http://members.dandy.net/~k0xp...y.htm"A series of measurements of coolant sensor resistance versus temperature were taken by immersing the bulb end of the sensor in a pan of heated water. The water temperature was measured using a wide-range digital thermometer kindly furnished by Dave Worthington with a specified accuracy of +/- 2 degrees Fahrenheit. Resistance was measured with a Fluke digital Volt-Ohmmeter with a specified accuracy of better than 1%. Sensors (including the thermometer) were placed into a hole punched into a sheet of kitchen aluminum foil which partially-covered the pan of heated water. The water was heated over a gas stove and stirred within the pan with a turkey baster syringe until both the temperature and indicated sensor resistance had stabilized to better than +/- 0.2 degrees F and 2 ohms for at least 10 seconds. Measurements were then recorded.

Note that beginning at about 160 degrees Fahrenheit, sensor resistance changes with temperature became very linear and predictable; the chart below the table illustrates this more clearly. Also of great interest is how closely each of four sensors removed from entirely different engines and even GM division vehicles, matched each other at most temperatures above about 160 degrees Fahrenheit. All of these sensors were removed from engines with over 100,000 miles and at least 15 years service.