View Full Version : DIY: CityLight with Fog Mod

Eddie Man
03-11-2007, 11:58 AM
I know this is a repost but I wanted to put my spin on it...
First of all, HUGE props to "FatAuto" for figuring this out. For reference >>> FatAuto's AW Link (http://forums.audiworld.com/s4b6/msgs/333541.phtml)

Here's how I did it and I've just include lotso pics for people who like pics [:)]

1. Identify wires (Position #1 & #2) on the light switch harness

2. Cut Wire #2. Allow for ample wire for step #3 & #4 below.

3. Strip Wire #2.

4. Crimp on Male Wire Tab Connector to #2 Wire.

5. Use these style wire tap for a fool-proof tap. The best wire taps money can buy, IMHO.

6. Crimp on Wire Tap onto Wire #1. Crimp far enough downstream to allow for the ease of Step #7 below.
FYI, I barely left enough room for mine, but for you guys, go further downstream (See Step #7).

7. Connect up Male Wire Tab to Wire Tap & Tape raw end of Wire #2.

8. Done, in 5 minutes time. Fogs w/CityLights Mod...
Whooot !!!!

Original Thread w/ Discussion: http://www.audizine.com/forum/showthread.php?t=124446

08-21-2008, 05:57 PM
is this feature with the parking lights or as day time runing lights?

08-21-2008, 07:16 PM
i wasnt sure wat citylights were but i searched around and found out i dont have them so how do i make this work for my car. (03 a4)

09-18-2008, 04:37 AM
DOES anybody know if this will still allow the fog lights to power on when you Unlock/Lock the car with the remote???

09-18-2008, 04:44 AM
Will this allow the fog lights to still power on when you Unlock/Lock the car with the remote????


11-14-2008, 11:37 PM

Can you please explain what exactly it is that this mod does ?? Does it allow you to switch on your fogs, even if your park lights are not switched on ?? Or does this mod permanently switch on your fogs as daylight driving lights ??

11-27-2008, 08:26 PM
Can you do this with out the VAG tool ?

Bit of a Newb to the audi world.

11-28-2008, 07:58 PM
Do you need the VAG tool for this?

01-12-2009, 01:00 PM

02-19-2009, 07:44 PM
that looks sick..but if i do that will i still have fogs for low beam use? and what do you do with the other end of the wire you cut?

03-14-2009, 07:01 AM
i just found this thread and i'm doing it TODAY haha

03-24-2009, 07:17 PM
Great DIY, just completed it, took 5 mins max. Love the site people keep the DIY post coming.

04-07-2009, 07:29 PM
Very exact tutorial. Great pictures. Thanks![up]

04-21-2009, 12:57 PM
would this be the same for halogen set up?? to run fog lights with parking lights??

05-04-2009, 03:27 AM
I did this on my B7 (2005.5) and it works, however when my lights are set to "auto", the green light behind the "auto" text flickers. Is this a simple loose or poorly connected wire problem or something else?

Winners Eat Pho
11-15-2009, 05:12 PM
Wonderful! This weekend it will be mine!

04-25-2010, 03:57 PM
Did you have to VAG your car to RDW before splitting/jumping the wire, like FatAuto did?

06-27-2010, 08:24 AM
I know I'm reviving a thread that's over 3 years old [o_o], but I'm not the most electrically inclined person. I read the below from Eddie Man, but it doesn't mention anything about having to VAGCOM, in order to getting the fogs to work separately....the post from Fat Auto does. Do you guys know if I can get the fogs to work separately, WITHOUT Vagcom'ing it?

Thanks for your help in advance!

03-17-2011, 09:08 AM
Looks like its a mod for US cars only, I assume ROW has this as a standard feature?

06-30-2014, 12:10 PM
From what i gather, this leaves the fog lights on all the time and removes the function of the fog switch on the dash. .

If I am incorrect please let me know. Also. What did you do with the #2 wire that was cut going down into the harness? Is this just left cut off?

If I were to do this mod I would jump the connection the same way as shown here without cutting any wires or cutting them to put a bosch relay in between. When the relay is activated the relay could close the connection to return the lights to normal function. When open it can be wired to supply the voltage to the fogs and have a switch to turn them on and off. This way you could turn the fogs off if you would like and the switch would retain its functionality.

To shut them off one would need to flip the switch which would close the relay connection and the lights would return to the stock function. This would be a lot more practical. You would be able to have the fogs used as DRLs and shut them on and off as pleased without losing the DRL's in the headlight switch. The switch when turned to headlight and pulled for the fogs would retain their normal function when the foglight switch is in the off position.

Any thoughts? We could write up the diagram pretty easy, I would just need to sort out which kind of relay and label the inputs/outputs. Would need to sit down and look it over but this should be a super simple mod and a lot better than being stuck with fogs on all the time and no functional fog switch in the dash. .

***Side note:
As a mobile electronics certified professional I have to advise against the use of a wire tap. These are terrible and cause electrical havoc and meltdown half the time. It is cheap to get a pen sized solder iron, use a sharp pic tool to poke a hole straight through the wire that you want to splice in to, no cutting needed and no pinching of the wire from the clamp on splicer. Feed a bare pigtail of wire through the hole you created in the main wire and warm it up, let the solder suck into the joint. Zip tie the pigtail to the main wire sideways with tiny zip tie. (now it isn't going anywhere) and wrap with a little electric tape for protection and finish.

_______ Pigtail/wire you are splicing in
--------------------------------- Main wire
Use sharp pick tool to poke a hole through the main wire large enough to feed the bare end of the other wire you are connecting through it.
Squeeze the little hole around the spliced in end you feed in, solder, zip tie down with tiny zip tie and cover with real electric tape.

You now have a solid spliced three way without removing the rubber from the wire or compromising the integrity of the strands within.

07-01-2014, 11:14 AM
There is a much better way to do this without cutting wires, I wouldn't do it this way at all

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08-04-2014, 12:42 AM
There is a much better way to do this without cutting wires, I wouldn't do it this way at all

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and how is that done?

08-05-2014, 09:42 AM
Yes - please share.

08-10-2014, 04:34 PM
FYI on not cutting any wires:

I tried piggy backing a wire without cutting- it allowed the fog lights to work with the city lights.. but for some reason my left low beam was not coming on. Voltage / resistance was fine. I traced it from the headlight harness to the switch. Everything checked out okay.

I ended up trying to source the problem and just cut the Yellow/Black wire and the low beam came back on and fog lights now work with the city lights!

In my case there wasn't an easy way to do this mod without cutting. Hope this helps.

08-11-2014, 01:43 PM
and how is that done?

Yes - please share.

He is probably talking about this method:


Just uses some electrical tape and a bit of wire, only takes a few minutes. If your headlights start acting crazy though, it likely means the tape has slipped off the pin.