Temperature gauge not functioning

Hello,

This could be that the gauge itself is going bad. A temperature gauge works by varying the electrical voltage to it. As the voltage increases to the gauge, the needle moves more to the hot side. The Engine Coolant Temperature (ECT) sensor is a bi metal sensor that works like a resistor in the electrical circuit. As the coolant temperature increases the bi metal expands reducing the resistance of the sensor and allowing more current to flow to the gauge. I have included the vehicle manufacturer test to see if it is the sending unit or the gauge down below in the diagrams, but it requires the use of inline resistors. If you have these great, but if not, the fact that when you flicked the instrument panel the needle on the gauge returned to normal tells me I would lean that the gauge is going bad. I have also included in the diagrams down below how to remove the instrument cluster as the temperature gauge is integrated into the cluster.
If you are looking at it from a "price" point of view, replacing the sending unit would cost considerably less than the instrument cluster. Taking the chance that it is the problem might be worth it, but you could be replacing a good part and wind up replacing both the sending unit and the instrument cluster. The decision is yours, but either way please keep us informed on what you find out.

Thanks,
Alex
2CarPros