I have an 03 R53 with rear fogs and all six toggles in place. The only time I use my fog lights is during times of reduced visibility conditions (like fog) and then I always turn on both front & rear fogs.

I would like to repurpose the rear fog switch to function as my rally light switch and have both front & rear fogs come on with the front fog switch only.

Has anyone ever done something like this and is it even possible?

 

Electrically, it would be a simple mod, as long as you are comfortable working with wiring and relays.

To make the front and rear fogs work together, first disconnect or cut the existing wires to the rear fogs. Run wires from the battery (or other power source) to the rear fogs, and put a relay inline. Run another wire from the front fog to trigger the relay. Now when you switch on the front fogs, the rear fogs will also turn on.

At this point, the wires that originally ran to the rear fogs are still controlled by the rear fog switch, but no longer connected to anything. You can use that signal to switch on/off whatever you want, such as operating your rally lights. Hook up the original rear fog signal to a relay, and use the relay as a replacement for your current rally light switch. When you turn on the rear fog switch, it will trigger the relay, which will turn on the rally lights.

 

is to leave the wiring for the rear fogs in place, and just tie the control lines from the toggle panel for the front and rear toggles together. That SHOULD work but may take some testing. The BCM will get the toggle signal at the same time for both front and rear.

The rear fog toggle then just is a loose wire that will go to ground when activiated. IT would be free for whatever you want to do with it.

Both methods should work, it just depends on what you want to do as to which would be the better knife to skin the cat....

Matt

 

No need for extra relays to run the rear fogs.

The rear fog does not run off a relay stock, it is ran strictly by the bcm.

Find the wire that goes to the rear fogs, run it to the front fog light relay. Now all will come on when the front fogs are triggered.

Now you can use that output you just freed up from the bcm to a relay to run whatever you want.

This way is about 75% less work than what was recommended above.

 

ive been thinking of doing this as well, but i dont already have the rear fogs installed. i got a hold of a 6 switch bank for cheap, but have been trying to get wiring figured out without opening the switches and wiring in my driving lights directly to the switch.

sorry to thread jack.

look forward to seeing how you get this figured out

 

The wiring is already in your car for the rear fog, but it is NOT in the car for the front fogs.

All the switch panel does is send negative trigger signal to the body control module to tell it to turn on or off various lights, roll up and down the windows etc...

The switches aren't capable of carrying any amperage so do NOT use them with a load through them.

 

Not sure if im completely wrong here, but then since the wiring for the rear fogs is there, can I technically wire front lights through that wiring?

 

I'd have to check my schematics but i'm pretty sure the rear fogs do not run through a relay therefore you would not want to run the front fogs directly to the power from the rear fogs. Instead run the front fogs from a relay and use the power to the rear fogs to trigger the relay.

 

Man this is something I had wanted to do on my car, but I wound up just placing the switch on the column.