I own a 2003 A6 2.7T MT6.

Normally the frontfog lights will only work with the low beams. They don't work with the high beams - which is goodness.

I would prefer to have the front fogs come on with the parking lights only. Reason: when it is really foggy out (or snowing hard)the low beam Xenons throw too much reflected light.

Does anyone know a simple way to rewire these? Or is it better left alone? PS - I don't care if the frontfogs end up working with both the parking and low beams. Ditto for the rear fogs.

 

find someone with a VAG tool (https://www.audiforums.com/m_200021/tm.htm), research the codes, and see if it can be donw with a "soft" re-wire...

ditto for the rear fogs

 

Shouldn't be too tough to do. I did this on a few other cars I've owned. A relay in a car has four main leads - one is constant power (or relay power) which allows the relay to actually function in the first place (sourced directly from the battery, through the fuse panel or fusible links). The second is a ground. Third is an input (in the case of lights, it's an input from the switch - turn the switch on, and power comes to this input). Fourth is the relay's output - when the switch is turned on and lead #3 feeds current to the relay, the relay closes and current goes out through this terminal. This is called the switched leg of the relay.

Basically the way it works is that the foglight power is cascaded off the low beams. When you turn on your low beams via the switch, that activates the headlight relay and turns on the low beams. The switched leg of the low beam relay (basically the relay's "output wire" which goes to the lights themselves) also serves as the main power for the foglight relay. Basically when the low beams are turned on, this powers up the relay for the foglights, enabling them to be turned on once you push the button on the dash. If your fogs are on, and you turn off the low beams, that also kills power to the fog relay and the fogs gooff as well.

In order to be able to use them with the parking lights only, you need to rewire. First, at the foglight relay, disconnect the constant power feed to the relay (and wire nut/tape wrap the wire you've disconnected, since it is an electrically hot wire when the low beams are on). Use a wire tap (or better yet, solder and heat-shrink) and run a wire from the switched leg of the parking light relay (the one that actually goes from the relay to the parking lights) to the constant power leg of the foglight relay (where you just disconnected the factory wire as explained in step 1). You're just switching the source of relay power from low beams to parking lights. With this done, power for the fog relay is now cascaded off the parking lights. If you wanted to, you could run a wire from the battery directly to the fog relay constant power leg (putting a fuse in there of course), and then you could use your fogs at any time, without any other lights. Not the best plan of course - it'd be easy to forget to turn them off and kill your battery, for example - but it can be done.

I don't see how this would cause any type of CEL as it's an auxiliary function that has no bearing emissions, engine or drivetrain operation, etc. Still, these cars seem to have CEL triggers on par with a **** dictator, so I suppose there's a chance that some component of the car's monitoring won't be happy.

Anyhow, with a service manual or CD you'll be able to see what wires are the constant and switched legs of the relays we're concerned with, and from there it's simply removing one wire from its connection at the relay, and replacing it with a jumper wire that you install.

Any questions on this, feel free to email or PM and we can talk over the phone to go through any questions. Hope it helps.

 

That's why I recommended the VAG route. Just about every fusible circuit is monitored for voltage output or currnet draw. Fiddling with them may not generate a CEL, but it could throw a code. My philosopy, with the Audi, is: If it can be VAG'd, VAG it.

Now, I don't know about about the vehicle in question, but I do know that mine has a couple of empty pods in the power/fuse block. Later on thiis summer (or, maaybe late fall, if/when I get lazy) I plan on adding a second set of fog lights AND a set of driving lights, independently controlled (i.e. NOT reliant on vehicle lights to be ON for them to work, and I'll be utilizing these extra spaces to power them (via relays, of course, and thanks for the refreshes course. now I don't hafta break out the old books, I can just stop by this thread). I like the idea of them enabled along with teh parking lights, though, so I may go that route, using teh parking lights circuit to trigger teh relay, and one of theblank push/pull switch slots on teh dash... we'll see.

Anyway, back to teh OP. You now have two options to pursue. Good luck, and, be sure and let us know how it works out. Post pics, too, damnit!

 

Thanks for the suggestions. Someone just posted a "fog lights rewire" tech article in the A6 forum which seems to answer the question. They use fuse taps across fuse 27 and 36. Looks simple and I'm going to try it.

 

Thanks for the info guys now I can change mine also.

[IMG]local://upfiles/18996/F880160E964E4713A39E56C2B4B2CC03.jpg[/IMG]

 

Be careful following that thread about rewiring through the fuse box. It seemed so simple...

Block 27 was not hot so I poked around with a ohmmeterand found an unused block that was hot. The panel decoded it as one of the two ABS slotsbut there wasn't a fuse in it. So I tried it. Big f'ing mistake.

My choices are to send the ABS module out for rebuild ($200 + labor to remove/reinstall) which is in play, and if that fails replace it for $1040. So be careful and learn from my bonehead mistake.

And be glad you're not married to my pissed off wife.