Last summer, the A/C on our 2012 Ford Escape stopped blowing cold air. We took it to our mechanic (who I trust). They checked for leaks but found none. They did an evacuation and recharge of the system. Cold air started blowing again! Then 2-3 weeks later, my wife says she saw a puff of smoke come out of the vents (not sure if it was smoke or vapor or what). The A/C stopped blowing cold air shortly after that. We took it back to the mechanic. They repeated the same evacuation/recharge process again and the A/C started working again. 2-3 weeks later, we saw the same puff and then no cold air.
That happened last Fall, so we waited until this spring to try again. Just took it back to mechanic. They checked the levels and the pressure was good before they did anything else. No leaks. They did the evacuation/recharge and the air is now blowing cold again. But, I have no reason to think it will last.
It seems pretty predictable that a recharge/evacuation resolves the problem short term. Any ideas why it’s not lasting? What, if anything, could I try to diagnose? Seems that my mechanic does not know what else to try.