Heater broke and then the AC

About five months ago, my front upper vents stopped blowing hot air. The vents aimed at the feet still blow hot air, but the upper ones do not. Now, a few days ago, my AC stopped working. There is still air blowing through the vents at full force, but there's no cold air. What's even stranger is that whenever I try to use the AC (even though it doesn't work), there is a weird emanating from the hood when I turn it off. Any ideas on what could be the problem would be helpful.