this is super helpful guys, i have this problem, it's a very easy wire to miss. In my case I removed the entire dash and didn't know where this little plug went into. So when I turn my A/C on Auto 60 degrees full blast, Hot air's coming out and it doesn't change where it blows out from (top/center) and only points downwards until you manually adjust it. Normally in auto mode the fan speed automatically adjusts as well as where the air directs to. (Feet usually when cold out and you're setting a higher temp). These settings while disconnected, not only does it not automatically adjust to these 2 commands, at 60 degrees even when A/C is on, it can be pushing hot air thru instead.

I had the same problem and found this thread. Just wanted to say thanks because mine was unplugged too and this helped me figure out what was wrong. 😎👍