I just bought an 03 2500 and I cant get thr heat to work. Ac works fine blows very cold, heat just blows air. Is there an actuator or door that works the heat? I've read about the door that sits above the blower that works fresh or recirculating air. But what about the climate temp control? Where would that actuator be located? I've googled till my fingers hurt and cant find any answers.

 

You're asking about the blend door, lots of discussion and videos on that subject.
You might have a bad heater core. You can see the two hoses coming from the water pump into the firewall on the passenger side. Drive the truck around to get the thermostat open and turn the heat on. Feel the two hoses, if one is warm and one is cool then there is blockage in the heater core.
If both are warm then it's more likely an airflow problem.