So my AC hasnt been working for a couple months now. its been nice and i usually dont use it anyway (more of a window guy), but lately i need it. So i checked my anti freeze and it was out basically so i filled it 2 weeks ago, checked it today and its fine. But heres something that might narrow down whats causing this. Lately when i have no AC or heat on the car sounds like its trying real hard to run. Sounds like the little engine that could. It makes a deep growling noise. But if i turn the heat on it goes away (or quiets down). What could cause all this. Compressor? Thanks for your help, please try to cool me down :)