Had this happen on my 2014 about two or so years back and it was the hvac blend door. The part is cheap, but install was horrendous. Theoretically it's possible to do it from behind the passenger upper glove box, but that was a no go for me so I had to remove almost the entire dash including the instrument panels and everything. It still beat the huge cost of repair that the dealership wanted to charge me though.
Basically it's just a switch that the auto hvac system uses to change from heat to a/c.