If the low beams are not working in a 1999 Jeep Wrangler which fuse do you change?

There isn't a single "low beam fuse" in a 1999 Jeep Wrangler. The low beam headlights are usually controlled by more than one fuse, and sometimes a relay. Furthermore, the specific fuse numbers vary slightly depending on the trim level and options of your Jeep.

To find the correct fuse(s), you must consult your Jeep's owner's manual. The manual will have a fuse box diagram showing which fuse(s) control the headlights. It's the best and safest way to identify the correct fuse to check and replace.

If the owner's manual is unavailable, you can usually find a diagram online by searching "[Year] [Make] [Model] fuse box diagram" on Google Images or a similar search engine. However, always double-check the diagram matches your specific vehicle's trim level.