[W126 Coupe] AC Problem Part 3

[Tom Oelsner]

ok...here we go again.  Just as a reminder;
Part 1. Get the AC running.  Replaced the compressor O rings, replaced the
receiver-drier, new AC belt, no leaks at all and rock solid.  Charged the
system.  cold air!
Part 2. Belt squeal.  Belt keeps loosening (stretching?). retightened twice
and loose again even though the idler pulley is tight.  Any ideas?
Jonathan, it is a Continental belt.
Part 3.  THE NEW ONE.  Had very cold air until about a week ago.  Now it is
only really cold if I am going above 75mph or if the outside temp is around
70F.  At lower speeds the air is somewhat cool at best.  Engine temp is
definitely in range  with AC on, 85C to 95C(?) and there is still plenty of
refrigerant in the system.  Any ideas?  Thanks for your thoughts.

Tom Oelsner