90 XJ Won't turn over.Starter bad?

The horn is the best test of battery condition. Put the lights on, press the horn, and see what happens. If the lights go dim and you don't hear normal horn noises, it's the battery.

Earle

This just happened to me, and it was a cracked battery terminal post, causing intermittent battery connection. The best place in the world, Jim's Automotive, in Placerville, CA, found it immediately, computer checked everything, and the battery was good, and I was back on the road, with a much better battery terminal, in an hour. It's two days later, and the Jeep is as great as it ever was.