I was sitting around trying to decide how to wire my fog lights up. I've seen people wire them directly off the low beam or run wires and have a manually operated switch in the cabin. I didn't like either solution. H3c bulbs are expensive, so having them on with my low beams seemed impractical. I didn't like the idea of running wire and having to mount a switch. I sat around and devised a way to use the current harness and an existing switch to run them

The pop up button is totally useless once you swap to Silvia lights. It's an on/off switch as well, which makes it a perfect candidate for fog light work. There are different options at this point to make this work.

1- You can drive the switch with its current power source. This will put no draw on existing systems, you won't have to open your interior up, but you will have to make sure you remember to turn the lights off as the power feed is not an ignition switched source. They will stay on if you leave the switch depressed and your car off.

2- Switched voltage. I used the Red/blue wire coming into the switch to power the switch. You only have fogs when you turn your lighting switch to 1 (marker lights on, but no headlights) and have the button depressed, but now you can set the switch and forget it. The drawback is that the illumination system shows a minor, minor amount of dimming.

3- Use the switch to drive a relay. This is the most desirable, but requires the most work. You would wire the switch up like in the previous option, but it would drive a Normally Open relay to supply power to the fogs. You could even use the old pop up switch power supply to be your switched power on the relay.



This digram has all the plugs of interest highlighted. The pop up motors are both supplied by a Brown(BR) wire that comes directly off the pop up switch. The Switch's on/off function is supplied by the Purple(PU) wire and completed by the Brown wire.

Power Routing for stock setup:Battery -> Fusable link -> Purple wire -> Pop-up Switch -> Brown Wire -> Pop-up motor



I had the good luck of having a chassis harness to dig through and follow wires to ensure that what I had planned on paper would work once I cut and soldered.

The only cuts needed will be at the switch, at the lights, and near the fusebox depending on how deep you want to go into this.

Tools needed:Soldering gun or iron (I prefer guns)SolderWireElectrical tapeOne Normally Open relay and relay base (Black 5-pin Relay)One Normally Closed relay and relay base (Green or Blue 4-pin Relay)Screwdrivers10mm socket and ratchet

The relays are easy to get ahold of, the bases will need to be pulled from a car. There is one 4-pin blue base in the driver side relay box that should be unoccupied on a US car. It's the relay for the daytime running lamps I think. And it's even labelled as a "Fog" on the relay box cover. The black 5-pin base will have to be pulled from a scrapped car.

First, remove your headlights and fish out your fog light plugs. If you have no plugs, you can make one out of spade connectors of the right size. Find the old pop up harness and open it up about halfway. Inside you'll find the Brown supply wire and the Black ground. Wire your fog light harness into these two.



Completed and wrapped:

I prefer doing it this way in the random case you might need to swap back to pop ups, you didn't totally remove the plug. If you want to remove it, I suggest cutting the plug, make your solder connections for the fogs, and then shorten the other wires to varying lengths to avoid shorts in the system, then wrap the whole mess.

Then remove the grey relay labelled 'H/L Ret Cont' from the passenger fuse box.





If you don't remove it, this relay, as an auxillary supply to the pop up motors, will energize the fog lights when you turn the headlights on.

To dig in deeper, you'll have to pull the gauge bezel shroud in the interior of the car. You need to get to the back of the pop up switch to rewire the voltage feed.

Once you've gotten to the switch's plug, you'll need to tap the Purple wire into the Red/Blue (R/B). The Red/Blue is part ofthe illumination system. When you turn the lighting switch to the '1' position, the switch feeds a Red/Blue wire which branches and goes to every part of the car that lights. Marker lights, combo lights, gauge cluster illumination. You get the idea. By tapping off this wire, you supply voltage to the fogs only when you turn your marker lights on.



Simply cut the Purple wire and tap it into the Red/Blue.

Now you have a switch that can be turned on, but will only supply the fog lights once the marker lights are activated. I like this solution as it makes the fogs independent of the headlights.

You can stop here and have working fog lights if you want. They will be independent of your headlights, but will draw on the illumination system (if you went that route) and they won't shut off with your high beams on. The next few steps will help you wire in relays to have them cut off with your high beams and use a dedicated power source to prevent drain on the illumination system.

Before you continue to the next section, I suggest reading up on relays. A great resource for that is here: http://www.autoshop101.com/forms/hweb2.pdf

I had a vague understanding of relays before I sat down and planned this project out. Afterwards, I had a solid understanding on basic 4-pin relay setups.

This section will be confusing. Even with a ton of pictures, it can be hard to describe how to wire in relays. I have an especially difficult time describing wiring, so please bear with me.

Since I have no A/C, I was able to use the spot in the relay box for the A/C relay. If you have A/C, it might be best to wire one or both of your relays outside of the box and strap them to something.

First you need to open up your driver side relay box. It's easy to get to the underside. First there is a plastic clip that holds it down. It is on the side that faces down. If you have no wheel well liners in, you can easily take something and hammer it out from the bottom. I used my screwdriver. Then slide it towards the fender and it should pop out. There are 6 clip tabs holding the bottom half to the top half of the box. Take a bladed screwdriver and pop those tabs to seperate the box. You should end up with this:



First you need to understand how to follow a relay pinout



There are numbers next to the pins in each relay. They correspond to the diagram shown on top of the relay (middle picture). In the top one, pins 1 and 2 would be the circuit for the selenoid coil. 3 and 4 would be your naturally closed circuit, and 5 is either your switched circuit or circuit breaking line (no wire or wire leads to nowhere). Nissan will remove the middle wire when they want to make a naturally closed relay that just breaks a circuit.

