First of all, thanks a ton for posting the instructions on how to rebuild the EATC unit. You just saved me the small fortune for the part, so pat yourself on the back and feel good about the time it took to write it all out for us!
Second...why I needed to rebuild it, or should I say, how I found out I needed to rebuild it. After almost 11 months of trying to figure it out...it all came together in the last 3 hours and now it's 1:24 a.m.
I have owned this truck for almost 3 years, I bought it from one of my best friends, who had owned it for 2 years. It's a 2002 F150 4WD SC and my friend bought it from a dealer in Phoenix, AZ who is a very good friend of his.
The dealer went to the auction down there specifically looking for this truck for my buddy in late 2004, early 2005. He finds this one, gets a killer deal, and the rest is history.
When said friend bought it...the only problem was that the AC/Heat only came out the panel vents. The dealer friend suspected it was a simple vacuum issue. My buddy never fixed it, he's not one to dive into a project on his own and the only diagnostic he ever received was the 5-minute Ford dealer quote of $1,200 "Your blend door is broken" quote. Needless to say...AC worked great, heat worked great, just only came out the vents. (And for those in the know, that also means the blend door is fine.) So he learned to live with it.
I buy the truck and live with it for about 2 years, but last December I'm just sick of not having defrost...join the F150 Forum and begin to learn about my truck from all of you. So...rule out the blend door, today I borrowed a vacuum pump...eliminate vacuum issues. Decide it must be the actuators, because I can hear the EATC unit working. Take off the panel/defrost actuator arm and attempt to manually move that mode door...start music here...door is flat out jammed/stuck and won't move at all. Makes no sense. I reach around, thru the panel vents that are on each side of the radio and begin to feel around, only because someone on this forum at one point said you can feel that mode door and move it with your hand (Thanks to that guy, don't know who he is!). As I'm feeling around aimlessly...My hand runs into a metal rod that is 1/2 plastic on top and 1/2 metal on the bottom. I turn this rod, thinking that it must be a control rod or something, but nothing happens. After a few seconds of not making progress I decide to pull my hands out of each side and somehow, truly accidental (or it was Divine Intervention), I knock that rod loose. I must admit, my first thought was

"Oh Crap", what have I done...knowing what it would take to break the whole dash down to fix what I broke. So I pull the rod out...it was a 6" flathead screwdriver! No freaking way. At this point it's about midnight and I'm about ready to go nuts in my garage alone,

just so excited that i finally figured out the 5-year mystery. I put it partly back together and then realize when I start it that the EATC unit is bad. So....following the directions, I rebuild the sucker in about 45 minutes, fire it up, and it works like it was brand new! (thankfully I had bought the o-rings earlier in the day, hoping I would get to use them).
So here is what I have determined happened...
Dealer friend buys the truck at the auction, so we don't know the history. I think the original dealer that was selling the truck at auction determined the EATC unit was bad, truck was only 24 months old at that point, didn't want to pay to get it fixed. Knew that in Arizona if the AC blew cold and in your face, nobody at an auction would question it. I think the screwdriver was put there on purpose to 'fake it' through the auction by blocking the mode door to the panel only. All these months of trying to figure it out and I'm positive it was a trick by the original seller/dealer....crazy.