After fog light retrofit?

[stefanhal]

Has anyone added aftermarket fog lights to a C7 with ACC? Every time I drive through fog or a snowstorm, I am reminded how disappointed I am in the penetrating power of the LED lights, and wish I had fog lights. I finally had enough and ordered some Diode Dynamics SSC2 Pro amber fog lights. Just debating the best mounting positions now.

I know the radar modules are in the normal fog light spots, and wasn't sure if anyone has added aftermarket fogs elsewhere on the car. I did search the forums but didn't see anything. I am thinking of attaching them through the honeycomb grill next to the ACC modules. Passenger side would be no problem -- the vent is blocked off behind the grill anyways. Only one I was potentially worried about is the drivers side -- there is an air duct behind the grill leading to a radiator. I am not sure what that radiator cools, but I don't believe the small size of the SSC2 pods will obstruct very much airflow.

Anyways, just wondering if anyone has some helpful suggestions before I start hacking things up. Also, I don't want this to turn into a thread about whether or not these cars need fog lights -- for your uses, it might not matter at all, but I believe they would make a significant difference in visibility for the conditions I sometimes find myself driving through.

[tuscani66]

Not sure where you could put them, not sure which C7 you have, but if you place them in an area that looks to be about right make sure you can still make adjustments (pitch/yaw or up/down left/right etc). Hate if you found an aesethetic location to place them but unable to make adjustments and just shines where you don't need it.

I debate foglights, even though the cornering lights are supposed to help/act like foglights, constantly; two of my DDs doesn't have fogs and bothers me.

[japanada]

I have a c7.5 w/o the ACC and have contemplated getting the ACC grill inserts and putting fogs in them.

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[rtbrjason]

I was disappointed to find mine didn’t have fog lights. I didn’t even look for them when I test drove it, just assumed it would have them. My 11 TT and 13 Q5 do. Not sure what if anything I’ll do about it. Those diode dynamics are really nice though. Almost bought some for my Ford Excursion but ended up selling it before I got to it.

I’m not sure what acc is but I don’t think I have it. Mine doesn’t even have a drop down door in the upper console for my glasses.

[japanada]

I was disappointed to find mine didn’t have fog lights. I didn’t even look for them when I test drove it, just assumed it would have them. My 11 TT and 13 Q5 do. Not sure what if anything I’ll do about it. Those diode dynamics are really nice though. Almost bought some for my Ford Excursion but ended up selling it before I got to it.

I’m not sure what acc is but I don’t think I have it. Mine doesn’t even have a drop down door in the upper console for my glasses.

ACC is adaptive cruise. The little eye ball things in the lower side grills

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[stefanhal]

Attached some images of my first prototype. It will probably be a couple more revisions before I get a final version I am happy with. There are a couple areas where the fit could be a bit better, and I need to fine tune the vertical and horizontal angles. For this version, I tried to approximate the ACC lamp angle, and will need to fit it on the car to get the angle right for the final version.

In this version, I made all the walls very thin in order to save on resin, as I was just testing for fitment and don't need the ultimate strength and durability for this prototype.

For the final version, I think I will need to spend the money and get the Formlabs 10k resin. I was hoping to avoid buying this, as their 10k resin is super expensive. However, these lights get very hot -- I powered up the light for an hour sitting on my desk, and the heatsink registered about 200F at the end of the hour. I know it shouldn't get nearly that hot during operation on the car, as there will be airflow around it. However, I try to design my stuff to last and for "worst case scenarios". Given the heat, the only resins rated to withstand 200F appear to be the high temp resin, or the 10k glass reinforced resin. I figure the extra cost of the 10k over the high temp is probably worth it for the increased strength and stiffness -- it's pretty close (in terms of specs) to the OEM plastic used by Audi in many areas around the engine bay, and it would still come out cheaper than getting this SLS printed by a manufacturing house.

IMG_5837.jpgIMG_5836.jpgIMG_5835.jpgIMG_5833.jpgIMG_5834.jpg

[Alabama]

Attached some images of my first prototype.

