After 3 days and a burned up fog light switch, I have finally figured out the wiring on the factory fog light switch and fog lights.
My Explorer didn't come with fog lights, and I tried to figure out the wiring before tearing into the radio bezel as I was painting a replacement radio bezel with the factory fog light switch. I got my radio bezel and all of the switches from a junkyard for $30, and after much frustration with trying to figure out the wiring for the factory switch, I decided to use a toggle switch, but also have the factory fog light switch just for looks (until I could figure out the wiring). I decided to check all of the switches from the junkyard to see if all the lights would work, or if I would have to change the rear wiper and defroster switch out with my existing (I did have to use my originals). When I tore into my radio bezel, that is when I saw that my Explorer had a fog light wiring harness attached to the radio bezel. The fog light switch was just a case with no innards or switch, but the wiring was all there. I had already attached my fog lights (OEM from dealer, not aftermarket), but didn't notice any wiring harnesses in the bumper for them. This was great, as I now could figure out which wire did what since it was already wired. If only I would have taken my radio bezel apart sooner.
Here are the results, along with how the fog lights should be hooked up to work with the factory switch, which is different than using an aftermarket toggle switch (obviously):
Relay:
30 - 15 amp fused power (to battery)
85 - 10 amp fused power (to park lights -AND- red/black)
86 - 10 amp fused power (to light blue/black)
87 - fog lights (positive side of bulb) -AND- 10 amp fused power (to tan/orange)
Factory fog light switch:
light blue/black - fog light power (to Relay 86)
red/black - park light power (to park light power source -AND- Relay 85)
black - ground
tan/orange - fog light "On" power (to Relay 87)
It seems you can hook relay 85 and relay 86 to factory switch light blue/black and red/black in any order, as they both work exactly the same, and need each other in order to complete the circuit (relay 85 to red/black and relay 86 to light blue/black -OR- relay 85 to light blue/black and relay 86 to red/black). Factory switch red/black is the power source for the fog lights to come on. If you attach red/black to the battery, the fog lights will always be on, even with the key off, which means you will have to switch them off every time you leave the vehicle. Wiring red/black to an ignition wire will have them come on only when the key is turned on, no matter what position the fog light switch or headlight switch is in. Wiring red/black to the park lights will have them come on when the park lights are turned on, key position doesn't matter.
So here is how I finalized the wiring. Since my fog light wiring harness was already wired into the stock location, I did not have to run wires from the switch to there respective locations, I only needed to splice into the existing wiring. I will explain as if you have to run your fog light switch wires from scrap (like I will have to do with my Ranger):
Relay 30 - to battery
Relay 85 - to fog light switch red/black -AND- from fog light switch red/black to park light wire (if you don't have a park light wire close by, splice it into the headlight switch, which is also red/black)
Relay 86 - to fog light switch light blue/black
Relay 87 - to fog lights -AND- to fog light switch tan/orange
Fog Light Switch black wire - to ground
If you have existing fog light wiring, hook it up this way (same as above, but you don't have to run the fog light switch wiring):
Relay 30 - to battery
Relay 85 - splice into fog light switch red/black
Relay 86 - splice into fog light switch light blue/black
Relay 87 - to fog lights, splice wire from fog lights to fog light switch tan/orange
Remember to always fuse any power wires, even if you splice into an existing wire.