Sporadically and never when I bring the car into the dealer, I have a clicking noise in the A/C when the fan blows toward the face. The noise even continues for a few seconds when the car is turned off.
Did the dealer connect to the OBD port and check for trouble codes from the climate control? Your description sounds like a blend-air door problem, but I’m not sure about the 07 Mountaineer in particular. If it is a blend-air door issue, there should be some stored codes about it in the climate control system.
Alternately, there could be something (like a leaf) touching the blower. Does the clicking speed vary with the blower speed?
I’m clearly no expert but that makes perfect sense to me. I’m planning on taking it back again on Wednesday since I only have 30 miles till the warranty is history!! I’m sure at 36,001 miles they’ll figure out the problem and it’ll cost me a fortune. I would hope he checked the trouble codes but you never know… Unfortunately the sound is not consistent or predictable.
Make sure that they document that you brought the car in during the warranty period with this problem and they couldn’t solve it. This way, when you come back with the same issue in a few hundred miles, they will have to fix it under warranty anyway.