I have a 2006 F150 and the temperature gauge climbs quick but the heat only blows through the vents while moving. when stopped, air is cool to luke warm.

When the radiator hoses are checked, the top hose is warm but the bottom hose is cold.

 

 

If the bottom hose is cold that sounds more like a coolant flow thing to me than an air flow thing. The blendor would affect the airflow not the coolant flow correct?

 

Are we talking bottom radiator hose or heater hose .Big difference . Blend door is a common problem but this seems different .Its like the thermostat is stuck open .Is this engine coming up to temperature. Is it got enough coolant in it, is it burped to remove air . Is belt tensioner working to drive water pump .This sounds like no flow or very little/blocked radiator ? .Makes me wonder how belt is routed .Last time I worked on step sons with no antifreeze, whole system had turned to rust mud --new engine .
At the very least flush system ,new thermostat /new coolant reservoir cap /burp it with top radiator hose .Use anti corrosion antifreeze .