Ac compressor won't kick off

Not sure on the exact model. I'm sitting in traffic trying to figure out why is going on with my ac. I have an 08 jayco jayflight with ducted ac. It just has the two knobs that let me set the temp and the other knob lets me put it on low cool, high cool, low fan, and high fan. Anyway, it blows very cold but if I try and adjust the knob so it's not blowing cold air the whole time the compressor won't kick off. It just runs until it freezes up. It takes about 3 hours for it to freeze up. Any ideas what I can do? I've never experienced a compressor that won't kick off.