Cat 247B2 water temp sencor

My 247 b2 water temp indicator in cab started a slight glow when I start a cold engine and gets brighter as the engine warms up. The water temp at the thermostat housing is always around 180 to 190 no matter how much I load or run it. I replaced sensor and it stil does the same thing. With the key on and the engine off and cold it has a slight glow on the indicator I can unplug the sensor and it goes out. I picket up a third sensor and tested the resistance change of all the sensors in cold to boiling water and all the changed about the same amount so I feel it isn't a sensor problem. Any one know how the wiring runs from the sensor to the temp light does it feed the computer and that feeds the light. Anyone have a wiring diagram or have had this problem Thank You nickct

Cat 247B2 water temp sencor