Home / DIYs / LED License Plate Bulb Options for a B7 Audi A4 & S4 (2005.5-2008)

 

LED License Plate Bulbs

Based on the popularity of my LED Interior Lighting post, and by popular request in the comments section, I decided to write another guide for LED License plate bulbs on a B7 Audi A4, S4 and RS4. They definitely look awesome, and are a relatively cheap mod at ~$30 total. Best of all, installation takes merely a few minutes and all that is required is a small screwdriver in most cases.

The trouble with this mod is that the with some B7 models (any A4, S4 or RS4 from 2005.5-2008), the installation of these bulbs sometimes causes a Light Out error. Personally, I installed mine and never had any problems with a bulb out error message or flickering issues, and I’ve talked to countless others who have never had problems either, but there are more than a handful of examples of those who have posted on Audizine who did encounter problems.

There are many theories as to which models or trim packages throw the Bulb Out error and which don’t, but from everything I’ve read, it’s mostly just luck of the draw/random. Many believe that if you have the multi-color information display in your gauge cluster (the LCD screen between your speedometer and RPMs) you are more likely to have an bulb out warning message, although Bulb Out errors do occur for the non-color version (those with only red colored pixels only).

Regardless, here are my recommendations – IMO it’s worth trying your luck as you can always revert back to the OEM halogen bulbs if you get a bulb out message, learn to ignore the bulb out message in your gauge cluster, or install an extra resistor to avoid this (more on this below). A few others have reported flickering issues with LED license plate bulbs, which can also be fixed using resistors.

For bulbs, look for a 39mm Festoon bulb that has a BUILT IN RESISTOR, or plan on purchasing your own resistor or load balancer to eliminate any issues. The built-in resistor is critical, as it will greatly reduce the chances of a bulb out message. The two options I’ve seen with the best reviews and success rates are

Option 1 – Buy “Error Free” LED License plate bulbs. Note they are not always error free for B6/B7 Audis due to our electrical systems, although they are less likely to cause errors than the typical 39mm Festoon bulb:

  • 42 Draft Designs – this is what I’ve been using for ~2 years without problems. They say on their site not to use these bulbs for a B7 A4, but that’s just so they’re not liable to accept returns in the case you get a bulb out error – essentially, you must assume all risk they might not work or work but product codes.
  • TunerDomes – their bulbs also include built-in resistors to help prevent error codes. I haven’t tried these personally but know a few people who run them. Like the 42 Draft Designs bulbs, a lot of people are running these successfully without any codes or errors, but a few here and there have reported error codes or flickering – again, it’s really kind of luck of the draw….(read a review here on Audizine from user Quattro)
Option 2 – Buy standard LEDs and install resistors 25 watt 10 ohm resistors. You can buy these on Amazon using the links below – be sure to get two bulbs but you only need one resistors. You may need the resistor regardless, especially if you have navigation or the color display in the dash. On my S4 I got a bulb out warning even though I was using “error free” bulbs – these bulbs were actually error-free in my 2006 B7 A4 strangely enough!

Bulb Installation: lift up your trunk lid, remove your license plate for a little extra wiggle room, then remove the two screws holding the light cover in. You’ll probably need a specialty screwdriver like the ones used on eyeglasses as its a very small screw. Then pull out the old bulbs and snap in the new bulbs. Be sure to test it before re-installing the light covers, just to make sure the bulbs are making contact (you may need to bend the contact points of the base) as well as to see if you get any bulb out errors first.

Resistor Installation: if you need to install resistors, you’ll need to remove the liner of your trunk to access the wires. There are two screws that come out using a Phillips screwdriver, pictured below. One is below the trunk release handle and the second one is in a similar location on the opposite side of the trunk. Once the screws are removed, then there are four clips on the top edge and four clips on the bottom edge which will release when you firmly tug near each clip.

LED License Plate Bulb Install Audi A4/S4

LED License Plate Bulb Install Audi A4/S4

Once the trunk liner is pushed to the side, install the resistor. You’ll want to tap the brown wire and the purplish-gray wires that are furthest to the left of the harness. I found easiest to remove the harness to install the resistor first.

