If the pressure was going too high there is issues with airflow at idle or he has too much freon in the system, or there is a restriction on the high side. I use this chart when charging non factory systems. What is you idle speed at when the AC is on? A good working mechanical fan should pull enough at idle.
All of that being said, if you wire in a trinary switch like we have been talking about it would solve most of the issues. Being a AC tech I would love to see the gauges with it running