I have an 07 ram 1500. The heat went cold last winter so I took it to a mechanic and he said my heater core was bad. At the beginning of this winter I had the heater core replaced and the heat worked great for about a week then went cold again. This time I changed the thermostat and still no heat. Burped the coolant system and still nothing. Had heater core flushed 3 times and still nothing. I've read all the forums and watched every YouTube video I can find on this but I've got no idea what it can be now. The only thing I haven't done is tear into the dash and check the doors and actuators. I have an endoscope on order that I plan to snake through the vents and see if anything is broken before I tear into it. I'm at a dead end and would appreciate any other ideas!