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norcalfocus01 04-21-2010 07:40 PM

How To Make Your Own Wiring Harness For Fog Lights
Do you want to put OEM fogs in your car, but have no stock wiring harness? This is the How To you have been looking for. This how to assumes you have some basic electrical knowledge and can run wires on your own. This will work for all years and models.

KeepItKauai (Cy) has helped me out with the diagram and some of the parts you will need.

I copied this set up out of my car. I had a old set of aftermarket fogs that I used the wiring from along with the OEM style fogs.

Parts Needed:
  • 12-15 feet of 14 gauge wire
  • Two position toggle switch (whatever style you like) or a OEM switch with the fog option
  • 12 volt automotive relay
  • Inline Fuse with a 20a Fuse
  • OEM Foglight Housings, Bulbs, Mounts, and Pigtails
  • Misc. Jointplugs, Wiring End clamps for grounding

Wiring Diagram

It uses a switched 12V source for pin 86 on the relay so if the car is off, the fogs won't stay on and drain your battery. It doesn't matter what voltage is being used for pin 86, just as long as it's switched. The wire will only energize the coil, creating a magnetic field and throwing the switch inside the relay. Just hit the fog switch and bamo, foglights.

Here is a picture of how I wired the OEM pigtails. I just took these out of a junkyard Focus then used the jointplugs to wire them to my new wires.

Next is where I mounted my relay, inline fuse and the ground I used. It so happened to be a OEM ground near by so I used it. Both fog lights and the relay ground to this spot. Also this is super close to the battery to make it easier to run from the relay to the battery.

Now you can mount your toggle switch anywhere you'd like inside your car. Mine is mounted on the dash next to the steering colum. You can also use a OEM fog light switch and run your wire to the correct pin on the back of the OEM harness. The later of the two is a cleaner look, but you will pay a little more for the switch.

So after running the wires and tucking everything out of the way you should have a nice new set of OEM fog lights in your car. I really hope this helps some people out. If you have any questions or coments please share.

captcurt_18 04-21-2010 08:31 PM

sick chris! im going to use this!

focus_kid_89 04-21-2010 09:52 PM

Very nicely done. This should help a lot of people.

tukaniSVT 04-21-2010 11:04 PM

Nice write up Chris.

Good job.


goinloco1 04-21-2010 11:06 PM

couple of suggestions.
Take a light to the auto parts store that has the help section (advance. oreily's, etc) if you would prefer new plugs. picked some up that way, but dont have the number anymore. should be able to match them with the light handy.
All wire joints exposed to the elements should be soldered, lightly coated with silicone, and then heat shrinked while the silicon is wet (will prevent shorting and also decay from water, salt, etc). solder and seal, you'll never have to worry about them. :)

norcalfocus01 04-21-2010 11:12 PM

Yes the joints should be sealed, thats why I use the heat shrink over the jointplugs.

Twytch 09-12-2010 08:08 PM

what about making a car that doesnt have foglight slots have them? did you just cut out the plastic from the lower grill? or was there more work that had to be done to install them?

disciplerocks 09-12-2010 08:53 PM

^You would need the grill made for fogs.

I added fogs and just ran them to the ignition. Would have wired to the switch if I knew which wire it was. Don't really need this now since they have been removed, but good write up. Should help a lot of people.

Mr.Bergner 09-13-2010 05:55 PM

Dude, thank you for this write up! I have the fogs installed and the OEM switch but it's not wired up yet. Gotta do that soon.

+1 rep!

Mr.Bergner 11-25-2010 08:47 PM

Okay, 20 years later and today was the first free day in awhile to wire up these badboys.

A quick addition to the how-to:

If you want to wire up a factory fog light switch, you will want to tap your fog light power into pin 83b. This will be the wire coming from pin 86 on the fog light relay. I tested each lead with a volt meter while turning the fog switch on and off. 83b was the only one that gave power when the fog light switch was pulled.

and....finally! I used cheap ebay fog-light houses. The old ones I got from a junk yard were yellowing beyond repair. These are nice and crystal clear, I also covered them in 3M clear bra material.

Camera makes it look like 14k HID's, but they're just the cheapest bulbs I could find.

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