I have never seen a Naturally Closed 4-pin relay from Nissan. They used these 5 pin relays instead, which are common to come by.

The bottom 4-pin relay usually comes in blue, but I have seen them in green.

I'll start with the easy setup first.



This will cut your fog lights off when your high beams come on. I ran a power line tapped off the high beam power signal (Red/Black) which was used to power my coil. It was then routed into the grounding system (find any suitable black ground wire under the relay box and tap your new ground into it). Then you would run the brown wire into and out of the switched side of the relay.



The more complex wiring uses an extra 4-pin relay to use the switch to complete a circuit that powers the fog lights. This will prevent any draw on the illumination system. In this one, I cut the purple wire that feeds power to the pop up switch. I checked and this wire's sole purpose in the car is to supply power to the pop up motors, so by cutting it by the fuse box, you won't be disabling anything. I ran this into one of the pins for the switched side. The outgoing switch was ran to the 5-pin relay (wire coloured blue in my diagram). I used a common ground for both of the relays to simplify and eliminate having to run too many extra wires.

Now that we're all completely confused, I'll give you a few pictures of the actual process.



This is where I tapped my signal wire for my high beam sensor. This is the 3 prong plug that feeds into the subharness for the headlights. You want to trim the sheath of the Red/Black wire and then solder your tap into it.



Wrap this up as it will see the elements. You can run it back through the hole the harness comes through.



This is where I made all of my cuts to run wires into the relay box. For the brown wire, be careful that there are 3 brown wires running through this part of the harness. The one you want is thicker than the other two. It's closer to a 14 gauge wire, while the other two look more like a 16 gauge. I grabbed a test light and pierced the one I thought to be the wire I needed, and then turned the fog light switch on. The test light lighted up and I knew I had the right wire.

I cut the brown wire and ran two long wires into the relay box. Make sure that you use heatshrink tubing whenever possible. I also cut the purple wire and ran a length of wire into the relay box for it was well.

Inside the box, you will need to remove two relays. The top right relay is a 4-pin base that can easily be converted for our fog light purposes. Take a bladed screwdriver and press it into the clip on the flat side that is against the box itself. Push down on the base and it will pop out. When you cut the wires, be sure to cut the wires at varried lengths to prevent any possible shorts. Repeat for the A/C relay base as well.

Take your first relay base (I started with my 4-pin) and wire all of your wires into it. For the 4 pin, you will want to be sure that you use the brown wire coming from the dash switch. If you use the other end, you'll never get your fog lights to work



My 5-pin base had a lot of thick White wires on it, so I figured out which was my ground and tapped it into the ground for my 4-pin base. I then wired my high beam signal into this relay as well as the wire that crossed over from my 4-pin base that carried the fog light power signal. Last to solder in would be the outgoing brown wire that runs the power to the lights.

On 5-pin bases, Nissan would sometimes include the middle wire. It depended on the application of the relay used. For ours, we don't need the middle wire. I tried my best to remove the wire completely, but it was stubborn. I ended up cutting it short and taping it off to prevent any shorts.

There is one very thick black wire coming off a retract relay base. I found this to be a good candidate to tap into for the relay grounds. On the cover it is listed as "H/L RET DOWN"

Once you have all of your wires soldered and wrapped, snap the relay bases into their new homes. Loom the wires coming into the box and snap the halves back together. Once you insert your relays, you're ready to rock.



It looks like they belong there.

Wow, thats a nice long write up. How long did it take you for the whole thing, research and work?

Cant wait to try this, Nissan has my car right now cause I am having ENORMOUS lighting issues but I will try this once the car is out.

Thank you very much

CMG wrote:Wow, thats a nice long write up. How long did it take you for the whole thing, research and work?

It only took a few days to plan out and less than an hour to the soldering for the lights and the switch. Doing up the relay should be quick and easy as well. I just can't solder very well one handed.

Updated the DIY to include my relay wiring. It's a bit rough in wording, so I'll try to clear up some of my wording later to make it more understandable. I do have a seriously tough time conveying my wiring methods to paper at times.

That's my old Silvia front! I miss you, Silvia front...

lol Good job man. When are you doing paint?

Spring time when it's warm enough to do paint.

so hi jacker, if you just want hook up the fogs to the pop up switch to were when you press/depress it the fogs come on/off you tap into the brown and black wire which are the power and ground?

Yep. But that circuit is switched on by the ignition, so you would have to remember to turn your fogs off after you use them, or else they'll stay on when you get out of the car.

oh ok, gotcha. I'll remember to turn them off......hopefully lol

Heh. I'm a moron when it comes to remembering to turn lights off, so I opted to have the fogs on an ignition switched circuit. But nothing carried the voltage required to power the 55w bulbs without some power drain, that's why I isolated the old pop up power circuit and used it to on a relay to power the fogs.

Thanks for the write up i was wondering how to do this.

i have a question. there are 2 prongs on my tripple projector fog not including the little tab thats under the rubber sleeve. do i need to wire the brown and black up to those 2 prongs any certain way or will female spades work? and i cut my brown wire where the button is in order to control sleepy eyes when i had my lids. will i be able to turn the lights on with this wire cut?

Hijacker, could you please send me a PM, I did the wiring today exactly as you said to do for the relays and the fogs are not working this way at all. I would just like to ask a few questions that are a bit unclear in your write-up.

Thanks