Tappin off the back air conditioning of a mini-van?

Anyone have any experience or comments with Tapping off the lines of the back air conditioning of a mini-van? We just had it done on our 2001 Villager (I didn't quite understand what my husband was getting done at the time) to save money. But I have an one year old baby that rides in the back/middle. Not very happy with the results, but not sure if I want to pay the money to get it fixed? I live in Upstate New York so the most we usually get is a 95 degree day. But I have really bad pollen allergies so it if is over 67 degrees out I am running the air.