I was doing a radiator flush and as I was warming the engine up I realized the temperature gauge wasn't moving at all. I haven't had this RTV very long. I have never seen it over heat but just hadn't realized that the gauge apparently does not work at all. When the headlights are turned on the gauge lights up so I know it is getting power. Is there a way to know if the gauge is bad or if it is something else? What else could it be?