Heater/air conditioner air conditioner/heater will turn on but will not blow air through vents, floor or defrost

No hot air or no airflow at all ?

heater control could be faulty or vaccum to control unit is not sufficient or possible air duct abstruction not letting switch from floor to defrost.

Often a sign of a blend door problem. The blend door or doors are in the heater a/c box behind the dash.

go by liquid coolant and check ur heat and ac fan it might be stuck or broken

sounds like there is a blockage in the heater ducts or the doors that open & close to direct the air are stuck or broken. maybe a bad blend door actuator

does it blow through the defrost vent only when you switch to vent/floor or does it blow through defrost and vent/floor? is it a switch that is just electric or a manual lever that you slide? the manual type will have that problem if the diverter or the linkage behind the lever(in the dash behind the panel......may be able to access underneath) becomes broken or disconnected so that the air is diverted to defrost regardless where you move it.if you can get to it, you will see what is broken or maybe a fastenerr fell off.

under the hood on the firewall there is a square boxlike cover beside the maxifuse&relay. there is a vacucum hose there that controls the vent shutoff had same problem with my 93 bonneville sse when purchased, check to see it has no cracks or has pulled out of rubber connecter .

yes those controls are vacuum controlle. Could be as simple as a bad hose or connection.

common problem, check under dash by the gas pedal if control arms are muving went selecting from ac to heat cuz this it is the control for the vents to go from ac to heat and to defrost.

Had the same problem. believe it or not i changed the gas cap and got heat all around. something about pressure.