My neighbor is trying to solve a problem with an Avenger of which heat comes out of the driver side ducting but the passenger side blows cold (ambient temp). He has checked and tried to burp the coolant of any air pockets and we have watched the vent door actuators opening and closing. Googling the problem, it seems that people point toward a clogged heater core but that makes no sense since it is nothing more than a heat exchanger, just like the radiator, with fins, tubing and one tube in and one tube out. If it was clogged, hot coolant would not course through the tubing leading to no heat to either drive or passenger side. And that heater core is not compartmentalized for driver and passenger sides.Therefore, I am inclined to think that there is a mixing door in the large, plastic case under the dash that is not operating. It is a common problem from what I see on the internet. As is the case, it is January in the Chicago burbs and even in the garage, life is tough. Wish I could somehow have that duct box in hand or a drawing cutaway of what is inside.