Ac Unit blows Hot air

We have had our Tahoe in the shop 4 times now. They have recharged the system, replaced and modified the computer to regulate the cold air. It blows cold air for a week or so, then at idle blow hot air.


Not a kid friendly Tahoe. Not sure what to do as they have done almost everything to try and fix the AC on this 2003 Tahoe.

Help?

did they check the compressor clutch? open the hood and look at the compressor when you turn the a/c on, does it engage? could also be a faulty pressure safety switch