AC Problem intermitant
 

New to the Forum here. I have a 2005 SLK AMG55.
Problem with the AC. Just had the condenser replaced to the tune of $1400 and now a new problem. I will lose AC and get nothing but warm outside air. This will happen when i turn the temperature setting up to get a little heat say 72* then later back down to 65* to get AC. The AC never comes on. To correct the issue if I stop and turn the car off wait 30 seconds then start up again I get AC. If I have the AC going and don't mess with the temperature setting it stays on and works fine.
I took it back to where I had the condenser replaced and this is what they came up with "an error code 9000. The technician monitored the system, when the vehicle runs hard, the duty cycle demand to the variable AC compressor goes to 100% while the pressure drops, the evaporation temperature starts to go up, so the engine returns to idle the compressor begins to be able to function again."
Bottom line they said I would need a new compressor that would be another $1600. To me it seems more like a control issue. Perhaps a sensor or a gate valve of some sort not opening correctly.
If anyone has had this issue on your car what did you find the cause to be? Any ideas would help.

Thanks for you input