That's exactly what Ford thinks... just dust and stuff has gotten into the system and is clogging it up repeatedly. They think that by taking it all apart and cleaning it all out, especially the evaporator, will do the trick. But I had some serious sticker shock! I'm a very handy guy and can do it myself... just need a repair manual with procedures on taking the dashboard apart and what not.
Anyway... I did a lot more research on this. I found out that you should clean your interior air filter every 15,000 miles (didn't even know there was one... lol). You would think Ford would suggest this when I'm in there for oil changes and check-ups. I found this 'how-to' (with pictures) on how to do it:
http://www.paulstravelpictures.com/Ford-Edge-HVAC-Cabin-Air-Filter-Cleaning-Guide/index.html
When I got to the air filter, I was SHOCKED with how much crud was on it. Dust... dead bugs... leaves. It was incredible. You couldn't even see through the darn thing. I don't doubt some of that was getting into my system. So I cleaned that all off.
Did more research... found out you can attach a shop-vac to the drain line to unclog them. Tried that, and viola, I had a river coming out of that drain tube.
But, I'm a little upset with Ford. They obviously did the same thing a couple of times before this to unclog it and they broke the clip that hold the drain hose into the car's floor (located to the right of the gas pedal under the carpet). Needless to say, when it was working after they cleared the lines a couple of times, some of that water was leaking back into my car and soaked the thick insulation under the carpeting. No too happy about that.
Anyway... did even more research and talked to a mechanic friend of mine. He said that mold can build up in the evaporator and cause the same issue. He said, with the air conditioning on, to spray some bleach right into the fan (just a few bursts). That would be enough to get inside the evaporator and kill any mold. So I did that. I get a nice refreshing whiff of bleach now when I turn on my A/C... lol (that'll go away after a day or two).
He also said to take a commercial grade air compressor and attach that to the drain tube securely after the car has been sitting all night on a dry night (to assure all the inner workings are dried out). Then, roll the windows down and turn the air compressor on and let it run for a minute or two. It'll force out any dust and leaves throughout the entire HVAC system in the car. It'll be a bit messy and require some cleanup obviously, but it does the trick.
He suggested to do that every 20k miles or so (on top of cleaning the air-filter regularly) and it should prevent the problem. Also said it should solve the issue as well (repeated clogging). If it doesn't, then it's time to resort to pulling the dash apart and ultimately the evaporator to clean it by hand.
I'm gonna cross my fingers and hope these solutions work. If anybody else would like to chime in, feel free! Especially anyone with information on how to dis-assemble and re-assemble the dash to get to the evaporator (in case I have to resort to that).