Dont know if what your saying is that the screen is too dark at night or that the screen automatically goes dark when your txting! If the screen is too dark go to settings and set auto brightness to off then adjust manually, this will keep the screen at a constant brightness, now if the screen goes dark when your txting, go to settings-general and set auto-lock to however long you want, from i minute to never. my preference is never, just because i txt a lot!!!! Hope i understood your problem...