So I installed my D3 yesterday in a 2003 F-150. I had to rip out the whole dash including my AC control in order to mount the D3. I put everything back together and plug everything back in, even accounted for all of the screws. Now when I start my truck my AC will only blow out of the panel instead of the vents no matter what I have the air set at. Any ideas?

Maybe a vacuum hose not attached.

u must of put something back in wrong or maybe crossed something. or could be some type of vacuum line

Do cars even still use vacuum lines to operate the baffles/dampers any more?

I haven't seen that in a long time.

My 2004 Ranger still uses it.You can hear the vacuum sound when you move the levers if its quiet.

Yes, as barbarrick as it sounds, the '03 F-150 still used a vacuum line to change settings. My money is on the vacuum connector on the back of tha A/C control panel. It is not an electical conector, so you may have just missed it. You wouldn't be the first person to do it.