Vaillant boiler high pitch sound /whistle

[Mrspine]

My Vaillant Main Combi 25 Eco - is making a very loud whistle sound / high pitch whine.

- if I switch off the boiler while its whistling the sound still continues for a few seconds before winding down (sometimes it drops in pitch gradually)

- the sound is just as loud outside at the flue vent

- it can come in and out while the boiler is on

Noone seems to know how to tackle this. Its really driving us crazy.

 

[Jajodu]

Sounds like the fan, does it only occur when the burner is going? Does it stop when the burner exstinguishes, if not it may be the pump.

 

[Agile-Services]

There are also sometimes gas combustion problems which can cause this effect.

For that reason I would always advise a competent gas registered engineer is called to diagnose.

It can also sometimes caused by a heat exchanger which is seriously scaled up.