I replaced my heater core and everything seems to be working great besides when I turn turn my setting to the floor it comes out the defrost vents. The vents and the dash vents work just fine when I turn those one though. I only really care because the floor setting is my favorite to use so I hope it's not something I have to take the dash apart to fix

 

Seems to me you likely put it together wrong.

When you put it to defrost does it come out the floor vents?