I have a 2010 Ford escape and just noticed this morning that when I turn the key, there is a loud thumping noise coming from the dash. It only thumps about 4 times then is done. It doesn't do it when my car is running or anything, only when I first turn the key, before even turning on the engine. It isn't battery related, it's more of a "thumping" than a "clicking" sound. I raised my hood to make sure it's not coming from the engine or anything and it is definitely coming from the dash part, by where the air comes out and hits the windshield. It makes the sound whether I have my air on or not....air still works fine. What could this possibly be? It wasnt making this sound last night.
Consider to check your dash settings for air flow and cooling or heating. Attempt to narrow down the focus by changing one setting at a time. I suspect you may be hearing duct work flaps or closures being activated without sufficient vacuum from the system.
If your dash control settings are commanding a flap movement and the vacuum necessary to create the movement is insufficient to do so, the flap may open partially and fall back.