What was happening was that occasionally, at night, I'd start my car, turn on the headlights, and the low-beams would be out and the high-beam indicator would be on. The high-beams, when I switched to them, were functioning fine. Now I haven't had the low-beams available for many days. I've replace the bulbs, so that's not it. I looked at the fuse I thought was responsible but it looks fine.

Any thoughts on what this issue may be? (It's a 99 Pro LX 4door)

 

might be mice chewing the cables or a short due some water

 

your bulbs do they have 2 or three prongs to conect.
if you have three change the pig tail the socket goes bad very comin problem with that socket you can get the pigtail at the local parts place. its a simple cut and splice the new one in