2003 Ford Explorer Sport Trac Question: my a/c stays running and my heater will not work to get heat

we have changed the thermostat and the switch and still the same problem when you turn the heat on it will not change over to the heater just runs the a/c . behind the glove box you can here the fan running but there is times that it will not blow anything into the truck as well no a/c or heat . the heater hoses are hot in and out