BMW Repair: ac 2001 z3 rodester 3.0, ac compressor, freon

Question
ac compressor engages and gets cold but after driving 20 min or so starts to cycle between hat and cold air aprox. every 45 sec. checked freon is at correct  pressure. condensor fan is engaged but clutch disengages and re engages i dont know if this car has a clutch relay if so where is it thans for any help you can give

Answer
Most likely freon is low. I'd start by assuring it's at a good level.  On the high end of the range is fine.  Spend $20 on a can/gauge at an auto store, and put some more in.  Cheap compared other things it could be.

From there, I'd track down the pressure switch and the relay, but I think both are far less likely than the freon.