My temperature gauge not working

Check the hoses under the hood and see if they are getting hot and you are getting heat in the car. I would check the coolant temperature sending unit. Make sure it is connected and the wiring is not damaged. If you have a multi-meter you could test it to see if it is working. The graph below gives you the values. So if the temperature outside was 32 degrees F. And the engine hadn't been run the sensor should measure around 8,000 ohms.

Now if the engine runs but the hoses do not heat up very much it is possible the thermostat is stuck open. Usually the gauge will still move in that case though, just not very much.