And, here's a poorly-written how-to I did in an e-mail to another fellow. I should have a made a project out of it, but when I was doing the install, I was more concerned with finishing + getting it right that I didn't feel like taking photos. Stupid in hindsight. I highly suggest checking out the projects from the other site that I linked to. These provide a clear diagram of the OEM switch's prongs and what they do (I call them prongs 3, 4, 5 and 6 because 1 and 2 are not there--the switch only uses 3-6). Also, steps [1] and [2] refer to the photo I linked to below. It's too huge to post here--it distorts the message field and makes reading the how to a pain in the ass.
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As for the fog light and switch, much of this is based off of memory and two projects on MyST. The specific process will depend on the brand of lights you get, as the harness is most important. I sat here trying to recall the specific process, but I cannot recall enough specifics to provide a clear how-to. But, I'll try to help as much as possible.
First, check out these projects: (a)
http://www.mysporttrac.com/mysportt...ToFordOEMSwitch/PIAAswitchtoFordOEMswitch.htm and (b)
http://www.mysporttrac.com/mysporttrac/projects/SecondFogSwitch/SecondFogSwitch.htm. (b) is essential for wiring information. Both were extremely helpful in my install.
Second, I've attached a photo with explanatory notes from when I was planning the install. I know I made it terribly unhelpful--two steps and sentence fragments. But, from the best of my recollection, here's how it goes.
Before you do anything, disconnect your battery and then turn on your headlights. The system needs to be dead because you're going to be tapping wires.
[1] Cut the bottom right ground wire that runs into the heatshrink harness. Make sure you leave enough wire on both ends of the cut. Connect the ground wire coming out of the relay coil to the fog light switch pin three (blue/black on the switch harness). Connect the other half of the cut ground wire to fog light switch pin 4 (black on the switch harness). What you've done here is establish the fog light switch as the cut off for the grounding of the relay power in (top right of relay in PIAA diagram, noted as "positive on/off from switch). When the switch is off, the circuit is not complete because the relay on is not grounded. When the switch is on, the circuit is complete and the power flow allows the relay to complete, thus allowing power to flow on the left side of the relay.
[2] Coming off the right side of the relay connection is a top white and bottom black wire. These run to the PIAA switch. Cut both. Tap the white wire to a power source. This is your power for the relay (noted above--this is what the fog light switch will cut off through the ground). I tapped mine to the parking light on wire. You can also tap it to an always-on source. I chose the parking lights so that I could only run the PIAAs when my parking lights were on (like the OEM fogs). When the car shuts the lights off (20 seconds or whatever after shutdown), it kills any power to the PIAAs, thus preventing an absend-minded draining of the battery. To connect the white to the parking light on wire, I ran a wire from the front left signal to the white wire (there is enough wiring in the PIAA harness, depending on where you cut it, to merely stretch it out and connect it). I do not recall which wire in the signal is parking light on (there are three--ground, parking lamp on, and turn signal on). I used a pin and a wire tester to check. DO NOT connect to the signal power on! If you do, you'll have blinking fogs!
Continuing [2], merely cap the black wire. The black was ground for the PIAA switch. The switch had a ground because it illuminated a small LED when the lights were turned on. No big deal.
So, when this is complete, you should have the relay powered (white to parking lamp) and grounded (relay out to fog switch, fog switch to cut wire from relay to remainder of PIAA harness).
Before I go on--details. To run the wires into the cab, I used a small drill bit to punch three small holes through a large rubber grommey underneath the steering column and behind the pedals. I pulled the grommed into the cab, drilled, stuck a hangar through and fed the wires through. Don't let the simplicity of the wording fool you. You will need a good flash light to see where the wires come into the engine bay, enough wire to route it against the firewall and inside fender (avoiding hot items), and to the relay. It's likely the hardest part of the install, if only because the process is not friendly to adult hands. When you drill, use a bit smaller than the wires so you get a near-air tight seal when you pull the wire though. Why three holes?
