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How To Make Your Own Wiring Harness For Fog Lights

94K views 81 replies 34 participants last post by  enjoilife329 
#1 ·
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.
 
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#5 ·
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. :)
 
#7 ·
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?
 
#8 ·
^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.
 
#10 ·
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.
 
#12 ·
i guess my question is where would you connect the lines from the harness to the switch? the contact that 83b where does that feed to? to the fuse box? or to one of the relays? i know in the owners manual it says for the 05-07 that relay r21 is for the low beams and the foglamps
 
#14 ·
+1 to Mr Bergner for the info on which pin on the switch it is.

Ill be using this how to this weekend, Im sick of my fogs not working. My car has the oem wiring and I added the oem fogs and they dont work for some reason. So ill just cut the pigtails off and wire em up myself.

Thanks norcal. [thumb]
 
#16 ·
You may also want to look to make sure you have the relay for the lights but it sounds like your ready for fog lights . And to answer your question , that should be all you need .
 
#28 ·
Duh I just re-read your question and the part about 83b. I didn't connect to a OEM fog light switch, but I would say you should be able to get a female slip connector to fit on that pin.

see this is where i am stuck at too, i have the OEM, Fog lights, the surrounds, the OEM switch, and the wiring harness. which the harness is not OEM. i have everything routed and it's grounded but i don't have it hooked up to the battery yet, cause i am trying to figure out where the female interface for the male pin 83b leads to, so i can connect it to the switched input on the relay. do i have to drill through the firewall or route it through a grommet that leads to the wiring for the light switch? if our cars are not prewired for fog lights, is there even a line that leads from the light switch on the female receptacle for pin 83b? if there is a line, does it route to a fuse box inside the car or in the engine bay?
You can either...

go through the fire wall, which there are holes already there to slide the one wire through.

or go behind the fender and through the plastic plug in the door jamb.
 
#31 ·
Sorry I didn't think about posting a pic on how I wired it up.

I basically trimmed the wire down and shoved it behind the harness next to the wire that goes to 83b. Usually I'd dab some hot glue there to hold it down but since I didn't have any I put a few pieces of electrical tape to hold it down, then secured it all with zip ties so it doesn't come loose. It's worked fine since then.



Probably the better way to do it is to use a splicer.
 
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