if coolant temp is 80-85C then viscous fan is good- doing it's job. Next time compressor cuts off - check the belt tension when it cuts off and when it works (engine off of course) Try twisting the belt sideways with your thumb and forefinger at a convenient place and see if there is more twist when the a/c cuts off than when it runs - if there is more twist when it cuts off - change the belt tensioner.