I have a 2002 screw lariat. my problem is this, the auto climate controol panel when put in A/C auto temp mode, with acceleration it switches from the air vent to the defroster vents. i had one mechanic mention its the A/C computer mumbo jumbo.... i dont have any clue. has any one experenced this or know what it might be???:

 

I would suspect a vacuum leak. To test the controller, dig through a few other threads in here, the self-test procedure is posted.

 

Search keywords "+defrost +vacuum"

Topic comes up every couple of weeks. Needs to be an FAQ.

Don't bother trying to find or run the EATC test, it won't be of any use in this matter.

Steve