BoilerFaultCodesThe 6 most common faults
Your boiler's control panel and its internal computer are not talking to each other, meaning the unit cannot receive instructions to provide heat or hot water.
Why it happens: This fault occurs when the data link between the boiler's control screen and its main internal computer is broken or interrupted. The most common reason is a loose wiring connection or a component failure caused by a power surge or natural wear and tear. Without this communication link, the boiler cannot process your heating requests and shuts down for safety.
Full guide for conYour boiler has stopped working because the water pressure inside your heating system has dropped too low to operate safely.
Locate the external filling loop (a silver flexi-hose) connected to the pipework underneath your boiler.Slowly open the valve(s) on the loop to allow water into the system until the pressure gauge reads between 1.0 and 1.5 bar.Close the valve(s) tightly and check the boiler display to see if the fault code has cleared.
Your boiler has detected that the water pressure inside your heating system is currently too high for it to operate safely.
Locate a radiator in your home with a bleed valve.Using a radiator key, slightly open the valve to release a small amount of air and water into a cloth or container.Close the valve once water begins to trickle out steadily.Monitor the boiler's pressure gauge until it returns to the green zone (typically between 1.0 and 1.5 bar).
Your boiler has detected low water pressure and is currently in a waiting period before it attempts to restart.
Locate the filling loop (a silver flexi-hose) underneath the boiler or near your pipework.Open the valves on the hose to let mains water into the system.Watch the pressure gauge on the front of the boiler until the needle reaches the green zone (typically 1.0 to 1.5 bar).Close the valves firmly and check that the fault code clears.
Your boiler is ready to heat your home, but it cannot currently pump enough water around the system to safely turn the flames on.
Check that all radiator valves throughout your home are fully openInspect the boiler pressure gauge to ensure it is between 1 and 1.5 barIf the pressure is below 1 bar, use the filling loop to top it up to the correct level
Your boiler has detected that there is not enough water circulating through your heating system to work properly.
Check your boiler pressure gauge to see if it is below 1.0 bar.Locate the filling loop (usually a silver braided hose with a tap underneath the boiler).Open the tap slowly to top up the system pressure until the needle reaches between 1.0 and 1.5 bar, then turn it off tightly.
on the Vaillant ecoTEC plus
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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