BoilerFaultCodesThe 6 most common faults
01
F.22 High DIY-safe
Your boiler has detected that there is either too little water inside the system or that the internal pump is failing to move the water around as it should.
What to try first
Check your boiler pressure gauge; if it is below 1 bar, use the filling loop to top it up to between 1 and 1.5 bar.Once pressure is restored, reset the boiler using the reset button or by turning the power off and on again.If the pressure is fine, try tapping the pump housing gently with a screwdriver handle to see if it is merely stuck, but do not open the casing.
02
F.24 High DIY-safe
Your boiler has detected that the water is heating up far too quickly, likely because there is air trapped inside or the pump is struggling to circulate water properly.
What to try first
Check your system pressure gauge; if it is below 1 bar, top it up using the filling loopBleed all radiators in the house starting from the ground floor up to the top floor to release trapped airRestart the boiler to see if it clears the fault
03
F.00 High Engineer
Your boiler is unable to read the temperature of the water flowing out of it because a sensor or its connection has failed, causing the system to stop working as a precaution.
Full guide for F.0004
F.01 High Engineer
Your boiler has lost the signal from the sensor that monitors the temperature of water returning to it, meaning it cannot safely regulate its heat.
Full guide for F.0105
F.10 High Engineer
Your boiler has detected a faulty electrical signal from its internal temperature sensor, causing it to shut down to prevent potential overheating.
Full guide for F.1006
F.11 High Engineer
Your boiler has detected an electrical fault in a temperature sensor that monitors the water returning to the system, causing it to shut down for safety.
Full guide for F.11on the Vaillant Turbomax 824/828
Circulating pumpPressure sensorFilling loopCentral heating pumpNTC temperature sensorAutomatic air vent
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