Turn on Your Early S197 Fog Lights Independent of the Headlamps

By Cameron Vanderhorst - September 20, 2019

Want to turn your fog lights on without your headlights? After much work, our forum members figured it out.

Not every modification makes your Mustang go faster, handle better, or look different. Sometimes, it’s the small things – subtle changes that bring the car closer to your ideal vision of an all-around performance machine. Like fog lights.

Thankfully, Mustang Forums is filled with knowledgeable enthusiasts who’ve done just about anything that could be done to a Mustang. There’s years worth of archives to search and sift through, but folks are still finding new things to do to their cars and new ways of doing them.

In one thread in the 2005-2009 S197 Appearance Section, our members have set out to figure out how to retrofit a different headlight switch that allows the fog lights to be turned on without the headlights.

As it turns out, this electrical upgrade requires changes to both the car’s hardware (switch and wiring) and its software. It seems like a lot of work to go through for such a minor modification, but it’s a fascinating read.

While swapping the switch is straightforward, the wiring modifications required to make everything work as intended require a measure of electrical know-how. Thankfully, some of our members are electrical whiz kids, and were able to figure it out.

With the aid of some wiring diagrams, they were able to figure out how the circuit worked. Unfortunately, it seems that, in addition to some electrical wiring modifications, they’d need to use a FORScan scanner for coding purposes.

They did figure out a workaround, which involved adding an additional toggle switch to the headlight switch module. It’s not as factory-looking as other solutions, but it does eliminate the need for expensive coding modules. Depending on how you look at it, it could be a simpler wiring job, as well.

Sometimes, it’s the little modifications like this that can be the most fun. Figuring out how to get the switch to work was like solving a little mystery. If you could change one electrical system on your Mustang, what would it be? Let us know in our forums!