2004 Overland. No heat on pass. side.

No, the problem is the blend door, reaserch blend door failures, tons of info on the web. A quick fix it now solution is this:

remove the glove box by opening it, and if you pop it pretty hard with your hand it will clear the stops - I have done it on several jeeps and never broken anything, remove the little slow open piston on the right. On the bottom there are three tabs that act as a hinge, two up one down, you can wiggle it out without breaking it. then, on your left you will see an actuator, remove it. Now in the area to the right of that the shape of the duct kind of curves around to an edge - vertical. Take a drill with a small bit and drill a hole and push hp am the drill as if you were using it as a rotozip, about 4 inches or so then to the left about 4 inches and them back down to where the seam is. there is a metal clip in the cut section connecting the top and bottom, pop it off and remove the piece of duct. Now, reinstall the actuator and turn on the heater, and go from hot to cold. you will see a door go up and down. now rach further back and you will find a second door that is in the down position. flip it up and stick something in to hold it up - I used the plastic holder frm a mach 5 razor, as was 8 degrees out side the first time I just fliiped it up thinking it would stay. Now reinstall the piece of duct, it will pretty much stay in place and use a bit of duct tape to seal. Ther is a produce on ebay i believe called heater treater that has a more permanent fix and i believe a few photos, as you will use the same access door you just made to install it. Make sure and use a vac to clean all of the little black shavings, best to have some one hold the vac while you cut. Do not use a jig saw, it will destroy the duct work. and dont forget to reinstall the plunger on the glove box when you put it back, and yes, just smack it it pop it back in place

Sounds like your heat ducts might be plug with leaves that's been sucked in from outside,or you might have broken hoses allowing the heat to escape under the dash your a/c would work fine because it comes out the top ducts most of the time.
good luck