I can tell you that that thermostat has a history of not making contact. I would bet big money that is the problem. if you go back on that job and that compressor is not running simply slap the cold control and you will hear the compressor and fan come on. There's another one similar to it with a rotary dial it's even worse. I make sure I've got both of them Cold controls in my truck at all times. It will do it again. I'm curious as to how you are positive the cold control is good.