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3rd Brake Light - Can use coupe parts? YES (See Post #9)

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    #1

    3rd Brake Light - Can use coupe parts? YES (See Post #9)

    The rubber gasket under the trunk mounted 3rd brake dries up, shrinks, and lets water in. This exposes the little green circuit board inside the unit to moisture, and it fails. The 'Check' light flashes on the instrument cluster, because stepping on the brake pedal doesn't send the acknowledgment to the ECU that the brake lights are working OK. The 'Brake Lights' warning light is also lit on the overhead panel, even though the 3rd brake light works fine.

    That's annoying, but not annoying enough to pay over $200 for a new 3rd brake assembly (PN 63251386147).

    One rumored fix to solving the blinking 'Check' light is to the remove the green board from the circuit and connect the +/- wires leading into it. Haven't tried that, but it sounds a bit hokey.

    If you buy a used 3rd brake light, it'll probably have the same problem as the one that's giving your grief. If not, it will soon.

    Got to thinking of another idea - Can I find that green circuit board inside of a coupe or sedan's 3rd brake light assembly and transplant it into my vert's assembly? Chances are good it's been dry since installed at the factory, so it should be working OK.

    Has anyone ever tried this?

    Thanks!
    Last edited by Aleman; 04-12-2016, 06:43 PM.
    R135 /// 1990 Alpinweiß II 325is
    └┼┼┘ /// 1993 Black/Black Convertible (sold)
    ..24
    Tags: None
    #2
    So I don't know the answer, but let's say it can swap. If the leak from the gasket killed your old circuit board, won't it kill your new one? You need a new gasket first, no? Can't get one without buying the whole assembly. Or are you planning to make one?
    '89 lachssilber vert - Frau Blücher
    '84 alpine 2dr - gone to the great beyond...
    '00 titanium 4dr e46 - bricked

    Comment

      #3
      Originally posted by Semblance View Post
      So I don't know the answer, but let's say it can swap. If the leak from the gasket killed your old circuit board, won't it kill your new one? You need a new gasket first, no? Can't get one without buying the whole assembly. Or are you planning to make one?

      If make one or try to seal the assembly with RTV.


      Sent from my iPhone using Tapatalk
      R135 /// 1990 Alpinweiß II 325is
      └┼┼┘ /// 1993 Black/Black Convertible (sold)
      ..24

      Comment

        #4
        i am not aware that coupes have that little circuit board but they may.

        i wouldn't use rtv. generally that stuff is shit. also, it is corrosive to metal so you know where i am going with that. i have not checked real oem, but can't you just buy a new gasket?

        i realize i am in a different meteorological area than you are but i have owned perhaps 4 or 5 cabby's and have never had this problem.
        sigpic
        Gigitty Gigitty!!!!

        88 cabrio becoming alpina b6 3.5s transplanted s62
        92 Mtech 2 cabrio alpinweiss 770 code
        88 325ix coupe manual lachsilber/cardinal
        88 325ix coupe manual diamondschwartz/natur
        87 e30 m3 for parts lachsilber/cardinal(serial number 7)
        12 135i M sport cabrio grey/black

        Comment

          #5
          Nah, can't buy just the gasket, not for my late model anyway. I was thinking of using RTV between the red plastic piece and the remains of the rubber gasket, not directly on the paint.

          Just a moment...
          http://www.realoem.com/bmw/enUS/showparts?id=BB13-USA-12-1992-E30-BMW-325i&diagId=63_0204


          Mine is just toast, so I will probably need to suck it up and spring for new unit. Here's the inside. The edge of the gasket has even separated. Flyboyx, maybe I should shop for a used assembly from the Houston area LOL :D

          Last edited by Aleman; 03-23-2016, 07:00 PM.
          R135 /// 1990 Alpinweiß II 325is
          └┼┼┘ /// 1993 Black/Black Convertible (sold)
          ..24

          Comment

            #6
            It appears that late model non-convertible E30's DO have the chip. I think it's a safe bet that the chip can be transplanted to a vert assembly to give it extended life. Check out part number 63251385187 from a 1990 coupe.
            Attached Files
            Last edited by Aleman; 03-26-2016, 05:48 AM.
            R135 /// 1990 Alpinweiß II 325is
            └┼┼┘ /// 1993 Black/Black Convertible (sold)
            ..24

            Comment

              #7
              Yours isn't that bad. You can reseal that easily. I would find another vert board as that is the correct part. I have a couple spares.
              "I'd probably take the E30 M3 in this case just because I love that little car, and how tanky that inline 6 is." - thecj

              85 323i M TECH 1 S52 - ALPINEWEISS/SCHWARZE
              88 M3 - LACHSSILBER/SCHWARZE
              89 M3 - ALPINEWEISS II/M TECH CLOTH-ALCANTARA
              91 M TECHNIC CABRIO TURBO - MACAOBLAU/M TECH CLOTH-LEATHER

              Comment

                #8
                Originally posted by reelizmpro View Post
                Yours isn't that bad. You can reseal that easily. I would find another vert board as that is the correct part. I have a couple spares.


