In my S70 and V70 you first open the ash tray. This exposes two screws on each side at the rear of the assembly that must be removed. You'll need a light to see them up under there. There is also a tab at the top around where the ash tray light lens is but if I recall correctly, the ash tray "drawer" and assembly will just slide straight out after the screws are removed. I can't say if it's the same for your 850 but I suspect so.
Anyway, if that is not what you are referring to, then.............uh...never mind.






