I have a 2006 Linclon Mark LT. When it is hot outside in the say around 90 degree range and the vehicle is sitting in the sun the blower fan will not come on either on heat or AC. If the vehicle is moved into the shade and or has been sitting overnight and the outside temp is much cooler the fan works fine in both AC and heater modes. This seems to be some kind of sensor issue and which sensor would cause this issue. i would assume this would be the same on a 2006 F-150 as they are normally the same.

Thanks