My 00' Excursion heater is having issues the rear works fine and blows hot air but the front only blows luke warm air?Are they on different systems or is there a duct problem? And if it is a duct problem anyone know where to start to look where this could be taking place?

 

The Excursion has 2 heater cores to the best of my knowledge. One against the firewall for the front and one in the back of the truck for the rear heat. There is a control valve under the hood that controls the front one. Its ran by vacuum and is a problem child on most late model fords. I would suggest starting there.