Yukon Climate control HELP

I have a '03 Yukon with climate control and the other day while running the A/C (Arizona), both driver and psgr side were good and cold. Then without touching anything, the psgr side started blowing EXTREMELY HOT, not just warmer, but HOT air. It wouldn't get cold no matter what I tried. The driver side, meanwhile was still cold. Shut vehicle off for a few minutes and when restarted, everything was OK and worked again. This has happened only a few times, but it seems to be only once every couple of weeks. Any ideas for me to try to test or replace myself. Due to costs, the dealer is my last option. Thx - PS- I've tried searching for similar threads, but haven't found anything relative yet.