Temp Gauge

Im still trying to get all the bugs out of my 89 xj. Everytime I turn the key I can getv the needle to bounce but once I start driving it never moves from the cold position. Either my motor is running very cool or the sender is bad. Am I thinking along the right lines or could it be something else?

Check the connection, it's on the back of the head.

if you ground the temp sensor the gauge should go in one direction, disconnected it should go to the other direction. if that happens you have a bad sending unit

Check your thermostat. I didn't have one when I bought my XJ, and the gauge always showed the engine was cold. Put a thermostat in, and all is well again.