If you're saying the actuator arm at the blend door is jamming, then the door is getting stuck inside the box. Try to find an access point and FLOOD the area as best you can with silicone lubricant spray. Then work the arm back and forth manually 100 times. This will sometimes lubricate a stuck seal on the blend doors that's kinked out of position.

We're entering the cooling season, and a 'broken' blend door defaults to cooling, so you've got some time to fix this problem. It's in the winter when you want heat that a malfunctioning blend door becomes a problem.

I just checked on YouTube and they showed an installation of a blend door actuator on a 2002 Taurus and they plugged the harness into it before installing it and it moved a quarter of a turn just like mine did and then when he moved the heater switch back and forth from heat to cold the actuator rotated left and right neither of my replacements ...

I just bought an 01 Taurus and the first day I drove it, the AC stopped working completely. A Google search (and this site) tells me it's most likely a broken "blend door", as this seems to be a common problem (and a TSB for it in 2002).

2005 taurus, had heat no a/c so I replaced temp control switch first, but notice nothing changed until I removed the blend door actuator and moved linkage manually everything worked fine. Replaced blend door with new.