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fog light schematic and DIY

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50K views 33 replies 25 participants last post by  absolutsnwbrdr  
#1 ·
tried to find a simmilar thread but had no luck. so if im reposting i appologize.

here is the stock wiring for your fog lights...
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WIRE COLORS
*fog light relay from top to bottom
red/blue
blue/white
black/white
white/black

*fog light switch from top to bottom
blue/white
black/white
yellow/blue
white/yellow
yellow/blue

*MB-10
blue/white

*FB-4
red/blue

there are 2 things keeping you from having your foglights indepoendent from your headlights...the headlight relay and the headlight switch.

HOW IT WORKS
the ground for the fog light relay is controlled by the fog light switch which is controlled by the headlight switch. and the fog light relays power is controlled by the headlight relay. cutting the headlight switch allows you to have your brights and fog lights on at the same time, but you still have to have your headlights on. to make them completly independent you have to cut the power to the foglight relay coming from the headlight relay and replace it with a sepperate 12v source. and voila.
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at the fog light relay you want to get rid of the blue/white wire, this is the power from the headlight relay, and replace it with another 12v source( i chose the cigarette lighter fuse). i dont like to cut and spice wires so i replaced the blue/white wire with a white one i had and moved the other off to the side.
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next you want to find a new ground for your fog light switch.
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BE CAREFUL... there are 2 yellow/blue wires on the switch. you want the one in pin hole #5(2nd on in from the right on the bottom)

if i left anything out or you have any questions let me know :D
 
#11 ·
When I installed my hellas I ran the 12V switch to relay to the fuse box under the hood for the h/l, but now I want to run a relay so I can switch them on and off too... So this is nice AND THANK YOU FOR FINDING THE RELAY! >_< COULDNT FIND THE MOTHER HUMPER.

Nice writeup.
 
#17 ·
this is a dumb mod and a dangerous one as well. It does short out your dash, I had to re wire all of it to make it work properly, Honestly who the hell has a damn wire hanging out of your fuse box... Looks like shit IMO. If you want to have the fogs on with your brights you should do it right and seperate the system completely from the headlights
 
#18 ·
Ive had this done for 6 months now and no problems. The wire is under your dash so no one sees it and only you know its there and if you did the mod correctly your fogs are separate from your headlights, meaning that if your headlights are on brights, lows ,or off your fogs will still be able to be turned on by themselves.

-Paul-
 
#29 ·
I second puddin's question. I don't know if I'm doing it completely wrong but I ended up frying a wire (one that I put in so it wasn't a big deal removing it). I don't have a white and blue wire coming from my relay tho. Pin 1-red/blue pin 2-red/green pin 3-white/black and pin 4-black/white. The red/green wire was already cut (guy who had the car before me probly tried to do the same thing) so I went ahead and grounded the red/green wire from the fog light switch and ran the other end from the relay to the cigg lighter just like in the picture. It works but my highs stay on and I don't have the option anymore to turn the highs on or off. So I tried rewiring back together as stock and just spliced into that red/green wire to another 12v source and it started a small camp fire under my dash lol. What am I doing wrong!! Do I have the wrong wire?
 
#30 · (Edited)
Bringing this back from the dead for Canadian RS owners since our wiring colours are a bit different for the wires involved.

-Pin 2 (red/green) in the fog light relay connector (pink) is to be hooked up to a 20A fuse with a wire. Fuse #4/Cigarette lighter will do (like in the first pics of this thread)
-Pin 5 (red/white) in the fog light switch connector (gray) is to be grounded to any bare metal.

Now, the fogs can be turned on whenever, independent of the parking light and headlights even when the is turned to just ACC. This actually bugs me a bit as it doesn't behave like the parking lights and headlights where the key needs to the ON position first. Another thing is the amber "ON" indicator of the switch doesn't light up. I'm gonna look into this a bit more when I have time. I did this mod this afternoon and left it as such because it was so simple to do.
 
#32 ·
Bringing this back from the dead for Canadian RS owners since our wiring colours are a bit different for the wires involved.

-Pin 2 (red/green) in the fog light relay connector (pink) is to be hooked up to a 20A fuse with a wire. Fuse #4/Cigarette lighter will do (like in the first pics of this thread)
-Pin 5 (red/white) in the fog light switch connector (gray) is to be grounded to any bare metal.

Now, the fogs can be turned on whenever, independent of the parking light and headlights even when the is turned to just ACC. This actually bugs me a bit as it doesn't behave like the parking lights and headlights where the key needs to the ON position first. Another thing is the amber "ON" indicator of the switch doesn't light up. I'm gonna look into this a bit more when I have time. I did this mod this afternoon and left it as such because it was so simple to do.
chose a different power source instead of fuse #4, in other words look for a source of power that comes on when the key is in the ON position.

the "on" doesn't light up because the bulb is dead.
 
#34 · (Edited)
BACK FROM THE DEAD!!

I'm running rally light pod on my 98 RS, with 2 driving and 2 pencil, each pair wired to OEM fog light switches. Everything works exactly as it should, but I want to run the light pod independently of the headlights (and with high beams). When I wired the switches, I piggybacked off the original fog light switch so that the switch illumination worked properly. But, this prevents me from controlling the pod as I would like.

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So I've been reading across the forums (FB, here, nasioc, scoobymods) and it looks like there is a good way to do this, and a few bad ways which result in fried wires/electronics.

This original post has some good information, but the diagram wasn't enough to convince me this was the right way. And it also doesn't quite match the supposed "right way" according to the description on Scoobymods (https://www.scoobymods.com/showthread.php/fog-light-mod-part-ii-485.html). The Scoobymods description is pretty good, but they don't provide a diagram, and they don't mention Pin #'s. I'm a visual learner so I need to see how the things are supposed to work and trace the current path before I start cutting. So I'm posting my observations and diagram to see if anyone picks up on anything I might have overlooked. I tried to post this on Scoobymods, but it won't let me. So here we go...

- The diagram here "looks" like the red/blue wire from FB-4 gets cut (white space over the wire trace). But there is no mention of it, and it wouldn't make sense to cut that wire since that comes from the fog light relay. So that has to be a graphical error.

- The description on Scoobymods and the description here both agree that a new 12V source (ign. switched) should feed the blue/white wire on Pin #1 of the fog light relay. However, the Scoobymods description takes this one step further and feeds that same new 12V source (ign. switched) in to Pin #1 of the fog light switch. This more closely replicates the original intended current path. Instead of the headlight relay circuit feeding both the fog relay and the fog switch, you now have both of those being fed from the same new 12V source (ign. switched).

- The description on Scoobymods indicates cutting/splicing the yellow/blue wire (Pin #5) of the fog light switch to the other yellow/blue wire (Pin #2). The description/diagram in this original post says to connect that wire from Pin #5 to ground. Thinking through this, all Pin #5 wants to see in order for the fog light relay to activated is a path to ground. Originally, that path was through the low-beam position on the headlight switch, which restricted the fog lights to only come on with low beams. Taking that wire directly to a ground, as shown in this original post, seems appropriate. It seems that splicing that wires from Pin #5 to Pin #2 , per Scoobymods, will send additional current in to the illumination control module. This little bit of current SHOULD NOT be enough to fry the module, but there doesn't seem to be a justifiable reason to do this. It seems more appropriate to just ground it.

So here is my draft diagram after all that. Blue and red are my notes.

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