i have an a4 1.8t 1998 and the a/c is now giving me problems. It decides when it wants to stay on or shut off. Sometimes i put the air on and the a/c runs fine for a while, then it just shuts the a/c off and all i have is hot air out of the vents, then sometimes it will randomly turn back on without me touching anything. I know i have freon cause when the a/c is on the air is cold. How do i resolve this problem? thanks