DIY: B6 A4 Dual Rear Fog Lights

[a4darkness]

DIY: B6 A4 Dual Rear Fog Lights
by Michael Hammond and Daniel Sekijima
[edited by a4darkness aka noti]

Every time I see a post about dual rear fogs, I always think about the fantastic write-up stashed away on my HD... not doing any anyone any good.

But, it needed some polishing. So I cleaned up all the text, hosted the images and here you are. Again, thanks to Michael and Daniel for their efforts.

Summary
These steps will show how to tap off of the left side fog light to power the right fog light creating duel fog lights. If this procedure is followed correctly, it will not cause conflict with the computer or tail light monitors. No warnings or errors will show when u start the car.

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Required Tools:






Also needed is a wire, about 6 feet in length(This should be more than enough, and there should be some left over.)
A 12 gauge wire was used for this write-up.
Note: Although the tap splicer as shown fits an 18-22 gauge cable it was jammed into the wire in for a tight fit with no issues.

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Step 1
Empty the trunk + remove the spare tire and and take off the carpeting as shown.
(Ignore the extra wires, they are for speakers/amps)




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Step 2
Locate the two screws found inside the spare tire well.




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Step 3
Remove the screws with a 10mm wrench. This will make it possible to remove the black plastic trunk guard.
To fully remove this piece, pull up were the arrows are shown in the picture above.
After removing the plastic trunk guard, this is what you'll see:




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Step 4
Locate the carpet circle plugs on both sides of the trunk. Then remove the screw as shown in the picture below.
FYI, these screws attach to the tail lights.




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Step 5
Now that the screws affixing the tail lights have been removed, begin to pull out the tail lights.
Proper tail light removal is like pulling a book from a shelf. Keep the outside part hinged and begin pulling outwards with the inside part of the housing.
There will be green plugs connecting the tail lights to the wiring harnesses.







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Step 6
After removing a tail light from the car, detach the green plug that is connected to the tail light. This will fully detach the housing from the car. (Do this for both tail lights.)
After the left housing has been removed off take notice of the bundle of wires.
Locate the wire that is grey w/ a white stripe in this bundle.
This is the wire that will be spliced to tap electricity to the right fog light.
(1) This is the 12 gauge wire, mentioned above, that will be used to run power from the left side to the right side.
(2) This is the grey w/ white stripe wire The flat head pliers, shown above, were used to crimp the wires in the splicer.





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Step 7
The picture below shows separating the carpeting on the right side of the trunk.
This is how access is gained to the tail light wire bundle.
This will need to done on both sides.



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Step 8
(1) Slowly work the the 12 gauge wire (red wire as shown) through the rubber seal.
An effective technique to accomplish this is the use of a screw driver to pull back the rubber seal.
Doing this will feed the wire behind the carpeting as shown in Step 7.
Place your hand into the area created by separating the carpeting from the trunk wall and feel for the 12 gauge wire that is being run through the rubber seal.
(2) Pull it all the way through so it is loosely following the original bundled wires.




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Step 9
Work the thin flexible wire through the rubber seal on the right as you did with the 12 gauge wire on the left side.
Pull it through so it can be seen as in (1) and (2).





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Step 10
Attach the thin flexible wire to the 12 gauge wire by taping the wires together and twisting or bending them together to make sure they stay connected.
[A coat hanger can be used for the 'thin flexible wire here.']





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Step 11
Pull the thin flexible wire through the rubber seal until the 12 gauge wire has emerged through the hole.





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Step 12
Cut the grey w/ white stripe wire leaving 4-5 inches of extra space
The extra space is just in case the splicing of the two wires doesn't go quite perfectly.





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Step 13
Splice the red 12 gauge wire and the wire just cut together, with the same splicer used as before, and you should be good to go.





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Step 14
Reverse the tear-down procedure as detailed above.
Connect the green plug back into the light housing and remember to use the book from a shelf technique when reinserting the light housing.
[editor's note: This might be a good time to test and see if all the wiring has been configured correctly as re-removal of the carpeting and trunk pieces would be a bit annoying.]
Use some force to both readjust the carpeting back on both sides and to bolt the black plastic guard back down (listen for a pop or snapping sound to signify the guard attaching correctly)
And don't forget to screw the tail lights back in. Then put spare tire + carpeting back in and please the following disclaimers + info

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[begin editor's addition]

There have been some very 'colorful' threads on most Audi enthusiast forums concerning the use of dual rear fogs. Okay, some have been downright nasty. Maybe you've been witness to one? Lobbed the obligatory grenade?

That said, regardless of anyone's personal opinion [including my own], as I'm [re]posting this DIY [which BTW I take zero responsibility for... please mod at your own discretion, thx], I feel inclined to also include some additional thoughts concerning this mod in hopes of quelling the omnipresent comments that emerge whenever this topic is mentioned. And rather than directly quoting, as to not drag anyone into this, I'll simply paraphrase what I believe to be worth mentioning... be it negative or positive and leave it at that.

