Temperature sensor, fans

Good afternoon, I am new here, I hope you can support me with this:
I have my pontiac grand am 2001, 6 cylinders, engine 3.4 l, a while ago a mechanic "fixed it" because they did not turn on the fans, what it did was disconnected the temperature sensor and the fans enter when lighting the car (which did not mention), the problem is that the problem is that the car began to hit the time The lever in reverse or direct also in the first change that the car makes another blow and the temperature is not indicated on the board (by the sensor disconnected). When I realized that the sensor was disconnected what I did was connect it and the blow of the car disappeared and I already shown the temperature on the board, but the fans do not turn on even at a high temperature, so I had to disconnect it again and the pounding of the car is still giving and again I have no temperature on the board. Could anyone support me to see a solution to this problem? I thank you very much.

Good evening, you must first check the state of the sensor by means