In the last month or so, nearly every time I turn on my car, there is a rhythmic clicking noise from the rear passenger side of my 2004 Chevy Trailblazer. At first, the noise was pretty constant. Now it seems to come on shortly after I turn on the car and last about 5 minutes. It almost seems like it tends to turn off after I take a right turn, but that could be a coincidence. My husband says the clicking is extra-loud near the vent just behind the 3rd row of seats, and suspects some kind of HVAC sensor problem. Here’s a link to a recording of the noise: http://www.flickr.com/photos/allison_dc/6866906382/ Any ideas?