The air blend door is inoperable. All air comes through the defrost vents regardless of the mode setting.
Air will constantly flow through the defrost vents regardless of the mode setting chosen on your Dodge Nitro. There are four different blend doors on your Nitro and they all direct air in different ways. Three of them are a little labor intensive to replace however the one your Dodge seems to be having issues with can be easily accessed. Without seeing the vehicle in person, it is best to enlist the assistance of a certified mechanic, such as one from YourMechanic, to go over your vehicle with you so the can make the proper diagnosis and repair to your blend door.
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