B7 Audi A4/S4/RS4 Reverse LED Lights DIY
Somewhere along the way, I was told that switching any bulbs in the tail light assembly would throw a “bulb out” warning no matter how hard you tried with resistors, so I never bothered – low and behold when I was browsing Audizine one day I found that myth to be busted with a user sharing his experience in what seemed to be a very easy DIY…so I bought the parts and am happy to report back similar success! I’ve included the exact products I used and a few extra pictures so that those who want to try this mod can follow along and see exactly how it’s done, so I encourage you to check out both the original post and my instructions below!
This is a write-up should work on any B7 Audi A4, S4 or RS4 from 2005.5-2009, although I haven’t tested on a cabriolet to confirm. If you’ve ever used a resistor before, this is a very easy DIY that should take no longer than 15-20 minutes per side and requires no special tools other than a wire stripper. If you’ve never used a resistor before, fear not as I’m going to go into a lot of detail about what they are and how they work so that you can follow along. Overall the mod is mostly for aesthetic purposes, and I have to admit it looks pretty cool – in terms of backing up, it might be a little brighter but nothing that is going to be dramatically different either way.
Step 1 – Buy the Correct LEDs & Resistors
First, you’ll need to pickup two 50W 6Ohm resistors (one for each side), plus two 1156 Reverse Bulbs that have a 360 degree light output. I purchased everything from Amazon using the links to the right. Resistors must be matched to both the LED bulb and the bulb it is replacing to create the “correct” amount of current the computer is expecting to see, so sometimes different bulbs can require different resistors – but this seems to be a very safe combination…
Step 2 – Remove the Tail Lights
This step is pretty easy and requires a flat head screw driver – the instructions are the same as the tail light DIY I’ve already posted, just follow steps 1-3, then disconnect the harness so that you have more working space. I also recommend wiping everything down with some spray detailer while you have the tail light removed, as it allows you to get all of the nooks and crannies you can’t reach normally.
Step 3 – Change the Bulbs
This step is very easy – the back of the tail light pops out by pressing in two tabs as pictured above, the the backing pulls off. You do not need to use much pressure for this step.
Once the back pops out, take the reverse bulb and push in and turn left to unscrew, then place the new LED bulb in and press down and turn right to secure it in.
Step 4 – Add & Test Resistors
In my other LED related DIYs, such as the DRL and License Plate write-ups, I get a lot of questions on how exactly to connect the resistors, so I’m going to go into a lot more detail here. On a conceptual level, you use a resistor to “bridge” two wires together, and this acts as a load balancer and adds a little extra electrical draw to counteract the LEDs drawing less power normally. Without the resistor, the system sees the new bulbs require less power, and incorrectly report a “bulb out” warning due to the bulbs requiring less electricity than expected. The resistor bridges these two wires and makes it so the system sees more current.
Start by stripping the blue wire with a red line, as well as the brown wire – these are the two wires you’ll bridge together using a resistor. You’ll want to expose about a half inch of wire to make it easier to use the connectors for the resistors, such as I’ve done above.
The resistor itself will have two wires coming out of each side – take one end and place into the connector in the outer most position, then the wire you want to tap into (the blue/red wire pictured above) for the other slot in the red connector. Make sure both wires are exposed where the metal clamp will come down, the tighten the connector to make sure that metal clamp is touching both exposed wire, thus creating metal on metal contact. Do the same for the brown wire, and you’ve now bridged the blue & brown wires with a resistor in the middle. Each side requires only one resistor, but two of the red connectors – one connector taps into the blue/red wire and one of the resistors wires, and the second connector taps into the brown wire and the second wire coming out of the resistor.
Lastly, mount the resistor itself using double sided tape somewhere low and out of the way so the tail light can go back in all of the way. Before firmly pressing the tail light back into place, turn the car on and put it into reverse with the tail light harness reconnected just to make sure you don’t have a bad connection, as the connectors can be a bit finicky and you need a solid connection for it to work. Once you’ve confirmed it is working, use pliers to press down on the resistor and ensure it is fully tightened and won’t wiggle, then wrap it all up with electrical tape to prevent a short and give it a little extra security.
Aha! You got around to doing this, that’s awesome. I remember I asked you about this exact DIY a few months ago. This is extremely helpful, thanks Nick! 🙂
Do you think there’s a bulb out there that will significantly increase light output? Seeing through my tint can be tough sometimes.
Btw, thanks for all the DIY post, Nick. I have to admit that your car swayed me from DG to BR. I have a lot of work to do though because like you, I hate chrome, especially on red.
I kind of doubt it RJ, the bulbs get plenty of power with or without resistors so the bulb out error will likely be more of an annoyance than anything – you’re welcome to give it a shot and prove me wrong though 🙂
And you’re quite welcome, you made the right choice with BR!
