It's interesting I guess that I do temperature control systems as a living. I decided to call up one of my sensor suppliers who I purchase NTC thermistors from all the time. I posed the question: "If you have a thermistor of a given range and you apply 6 VDC to it or 12 VDC to it, what will be the measured result?" He said, UM........
However, he stated that thermistors are rated in applied voltages and are self-heating at those voltages. The ones we use in our business are 0-5 VDC as applied to the temperature measuring circuit. This would translate closely to 0-6 VDC in the truck. He also stated that if you apply 12 VDC to the same circuit, the thermistor would then tend to overheat, causing its internal resistance to fall which would translate to a higher reading on the gauge itself. I do believe that this may be what is happening in my case. I am applying 12 VDC to the original sender circuit and the gauge is reading 135 degrees when the actual temperature is 180 degrees or so. Therefore, I think that a 12 to 6 VDC voltage reducer is needed in the circuit to the gauge. This might possibly change the final reading and make it more correct. I'll experiment with this next.
