Why doesn't my new blend door switch not rotate with the ignition switch on acc.?

undercharged--overcharged--compressor failure--blown fuse/relay--mode door vent--climate control failure--

Blend door actuators could be bad, or vacuum leak in hoses.

On the motorcraft parts web site, you can blow up
a picture of the HVAC Blend Door Motors & locations,
as well as part numbers

You can get failed motor from Amazon

With knowing where the motors are located, try switching
the air flow modes manually, to see what positions do not work

Then you know what motors to replace

I also have professional scan tool software & can see the codes
for the motors in enhanced data.

The-- Vent Blend Doors-by name

Defrost-up top
Cabin -the vents as you say in the middle & on the sides
Floor
Recirculate-under the glove box
Blend Door -under the dash on your print

Possible bad blend door actuator .some gm cars can be relearned to the new climate control head

Usually this is a problem with the blend doors under the dash. You either have a vac leak, a dead motor, or a faulty door.
The control opens and closes the doors to direct air thru the heater core and evaporator core along with directing air thru the vents.
When a problem occurs, the default position is the defrost vents to make sure the windshield remains clear.
You can do an internet search for "repair durango blend door" for more info.

The most common cause is a bad blend door actuator which controls air flow throughout the cabin. When air flow only flows from 1 section (either floor, vent, or defrost) it's an indication that the blend door actuator is either stuck or broken.

To the Chevy Trailblazer....The HVAC system on your vehicle has small blend doors (About 4 by 3 in.) in size ...these doors will sometimes stick or the plastic rod hinge that it rotates on will break and it will not redirect the air flow..You could double check connection at the switch and for spot wear...sometimes it
also be the ( BLEND DOOR MOTOR/ACTUATOR ) This is what opens and closes the doors..It is very important to know the exact problem...To save money BEST thing to do is take to a dealer and tell them to scan your HVAC system and describe what I have stated...The dealer TECH 2 scanner will tell you exactly where the problem is...I worked for GM 2 yrs. I have changed blend doors before, sometimes you have to remove dash and that would cost very much so it is best to know exactly where problem lies....It could be the motor or switch which would be a little cheaper.....I hope this helps .Metalpoet

probably the blend door not opening fully. Do you hear a clicking under the dash by passenger's feet? If not, try calibrating the system:

1. Place the ignition switch to the OFF position.
   
2. With the Mode knob in the PANEL position, press and hold the AC button for 5 seconds.
3. Rotate the Mode knob fully counterclockwise.
4. Rotate the Mode knob fully clockwise.
5. Rotate the Mode knob fully counterclockwise.
6. Release the AC button.
7. Wait 40 seconds for the HVAC control module to self-calibrate.
8. Start the vehicle.

If this doesn't work, your actuator may have failed. Look under the dash to see if any of the actuators on the heater box are trying to turn when you change the temperature setting. Unfortunately, I cannot find aftermarket parts for your heater, so if the door isn't working you may need to go to the pontiac dealer. Let me know if you have questions.

There are two possible problems, a stuck blend door (this common) or the door controller has lost synchronization. The first requires disassembly of the dash and the second can be done with the following procedure'
Pull the HVAC-B (#36) fuse for 30 seconds (located in the rear fuse panel under the seat), then put it back in. Then turn the ignition switch to RUN (no need to start the engine). Don't touch ANY controls for 90 seconds. I don't think it matters what position the controls are in, but some people think it works better if you have the HVAC system turned off. After 90 seconds, the actuators have gone through their paces, the controller has new memory data on the end stops of the rotation of each actuator, and you might be good to go

check or loss of vacuum to mode control switch in dash ac control. these are not blend doors, they are air flow control, a blend door controls the air temperature not where it comes out.