I have a new problem with my A/C. Air is cool and has not changed, but now everytime I start my car there is a problem with the A/C. For the first 30 seconds or so after I start the car, I hear a lid closing sound that will alternate from a left vent or right vent inside my car. As if the A/C unit is trying to suck air but can't make up its mind where to get air? This will happen everytime I start the car. Will stop everytime after about 20-30 seconds. Any advice what is the problem?