Not sure why the display would not come on. With newer systems, the display will go to a "walking dot", where it will show just a scrolling dot on the display. Is this what you're seeing? If so, when you press any button, the normal display will come back up.
On older systems, if the display goes bad, but the unit is still operating, try this. With the system on, disconnect the tri-sensor cable and see if the warning light comes on. If it does, then the unit is operating with just the display being bad. If no warning lights, its possible that your control board is bad.
