How to: install fog lights-no existing factory wiring
This how to is for adding either factory fog lights or aftermarket lights using stock fog light switches. I had no factory wiring whatsoever in my particular truck so I had to run my own. Two wires per circuit have to go through the firewall (ones the signal wire for the relay & the other is power for the on indicator) I mounted my relays close to the battery on the fender to avoid having a long run of "hot" wire to pin 30. This is how my truck is wired and it works perfectly.
*Always disconnect battery negative before performing any electrical repairs or upgrades*
**ONLY install related fuses AFTER you've double checked your wiring** safety first
-Pin 30 to battery positive (fused 20amp)
-Pin 85 to switched or constant power (fused 10amp)
-Pin 86 to BL/BK or terminal 3 on switch
-Pin 87 to lights AND T/O or terminal 6 on switch
-Terminal 6 -Tan/Orange to Pin 87 on relay
-Terminal 5 -Red/Black (or Light Blue/Black) to dash Illumination
-Terminal 4 -Black to good grounding point
-Terminal 3 -Blue/Black to Pin 86 of relay
-Pin 30 on relay goes to positive battery post, fused (20 amp) very close to the battery itself. If that fuse blows the wire between the battery and the fuse holder WILL STILL BE ENERGIZED! Keep that fuse close to minimize fire/shock danger.
-Pin 85 is power & you have a choice of which kind, switched or constant. I chose to run constant power to Pin 85 for those times I need light but can't be bothered to turn the key. Again use a 10 amp fuse on this wire close to your splice. This may be overkill as whichever circuit you choose will be fused from the factory but for under $5 it's worth adding some protection here.
-Pin 86 goes to the blue/black wire or terminal 3 on the fog light switch on the radio bezel. This is one of the two wires that penetrate the firewall, this wire is the "negative switching" you hear so much about. In this setup Pin 85 is the positive side of the relay making Pin 86 negative. All Ford did was put the switch here, making a connection to ground completing the circuit. Pretty clever really, in this setup if this wire shorts on the firewall or anywhere else the lights will simply come on, rather than sparks and blown fuses or worse.
-Pin 87 goes to the fog lights themselves. I grounded each light on the core support close to each one but you may want to run the ground back to the battery itself, I didn't. Here's where we run that second wire through the firewall, splice into Pin 87 either on the wire or the terminal itself and connect the other end to the Tan/Orange or terminal 6 on the fog light switch. This wire provides power for the on indicator, since it's tapped into the same wire powering the lights it will only light up the little indicator when the lights are on.
That's it for under the hood, now it's time to finish wiring the switch.
-The Tan/Orange & Blue/Black wires are already hooked up leaving only two to go.
- The Black wire (terminal 4) is, you guessed it, a ground! More like THE ground, remember negative switching? Here's that path to ground. I grounded mine to a bolt behind the stereo someplace, use a multimeter and make sure your grounding point is good.
-The final wire will either be Red/Black or Light Blue/Black depending on year, no matter, it's terminal 5 and performs the same function whatever color it happens to be, that function being dash illumination. I tapped into the LB/BK on the climate control since it was right there but you can use the same connection your aftermarket stereo does. This will illuminate the little picture of a light on the switch, if your bulb is still good that is.
And that's it, double check your connections, double check your wiring, hook up your battery, install a 10 amp fuse in the holder on pin 85 & a 20 amp fuse on pin 30 and go push that button! Just don't blind yourself with all that new light.