Temp gauge doenst work, sensor???

my temp gauge doesnt show anything. it sits just below 100F. i thought the sensor wasnt threaded in far enough. i tapped the hole and put in a new sensor. the gauge still shows 100F. could the gauge be broken? where can i get a replacement? thanks

What year XJ? Need to know, because the polarity for the gauges changed in 1991.

its a 93