AC won't turn on

I own a 1999 olds intrique with 57000 miles on it. I just had my air conditioner( compressor, condenser ect ) fixed last year. It worked last year fine. Now when I hit the air compressor auto button on the dash the green light flashes and then goes out and it doesn't kick on the AC. Also the outside temperature is displaying 20 degree Fahrenheit when it is 80 degrees outside. I am thinking that the AC won't kick on because it is thinking that it is to cold outside because of the incorrect outdoor temperature display. Any ideas on how to correct the situation.