It started about a week ago. And now it happens every time I change the heater or ac from the defog/defrost mode back to the off position on the dial to change air flow direction. Or if I go from floor back to the off position. It's also only when I go back to the off position. It makes a loud annoying popping sound, and it makes about 5 or 6 pops and then stops. Its a 2006 mustang
GT. Has anyone experienced this before, know how to fix it, or what is causing this?