Itcmikem, Your on top of it but still might need a little help. The variable resistance of the sensor much be matched to the gauge, but we already know this. If you got a variable resistor (0 to 500 or 0 to 1000 ohms) plus an ohmmeter and a themometer you've got it licked. Put your sensor in a pan of water but suspend it so the end with the wire lead doesn't get wet. Hook your ohmmeter to the sensor wire lug and the metal (brass?) base. Put it on the stove and build a fire under it. When the water temp. reaches say 180 degrees read your ohmmeter. What the heck, take an ohm reading every 10 degrees above 100, you'll see why below. Your done with this part. Clean up the kitchen before your wife catches you. At your truck, hook one end of your variable resistor to the wire from the gauge to the sensor. Ground the other side of the resistor. Turn your switch on. Vary the resistor until your gauge reads say 180. Turn key off and remove resistor from system. Read it's value with the ohmmeter. This value is what the gauge wants to see at 180 degrees. If the reading from the hot water test doesn't agree, then you need to find a sensor that has the right resistance for a this temperature. You can carry this test even further by using the variable resistor to give you such values as when the needle comes off the "cold" peg. Also all the values of temperature, 170, 180, 200, etc. Hope this helps.
