The blend door actuator in the 2008 ford taurus is known to break and fail, partially because of the composite makeup; the internal gears are plastic, designed to absorb the impact of failure so a more serious break doesn't occur. as such, when one or more teeth sheer, you'll often get a loud clicking noise, in addition to lack of proper function. replacement is, fortunately, quite simple and inexpensive. the replacement part can be found for around $ 25 to $ 30, and the tools required are an 8mm socket, ratchet, and extension. remove the glove box, and you'll find the blend door actuator on the left side of the area that becomes visible. remove the electrical connector and the two bolts that secure it, and install the new part the same way.