Keep going; this is clever. For no good reason I have a fond attachment to PIAA on past cars but had no idea how to mount them reasonably on a C7 S6.

[rtbrjason]

I came across these on eBay.

https://www.ebay.com/itm/Lower-Bumpe...-127632-2357-0

It says they only work with acc unless you know how to modify them. Not sure I want a random switch installed in this car for them. For the money, they might be worth trying. Possibly wiring them through a relay to just be on when the car is running.

[pstuu]

I have Diode Dynamics SS3 on my A6 without ACC

IMG_1769.JPGFullSizeRender.JPGIMG_2359.JPG

[japanada]

I have Diode Dynamics SS3 on my A6 without ACC

How did you wire them in? I was thinking it may be possible to wire them into my factory LED fogs in the headlights on my C7.5 S6. Also did you buy the audi ACC grills?

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[pstuu]

How did you wire them in? I was thinking it may be possible to wire them into my factory LED fogs in the headlights on my C7.5 S6. Also did you buy the audi ACC grills?

Sent from my SM-G998U using Tapatalk

Yea I got the grills off eBay and the harness runs to it own independent switch under the dash to avoid coding issues

[petarat]

Where did you put the switch? I've been thinking about putting a single tall light bar somewhere behind the grill but I can't think of a good spot to put the switch for it that isn't in your face as aftermarket or somewhere that's not gonna get bumped by a leg.

[pstuu]

Where did you put the switch? I've been thinking about putting a single tall light bar somewhere behind the grill but I can't think of a good spot to put the switch for it that isn't in your face as aftermarket or somewhere that's not gonna get bumped by a leg.

I have the switch mounted under the dash, no problems with hitting it with my leg

[stefanhal]

I think it should be possible to use the factory fog light button to switch lights on/off, but I'm curious if anyone has done it before. From what I could tell based on wiring diagrams, the oem lights switch communicates over a LIN bus connection. I took a brief look at the LIN bus comms protocol, and it appears to be a one-wire protocol and comms are only initiated by the master device, and not the slave device. From this, I assume that the master electrical control panel polls the light switch "slave" device for any button presses on a regular interval. It should be possible to sniff this communication with an arduino (or custom microprocessor circuit if you're capable of designing/building it) and drive a relay whenever you detect the "button on" communication.

This is all theoretical so far, as I haven't gotten to the stage where I am working on control circuits yet. But I will update once I get there. If anyone has done something similar and has advice, I am all ears. One thing I am not sure about -- there are four wires going into the light switch. One for ground, one for power, one for LIN bus comms, and an unknown fourth wire. Anyone know what the fourth wire is for? I did order an extra headlight control switch off eBay so I can try to investigate this further without removing the switch from my car whenever I have some free time to play around with it.

[stefanhal]

Quick update in regards to the electronics. I decided to make an adapter to tap into the LIN bus, instead of hacking a splice into the stock wire harness. This way it's very easy to remove and install, without impacting the stock harness at all.

The spare headlight switch I ordered off eBay came with a wire pigtail attached. I used that, then designed and 3D printed a mating plug housing. I just used standard header pins on a small piece of cut out PCB. The only long-pin headers I had were cheap ones from China, which I kind of regret using because they have a flatter, more rectangular "stamped" metal profile, whereas the OEM pins have a more square profile (like the higher quality TE/AMP pins you can buy). I did have some nicer TE/AMP pins, but they were of the shorter 6mm length. They would have still made contact with the plug, but they would be shorter than the OEM pins. So, I went with the cheaper import pins instead -- they still make contact just fine, but the flatter profile bothers me a bit. Used epoxy to locate/hold the PCB securely in the housing, and hot glue to fill the rest to give some extra strain relief to the wires.

