I have a 1992 240 with 190,000 miles and a converted R-134 AC system. A few months ago, the AC started acting up, and now it doesn't work at all. When the car was in forward motion, I could hear the compressor kicking on and off rapidly, making a clicking noise that at first made me think my speedometer cable needed lubrication. As the problem progressed, the compressor would stop kicking on altogether and started functioning only when it seemed to feel like it. For the past month, I have only seen it work once. When the system is running and the car isn't in motion, it sounds fine and there is plenty of R-134 according to my pressure gauge. When you start driving, it starts in with that clickclickclickclick crap again. All the wires I can see in the engine bay seem to be okay. My dad says he thinks it's the AC pressure switch. I can't tell by looking at it. Any ideas? Thanks!