No Heat!

I have a 2000 Ford Expedition Eddie Bauer I am getting no heat at all front or back cleaned out heater core changed water pump and thermostat had sytem flushed don't know what to do next

I had this happen to my f150 and it turn out to be the door motor in the hvac box. This would turn the door from heast to a/c. I found mine on the tranny tunnel or hump, little whitish box three screws and a plug in clamp.