BoilerFaultCodesThe 6 most common faults
Your boiler has automatically shut down because the internal water pressure has dropped too low to operate safely.
Locate the filling loop valves underneath your boiler or near your hot water cylinder.Open the valves slowly to let mains water into the system until the pressure gauge reads between 1.0 and 1.5 bar.Close both valves tightly and reset the boiler using the reset button.
Your boiler was working but has suddenly turned off because the flame has gone out and it cannot manage to relight itself.
Check if other gas appliances, like a hob, are still working to ensure your gas supply hasn't been interrupted.If it is freezing outside, check the condensate pipe (the plastic pipe leading outside) for ice and defrost it with warm water.Press the reset button (a flame symbol with a cross through it) for five seconds to see if the boiler restarts.
Your boiler has stopped working because the water pressure inside the system has dropped too low.
Locate the filling loop valves underneath your boiler or near the pipework.Open the valves slowly to allow water into the system until the pressure gauge reaches between 1.0 and 1.5 bar.Close both valves firmly and reset the boiler using the reset button.
Your boiler has lost its connection to the temperature sensor, meaning it no longer knows how hot the water is and has stopped working to keep you safe.
Full guide for F.00Your boiler has lost the connection to the sensor that monitors the temperature of the water returning to the unit, causing it to stop working for safety reasons.
Full guide for F.01Your boiler has stopped working because a sensor that measures water temperature is providing an incorrect signal, so the system has safely shut down to prevent overheating.
Full guide for F.10on the Vaillant ecoFIT sustain 430
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
Avoid the next call-out bill
Monthly cover means no unexpected bills when your boiler breaks down.
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