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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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#36 ·
Hi. I have fitted the OEM switch with the fog light position and the spots are already fitted in the bumper. A replacement bumper was fitted after the old one hit a bollard. However, there is no harness to connect the fogs.
The connector on the light switch does have the Green/Yellow wire that supplies power for the fog lights.

According to the Haynes manual, this wire splits into two green/white wires, one running to each fog light. This implies that I can splice into this wire on the back of the switch and feed directly to the spot lights without adding any other relay or fuse. Is that correct?
Secondly, Where does that wire from the light switch go? If it runs to somewhere in the engine bay, It would be much easier for me to join into it there than to try and run a wire from inside the car. If I do have to route it from the car I cannot see any obvious grommets or holes I can run it through in the drivers footwell.
Any help or advise would be greatly appreciated.
 
#37 ·
OR you can do what I did.
I had a member on here make me a 2wire harness.

I used the middle wire of the grille lights as my soruce.
I cut the wire and ran light off of that. I cut the ground wire in two and spliced the turn signal and fog lights back it.

its been working for alomost a year now.. and NO it doesnt blink
 
#40 ·
Im honestly not sure what it is.

I have it wired up according to the wiring diagram in the OP.

The wire sticking in the harness didn't fit because of the plastic insulation on the end of female pin connector I have on there.

But what I did was drill that part of the harness to make the hole bigger so the female plug would fit inside it and the harness could plug all the way into the switch. Once it was plugged all the way in I double checked to make sure the female connector was snug on pin 83b and plugged it all the way in. But no fogs, headlights and everything worked as normal though.
 
#42 ·
I have an 07 zx3, and i bought a oem switch from a local junkyard for $7. IT was from an 02, and i thought it would just pop in..i was wrong. I noticed that the housing was all the same. so i took off the front cover from my stock one, and then the front cover from the one i bought. I used the housing from the older focus, and just had to swap some piece, and it all fits and works. I just have to wire up the fogs/relay...no biggie
 
#43 ·
fog light wiring

hello from england, i have a 2004 1.6 lx this is the model that does not come with front fogs as standard. ive got the fogs and switch from a breakers yard, but cannot find the wiring loom, having searched the internet ive discovered focus fanatics, and even better this post on how to wire them up if the weathers good tomorrow i am going to atempt this project, im going to use the factory switch and tap into 83b wish me luck, tony
 
#44 ·
im from england and have a 1.6 focus, that has no front fog lights as standard, ive got a set and a switch from the breakers yard, ive looked under the car for the wiring loom but cannot locate it, after searching the internet ive found focus fanatics, and com across this post that answers all my problems, if the english weather is good tomorrow i am going to tackle this project, im going to use the standard ford switch, and tap into no 83b and hope i get a result, the original switch that anly pulls out once for the rear fog light has the same amount of wires coming out the back, thats why i think the wiring loom is there already, wish me luck, best regards tony
 
#45 ·
hi ive just joined the forum i have a 1.6 lx and am trying to fit front fogs, ive got a new ford switch and there are the same amount of wires coming out of borh switches, my question is did you have to go through the firewall or did you pick it up inside the engine bay, ive looked allover the car for the extra loom dut had no luck, all the best tony
 
#46 · (Edited)
Hi Tony. I have a 1999 Focus CL and had the same problem as yourself. The extra wire for front fogs was in the plug that connected to the light switch. After hunting for ages, I concluded that the loom for the fogs wasn't there and had to make one. I have no idea where that wire from the light switch goes. I couldn't follow it without taking the dash apart and I wasn't going to do that so I ran a wire through the firewall and used a skotchblock to join it to the foglight wire on the switch and it all works fine. I'm afraid you'll probably have to do the same. Hope this helps!
 
#48 · (Edited)
Yes, I did just tap into 83b using a skotchblock. The Haynes wiring diagram shows this wire just running directly to the fog lights so I just ran the wire directly to the fogs and all is fine. Again, looking at the diagrams, there is no additional fuse for fogs, although I did put a 15amp fuse inline. Not because it is needed but to protect the light switch from damage should my home made harness somehow short out. That way my fuse cops it before the switch does. I picked up my grounds from within the engine bay. The nearside one is grounded to the -ve terminal of the battery and the offside one is grounded with the nearside lights to an earth point near the offside front of the engine bay.
Here is how I got the wire out to the engine bay. Maybe not the best way but I didn't want to drill holes and I couldn't find anyplace or grommet I could just shove it through.
http://www.youtube.com/watch?v=6RXDHrjusHw
 
#51 ·
fog lights

Thank you for your help on this subject I've just gone out to the car and checked that the lights work it looks good my new switch has the dimmer for the dash and when I pull the switch out the symbyl for the front fogs lights up I will tackle this tommorow from my understanding there is already power going to the switch my plan is this from 83b down to the fogs to the green and yellow wires black to earth using the fuse after the switch I will give it ago, once again thank you, have a nice weekend, best regards at all times tony ruff
 
#58 ·
just wired up some fogs, but i want to get rid of the aux switch on go thru the headlight switch. glad i saw this.
 
#59 ·
For reference purposes here is the wiring diagram and adjustment how-to from the dealer kit.

The dealer kit uses two relays that insures that fog lights are not on while the high beams are on. Apparently it's against DOT regulation to have fogs and high beams on at the same time.



 
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