Air conditioner

Heat-A/C vent controls are vacuum controlled, so you have a cracked vacuum line, or pinched hose in dash. If you're handy take glovebox out, and then start car (have a flashlight handy) to see what's not moving correctly.

If your heater control is digital it may need to be replaced. Air coming out of the defrost and or floor vent is typical of a bad control module.

Had the same problem. Bought a rebuilt ac controller from Automotive Scientific. Works perfect. Fix the problem immediately and its a fifteen minute swap. Don’t mess with the core as its another $50 bucks if the core is unusable. If the problem is in the vacuum controlled controller under the dash or in the interior flap itself, it is a major replacement problem. Entire dash has to be removed to get at it properly. Not a cheap date.