replaced the a/c blend door actuator and now it's stuck on heat on 2005 Ford Explorer

i just replaced the blend door because it was stuck on a/c. the a/c worked great, but now it's getting colder out i went and bought the blend door and replaced it. after i hook it up and connected everything, i turned on my explorer to check to see if everything is work the way it should. I put it on heat it works great now it down switch to a/c. what would cause this? I did reset the computer and that didn't fix the problem. Please Help

Asked by for the 2005 Ford Explorer
re setting the computer does nothing.

verify that the motor is installed correctly. it is the most common failure.