LED License Plate Bulb Install Audi A4/S4

I find it works best to strip part of the brown wire and gray/purple wire first so the resistor makes good contact, as I find the red-plastic splicers don’t always cut all the way through. It doesn’t matter which wire you attach to which, just make sure the resistor bridges the brown wire and gray/purple one. Warning: the resistor gets VERY hot VERY quickly so don’t touch it once you’ve turned the lights on. I mounted the resistor using 3M double sided tape and then plugged back in the harness and turned the car on to test that the lights still turn on and no error warnings – success! If you still get a warning, go back and check our connections and make sure the exposed wires are lined up correctly within the red plastic splicer.

LED License Plate Bulb Install Audi A4/S4

Disclaimer: I’m not responsible if you buy any bulbs and they don’t work, nor any damage you may cause to your car while working on it. Any modifications you perform on your vehicle are done at your own risk. That being said, there isn’t too much of a risk of causing any damage here, except you may be out the cost of LED bulbs in the event they flicker or cause a bulb out message.

LED License Plate Bulbs

 

About the author: Nick Roshon

 

Nick Roshon is a blogger who is passionate about Audis and European cars in general. He owns a 2006 S4 and before that had a 2006 A4. His driving experience includes numerous track days throughout California, Nevada and Arizona. In his day job, Nick is a digital marketer and lives in San Diego, CA, USA.

 

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47 Comments

  1. Hi,

    Quick question, you said to look for a 39mm bulb and meanwhile the 42 Draft Designs link connects to a 42mm bulb. Which size will work in the b7? I just ordered to 42mm and then saw that you said 39mm

  2. Yeah you’ll want 39mm bulbs. I must have linked to the wrong product, I’ll update that now. I’m really sorry about that – hopefully you can return them before trying to install – 39mm is kind of a tight fit so there is a good chance 42mm will be too big. Really sorry dude…

  3. No worries man! Thank a lot! Your blog is sick and your car is looking fresh

  4. Thanks Matt! Really appreciate it :)

  5. Hi Nick,
    The one on your car (pictured on the page), is it the blue or white led? I would like to mimic that of the lexus color.
    Thanks

  6. Those are the white, believe it or not. I think they used to call it “Cool White” but now it’s just listed as white. Hope that helps and be sure to let me know how it goes and what you think of the color….

  7. Hi Nick,

    I got the led’s for the license plate. They look great, but unfortunately, the light error message came up. I looked at the website to add the extra resistor, but that seems like alot of work. Any other ideas? can this be fixed via vag-com?

    Thanks,
    JR

  8. Nothing in VAG COM to help unfortunately – you’re only options are the resistor or just live with the light out warning…wish that wasn’t the case :(

  9. Pingback: Featured Ride: Ryan’s B7 Audi A4 | Nick's Car Blog

  10. 42 Draft High Intensity 39mm in Cool White have been sold out for some time. Cool White in the regular 39mm are sold out as well, would these work though just in case they come in before the High Intensity? Any other suggestions beside the two mentioned above?

    Thanks!

  11. Really any 39mm LED with a built-in resistor should work, I think there are several other brands that make them – look for something that is supposed to be Error Free or has a CAN-BUS installed. Something like this might work nice: http://store.ijdmtoy.com/Audi-A4-Error-Free-LED-License-Plate-Lights-p/led_01_sku29.htm

  12. I bought a pair of 39mm from 42 Draft Designs, the built-in resistor does not work?
    what should i do? Is there any brand out there is workable?
    Thx!

  13. It doesn’t work as in the bulb doesn’t come on at all? Or it doesnt work in the sense of the LED turns on but you get a bulb-out warning. If the former, return the bulb, its probably defective. If the latter, you’ll need to install a load balancer or extra resistor.

  14. it is working, but the LEDs are flickering & have bulb-out warning too.
    I guess I have the mutli-colored Dash (red & orange).
    thx for reply; it is a nice blog.

  15. Hey Nick,

    I’ve tried a few different brands of 39mm led bulbs but none seem to work. I heard it could be due to having a navi system? I was wondering if the 42 Draft Design bulbs have built on resistors. I have a ’06 audi a4 non s-line with navi package (multi-color display). Any help would be great!!

  16. When you say they don’t work, what do you mean by that? Do they flicker, do they cause a bulb out error, or do they not light up at all? The cars equipped with Navi and color DIS (driver infomation system, the screen in between your speedo & tach) tend to have a harder time with the LED license plate bulbs for whatever reason, but I know it can be done as my buddy Blake has them on his RS4 with navi + color DIS, he just had to add an extra load balancer to get the bulb out error to disappear.

