Usually if your headlights aren't kinda dim at night, then the alternator is charging. Do check your grounds, & you should have on from the battery, to the block. Also one from the battery to the tub. I even like to run a ground strap from the block connection fro the battery, to the alternator case.
That said, most of the problems with the center gauge pod in a YJ can be permanently solved by following this procedure.
Guages not working - JeepForum.com
If you do it, you'll see what I mean if you start it up & move the connector a little. The gauges go nuts. This fix works, & you are welcome to bookmark it for other YJ'ers on this, or any other message boards!