My 2008 Ford F-150 King Ranch blows the air out of the correct vents when set for them but it's not warm. I've replaced the thermostat but it didn't help. Is there a valve in the coolant lines or a baffle etc in the air routes to control the temp of the air flow

 

Did you check to see if there is hot coolant circulating through the heater core? Check both hoses, engine up to temp and heat on high...

There's no valve in the coolant lines.