My Saab thinks it's winter!

95 degrees out and my Saab (1997 900SE Talladega) has the heat turned on! I though it was the AC out of freon and stopped off at my repair guy (at 5 p.m. Friday). He took a quick look and said the freon was fine but the Auto setting wasn't turning off the heat for some reason. He manually switched it to AC for me and the AC is blowing nice cold air. This problem started a couple of weeks ago when I got ambitious and "recalibrated" the AC. It's been getting steadily less cool since then and additonal recalibrations have made it worse. Any ideas? I'll take it in for a longer look on Monday but would appreciate any suggestions on what to check in the meantime.