A/C intermittent at Operating Temp.
 

I have a 2002 Rodeo Sport, i noticed when i have been driving for about 10 minutes or so, the AC will start blowing warm muggy air, usually when at a stop light and while driving sometimes as well. This is my mothers car and im going by what she has told me. My first guess was the compressor was bad but i decided to post this before installing since its a 350 dollar part. She recently got her AC recharged as well because she thought thats all it was but it continued. Any suggestions?