I replaced the thermostat and thermostat housing in my 2012 Chevy Cruze a year ago with no problems until recently.

The car is sending a message that reads "Engine temperature high, turning off A/C" and then turns on the fan. The fan will not stop unless car is turned off or the battery is disconnected. It will run fine for a few days after that, but the message and the fan problems will always come back. I should mention, the car is never overheating, but does run cold on occasion before the message appears. It stays on the lowest temperature setting. I took it to the mechanic, and he thinks that the thermostat needs to be replaced again. I think it is the coolant sensor, which was not replaced and is still original to the car. Normally, I don’t disagree with my mechanics, but he seemed to disregard what I was saying about the message because he couldn’t get it to appear. There is no check engine light and no codes appear when it is checked. Any thoughts?