what would cause the heat to blow out of the defroster instead of the foot area?

What is your question?

I have a 2011 dodge nitro heat and I just had my thermostat and heater core replaced to fix a no heat issue. After driving around today I noticed that when I have the heat set to blow on my feet, it blows out of the defroster and not the feet. When I have the heat sent to face level and feet, the heat blows at face level and through the defroster. It seems that the heat will not come out at the feet at all and is diverted to the defroster. All other heat settings work as they should. Any ideas as to what would cause the heat to blow out of the defroster instead of the foot area?

How long has your 2011 Dodge Nitro had this problem?

2 days