                PM'd
                R135 /// 1990 Alpinweiß II 325is
                └┼┼┘ /// 1993 Black/Black Convertible (sold)
                ..24

                Comment

                  #9
                  How To: Coupe 3rd Brake Check Chip into Vert Transplant Procedure

                  Ok, so this weekend I confirmed that you CAN indeed transplant the 3rd brake light check chip from a late model coupe or sedan into the 3rd brake light housing on a late model convertible 3rd brake light housing in order to stop the check engine light flashing and to turn off the overhead check panel light for Brake Lights(!).

                  Before you do this, though, confirm the symptoms:

                  1) Is your check engine light flashing even after you step on the brake pedal after starting the car?


                  2) Is your Brake Lights(!) warning light on?


                  3) Do all your brake lights work when you step on the brake pedal?


                  If all answers are 'Yes', then you need to take a look at the insides of your trunk-mounted third brake light (remove tool tray, then 6 or 7 screws fastening the housing to the trunk). There's a chip in the housing that communicates with the ECU and let's in know that it's present and functioning properly. Water and dirt get into the 3rd brake housing and corrode that chip. If it looks like this in there, you probably need to replace that chip.


                  Rather than blow $200+ on a new convertible 3rd brake light unit, or buying a used one potentially with the same problems, go to eBay or your local junkyard, and buy a 3rd brake light unit for about $25 or less that lived its entire life inside a nice dry coupe or sedan.




                  You can cut the chip from the coupe/sedan unit and solder it into the vert unit.
                  *Snip Snip* Be sure to leave as much wire on the chip as possible.




                  Solder the new one in place of the old decayed chip. Clip one wire off the original chip at a time to BE SURE that you get your connections right (2 green, 2 brown)


                  All connections completed!


                  I sealed up all the many many cracks in the red plastic with clear silicone caulking and installed a new Osram bulb before putting it all back together.


                  And added a couple drops of silicone to hold the chip in place and buttoned it all up.



                  After this, I started up the car, saw the flashing 'Check Engine' light, stepped on the brake pedal, and the CHECK ENGINE LIGHT TURNED OFF with no lights on the overhead warning panel! Awesome.

                  This looks like a lot of work, but that's just because I added so many pics. The whole operation took me about an hour to do.
                  Last edited by Aleman; 04-12-2016, 06:41 PM.
                  R135 /// 1990 Alpinweiß II 325is
                  └┼┼┘ /// 1993 Black/Black Convertible (sold)
                  ..24

                  Comment

                    #10
                    Nice write up, I just deleted it

                    Comment

                      #11
                      I did a bypass on my Cabrio chip and it worked for a while but this seems like a better solution, especially since the 3rd brake light really has no value (well had no value before this post lol)
                      Seat Shocks....I have passed the baton to John Christy from Ninestitch. Email John or Garrett at ninestitch1@gmail.com

                      https://www.r3vlimited.com/board/sho...86#post4944786
                      Alice the Time Capsule
                      http://www.r3vlimited.com/board/showthread.php?t=360504
                      87 Zinno Cabrio barn find 98k and still smells like a barn. Build thread http://www.r3vlimited.com/board/show...20#post3455220

                      Comment

                        #12
                        Originally posted by rcsoundn1 View Post
                        Nice write up, I just deleted it


                        Did the check engine light continue to flash after the delete? I assume not...

                        I didn't want to have to fill the hole left where the wires go thru the trunk lid, so I needed to properly fix the bastard.
                        R135 /// 1990 Alpinweiß II 325is
                        └┼┼┘ /// 1993 Black/Black Convertible (sold)
                        ..24

                        Comment

                          #13
                          Originally posted by jeffnhiscars View Post
                          I did a bypass on my Cabrio chip and it worked for a while but this seems like a better solution, especially since the 3rd brake light really has no value (well had no value before this post lol)
                          I swapped my trunk for a coupe trunk because my brake light, while working completely fine, was letting tons of water in my trunk. How did you bypass it?

                          Sent from my SAMSUNG-SM-N910A using Tapatalk

                          Comment

                            #14
                            No check lights at all. I connected the 2 black wires with green stripes together

                            Comment

                              #15
                              Originally posted by rcsoundn1 View Post
                              No check lights at all. I connected the 2 black wires with green stripes together
                              Thanks man. I'm pretty sure we talked about this when I changed my trunk at the beginning of the winter, just haven't seen my car since. Taking it out this week and I'm going to set this up.

                              Sent from my SAMSUNG-SM-N910A using Tapatalk

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