I have rebuilt the entire ac system from the firewall to the compressor , I have been told to replace the orafice tube and it’s suppose to be in the ac line from the condenser to the evaporator! I have looked for hours for the orafice tube location , took apart every fitting to put new o rings in and still have not found the orafice location ! I am wondering if it does not have one and instead has a exspansion valve inside the cab with the evaporater , no one can give me any info on this , any help out there ?