I have seen several post about the heat and ac blowing through the defrost but mine will not blow any heat or ac at all. My good friends just wrecked their family vehicle and I'm going to loan them my truck but I want to fix my heat before they use it with there baby in the backseat. I've check for freon leaks this summer and found nothing. But this winter the heat isn't working. Just blowing air that's it. Any help will be appreciated.