Without being able to see it, of course this is only a guess, but based on your description, it sounds like the problem is with the temperature door and its actuator. Unfortunately that also means there's a computer involved. Computers on newer vehicles cause a real lot more problems than the non-existant "problems" there are used to solve. Most likely, in their diagnosis, they moved the temperature door to see how the computer would respond, or if it even would do anything. To verify this, you can check if the AC compressor is running and if the metal pipe going to the firewall is cold. If that pipe is cold, the AC is still working. It's just that the temperature door is set to "Hot" and has to be manually moved back to "Cold".
Tuesday, September 3rd, 2019 AT 3:30 PM