I just had an issue with mine and discovered it was user error. It felt as if warm or barely cool air was coming from the vents. I found that I had the fan set to low instead of auto. The compressor would kick off when the required temp was met and then the fan would continue to run filling the trailer with humid near ambient temp air. Like a dog chasing it's tail, it didn't cool very well, I don't think the compressor could compete with that. Be sure the fan is set to auto.
'16 2500HD Dmax