Great advice from Molson02536! I had a similar problem in which only my driver side blew warm air after about 3 minutes of drive time. The passenger side would be COLD.
I could turn my engine off and restart, and it might clear up or it might not.
Living in South GA,this was a big comfort issue. After searching on the web, I found that disconnecting the battery terminal for about 30 minutes (another website told me to try this first) corrected the issue. I have had zero issues with my AC since. I wanted to give it a try prior to posting my success story here. I hope this helps. Good luck.