BoilerFaultCodesThe 6 most common faults
01
F.22 High DIY-safe
Your boiler has detected that there is not enough water inside the system to operate safely, which has caused it to shut down to prevent damage.
What to try first
Locate the pressure gauge on the front of your boiler.Check if the needle is below the 1.0 bar mark.Use the filling loop (a metal braided hose or key under the boiler) to top up the system pressure until the needle reaches between 1.0 and 1.5 bar.
02
S.32 High Engineer
Your boiler has detected that the fan is not spinning at the correct speed to keep the internal components safe, so it has paused operation to prevent damage.
Full guide for S.3203
S.33 High Engineer
Your boiler is struggling to breathe because it has detected an issue with the air intake or exhaust system.
Full guide for S.3304
d.11 High Engineer
Your boiler is signalling that it is unable to detect or communicate with the external water pump responsible for moving heated water around your home.
Full guide for d.1105
d.21 High Engineer
Your boiler is struggling to detect that the flame is lit, so it is turning itself off to ensure your safety.
Full guide for d.2106
d.24 High Engineer
Your boiler is struggling because it cannot detect that the air required for safe combustion is flowing correctly.
Full guide for d.24on the Vaillant ecoTEC plus Aquaplus
Central heating pumpPressure sensorSystem expansion vesselFan assemblyPrinted Circuit Board (PCB)Air pressure switch
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 Vaillant 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