  17. It lights up, but with any bulbs i’ve tried the error message comes up. Ima try and put a the load balancer and see if that works.. Thanks again!!

  18. I know this is an old post, but I was wondering if you Nick, or anyone else had trouble removing the damn license plate screws. I bought the the bulbs over a year ago but i gave up on the initial install because i couldn’t get the light cover off and started stripping the screw. Frustrating but i have no other ideas and i left the halogen bulb as is for the time being. I read in different places people strip the screws and end up replacing the whole license light housing, which i am trying to avoid.

    thanks in advance

  19. I remember them being tough too. I went to the hardware store and picked up a set of smaller screwdrivers intended for eyeglasses and such, and then just used a lot of force to hold the screwdriver down while I twisted. In my opinion its easier to unscrew them with the trunk halfway open – consider getting a buddy to hold the trunk in that position while you use the screwdriver.

    If it does strip, you could probably drill out the screw, then just replace the screw itself. I don’t see why you’d need to replace the whole housing for that…

  20. Any idea on whether 42 draft design bulbs will work with the resistor from the link above?

  21. The 42DD bulbs may not need any resistor at all; if it does, I’d give the ones above a shot. If those happen to be overkill you can always downsize the resistor some.

  22. Hey Nick, I hope you still check here.

    Basically, I cannot get 25w10ohm resistors locally and I am bringing my B7 to a mechanic tomorrow to do this for me. I CAN get 25w5.6ohm resistors though, and I am wondering if you think they will work?

    Also, do I need to get a special guage of connector wiring to wire it correctly? Lastly, shouldn’t I also heatshrink the resistor and the wiring to double side tape them easier and to prevent fire from how hot the resistor will probably get?

  23. Hi Damir,
    Of course I still stop by!

    Those resistors should be fine, although you wont’ know for sure until you plug them and find out. There isn’t any risk of trying as they’re close enough, so hopefully they’ll do the trick. It’s not an exact science in the car is looking for a certain range of electrical current flowing from these bulbs, so too much current is bad and too little current is bad but as long as you’re somewhere in between it should be fine.

    The resistor will get very hot and melt anything you put on it, so keep that in mind.

  24. Wow, thanks for the quick response Nick!

    So if they do get very fast, how did your 3M double side tape hold up?

    I went to a local electronics shop and spent some time with an older gentlemen who seemed knowledgeable. He suggested that I use silicone glue to attach it to the bar metal of the trunk if the resistors will be getting hot, because they will burn any tape near them. Apparently silicone glue holds up well to heat.

    Also, did you ever have to replace your resistors? How long did you have them installed for? Apparently, they die quickly if they are heated up.

  25. @Damir – I’m still on my original set of resistors, so far so good. I have no idea if the double sided tape is still holding or not, but as far as I can tell it seems to be doing fine. The glue is a good idea, I like that…

  26. Alrighty, thanks again for the reply Nick. We’ll be tackling this tomorrow actually so I’ll post back if we ran in any issues :) For reference, how long have yours been installed for? Has it totally eliminated the bulb out error or is it still triggered sometimes?

    Thanks for the guide!

  27. @Damir – my pleasure. The resistors have been installed since March 2012, so about 7 months now. I haven’t had any warnings since they’ve been installed, not even a temporary one.

  28. Update: error is gone using 2 x 25w5ohm ceramic resistors. Costs to get this done was not cheap, nor were the resistors easy to find locally.

    Paid ~$10 for the LEDs
    $30 for electrical supplies to get this DIY done (including the silicon glue)
    $60 for an hour of my mechanics time to get it done because I don’t know the first thing about electrical stuff like this

  29. @Damir – thanks for the update, and glad you found something to work.

  30. Hey nick,

    I used the same resistor you did, and it does get HOT. I checked it with an IR gun, and it gets upwards of 220 degrees. It’s touching the trunk, and after being on for about 25 minutes, the outside of the trunk is almost too hot to touch. Is this anything you, or anyone else has run into?