* Having both fog lights illuminated is often perceived as 'brake lights being on' which can be confusing / annoying / dangerous to other drivers.
* The purpose of a single left rear fog is: during times of poor weather / low visibility, it acts to warn vehicles approaching from the rear that there is another vehicle ahead of them and / or to appropriately signal to which side is ok for the approaching vehicle to pass on.
* The use of a single rear fog light is used commonly / primarily outside of the US.
* Many law enforcement officers are not familiar with the concept or use of a single rear fog light and will often perceive there to be a non-working tail light on said vehicle. Many have been pulled over and some even issues citations.
* The use of dual rear fog lights in the US is legal if, between brake and fog lights, there is 10 cm of space. The B6 A4 does not have this required spacing.
* A good rule of thumb for B6 drivers with single or dual fogs... use them only as necessary in the most inclimate of weather or visibility situations.

[Charlescrs6]

Nice. The only thing though is that you can tap the wires on each side from inside of the car. If you pull back the carpet on each side you'll see the wires and where they go into the sleeve. Find the one with grey and white stripes and you're good to go! That's how I did mine.

[a4darkness]

^^ good to know, thanks for that addition.

Always felt bad about not re-posting this, figured it should be shared in some capacity with the group.

[dirtybrd]

But it's dumb and unsafe to have. It looks like your brake lights are on when you turn on the rear fog light, that's why Audi design only one side to work.

[absolutegtr]

But it's dumb and unsafe to have. It looks like your brake lights are on when you turn on the rear fog light, that's why Audi design only one side to work.

Also why its on the drivers side of the car.

[alexza4]

Good job on the write up man, but i'd have to agree with others. It is very distructing when you drive behind someone with the rear fog light on, it is way too bright. i can imagine that with two on it will be even worse. Its actually illegal in most states to drive with rear fog on. BMW actually disables this feature for US bound cars, i'm surprised that Audi does not.

[a4darkness]

Thank you alexza.

For what it's worth, I'm really not a fan of this mod either as I don't see it having too much practical purpose or frankly being that safe. I've not done it on any of my three A4s. But, someone was asking for it and since I had the info... /shrugs

When I was down south in SoCal, I saw A4s, S4s, an All Road and even a A8 with this mod + some w/brighter lights and it's pretty obnoxious. But there's no mistaking seeing the vehicle. My theory was that this was a 'don't tailgate me' or 'these are on so you don't keep texting and rear end my car' mod. Make sense?

The only reason why I got my hands on this write up was part of my idea to use the rear fogs as secondary reverse lights. [My recently deceased A4 had 5% tint which significantly decreased visibility out the back windows at night.]

That said, I'd still love for someone to come up with something useful or clever for the bastard rear fog[s].

[OxfordA4]

I do agree with many of the negative opinions, but I have extremely bright bulbs in my rear markers so I have no use for my rear fogs.

I did this mod so that I can turn my rear fogs on as sort of a faux set of break lights, tapping them or turning them on to cause tailgaters to back off.

[Silveravant]

My B7 A4 Avant has both fogs oem.

[paul3x16]

i did mine thanks but you dont have to pass the cable through the firewall just clamp it from the inside, follow the grey and white stripe wire :)

[fdruiz011]

But it's dumb and unsafe to have. It looks like your brake lights are on when you turn on the rear fog light, that's why Audi design only one side to work.

I only use mine when it is hardcore snowing and foggy at the same time up in the mountains. I hate when people misuse them, but if you saw the weather we have up in the mountains in Washington, you would definatly consider using them, for your safety.

[SJorge3442]

hmmm. No wonder I could never get the other side to light up..... I use the rear fogs to get ass hole drivers to back away from my car. Works pretty good. I'd like to convert them to super brights, or maybe make it so I can flash the reverse lights with the rear fog light switch.

[ADCS]

I use them for carpool lane anti-tailgating lights. They work great.

[walky_talky20]

I'd consider adding these to the brake light circuit. Super brake lights FTW.

And then tag them on with the reverse lights to a separate momentary switch for tailgaters. Double-tap for those that ride too close. Would need some relays and diodes to make it work the way I want.

[SJorge3442]

I'd consider adding these to the brake light circuit. Super brake lights FTW.

And then tag them on with the reverse lights to a separate momentary switch for tailgaters. Double-tap for those that ride too close. Would need some relays and diodes to make it work the way I want.

Let's do it!!! I think you should write a diy for everyone.

Sent from under my car

[a4darkness]

Jesus necrobump. The dead have been raised.

And there's already a DIY for Quad-quattro Style Brake Lights.

[SJorge3442]

Jesus necrobump. The dead have been raised.

And there's already a DIY for Quad-quattro Style Brake Lights.

thanks for the post. Thats a good start of how to get the quad style rear brake lights (I will probably do this, this weekend now), but we were talking about throwing the reverse lights into the fog light wiring as well. Just so we have something to flash. Obviously at this point, it should be no harder than sending the reverse light wire to the fog light wire. Right?

[walky_talky20]

My thought was to have these dual fog lamps come on with the brake lights OR the reverse lights. And have the Rear Fog Lamp switch still only drive the left bulb. Obviously need to use diodes to isolate the circuits to make that possible.

And add an extra switch for tailgaters. If that switch could light up every last bulb on the rear of the car, that would be ideal. Might require some testing to see what looks the best. I want it to look "different" so they know I'm not just hitting the brakes...I'm sending them a message. The regular Reverse+Fogs mode might work well enough, and would be simpler to do.