I'm helping a friend with his 2006 5.7 Hemi. The heat works when you first turn the fan on for about 30 seconds and then fades to cool. What I've discovered: 1. The truck doesn't seem to be overheating, It comes up to temp and doesn't fluctuate. Coolant level is fine and radiator seems to be working. 2. The recirculation door is broken and has been removed. 3. The mode selector (the one that changes where the air is blowing) doesn't work. I assume that the door is broken on this as well. 4. Hot/cold air mix seems to be working. Motor will move the doors and it feels as if the bottom door is at least intact. I didn't take it apart far enough to test the top door. 5. Only one of the lines to the heater core gets hot. I checked after the truck had been running for about 20 minutes. After about an hour both lines were hot. 6. Turning the fan off for a minute and the turning it back on will result in the same hot then cold cycle. I'm unsure of which direction to go with this thing right now. Any help would be appreciated.