HUD/Sight head altimeter stuck on 1900?

[Bog9y]

Sorry if this has been explained somewhere but I have been searching for a while now with no answer.... but...

Can someone please tell me why the altitude on the HUD/sight head seems to be stuck on 1900?  It does not move at all no matter what my altitude. 

Did I forget to select something or flick a switch? 

 

Many thanks 

[jaguara5]

It's the max displayed altitude . null

[Bog9y]

Ok but I had 1900 displayed even when I was well below 1900 agl. It displays 1900 on the ground even.

 

[bones1014]

it is a barometric instrument so is affected by your "Slaved altimeter barometric pressure setting" on your primary altimeter.

[Bog9y]

Yep, I was an idiot. Turns out where I was flying had an elevation above 1900! Flew closer to sea level yesterday and the altimeter in the sight worked fine!