The air conditioner doesn't cool down the car under normal driving. on 2010 Dodge Avenger

The center right vent blows cold air the others are warmer.I bought the car on 06-12-2010 and has 16581 miles.
It takes 20 to 30 minutes on the interstate to cool the car down on hot weather with whole car air on. Had the dealer check it twice, they said everything okay, air at right temperature. No answer why one vent blowing cold and others warmer.I asked about restricted air flow, no answer. When I say warmer I mean it's cool but not the same as right vent which seems the right temp.I checked the internet and found a few others(2)who have experienced the same concerns. THANKS, John

Asked by for the 2010 Dodge Avenger
you have a door actuator problem. there are like 4 under the dash.they control all vents and one controls fresh air, i would think the fresh air door is good cause you have cool air in the center duct. they are approx 256.00 each but i belive they are all the same part # just in diff locations.3 are easy to change and one is like a 5 hr job.
Thanks for the reply and information. I plan to talk to the service manager on my next visit.
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