il buono

I already solved my problem, but I'll go ahead and write down my experience for future reference for others. Tl;dr: Bad headlight switch

I ended up driving my 1999 XJ to work the other day. Upon returning home at night, I encountered no dash lights on with my headlights working. It wasn't till the following day that I also found out my tail lights also weren't working with the headlights on. The rear lights would work fine though when applying the brake and using the turn signals. I go to research various forum posts with people saying it could be a variety of things (bad headlight switch, bad ground, blown fuse, messed up stereo wires, bad bulbs, etc.).

The fuses in the interior junction box were all good. I go to inspect the PDC and see that the 20A Fuse 17 (1997-1999: Headlamp Switch, Data Link Connector, Rear Fog Lamp Relay ) was blown. I replaced it with another fuse. It blew the moment the headlight switch was used. I proceeded to order the headlight switch from Amazon, so I decided to look for other possible issues prior to delivery today. With the posts I saw online, people would say it could be another issue beside the headlight switch causing the problem. The engine bay grounds checked out and the interior wires all looked pretty good. I check out my bulbs and they're good as well. I also removed the rear hatch and side trims to see if the previous owner did anything back there. All appeared good. The wires below the dash looked good.

I came across wiring behind the stereo the previous owner did to install an aux jack. The antenna cable was also attached here. A couple of sections of the wires were pretty smashed in and I thought this could be causing the problem. I removed the adapter and relocated the antenna connection back to the factory position on the stereo. I go to put another 20A fuse in to test it out. Nope. It blew again.

Once the headlight switch arrived, I put the new one in and tested it. That solved it. So if you're having light issues and just the PDC Fuse 17 is blowing when using the switch, I would check out the headlight switch.

boxburn

Glad you found the issue and thanks for sharing the solution.

Do you have a headlight relay harness installed on your Jeep? If not it's a good idea to fit one to prevent killing another headlight switch and reduce electrical stress on the original loom.

il buono

I actually do have one on the way that is arriving this Saturday. I will also be replacing the sealed beams with E-code housings.

boxburn

Good stuff