Sometimes while driving my ac begins to blow ambient air. Sometime I can increase rpms and it will begin to cool. Sometimes it blows cold while slow driving, other times it does not. Sometime at higher speeds it blows cold, other times it does not. Shop evacuated the system and installed new orifice, recharged it and still have same issues. When it is working its cold as heck. Seems something is telling the compressor not to run. I'm at a loss.

 

The info you are supplying is incomplete.
Need to know year, model and if any other work was done to your vehicle.
If , for instance, someone dislodged a sensing tube that tells the compressor when to turn on or off that is unknown That is just one example. Provide as much info as you can, thanks.

 

Thank you. 2006 F250, 6.0 diesel. Replaced fan clutch and orifice, other than that no work has been done. I don't want to believe its a compressor issue as when it does work it gets as cold as ever. Just seems to be no rime or reason when it decides to stop blowing cold air. If it was a gas engine I could understand why increasing rpm's could help in cooling (vacuum). It even blows cold at idle and that is when the a/c is least efficient, low compressor speed and minimum air movement across the condenser. Hope this helps. Thank you.