1997 Ford Expedition no heat

I need to know a few things. First, is the engine running at normal temp? If so, with the engine running, hot, and the heater on high, feel both heater core hoses. They should be hot. If one is and one isn't, chances are the core is plugged. If both are hot, then there is an item called the blend door. Its position determines whether you get heat or AC in the car. It could be stuck or not working and only allowing the AC to go through.

Let me know what you find.

Joe