85 is a bit cool for the hot side. Try to get it between 88-92. There are a few possibilities for why he isn't using the hide. The few that immediately come to mind are that the hot side is too cool and/or the hide is to large for the snake.

Check out these two threads, they cover care and cage heating:

http://ball-pythons.net/forums/showt...ius)-Caresheet

http://ball-pythons.net/forums/showt...t-Thermometers