BoilerFaultCodesThe 6 most common faults
Your boiler has switched itself off because it has reached an internal temperature that is too high, often caused by a blockage or poor water flow.
Check that all radiator valves are fully openEnsure the boiler pressure is between 1.0 and 1.5 barPress the reset button (flame symbol with a cross) to restart the boiler
Your boiler has detected that there is not enough water pressure or flow to operate safely, causing it to shut down to prevent overheating.
Check the pressure gauge on the front of the boiler; it should be between 1 and 1.5 bar.Locate the filling loop (usually two silver braided hoses) underneath the boiler.Slowly open the valves to let water into the system until the gauge reaches 1.5 bar, then ensure they are closed tightly.Press the reset button (indicated by a flame with a cross through it) to restart the boiler.
Your boiler is heating up too quickly because the water inside isn't moving fast enough, usually due to trapped air or a struggling pump.
Check that your radiator valves are fully openBleed all radiators to remove trapped air from the systemCheck the boiler pressure is between 1.0 and 1.5 bar and top up if necessary
Your boiler is failing to light the gas flame despite several attempts, meaning you currently have no heating or hot water.
Check that your gas emergency control valve is in the 'on' position.Verify if other gas appliances in your home, such as a hob, are receiving gas.If you have a pre-payment meter, check that you have active credit.Press the 'Reset' button (indicated by a flame with a line through it) for five seconds.
Your boiler has lost its flame while running and cannot manage to relight itself, likely due to a problem with the gas supply.
Check if other gas appliances in your home, like a hob, are working correctly.Ensure your gas meter has credit if you use a prepay system.Ensure the gas isolation valve under the boiler is fully open.Press the 'Reset' button (flame symbol with a cross through it) to restart the ignition sequence.
Your boiler has paused because the internal fan is not spinning at the correct speed to safely clear waste gases.
Full guide for S.32on the Vaillant aquaPLUS
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