So a bit more on this.
I confirmed the compressor is turning off and on with the dash switch as it should
The compressor is not cycling often which would indicate a low freon situation
Temp of the blowing air seems to be unchanged by turning AC on or off or moving the dial from hot/cold
At this point I'm leaning toward an issue with the hot/cold dial.
I dont have means to take it to the dealer and I doubt they would cover under warranty anyway.
Electric heat surprised me a little too looking through the manual.I would be surprised if you found that your tractor actually had electric heat for the cab.
Often cooling issues are plugged condensers or evaporators as well as plugged up cab air filters.
Or dampener controls it seems like on RK's.