You should bring it in to your Ford dealer and speak to the Service Manager about this, az.dsrt. He is in the best position to look into this for you. If you need further assistance, don’t hesitate to PM me.I read thru some old threads on this, I know it's one of the AC actuators. Fortunately, it only lasts 2-3 seconds but is loud and dang annoying. I can reproduce the sound at will by simply changing the AC vent control from feet to front. From what I've read, there are 3 or more actuators. It's still getting near 90 here in Phoenix, I use the AC every day. It seems like the sound is coming out the two center vents. Is there an easy way to figure out which actuator?