Bap bap bap bap

For the past day, when I turn on my 2008 Ford Taurus X, i hear a repetitive flapping sound for about 15 seconds. It seems to be coming from the center of the dashboard. It sounds like " bap bap bap bap…" My son said it sounds like a metronome. Is this bad??

That noise is probably from a defective blend door actuator.

http://www.rockauto.com/catalog/moreinfo.php?pk=3763581&cc=1440075

Common problem on Ford vehicles.

Tester

+1 for Tester.

…of which there are three ( or four, if dual zone system. ).
So to buy one you’d have do define which or take it to the shop.

Does anyone put ‘‘stuff’’ up on top of the dash on a regular basis ?
Sometimes debris will cause a blend door to stick. Replacing the actuator may mean removing the obstruction as well.