Temperature sending unit problem.

You can determin the curve of the sender. Fill a sauce pan with room temp water. Suspend the sensor in the water. Attach an ohm meter to the body and the center post. Be sure the center post and lead dont get in the water. Now turn on the stove and take water temp and ohm readings every 10 deg till the water boils. Plot in excel and there you have it the curve of the sender.