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DIY: Replace Individual LEDs in Tail Lights

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  • DIY: Replace Individual LEDs in Tail Lights

    Originally posted by heinzboehmer on M3F

    (Slightly edited just to remove unnecessary info)

    LEDs used in this DIY: Click Link

    "The first step in doing this is getting the tail light open. The housing is sealed and glued to the lens, so the most logical way to approach this would be to separate the lens from the housing and then re-glue it. However, after reading through some forum thread of others attempting to do something similar, it seems like actually reassembling everything is notoriously difficult. With this in mind, I decided to cut the housing of the taillight and then glue it back together. I was a bit worried that it would be hard to align (especially because one of the screws that mounts the taillight to the car is on the part that would be cut), but the housing is actually attached to the rest of the taillight by five torx screws (T10?), which means that alignment issues are nonexistent. I forgot to take a picture of the taillight after making the cuts, but here I have outlined where I made the cuts. Note that the cut on the right side is not actually on the face of the housing, I was afraid that I would hit the board if I did this, so I decided to cut along the side where the rubber weather insulation normally sits.

    Also note that there is an area towards the bottom that I had to cut out after making the original cuts. This is because the board actually extends all the way to there and is impossible to take out without removing this part.

    Once the housing is cut and the five torx screws removed, you will see that there are a few more torx screws as well as a couple of plastic pieces that the board snap into. Remove these and then the boards can be easily pulled out (again I forgot to take pictures of this step, but with the tail light open, it's pretty self explanatory). One thing to note is that there is a small board that hosts a single LED for the side of the tail light. I accidentally broke the mount for this board when pulling it out, so I had to reattach it with double sided tape when reassembling it.

    Once the boards were out, I used a multimeter and went through all of the LEDs to find which were the ones that had gone out and marked them with a sharpie. Once I identified them, I cut them off with an xacto knife. I originally tried to heat them up with a soldering iron and pull them off, but given their size and the fact that they have four leads made this extremely difficult. With the bad LEDs out, I scraped the area around the original pads to increase the contact area of the solder. I originally planned to use solder paste and a heat gun to attach the new LEDs, but ended up just going with regular solder and a soldering iron. Luckily, the leads on the LEDs extend to the sides, so the solder actually has something to hold on to. Here is a picture showing already replaced LEDs and a prepped area for soldering on the least one (please excuse the messy soldering, these things are REALLY small so it's hard to do a good job).

    Note that one of the LEDs I soldered on is crooked. This is something you definitely want to avoid, as the lens requires them to be lined up in a very specific spot in order to spread the light out correctly. You want to get them lined up as closely as you can with the original mounting positions. Luckily that one ended up only being rotated (not displaced) so it still worked fine with the lens.

    With the soldering finished, I applied 12V and GND to the appropriate connector header pins to make sure everything was working fine.

    You can clearly see that the LEDs I bought match the factory ones perfectly.

    Here's a diagram showing what each pin on the tail light harness connector is wired to.

    The last step is to get the housing back together. Put the board back into their place, reattach all plastic brackets and screws (remember to clip the boards into the brackets) and reassemble the housing using the screws to align everything. I grabbed some JB weld I had lying around and put it on the cuts I made. It's definitely not necessary to maintain the structure of the light (the screws do most of the work here) but I wanted the light to be sealed in order to avoid having water get inside. Here's mine all sealed up.
    (Could possibly use butyl/ribbon sealer to reseal the housing for ease of access in case future disassembly is needed.)

    And here it is on the car with all the LEDs working.

    Last edited by bran.stum; 03-21-2020, 12:33 PM.

  • #2
    Nice DIY here, instead of JBWeld, using Butyl/Ribbon Sealer to reseal the housing may be a good option to allow future disassembly if a repair is needed again.
    Current Garage... '00 R11S, '09 HP2S, '12 R12GSA, '00 Gray 332iT (SOLD), '00 Black 323iT (wife's), '02 Alpine 325iT (Eileen, Track Wagon), '02 Japan Rot 325iT, '04 IR ZHP Sedan

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    • #3
      Originally posted by George Hill View Post
      Nice DIY here, instead of JBWeld, using Butyl/Ribbon Sealer to reseal the housing may be a good option to allow future disassembly if a repair is needed again.
      Good idea! I'll add in a note at the bottom.