guide for E00-71105
E80-451 Emergency Engineer
Your boiler has detected an issue with its internal gas supply system which is preventing it from heating your home safely.
Full guide for E80-45106
E00-737 Emergency Engineer
Your boiler has detected an issue with the fuel supply or combustion process, meaning it has safely shut itself down to prevent unsafe operation.
Full guide for E00-737on the Worcester Bosch 24/28/35 CDi MkII
Air pressure switchFan assemblyVenturi/tubingGas ValveWiring HarnessGas Valve Solenoid
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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