BoilerFaultCodesThe 6 most common faults
01
214 High Engineer
Your boiler has detected that the internal fan responsible for safely removing exhaust gases is not spinning, so it has shut itself down to prevent unsafe operation.
Full guide for 21402
215 High Engineer
Your boiler has detected that the internal exhaust fan is spinning faster than it should, so it has safely shut itself down to prevent damage.
Full guide for 21503
224 High Engineer
Your boiler has detected that it is overheating and has automatically switched itself off to prevent damage to the internal components.
Full guide for 22404
227 High Engineer
Your boiler is trying to start but the internal burner is failing to catch and stay alight.
Full guide for 22705
229 High Engineer
Your boiler has stopped because the flame inside it went out unexpectedly while it was running.
Full guide for 22906
233 High Engineer
Your boiler's main computer brain is having a communication error, which means it cannot safely control the heating or hot water functions.
Full guide for 233on the Worcester Bosch 24/28/35 CDi MkII
Fan assemblyFan wiring harnessPrinted Circuit Board (PCB)NTC temperature sensorCentral heating pumpHeat exchanger
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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