I believe the clutch can also dis-engage if the magnet in the AC compressor clutch becomes worn/rusted f'd up. Some people replace the clutch bearing, others the whole compressor. You can also check the high pressure sensor on the condenser. It will be on the silver thing, to the upper left of the engine, with a wire loom connected to it. Can't miss it. It has a schrader valve so you wont loose any refrigerant. I believe I replaced mine for around $17 from car-quest. Either way, you can throw parts at it (like I did) or just have someone diagnose it at a shop. First would be to check refrigerant level, since this can cause the compressor to stop. Good luck!