Okay we have the carpet out and blend door and everything out of my truck. Supercrewzn and Westtn it wasnt clogged btw. And the blend door looks to be fine but when on low fan it blows hot but when i turn the fan speed up it just gets cooler.
Are you sure you don't have a too low thermostat or its stuck open? Have you felt the upper and lower radiator hoses? did you feel both heater hoses? All hoses you be hot to the touch when fully warmed up.
Then its gotta be the blend door. That's all that's left unless there is an air pocket in the cooling system.
When you service the thermostat or flushed the system you did not let the truck sit there and idle to work all the air out of the system. It is really easy. All you do is take the reservoir cap off and let the truck idle. It is called burping. What I did to mine cause I had a similar problem was start fresh so I could eliminate these things was. Go to Ford and bought a new reservoir cap. There is a updated one, and it is very cheap. New thermostat, thermostat gasket. Just add some more coolant let the truck idle and burp and you should be ok.
I would also recommend getting a coolant flush done, just to make sure any crap in there is out. Go buy some flush from Napa, put it in your upper radiator hose and drive it to a local shop with a flush machine.
