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How-To mod the 2004/2005 fog lights to turn on with 12 volts

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21K views 41 replies 24 participants last post by  SpustaSTI 
#1 · (Edited)
How to mod the 2004/2005 fog lights to turn on with 12 volts.

I am not responsible for any damage that can occur with this mod.
Also know that it is illegal to drive with only your fog lights on in most states.

This mod is very simple to do and can be done to any Impreza that has the factory fog lights installed.

Tools needed:
- Long 16/18 gauge wire. (To tap into 12 volt turn on source)
- Heat Shrink Tubing. (To insulate the relay leg)
- Electrical Tape. (To hold everything in place)

What needs to be modded:
- Just the fog light relay next to the fuse box.

How to mod it:
- Unscrew the plastic panel under the dashboard. (Remove the plastic screw by the left door jam / dashboard area and unscrew the two screws on the bottom to take that piece off)
- Once the panel is removed you will see relays on the right of the fuse box.
- The third relay from the bottom is the fog light relay. (This is what you need to unplug and mod)
- Using two flathead screwdrivers on each side, unplug the relay.
- The Top Right leg of the relay is what senses 12 volts and switches the internal switch inside the relay.
- Bend the leg back so it folds over the side of the relay and points towards the opposite direction.
- Place some heat shrink tubing over the 16/18 gauge wire, then insert the wire into the hole in the relay leg and insulate it with the heat shrink.
- Wrap a little electrical tape around the relay to hold the wire in place and to make sure it doesn't get tugged or pulled off. Make sure you don't tape where the relay has notches to slide back in.
- Wire that wire to any 12 volt turn on source and the fogs will go on. I wired it up to the accessory on from the stereo harness.

I noted two things after this mod:
The switch fog lamp on indicator acts like it did before the mod. (It does not light up unless the headlights are on)
The fog lights turn off when the high beams go on. (I think this is to limit the amp draw possibly)

I have a picture that I drew on that should help.

Have fun with your new modded fog lights. :)
 
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#2 ·
Also, I think the other relay leg is just a 12 volt source to power the lights.

You can bend or attach a 12 volt constant power run somehow to one of the 12 volt source relay legs and I think that the fogs will stay on with the highbeams. I think that the system cuts power to the relay when you flash the highbeams. I sorta like the fogs going off with highbeams. -( Makes more of a signal type of thingy, you can flash people in front of you and it is way more noticable)

I just wasn't ready to do that mod at the time. Maybe later. Also modding the relay is cool cause you can buy another one to revert it back to stock easily.

Just be careful, you don't want to fry anything... :(
 
#12 ·
Is that checked with eletrical diagram ? Otherwise fogs can be powered from stereo circut.
If everything is ok it should be enough just connect two legs(main power 12 volts and sensing one) with diode.
Can anyone post wiring diagram for this relay ?

andrius


LESLIEx317537 said:
Also, I think the other relay leg is just a 12 volt source to power the lights.

You can bend or attach a 12 volt constant power run somehow to one of the 12 volt source relay legs and I think that the fogs will stay on with the highbeams. I think that the system cuts power to the relay when you flash the highbeams. I sorta like the fogs going off with highbeams. -( Makes more of a signal type of thingy, you can flash people in front of you and it is way more noticable)

I just wasn't ready to do that mod at the time. Maybe later. Also modding the relay is cool cause you can buy another one to revert it back to stock easily.

Just be careful, you don't want to fry anything... :(
 
#17 ·
Yes, but why deform the relay socket when you can deform the relay spade?
If you want to revert back to normal, then all you do is bend back the spade or get a new one for 25 buks.

If you do it your way, you may need to do more mods unsolder etc.... I try the easiest way and non permanent.

Also getting behind the relay socket is harder. :)
 
#20 ·
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#21 ·
sti gsxr 1235 said:
One question, Is there any way to wire it up so that when you push the fog light button it goes on no matter what lights are on??? For example I could just drive with my fogs or my fogs with the parking lights or head lamps fogs and parking???
This is exactly what this mod does. I did it on my 06 STI without a hitch. As long as the key is in the ignition, the fog lights are controlled independently by the switch. You WILL be able to use it just like in each of your examples.
 
#25 ·
Stargazer said:
This is exactly what this mod does. I did it on my 06 STI without a hitch. As long as the key is in the ignition, the fog lights are controlled independently by the switch. You WILL be able to use it just like in each of your examples.
I have an '07 STI Limited and tried doing this mod. I'm having a real hard time trying to remove the relay. Before I go any further, are we sure this mod works for an '07 STI?
 
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