AC stuck in defrost mode

Hi and welcome to 2CarPros.com.

Based on your description, the mode door actuator is bad. Here is a link that discusses and shows in general how one is replaced:

https://www.2carpros.com/articles/air-vents-stay-in-the-defrost-position

Next, here are the directions specific to your vehicle for replacement of the part. All attached pictures correlate with these directions.

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MODE DOOR ACTUATOR - DEFROST/PANEL/FLOOR DOOR
Mode Door Actuator - Defrost/Panel/Floor Door
Removal and Installation

NOTE: The defrost/panel/floor mode door actuator can be accessed from below the driver side of the instrument panel.

NOTE: It is not required to install the new defrost/panel/floor mode door linkage parts included in the defrost/panel/floor mode door actuator service part kit if only the mode door actuator requires replacement and the linkage parts are not broken or binding.

Mode door actuator and linkage

1. Remove the 3 defrost/panel/floor mode door actuator screws.

2. Disconnect the defrost/panel/floor mode door actuator electrical connector.

3. Remove the defrost/panel/floor mode door actuator.

4. Manually operate, and inspect the defrost/panel/floor mode door linkage for incorrect placement or damage.

Mode door actuator linkage only

5. Remove the mode door linkage.

1. Depress the tab and remove the panel door lever.

2. Remove the floor/defrost door intermediate lever screw and floor/defrost door intermediate lever.

3. Pull straight outward to remove the floor/defrost door lever.

Mode door actuator and linkage

6. NOTE: When installing the mode door actuator, make sure that the panel door lever and floor/defrost intermediate lever are correctly aligned with the mode door actuator cam.

To install, reverse the removal procedure.
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I hope this helps. Let me know if you have other questions.

Take care,
Joe