Sounds like a problem I had a while back, and from what I found online it's a decently common problem with the Rams (I don't know at what point they fixed it).
There's a little flap, or door (under passenger side dash - behind glove box) that changes position when you choose fresh vs. recirculated air. The flap is supposed to be vertical (blocking off access to the interior of the truck) for fresh air, and horizontal (blocking the flow from outside) for recirculated air. There is a little motor that turns this door to each position, and the way it is attached to the door is the flaw. The motor turns a little rod that's about 3/4" long that is seated into a matching hole on the door. The other end of the door just rotates like a simple hinge. The problem is, the little "hole" that is on the door that accepts the rod from the motor is made from crap plastic. On mine, the plastic broke clean in half, so there is nothing holding the door in place. The door fell down, and was laying flat against the blower (at the bottom of the whole assembly blowing straight up) blocking most of the air flow.
I had the same problem, the air was the right temperature, and coming out of where it was supposed to, just not nearly as strong as it should have. I just pulled the door out (and the little piece of broken plastic that was lodged in the blower - how I was forced to solve the problem) and got full "blowing power" back. Sure, that's kind of a lame fix, because now I can't choose between fresh or recirculated air, BUT... I don't really ever care anyway.
You'll know this is the problem if, when you take the blower off from under the dash (simple, a few screws), there's a piece of plastic (mine was covered in foam) laying right there. Here's a pic of the door, broken piece and all.
Hope this helps.