I have a CAT 3116 that the grid heater stays on long after the truck has started. Is this normal? It will go off but it takes a few minutes. It seams to draw the voltage down on the batteries substantially (9.5-10 volts) even while its running. I know that it has a control module but I am not sure exactly how that works. I would like to know what situation tells the module to turn off. Is it looking for oil pressure, water temp, intake temp? I am hoping that someone has experience with this. Thanks.