the connector that bolts to t-stat outlet location is pretty prone to exposure and the copper oxidizes. end result... temp guage goes crazy. if you turn your wipers on and it changes the reading or turn the heat on in the car and switch it from 1-4 and watch the gauge and moves from you doing any of that i would buy a new ground cable from RockAuto.com. either that or if you have high strand 4 guage and a little experience you can attempt to make one.