Hector4610

I am a first time Audi owner and first time posting to this forum. My 2007 A8L with 99K miles (which I’ve owned for less than a year) has a rear right inner tail light problem that I cannot figure out. The brake light will not turn on when pressing the brake pedal. Below is a list of everything I have done to troubleshoot this problem.

I have tried everything I’ve read in this forum and elsewhere with no luck. Any help would be greatly appreciated. Basically the symptoms are:
- Rear inner tail light does not light up when brake pedal is pressed.
- There are no dash warning lights.
- At night when the lights are on, the LEDs are lit but no brake lights when brake pedal is pressed.
- The light bulbs are both good. Reverse light turns on and the night light turns on as well.
- The rear left inner tail light is fully functional.
Trouble shooting list is as follows:
- I thought that since I had replaced the left inner tail light assembly a couple of months ago I would just replace the right assembly and that would be it. But no, that wasn’t it. The light assembly I purchased is an OEM part and it did not solve this problem, same symptoms.
- I filed/sanded the ground contact (brown wire) on the harness that connects to the light assembly. I also, while I was at it, filed/sanded all the contacts on the connector. No luck with this.
- I placed a jumper wire from the car’s harness ground (brown wire) to the light assembly’s ground wire (white) on the other side of the light assembly connector. No luck with this either.
- Cleaned ground contacts on the car by the right side of the luggage compartment next to the battery. Removing, sanding and replacing. I also removed and cleaned the ground connection that’s behind the rear seat near the back window. No luck with this either. Of note: neither ground connections looked corroded or dirty.
- I removed the left light assembly connector and while the brakes were depressed I took voltage readings (on both left (good) and right (faulty) sides) so I could compare. The readings were as follows:
o LEFT RIGHT
Pin 1 - .00vdc Pin 1 - .01vdc
Pin 3 - .41vdc Pin 3 - .61vdc
Pin 5 - .39vdc Pin 5 - .39vdc
Pin 7 - Empty Pin 7 - Empty
Pin 2 - 11.08vdc Pin 2 - 11.06vdc
Pin 4 - 12.40vdc Pin 4 - 12.39vdc
Pin 6 - .36vdc Pin 6 - .37vdc
Pin 8 - Empty Pin 8 - Empty
As you can see the voltage readings on both sides (left and right) read practically the same. This, I believe, leads me to a conclusion that the problem is within the rear right inner tail light assembly itself. It would seem that I was sold a defective light assembly.
As many of you can attest, these light assemblies are very expensive. I wanted to get some confirmation to my conclusion before I spent another 3 or 4 hundred dollars purchasing another light assembly. This forum is such a great source for help. Normally, some research on the forum would be enough for me to solve most problems. However, this problem has stumped me. Appreciate any help from my fellow Audi owners.

chokboywonda

Did you work this problem out?

silkworm

Can you swap the two inner tail lights just for testing purposes?
As far as I know, the connector should be the same.

If the left one (which after swapping will be on the right side) will lit and the right one (which will be on the left) will not, then you have a faulty, new tail light.

dvs_dave

Hector4610

Thanks for all the help. I haven't solved the problem yet but am still trying things out. I got the part from Audiusaparts.com and supposedly it was a new OEM. I did try the left one that works on the right and it didn't work (the connectors are the same just different color wires).I'm not sure about the face lift question. Not sure how to check that. Forgive my ignorance on this but can you give some more detail on how to check. I'm picking up, from the dealer tomorrow, the tail light connector on the car side harness to replace it to see if there is an issue with corrosion. I'm also going to try swapping left and right again to make sure one more time. So if the left that works doesn't work on the right the problem would appear to be elsewhere other than the tail light assembly itself. I have this month and next to fix this problem before I have to get the car inspected. More to follow in a day or two. Thanks again to all trying to help.

MP4.2+6.0

Final facelift and the one that affects tail lights was MY2008 for USA. Simplest check is if you have round front foglights in front for any motor version, it's pre facelift. If the front foglight are more rectangular/trapezoid shaped it is post facelift. Pre facelift taillights have the LED's sort of in a generalized grid pattern, while post facelifts have a more distinct pattern, plus some tweaks to back up light appearance. Top right below is pre facelift, and big part of image is post facelift.

Hector4610

Thanks MP4.2+6.0 - Mine is pre-facelift as depicted in the upper right picture. I will do some more testing tomorrow and post results.

Hector4610

Thanks to Silkworm for suggesting something I should've known. Swapping the inner lights proved that the new light is faulty. When I placed the working left inner light on the right and the right new light assembly on the left, the light from the left worked on the right. The faulty new light of course didn't work on the left either. So this proved my theory that there was a faulty new light. I noticed on the box of the new light that there was an additional sticker to another customer back in Sep 2017. It looks like that shop returned the light and the vendor shipped it to me without checking that it was working. I contacted the vendor and after a couple of email exchanges they said that I had to return the light assembly for them to check it out before going forward. They sent me a priority mail shipping label for me to return it. I'll put it in the mail tomorrow. As soon as I get the new, and hopefully working new light, I'll install and get back to all on the results. Thanks to all for the help.

Hector4610

I'm back and the problem continues. I did swap the lights and the left that works did light up in the right. But the new light will not light up on the right nor the left. This is the third new light I've tried and this last one was from a different source. Two lights from AUDIUSAPARTS and one from a local dealer here in Virginia. Someone mentioned the brake light switch. Well, I just changed it and the same symptoms. Man, this is crazy. If anybody has any other ideas i'm all ears.

silkworm

Please write here:
- the part numbers of the tail lights you bought for the right side;
- the part number for your left tail light;
- your VIN.