Tech Article Title Author Date
Dual Rear Fog Lamp Modification Matthew LeBlanc 2001

Credit given to Scott (GADGT) who wrote the original tech article for which this article was based upon.

These instructions may also be used for replacing brake/tail lights for A4/S4 models You assume all responsibility for any and all results obtained by following this article. You do so at your own risk. You are solely responsible for any damages financial or material. This article is only applicable to 2001 S4 6-speed although I'm sure that this mod will apply to 1999-2001 S4/A4. Read this article in its entirety before attempting the procedure.


Are you tired of being told, "you have a tail light out"...well add another bulb to your S4/A4 and voila! Two rear fog lamps. There is one catch; you need to Dremel some plastic before inserting the bulb! That's pretty much it.

I started looking into this mod and found that the A6 requires installing a new bulb housing and tapping the existing wiring, but once I got inside the tail light area I discovered that there was a spot for the bulb. AoA just made it difficult to install a bulb without modification...but AoA did leave the bulb housing and wiring live and in tact.

Tools and parts needed:

  • Dremel tool or Drill & 1" wood boring bit
  • 1156 bulb. These are the same bulbs as all the taillights.

    Accessing the fog light assembly:

    On the S4 model, there is a small-upholstered box that is wedged in the corner closest to the passenger-side brake lights; remove that box by pulling it vertically, and put aside. Next, pull back the sound proof carpeting housing that is on the inside of the trunk lid on the passenger side. It is secured by two standard auto clips see picture below (circled in red).

    Once you have removed the two clips, pull back the soundproof carpeting and you'll see the tail light assembly. There are three plastic clips holding it in place. First loosen the clip closest to the outside of the car, then the top one, then angle the whole assembly towards the front of the car. (see picture below):



    Now inspect the right fog light assembly. You will notice a silver plastic cap that prevents you from being able to insert the light bulb and the bulb harness fixture. You will need to remove this plastic cap. You can remove the cap in one of several ways...with an exacto knife, Dremel tool, or by using a one-inch wood boring bit and a drill.

    Installing the right fog light:

    Insert the bulb into the now connected new bulb fixture and place into the hole that was made available when you removed the silver plastic cover. Insert it and firmly twist it to the right to make sure it locks into place. Start the car and test the lights. Tuck your wires into place and use you plastic quick ties to secure all wiring. Reassemble the inside trunk cover remembering to replace the two clips you removed.

    Don't forget to vacuum, before reassembling. The Dremel tool makes quite a mess with little plastic shavings, and we don't want those melting on any of the bulbs causing any problems: smoking, flaming, shorting, etc. Drive safe and have fun!


    The result is...when the rear fog is engaged both rear fog lights will illuminate giving your car more visibility in poor weather conditions.


    There has been some discussion over the legality of the dual rear fogs in some states, although they are available as stock on some other european automobiles. Please check with your local law enforcement agency about laws pertaining to the rear fog lights.

    Virtually all European cars (and US and Japanese cars for the Euro market) come with rear fog lights. They come with them being on the drivers side. One bulb. Left in continental Europe, right in GB. Why? Simple. It is about recognizing danger fast. The two red lights are the tail lights of the car in front of you. No imminent danger, unless you are very much faster than the car in front of you. You see two bright red lights: The guy in front of you is slamming into his brakes, so you better do the same unless you want to rear-end him. One bright red light: it is foggy, and you came close to the guy in front of you, close enough for you to see him. Keep that distance, do not come closer. That is why it is absolutely verboten to drive under normal conditions with the rear fog light on; only in very foggy conditions with less than 50 m (around 150 feet) of visibility. It blinds, it irritates. And, of course, you are in deep yogurt if you see  three bright red lights and two less bright lights: It is foggy, you are freaking close to the car in front of you, and he slams into his brakes...

    BTW, that is also why turn indicators mandatorily had to be orange: You could distinguish it purely by the color, you did not even have to wait until you see something starting to flash.

    However, in the US nobody knows all this, so it is sort of irrelevant.

    Just food for thought