Pin 6 on the fog light switch (orange/pink on the harness) is the on-indicator for the fog light switch (the little green LED that glows when the lights are on). You will need to connect to the harness and run a wire to the PIAA harness where I labeled it "junction of ground from lights, PIAA . . . etc." Using a knife, slice the shrink wrap enough so you have enough wire to, using a wiretap, tap either fog lights white (power) line to the line you ran from pin 6 (orange/pink). By doing this, when you press on the fog light switch, the relay circuit completes, and power flows to the lights. By tapping one white wire for power to the switch indicator, your LED will illuminate. Don't worry about grounding for this illumination--it's taken care of by switch pin 4 (black on the fog light switch harness to ground on the PIAA harness).
One of the easier parts now. Illuminating the fog light switch so that it lights with interior lights on and dims. Pin 5 on the fog light switch (pink/black) is illumination. Using a connection wire (if you use my harness, you'll notice I cut the wires a bit short--you'll want about a six to twelve inch wire attached and taped), connect pink/black to the illumination for your 4WD switch (also should be pink/black). Test it by turning on your interior lights.
At this point, all wiring should be complete. All four wires from the fog light switch are connected to the proper source. The power in to the relay is connected to the parking light on source (or whatever you connect to).
The last connections to be made are the true power in positive and ground negative (noted in PIAA diagram). To the rear of the battery is an auxiliary power off point. You need to flip forward a small plastic cover/door, and you'll see two metal terminals with bolts. Connect the white battery positive to either terminal and bolt it right. Route the wire so the plastic cover closes. On the right of the engine bay towards the front (aka the left front inner fender), you should see a screw with a wire attached via an O ring connector. This is a ground point. Connect the ground (which I erroneously labeled battery ground in the diagram) to this point.
The wiring is complete. Now, you need to mount the relay coil itself (in the diagram, I did not label it, but it is in the top middle with PIAA on it). Also in the front left of the engine bay, you'll find a hole in the inner fender wall. Using a metal screw, screw the coil piece into the metal hole. It will be snug when tightened. Then, connect the other end (wires out, where you did the splicing) to the coil. Everything should be complete now. Using electrical tape, tape wires that you ran from the cab to the coil (if you did not already). Make sure everything is routed away from moving parts, heat, etc. The best route is against the firewall and then along the left (driver's side) fender.
Shoot. Where am I now! Okay. Take the PIAA wiring that runs to the lights itself and run it down the left fender, and through the opening where the engine bay opens to the left front wheel well. Now you have your connections for the lights on the outside. I removed the plastic piece below the bumper and ran the wire to the left and right side, then reinstalled the plastic piece (from what I recall, there are three screws in the front of it, and 2 on each side). The rest there is details--if you have the safari bar on, bolt the lights on and connect them.
Again, secure all wiring that runs to the outside. I taped all connections (lights to harness) and wires where I could.
Test them out. If all went as planned, you will connect the battery, turn on the parking lights, and then push the fog light switch. The lights should fire, the LED on the switch too, and you should have interior illumination of the switch.
One thing--when installing the switch in the bezel, you'll need to unbolt the bezel and pull straight out. Disconnect wiring to the other switches and replace them in your new bezel. Teh fog switch screws into the bezel using screws and a mounting plate that *should* come with the bezel (on the rear). If not, use the plate and screws from your stock bezel (should be the same). The wires from the switch to the grommet run through the dash, along underneath the dash (tape-piggy back them to the wires you will see running laterally underneath the dash) and to the grommet.
I hope I did not leave anything out--I don't believe I did. But, be aware of my instructions as well as the projects on MyST. And, as you go, test your work as you go--e.g., the internal illumination.
If you have any questions, feel free to contact me. I will snap a few shots of what I can tonight and send them along. They should help with some of my explanations.
Also, I apologize for the rambling as I went on. I should have done a project for this (the two existing projects were dang helpful, but did not provide enough photos of the bezel work, grommet wiring, etc.--simply concepts, but always helpful to see).
Best of luck.
Link to huge photo of where to cut a PIAA 510 harness:
OEM fog light switch harness (get from salvage yard):
], as I wanted to be able to turn on the PIAAs with parking lights, low beams or high beams. I then ran the ground wire through the firewall to the OEM switch in, and from the OEM switch out tapped into the ground wire on the PIAA harness (back through the firewall). In addition, I ran a wire from the PIAA hot to the lights to the OEM switch LED pin so that when the lights are on, it'll also have the switch LED on.
