Ron,

If you used the specified Fenwal thermistor, temperature tracking will be more accurate than the original assuming it wasn't damaged during installation. (The thermistor leads should be sinked with clips when soldering.) A trimming resistor is not a solution in any event since the thermistor and display curves are not linear.

It is easy enough to test the accuracy of both the thermistor and the display unit, but first a couple of questions. How much of an error are you getting? Where is your sensor located -- in front of the radiator or in the left front bumper?

The reason your temperature readings are in C is because that's the version of your display unit. You could replace it with an F-display version, but it's probably cheaper to adapt to C with the rest of the world.

Give me a bit more information and I'll be glad to help you do a more thorough diagnosis of the inaccuracy.

Barrie