[finally03gt]

I was recently shopping for new headlights for my 03 GT. In the process I found a "fog light high beam kit". It was a wire harness with a control module that prevented the fog lights from cutting off when the high beams are turned on. It got me to thinking and I pulled wiring schematics for the system, and here is what I discovered. The fog lights ground runs through a "fog light interrupt" relay in the main relay box above the left wheel just behind the battery. When the high beams are turned on, the relay is energized and opens the ground circuit for the fogs, and they go off. So, why spend money (even if if was only $13 + S&H), and add wires to your car. I removed this relay and broke off pin number 2, then reinstalled it (you need the relay in place to complete the ground circuit). This is the pin with the pos. voltage coming from the high beams. With out this pin the relay does not energize and the ground circuit for the fogs stay closed and they stay on. Quick, easy, no money spent and no extra gear to install. Hope this sheds some light on the subject.

[Stewie88]

very nice i was wondering about this, but can you be a bit more descriptive im still trying to do it

[finally03gt]

Between the battery and the strut tower is a electrical box labeled "Power Distribution Box" In this box there are several relays and fuses, two of these relays are smaller and rectangular. The one at the back of the box on the most inside corner should be the fog interrupt. I believe it is labeled on the lid as well. Remove this relay and look at the contact blades. (Also at this point if you want to be sure you have the proper relay you can turn the headlights and fog lights on, but the fog lights will not work with the interupt relay removed.) There are two contact blades parallel to the short side of the relay and three parallel to the long side of the relay. They are also numbered 1-5 (in very small numbers beside each contact) With the two larger contacts up, remove the left pin of the three small ones. The picture is really bad, but it shows the orientation of the contacts. Hope this helps

[00redgt]

this wont burn anything up will it

[finally03gt]

Short answer, no, it should not have any adverse effect. From the wiring schematics pins 3 and 4 are a normally closed circuit that completes the ground for the fog lights. Pin 2 is the positive voltage supplied to the relay when the high beams are turned on, and pin 1 is the ground for pin 2 that completes the circuit to energize the relay and open up the ground for the fog lights, thus turning them off. There is a 5th pin on the relay itself, and the drawing does not show this pin. My GUESS is that this is either a common, or just a dead pin from using generic relays. In summary, all that we are doing by removing pin 2 is terminating the path of positive voltage from the high beams, just like disconnecting a wire and taping if off.

[Stewie88]

+1 Dude, badass i just did it took 1 minute, how did you figure this out man.

[finally03gt]

LOL... tks man. Like I said, I saw the kit online and it made me wonder what the kit was bypassing, so I pulled the wiring drawing off of my online chilton membership. Glad yall like it. While we are talking about lights, can anyone recommend a GOOD fitting headlight assembly? I ordered new headlights and am very dissapointed with the fit.

[Stewie88]

what headlights did you order?

[finally03gt]

I ordered off of e-bay, but the add said they were JDM.

[99GTCobraMIX]

wow that was super easy haha and looks awesome, still need to test it at night tho

[R3dFyre02]

a while ago i believe it was jazzer that posted a quick how to on making a jumper out of a coule inches of wire and two male spade terminals and plugging it in instead of the broken relay like you did. same outcome. did it to mine for a while, then got nailed at a safety inspection for it... never realized that it is a safety issue that when you turn on your high-beams because you NEED MORE LIGHT having your fog lights staying on is a bad thing,....

[Matt Cramer]

I see nobody's mentioned *why* fog lights are normally set to only come on with the low beams, so I will. The fog lights are intended to feel your way through very thick fog, so they are only right in front of you and don't send much light down the road. The high beams are meant for seeing distances, and don't have as much foreground light so your eyes can focus down the road better.

You wouldn't want the high beams on in the sort of fog the fog lights were really intended for, and the stock fog lights don't add much illumination down the road where the high beams are pointed. So this mod would pair best with replacing the fog lights with long range driving lights.

[R3dFyre02]

here is a link to what i was talking about from Jazzer. simply jumper pin 3 and 4 after removing your "foglight interupter relay" or relay #5 under your hood.

foglight install for 99-04 Saleen - MustangForums.com

[mjpjr45]

I did mine a while back, using a jumper. I found a link on line and used their instructions. The only problem was their instructions were wrong and I ended up blowing a few fuses. After some diagnosing with my multi-meter I figured out which leads to jump and did it. Been using them for a while now with no problems. If I need to go back to stick all I have to do is pull my jumper and re-install the relay.

[dachuckster]

How about for 2010 GT?

[finally03gt]

Not sure about the 2010. Probably very similar, but would have to see a print to know for sure. Still a bit new to find one(a schematic) online easily, unless you purchase a subscription or something. Also, the post from Matt Cramer is accurate. I did this mod b/c with the high beams on it left a dead spot right in front of the car, and I was driving a lot of 2 lane country roads at night, and wanted the distance for spotting deer and such, but also the area of the shoulders just to the left and right for smaller critters.

[6ER THEN I 8ER!]

i only run a low beam so i don't have to worry about this

[Keredstg]

Figured I'd add some pics to this. They are crappy iphone pics with very little lighting but better than nothing. This was performed on an 04 Mach 1.


Between the battery and the strut tower is a electrical box labeled "Power Distribution Box"


In this box there are several relays and fuses, two of these relays are smaller and rectangular. The one at the back of the box on the most inside corner should be the fog interrupt. Remove this relay and look at the contact blades.

Also at this point if you want to be sure you have the proper relay you can turn the headlights and fog lights on, but the fog lights will not work with the interupt relay removed.

There are two contact blades parallel to the short side of the relay and three parallel to the long side of the relay. They are also numbered 1-5 (in very small numbers beside each contact) With the two larger contacts up, remove the left pin of the three small ones.



Plug it back in with the pin removed and test away.

[Jazzer The Cat]

Excellent write-up and great work, finally and perfect images and description, as well, from pepe kered (appears to have retired from MM's, though )

I prefer to use a jumper than wreck the function of the relay, but either will work fine

Jazzer

[luke1333]

i need to try this!! nobody has burnt anything up yet?