Everything works on a/c but only have def. no dash vents

those are A/C distrubution box under dash actuator dampers
all cars made are different locations
there are 3 or 4 of them. temp/mode/ recirc,
its not stuck in heat mode so the blend damper is ok/(closed)
mode is busted.
feed and Def ok
but front vents dead you say? if yes does heat work to front vent too?
blend in cable drive so is not that.
OH OH< it has VACUUM controls, a pain that. locking hand vacuum pump to test all that.
to work on this take a real service manual and HVAC chapter
covers HVAC vacuum controls at the dash, test by test.

the valve on the dash control is vacuum
in need vacuum to it to work
and the vacuum out of mode set to dash vent? goes to dash vent
vacuum servo the colored hose tell that.
if the control sends vacuum to a colored hose in Vent mode
then follow that hose the vent servo .


the secret is here, find out which one is for front vent servo
and follow the correct color to the correct vacuum actuator servo
then test it.
I do not have the color hose secret.
the actual damper ,we do a leak down test on all of them
they crack the diaphragm inside and go dead.

this may be same
https://www.justanswer.com/dodge/8qjf8-dakota-problem-cant-figue-95.html

You forgot to say what vehicle you have, it makes a difference, but it sounds like a mode door problem, check for a vacuum hose broken or knocked off under the hood, listen at the dash with the blower off for movement as you move the control from def to vent to floor to def. if you don't hear movement the mode door actuator may also be bad. I hope this helps. Take care.

Maybe a problem with actuator doors under the dash or dash controls. If vacuum controlled and vacuum is lost, it should default to defrost.

You may have to check if squirrel cage came loose from motor shaft?

If the van is older than 2001 it could be a vac leak going to the dash controls or the blend door actuator.

if its just the vents that dont work, check the actuator or cable (that controls the vent, def, or floor) on the hvac box under the dash.
If no air flow at any time, you probly have a plugged up box. remove the blower motor and clean out what you can, also remove the grate under the wiper arms and clean them out.

There is a stepper motor in behind the dash that controls where the air is distributed to.They are hard to get to,expensive to replace and almost impossible to repair so you might want to just live with it.

Your Blend / mode door inside the heater ac blower box. is stuck or not moving completly into place.

Hi,
It sound like it’s one of two things ;
1. It could be the function control knob on the dash is no good or that the vent/ def. door control motor is no good possibly seized up.
2. Secondly the thong that I would suspect is that the door itself is jammed in the on spot.
Please let us know for future assistance.
Thanks
Fame !

it sound like its one of two things 1 it could be the function control knob on the dash is no good or that the vent/ def. door control motor is no good possibly seized up. the second thong that I would suspect is that the door itself is jammed in the on spot

The blend door in the heater box itself is what directs the air to where it needs to go as per selector switch. The heater box is located under the dash.