BoilerFaultCodesThe 6 most common faults
Your boiler has stopped working because the water pressure inside the heating system has dropped too low.
Locate the external filling loop, which is usually a silver braided hose underneath the boiler.Open the valves at both ends of the hose to allow water into the system until the pressure gauge reads between 1 bar and 1.5 bar.Close both valves firmly and ensure the hose is disconnected if required by your specific installation.
Your boiler is struggling to light its flame properly and has failed multiple attempts to start up.
Check that your gas emergency control valve is in the 'on' positionIf you have a prepay gas meter, check that you have sufficient creditCheck if other gas appliances, such as a hob, are working correctlyPress the Reset button (indicated by a flame with a cross through it) for five seconds
Your boiler has encountered a general electronic or system error that it cannot identify specifically, causing it to shut down for safety.
Locate the reset button (indicated by a flame with a line through it) on the boiler control panel.Press and hold the reset button for five seconds.Wait for the boiler to restart; if the code persists, contact a Gas Safe engineer.
Your boiler has lost its connection to the sensor that measures how hot the water is inside it, preventing it from heating your home safely.
Full guide for F.00Your boiler has lost its connection to the sensor that monitors the water temperature returning to the unit, causing it to shut down for safety reasons.
Full guide for F.01Your boiler has stopped working because a sensor that monitors water temperature has developed a faulty faulty connection or failed completely, causing the system to shut down for safety.
Full guide for F.10on the Vaillant ecoFIT Pure 835
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