My 2000 A6 has the fog lights set up so they can only come on with the low beams per USDOT regs. Well, in Europe, they can come on with only the parking lights, which is nice in thick fog to reduce back glare(Irionically, many domestic vehicles come setup so the fogs can come on with only the parking lights.). This how-to is a variation on a tech article availible on I decided to do it a little differently than the author of the article, but credit him for coming up with the basic concept.

The major difference in the way I decided to do this mod is instead of using fuse taps, I created a different source for the feed side of the fog light fuse (36).

I wanted the fogs to only be able to come on with the parking lights (which is actually set by the switch mechanically.. You can't pull it to fogs in the off position) so I used the parking light feed. Since this is a low current curcut, not up to the task of powering the fogs, I used it as a trigger for a relay.


The gray and black wire with the tap on it is the parking light on feed for the right side. (it doesn't matter which side you use). This will be the trigger for the relay.

The wire with the butt connector is the FEED wire to the #36 fuse (fog lights) which is yellow with a gray stripe. The side heading INTO the fuse box is the one you want to splice the new wiring into. Cover the bare end of the wire you cut with some tape.

I tapped into one of the #30 studs on the relay block for constant for the relay.

Here is the relay all wired up, and mounted. The terminals are: post 30 is constant, from the fuse block. post 85 is to ground. Post 86 is the wire from the parking lights. Post 87 will feed into the fuse block, the yellow/gray wire.
And, the finished product. Cool, eh?