Hi I have a 2001 F150 V6 engine, and not sure if the heater core is bad or there is something else going on. so this is what i have done so fare, started the motor up while cold and only one of the hose's get hot, there is no smell of antifreez in the cab and everything is dry also. once the truck is warmed up you can feel a slight heat coming out but as soon as you start to move down the road it turns cold. What do you think?

 

Sounds more to me like a blend door problem or you have a vacuum leak that is not allowing the HVAC system to operate correctly. I would look into that first. The vacuum lines for the HVAC start at a soleniod behind the battery, then run into the cab.