With the ignition on and someone watching the temp gauge, briefly and i mean briefly touch the temp sensor wire to earth [engine block, intake manifold, head, etc etc]. DO NOT HOLD WIRE ON THE EARTH, JUST BRIEFLY TOUCH IT. If the gauge moves it's the sensor end that is faulty. If it does not move problem is somewhere between sensor and gauge. Could be connector at back of centre console. I'm betting on sensor or connection to sensor.
Sensor is nothing but a resistor that changes it's value as temperature changes and your temp gauge is nothing but a volt meter connected to earth via the temp sensor. As temp goes up and down resistance of sensor changes and gauge reads the different voltage. This is why sometimes if you put a lot of teflon tape on a temp sensor it will not read as you are insulating it from the manifold [earth].
Lets us know how ya go.
This should have been posted in the Tech section of the forum. Either
HERE or
HERE Just for future reference :22
Admin may consider moving it to correct section??