BoilerFaultCodesThe 6 most common faults
01
EA High DIY-safe
Your boiler has tried to light several times but has failed to detect a flame, causing the system to shut down for safety.
What to try first
Check if other gas appliances in your home, like a cooker, are working to ensure gas supply is active.If it is freezing outside, check that your white plastic condensate pipe is not frozen or blocked.Ensure your gas meter has credit and the emergency control valve is in the 'on' position.
02
C1 High Engineer
Your boiler has stopped working because the fan that removes waste gases is not spinning fast enough to operate safely.
Full guide for C103
C4 High Engineer
Your boiler's internal fan is running constantly and won't shut down, preventing the system from starting its normal ignition sequence.
Full guide for C404
E2 High Engineer
Your boiler has lost its ability to measure the temperature of the water leaving the unit, causing it to shut down to prevent overheating.
Full guide for E205
E9 High Engineer
Your boiler has switched itself off because it has detected that the internal water or exhaust gases have reached a dangerously high temperature.
Full guide for E906
F7 High Engineer
Your boiler thinks it can see a flame even though it should be turned off, so it has shut down for safety.
Full guide for F7on the Worcester Bosch Worcester 25/30 HE
Ignition ElectrodeFlame Sensing ProbeGas ValvePCBFan assemblyPrinted Circuit Board (PCB)
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