I have a 2011 f150 xlt 4x4 and if the heater is on when you start the truck it works great but if you try to turn it to a/c it switch just fine but if you switch back to heat it blow cold air still. Sometimes restarting the truck works and sometime it just has to sit for a while. Anyone know what is wrong with it?

 

Sounds like a blend door motor going bad..