Help. 2021 579 that randomly started blowing hot air

My t600 did nothing but explode the yorks, the sanden design has been around since the 70s, does a great job, the one replacement on sanden was due to a clutch failure (and it was an integral part of compressor, non-serviceable, NOT because my chinesium cheap sanden died)

 

Put a gauge set on it first. You need to see if it has any refrigerant in it. If you've got enough static pressure (say 50 PSI or better) and the compressor doesn't engage, wiring issue is likely. If it kicks on and the low side immediately drops to zero and the clutch cycles off, you've leaked out the refrigerant.

 

Check your pigtail connections to the pressure switches under the hood. I had a T680 a while back that did that to me and that's what it was. Poor connection to the pigtail on the high pressure side I believe it was. It would blow cold, hit a bump blow hot, another bump blow cold.

 

Hot or warm?

if it is hot, then it is the controls of the hvac system, if it is warm then it could be an ac