air vents not changing?

vents don't change from defrost to floor vents.

Yep, this happens when the mode actuator goes out. here is the location so you can change it out to fix the problem. You will need to recalibrate the parts once installed.

Alternate Method (without Scan Tool)

Note: Do not operate any HVAC controls while the HVAC control module is calibrating as this may interrupt the process. If interrupted, improper HVAC performance will result.

Ignition OFF Vehicle OFF
Remove the HVAC control module fuse for a minimum of 10s
Install the HVAC control module fuse
Start the vehicle
Wait 40s for the HVAC control module to self-calibrate

Check out the images (below). Please let us know if you need anything else to get the problem fixed.