01 neon question

picked up a 2001 neon today with 50k have three days, have to take it to dealer tomorrow with today being a holiday couldnt get any work done but they have to replace the front winshield and when i drive it and put on the a/c the car stutters when going from like 0-15 and also at 55mph trying to figure out what it is, i know they will fix it but i want to know what to look for. any info is appreacaited.

thanx