Looking for help on what problem could be. Have a 2008 cobalt LT and every so often neither the AC or heat will work. I turn the car on and the AC light will come on but nothing blows hot or cold. Might do that for a day or two or sometime next time when I turn the car on everything will work fine. Been doing this once at least once a month for the past 3 months or so anybody have an idea what the issue could be?