What brand or type of double-sided tape did you use for mounting the resistor? About to get this mod done and want to make sure nothing burns or melts afterwards. Appreciate the help!
I just used 3M Exterior/Outdoor mounting tape, it’s super heavy duty: http://www.amazon.com/gp/product/B00004Z4BV/ref=as_li_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B00004Z4BV&linkCode=as2&tag=niscabl-20&linkId=RHP2HVCF6S5CVCHN
Thanks a lot! I really appreciate the help and all the instructional assistance.
My pleasure, Kevin!
Would it be possible to do that to all the rear bulbs ?
As in the tail lights? From what I’ve been told, no, but I haven’t tried myself. Most people just buy LED tail lights if they want to go that route, such as what ECS Tuning or eBay sells.
But if I wanted to replaces the stock bulbs with led bulbs for the rest of the light cluster as in turn signal and brake lights… Would I need to wire other resistors in ?
I dont like the eBay /ecs cluster. And plus there a bit pricey.
But I do like the brightness and quick on/off time of leds.
Yeah, you’d likely need additional resistors for each bulb you replace, but as far as I know this is unchartered waters so not sure what resistors and bulbs you’d need here. There was a guy named “unslanted” on Audizine who took the aftermarket LED tail lights on eBay and split them in half and then mated the OEM lenses/outers to the aftermarket LED inners to make lights that looked OEM on the outside but were the aftermarket LEDs on the inside. It was pretty cool and worth considering if you can pick up a set of stock tails for cheap that you’re comfortable chopping up…or if you try to just replace the bulbs let me know how it goes, would love to post up the DIY here!
Yeah nick I’ll look into it. To be honest I haven’t even looked at the wiring harness to the back of the tails. But from the picture it looks like there is just one cable to the taillights… And since there is a resistor in that one harness where on earth are the rest gonna fit. I did however do this on a mk4 golf (no resistors or anything needed ) and it looks amazing. Instant on / off (looks really good on the incidators)…. And super bright!
Sucks that I suck at anything electronical! Fall in this idea haha
I did this but the resistors I used where 25w6rj and those things got really hot. As in I took a thermometer and peaked 210°f. I know it might be the resistors but did the one’s you slapped on got hot what so ever ?
Yeah they got really hot too – all resistors do, that’s a sign they’re working. Yours are actually lower wattage than mine and same ohms, so I’d think yours are probably a little cooler than mine. I still haven’t had any issues or problems with mine and going on a year now…
Good write up! I saw the question posted above but by this time, has anyone replaced the tail light and indicator with led bulbs?
Hi Reeza – the most common way to do this is to go out and buy LED Tail Lights from ECS Tuning or eBay – I haven’t heard of anyone replacing just the bulbs, they typically go for an aftermarket tail light at that point. The ones made by JOM sold by ECS Tuning look pretty decent IMO, but I prefer the stock look. I’ve also seen people mate the back end of the LED tail lights with the lenses of the OEM ones to keep a stock look but with LEDS behind it…
Since its JUST a reverse bulb will the bulb out buzzer only beep when in reverse ?
Hi Chris – I can’t confirm based on first hand experience since I installed the resistors right away, but my understanding is that the system checks all of the bulbs on start-up and current runs through the bulbs whether on or off, so there is a decent chance it will come on regardless of whether in reverse or drive/neutral. That being said my DRL bulbs only throw an error when the DRLs are turned on, so there is a chance you wouldn’t need em – but I’d just go with resistors, they’re easy to install and you won’t need to fuss with it again.
I’d love to do the brake and marker tail lights as LEDs, but I noticed they are not double filament bulbs like everybody else uses on other cars. That means Audi is changing the bulb brightness using either voltage or dwell pulsing. I don’t think an LED would react correctly. It would probably be on full bright all the time if it worked at all and didnt freak out the computer.
Correct. The only way to change the brake bulbs that I know of is to change to an aftermarket unit (or swap out all of the internals with one), but the aftermarket units don’t look as clean IMO.
what does each wire do??? what is each wire???? like brown equels what light or green wire equals what light???? I need help? ASAP
Fairly sure that blue & brown are both for reverse, and usually black is a ground, so the other two are probably the brake bulbs. There will be two wires for each bulb.
Okay but i have a 4 bulb back plate right so does that mean if i need to connect a trailer hitch wire I would have to connect two wires and then the wire from the trailer light? For the four pin?
Oh man I have no idea on a trailer bulb wiring, I wouldn’t think you’d tap into a tail light for that. Maybe check out this link instead: http://www.audizine.com/forum/showthread.php/493283-B7-avant-trailer-hitch-wiring-install
Do you know what gauge wire is in the factory 5/6 pin connector?
I believe it is 18 gauge, like this: http://amzn.to/2BUxFD9