Update
I took the car to work and left her my truck. When I started her car, the A/C was blowing cold but making a hissing noise every now and then. Does this help identify the problem?

I'm having an issue with the A/C in my wife's car. She was on her way home and the car stopped blowing cold air. When she came home I went to take a look at it and honestly I dont know what to look for. I started the car and listened for the compressor to kick on and it did, but still got hot air. I...