  31. It’s normal for the resistor to get super hot like that…it’ll definitely burn your fingers if you touch the resistor directly. In terms of the entire trunk getting too hot, I have not had that issue. That’s very odd. I’ll test again after a long night drive, but maybe you may want to try to mount the resistor on a bracket and not on the trunk directly if that continues…

  32. I noticed you used the two sided tape to mount it to the trunk, I’m sure that’s insulating it. I had it touching the trunk metal directly to let the trunk act as a heat sink for the resistor. That may not be the way to go. I’m going to get out in the garage in a little bit and rearrange the resistor so it is not touching anything and see how that goes.

  33. hello Nick, I ordered the can bus leds so I wouldn’t have any errors but it’s still giving me the” license plate light out” error on my dash. is it ok to order and install the resistors you linked above along with the can bus leds? from whatever little knowledge I have, I thought the can bus ones already had resistors in them and idk if adding another resistor in conjunction with the can bus leds will work or cause issues?

  34. Shawn,
    The Audis are so finicky that often the CAN-bus LEDs still don’t work, in which case you have to add an extra resistor on top. How much of a resistor you need to add is a tough questions as it’s hard to determine how much of a built-in resistor the LED came with. You may need to experiment with a few different sizes to find out.

  35. Will do, Thanks for the quick reply. i had one other question. what are your thoughts on wrapping the resistors with like electrical tape? think that might help with the whole resistor heating up and touching/melting stuff

  36. The tape will eventually melt so you may just want to mount it to a heat sink or piece of metal if that’s your concern.

  37. Thanks for the info on this. I tried it on my 08 Cabrio and it prevented the bulb out indicator from coming on, but mounting the resistor is an issue. The trunk lid on the cabrio is some type of composite, not metal. I used 3m and some insulating tape to create a barrier. Because I was concerned about the heat and fire risk, I installed it and watched it for about 20 minutes with the lights on and the trunk liner off. The resistor heated up to the point where it burned the adhesive and dropped from the trunk. Those that have used this method should definitely re-check to make sure the resistor hasnt dropped. I ended up uninstalling and living with the error message.

  38. Oh geez, that is interesting on your trunk versus the sedan trunk. Glad you tested it!

  39. Christian shatto

    GREAT POSTS! I found ur post b/c I installed new LEDs last night,and they work great, but warning light :( I can fix car audio amps, but can u please provide more detail where u removed cover and installed resistor( can’t tell from ur pics- btw, I’m b7 2005.5, 2.0 L

  40. Hi Christian – there are two pictures of that, but basically remove the trunk liner on the inside of the trunk and there is plenty of room to mount resistors as well as find the wires. The two pictures I have that show red are the inside of the trunk, not anywhere near where the bulbs mount. Does that make sense?

  41. Hi Nick,
    Bringing this post back, I just have a couple questions. I had my resistor installed and it worked great, and then just the other day it stopped working. So I checked to see what was going on, and it turns out it must have detached from the double sided tape and melted thru the wire because it was all burnt up. The resistor itself was also silver as though it had burned off the gold plating somehow.. Do you think I got a faulty resistor? I have some installed in the engine bay area for my DRLs and they are still gold and holding strong. Also, would you have any suggestions where to mount the resistor besides where you show? That’s where I had it originally. Thanks a million!

  42. Hi Calvin – they do go bad sometimes, I would just buy another one and replace it. They take on a lot of heat. You could maybe try a different wattage/ohm resistor that runs a little cooler, I’ve heard that 25w5ohm resistors will work just fine as well.

  43. Ah gotcha, I will give it a shot. Thanks!

  44. The wires you indicated to tap intowas the purpleish gray and the brown one. I followed those wires and it seems it connects the right taillight/breaklight. Are those the right ones? I felt like it wasn’t so I tapped into a gray and one of the brown wires directly on the connection for the license plate lights. The resistor heats up and gets hot but I still get the error. Which wires should I be bridging exaclty?

  45. Hi David – the wires pictured in the post aren’t anywhere near the tail lights, are you sure you’re looking at the right wires? These wires should be right above the license plate area in the center of the trunk lid.

  46. Hi Nick
    2006 Audi a4 b7 2.0tfsi

    Mine dont even come on..
    And i get the bulb out error?!
    Wrong bulbs or…luck of the draw audi error

  47. Try reversing the polarity, aka taking the bulbs out and flipping them around – some LEDs have a negative and positive end, so if you put them in backwards you won’t get any power.

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