I own a 91 XJ and I am having problems with my temp gauge. It shoots up past 260 at initial start up and does not move. Every so often it will bounce back and forth from a reading to nothing. I replaced the sensor that is located on the thermostat housing but that did nothing. I heard there is a temp switch sensor? Anyone know where this sensor is located?

 

As you look at the engine from the front its on the right rear of the cylinder head, also check the grounds on the passenger side of the engine by the oil dipstick at least one of them grounds the instrument cluster

 

Thanks for the help. I took the connection off and on a couple times and then tested it around town and it seems to be working now. Thanks again