If I were going to do this again, I think I would do it the "proper" way -- i.e. using genuine TE plugs and pins. It is just an MQS plug, which is a current and stocked item at most online warehouses. The stock plug with female terminals (what is currently on the OEM wire harness) is model number: 1670988-1. Audi also has their own PN on it: 8K0 973 754. This TE part seems out of stock at many online retailers (probably supply chain issues), but the Audi part number is in stock at a few places. The receptacle that takes the male pins would be TE part number 936121-1, I believe (didn't order it so I can't 100% verify). You'd need male pins as well, and here is an example that I believe would work: 963730-1. But obviously order the pins for the wire size you're using. Also, if you've gone through the trouble to do it right, don't do a half-hearted job with the crimping. Please don't just squeeze it with pliers. The proper crimp tool, I believe, is TE 58611-1. Stupid expensive when new (all really good crimpers are), but sometimes you can score one on eBay for cheap if you get lucky. A cheap set of open barrel crimpers off Amazon would likely also do the job (and certainly do it better than pliers).

Haven't had time to fully analyze the LIN bus data yet, but I believe the fog light switch reports on pid 0xC, but I could be wrong. I am still a little bit confused by this pid, as I only seem to get 6 bytes of data sent, which doesn't seem to match up with LIN specs. I will try to do some more analysis on it this weekend. If anyone else has info on it, please share. I attached an example capture.

0xC_Cap.jpgIMG_5854.jpgLight_Switch_Plug.jpg

[Dr.Chill]

I'm grateful to have found this post, yet I still have questions. The unconnected three wire pigtail directly behind the ACC is JUST for the ACC, right? I thought I could wire in my aftermarket fog lights (with an angel ring and multi light color center) yet I blew a fuse to the "front fog light" button. I was thinking I might have to run a separate set of wires, relay, and fuse to that switch. Then, I read about the LIN bus, comms protocol, slaves, cheap China pins, and all of that is way over my head. Am I too naive to hope that I can just simply wire it to the switch with a simple setup? I should mention the fog lights I purchased have a remote, so the switch would only be connecting power or removing power.

[stefanhal]

I'm grateful to have found this post, yet I still have questions. The unconnected three wire pigtail directly behind the ACC is JUST for the ACC, right? I thought I could wire in my aftermarket fog lights (with an angel ring and multi light color center) yet I blew a fuse to the "front fog light" button. I was thinking I might have to run a separate set of wires, relay, and fuse to that switch. Then, I read about the LIN bus, comms protocol, slaves, cheap China pins, and all of that is way over my head. Am I too naive to hope that I can just simply wire it to the switch with a simple setup? I should mention the fog lights I purchased have a remote, so the switch would only be connecting power or removing power.

If you want to use the stock fog light button, I don't think there is an easy way of doing it. That's because the stock button does not act like an on/off switch. There is actually a circuit board on the light selection switch area that acts like a mini computer. It communicates with the rest of the car via LIN bus. The fog light "switch" is just a momentary contact that tells this circuit board that the user depressed the fog light button; the circuit board then communicates over LIN bus that the fog lights were requested to be turned on. I didn't spend the time to fully decode the protocol, but I believe a central processor receives this data packet informing it that the user requested fog lights, and responds saying that this request has been received, turn on the indicator light. Then the circuit board turns on the indicator light on the button, letting the user know the request has been completed.

All that to say, there is not a good way of using the stock buttons without decoding the LIN bus. Something like an Arduino would be the easiest and most affordable solution. The Arduino would decode the LIN bus comms, and then can trigger a relay to turn on/off your lights.

The easiest option would be to install your own physical on/off switch somewhere around the dash.

One potential option I never explored was to tap into the headlight harness and use the power going to the "fog" lights (I believe they are called "all weather" lights by Audi and are really more wide angle cornering lights than fog lights) to trigger a relay which powers your own fog lights. Couple things to keep in mind here -- the all weather lights turn off automatically at highway speeds. I don't know what the exact cutoff is, but I believe it's somewhere around 50 or 60mph. There is also hysteresis here (it turns off at a higher speed than it re-activates at, to avoid constant on/off when you're traveling right around the setpoint). I don't know which wires on the harness control the all weather lights, and where the easiest access point is for them. The all weather lights can be enabled to turn on when cornering -- if you have this option activated and you have tapped into this as a signal wire for your true fogs, your fogs will turn on whenever you turn the wheel going around a corner.