Have read the archives and found nothing pertaining to my problem.

Problem is engine (dash) ac pumps lots of cold air at idle, but at highway speed it warms up with still some cooling.

I do know that sometimes it is a clutch problem where the high pressure switch will shut down clutch, but not re-engage until the engine slows down.

I do know at higher engine RPMs the pressure will build up and this may open the clutch via the high pressure switch.

Anyway looking for good thoughts on this subject.

Check the heater valve in the genny compartment - I had a similar issue - the valve was partly open because the cable had broken.

Check to see if the blend door that controls the outside air is open. You will have to take the top of the dash or the front off, but it is usually vacuum controlled and the vacuum motor can leak when underway. You may need a new vacuum motor, or perhaps there is a vacuum leak in a hose, the control assembly, or the check valve on the engine (for those whose coach is a gasser).