no air or heat from vent when i push vent, but when i push a/c or defrost I get air

how do I get under the dash, how do u check the aoto matic temp control

It's just a matter of getting a flashlight and crawling down under both sides of the dash and visually inspecting. The electronic automatic temperature control has a self-test feature that is internal to the unit, but I would recommend a qualified technician get involved with this one.