2003 f150 5.4l Fx4---
I am wondering if the black vacuum line that runs from near the battery through the fire wall, across the top of the A/C, is the one that controls the direction of the air flow from floor, defrost, or panel?

Mine blowing in defrost only so I'm guessing it's a vaccum line?

 

EDIT: SEE POST BELOW THIS ONE






This is the Vacuum Connector End View—Electronic Automatic Temperature Control



1. NOT USED
2. RED-PANEL/DEFROST DOOR
3. BLUE-PANEL/FLOOR DOOR
4. BLACK-SOURCE VACUUM
5. WHITE-AIR INLET DOOR
6. YELLOW-PANEL/FLOOR DOOR

 

THIS MAY ALSO HELP

 

IT IS FINALLY FIXED!!!!!!



I changed the 4 o rings inside the EATC or head unit. $2 for parts.

I followed these instructions!!!!

Repaired my EATC module today. - MercuryMarauder.net Forums



thanks JACook

 

thanks for the update. always heard that was an expensive repair. sounds like its pretty cheap if you take the time to dig in. wonder if the manual system has o-rings between the ports ???

 

I'm going to check to see if this is what's causing my automatic climate control to not blow at all, unless it feels like it. Thanks for the info.