Dash vents will not blow air. Defroster and floor vents blow fine.

check vent flaps inside the blower unit....

Sounds like the gear to adjust the flaps is broken or misaligned. May have to disassemble dash to discover problem.

It is a vent door actuator motor on top of the blower box,the dash has to be removed and set in the seats to replace the actuator motor.Cost for the part is about 50.00 dollars

its a problem with the switching mechanism. you have to look up under the dash to see if you can see where the switching mechanism is. if you can not see it from there youll have to remove complete center dash

it sounds like the switch lever for the vents, floor and defrost is not switching the vent door that goes to the defroster hose. You need to pull the switch consol out loose from the dash and follow the cable for the defrost that goes to the hose for the defrost. You might also have a broke switch that won't pull the cable enough to open the air for the defrost hose.

It sounds like the door on the defroster isn't opening. Check for a vacuum leak and also check the temp.control valve this should have several vacuum hoses coming from it. This valve controls all the doors, Bi-level, Defroster, and Floor positions.

Check for vacuum hose leak.

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.

check for vac leaks under hood and dashbord