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 itself correctly and has failed multiple attempts to start up.
Check if your gas supply is turned on at the meterCheck if other gas appliances, like a hob, are workingPress the reset button (flame symbol with a cross through it) for five seconds
Your boiler has encountered a general communication or system error that it cannot identify with a specific sub-code, causing it to stop running for safety.
Turn the boiler off at the main electrical switch or fused spur.Wait approximately 60 seconds.Turn the power back on and press the 'Reset' button (indicated by a flame with a cross through it).
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 418
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