Temperature Gauge Issue

I have had more than one bad sensor new out of the box. The ones you buy at the parts store are crap. You might try an OEM one from a dealer.

If you measure the resistance of your sender with an ohm meter, it should read from about 60-80 ohms when it is cold. About 20-30 ohms hot with the car warmed. The bad ones I measured read about 2000, so an obvious difference.