1996 Interior Knowledge needed

I had my rear defrost switch out the other day and next to the defrost switch harness is another harness complete with light socket for illumination. whats this blank harness for and where does it go? It seemed like larger guage wire. Thanks

Factory fog lights. You'd need the harness from right underneath your airbox to the lights by the bumper. You will also need the switch, relay, and fuse for the system to work. Keep in mind if you did not have the right options in your Jeep the wiring for the relay and fuse will not be there. I picked up the switch and panel assemblies from the boneyards for both my 94 and 96 and use the switches to power an aftermarket relay and lights.

Some wire colors would be helpful. It may be the harness (end) for the fog lights if you don't already have them installed.
Post up the wire colors and I'll post a partial schematic.

If you get the switch panel from another jeep that includes the switch for the factory fog lights, it will connect to the harness that you found with the light harness.
I did this on my 90 jeep. I looked in the engine bay to see what this switch might control. I noticed where the harness for the headlights, turn signal lights etc plugs into the main harness on the drivers side of the engine bay. (It may be covered by your airbox if you still have one) The main harness part had an extra wire coming to it, but the harness that went to the externel lights did not continue this wire. It was the only extra one, and after a bit of testing with a multimeter, it was abvious that the switch that controls factory fog lamps gave +12v to this line. I believe the wire was green, but i can double check if you want me too.
So what i did is i just straight wired in fog lamps to this wire and it worked great. Looking back however, (i should have thought about it but i was being stupid) i needed to put in a relay (im sure a standard 40 amp relay will do depending on what you want to install). After running it this way for some time (maybe 6 months or so) i started to have problems with my headlights. Turns out that my dimmer switch (the one that you use to turn the headlights on (there are too you know)) was overheating. It got so hot that it melted the wiring harness to it.
I would definetely recommend putting a relay in (and of course a fuse from your battery to this relay), but other then that it should be ready to rock and roll.
Feel free to ask any questions you may have... i hope this helps!

Do not reuse the existing wiring, for the reason of melted wiring on the Headlight dimmer. That is why I went aftermarket for all my wiring relay and just used the factory switch. You can control it better yourself as far as what it powers for higher wattage lights. It's easier for the non electrically inclined or the cheap like me

The amount of current that is needed on the switch side (86 - Switch /85 - Ground) of a standard 12v relay is minimal. Using the existing wiring to control this side of the relay with the factory switch will be just fine unless the wiring is already damaged from another issue.
If it makes you feel more secure to run your own wires from the factory switch to the switching side of the relay, then by all means go for it. If you dont want to, you will be fine using the existing wiring ONLY if its used to control a relay.
Its all up to you the reader to decide which route you would like to take...

Hope that helps.