I have a 1997 chevy silverado 4wd 5.7l v8 ext cab. I am having trouble with my ac and heat. I have my heat or ac on high and no air comes out. When I am driving down the road it will come back on but maybe for a couple seconds. It worked on low for a while to but then stoped. Now it will only work on high every once in a while. I tried replacing the resistor but that didn't work. Does this make sense? Does anyone have any other ideas?