If you can move it freely, and it isn't changing the temperature of the air coming out of the vents with the jeep running, I'd suspect the door is no longer attached to the part you are moving. If you can you rotate it more than 180 degrees, that would pretty much prove it isn't properly attached. This video shows how much it should be able to turn
(No Heat Jeep Trouble Shooting)
If the heater core lines are close to the same temperature going in and out, then it isn't blocked and is working like it should. When the heat is working properly with air also passing through the heater core, the return line will be slightly cooler than the line going in, but still hot to the touch.