3RD brake light wiring question

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  • KeeperJones
    Wrencher
    • Jul 2004
    • 240

    #1

    3RD brake light wiring question

    So I pulled my cabrio 3rd brake light today and am a little confused on the wiring. There are four wires. So I am looking at my Bently and not getting too far. The green/red comes directly off the switch. One of the green/black comes from the active check control unit, which I am guessing is related to the check panel. The other green/black goes to the rear light check relay. The brown is shown ending with three lines of decreasing size under it. If I remember right it signifies a ground and I am guessing grounds the little circuit board that all the wires run through.

    So a couple of questions. I pulled the brake light and snipped the wires. I am going to use a Zender spoiler with a 3rd brake light that only has two wires. Do I need to pull the circuit board out of the oem light and use it? Or if I just use two wires (I assume it is the green/red and the green/black going to the rear light check relay) will it cause any issues with the auto check system?

    I am not putting the spoiler on until next weekend and I need to get the brakelights working again. Is crossing the green/red and the green/black the right thing to do to get them working temporarily?

    I searched around a bit and couldn't find anything on the wiring, hopefully not because it a total noob question. Anyway, thanks for any advice.
  • KeeperJones
    Wrencher
    • Jul 2004
    • 240

    #2
    Ok, so I am glad I checked first. Green/red and brown get the light working and connecting the two green/black bypass the check system for the 3rd light.

    BTW, cabrio owners, you might want to pull your trunk lid 3rd brake light and inspect it. I had some serious rust going on an otherwise rust free car.

    Comment

    • Disaster Inc
      E30 Addict
      • Oct 2007
      • 429

      #3
      Hey, thanks for the info. My Cabrio has an is trunk lid, so the light has been on the check panel for a while. I'll try jumping those two wires, then only one check light to go!
      sigpic

      Comment

      • KeeperJones
        Wrencher
        • Jul 2004
        • 240

        #4
        yes

        It worked for me. I bought a zender with a 3rd light from elguapo84 and am doing away with my oem. Because it is LED it is not monitorible. I couldn't believe the rust under there. There was no eveidence in the trunk or outside.

        Comment

        • DaveSmed
          E30 Fanatic
          • Apr 2007
          • 1406

          #5
          Good stuff. Guys with rusty lids, you have the early or late style third brake light?
          -Dave
          2003 Lincoln Towncar | 1992 BMW 325iC | 1968 Cadillac Deville

          Need some help figuring out the ETM?

          Comment

          • Disaster Inc
            E30 Addict
            • Oct 2007
            • 429

            #6
            Originally posted by DaveSmed
            Good stuff.
            I agree us Cab guys gotta stick together. The way I look at my car is yeah its cool. and "Hey by the way, the top goes down"...then it becomes way cool......Chicks love it...Cabs FTMFW!
            sigpic

            Comment

            • cactusjacks1
              E30 Fanatic
              • Sep 2004
              • 1216

              #7
              So, if you have completely done away with the third brake light, you jump the 2 wires (keeperjones talks of in post #2) & the "brake light" warning bulb on the "check board" will go out??
              [I

              Comment

              • DaveSmed
                E30 Fanatic
                • Apr 2007
                • 1406

                #8
                Originally posted by cactusjacks1
                So, if you have completely done away with the third brake light, you jump the 2 wires (keeperjones talks of in post #2) & the "brake light" warning bulb on the "check board" will go out??

                Yup.
                -Dave
                2003 Lincoln Towncar | 1992 BMW 325iC | 1968 Cadillac Deville

                Need some help figuring out the ETM?

                Comment

                • cactusjacks1
                  E30 Fanatic
                  • Sep 2004
                  • 1216

                  #9
                  Originally posted by KeeperJones
                  Ok, so I am glad I checked first. Green/red and brown get the light working and connecting the two green/black bypass the check system for the 3rd light.

                  BTW, cabrio owners, you might want to pull your trunk lid 3rd brake light and inspect it. I had some serious rust going on an otherwise rust free car.
                  You have found a real simple fix - I made a jumper wire to connect the 2 & WALA !! brake warning light on the check panel is OUT.

                  Any hints on the SRS light staying on when you replace the air bag steering wheel with a non air bag one??

                  Thanks a 1,000,000 !!

                  Jack
                  [I

                  Comment

                  • DaveSmed
                    E30 Fanatic
                    • Apr 2007
                    • 1406

                    #10
                    Glad to hear it helped.

                    Under the drivers knee bolster, there is an orange box near the ABS computer. It has 4 (IIRC) orange connectors. Unplug them. No more light.
                    -Dave
                    2003 Lincoln Towncar | 1992 BMW 325iC | 1968 Cadillac Deville

                    Need some help figuring out the ETM?

                    Comment

                    • rkettner
                      Grease Monkey
                      • Jun 2007
                      • 367

                      #11
                      the third brake light can also be the source of water getting into your trunk as i found out.

                      Comment

                      • Garageaholic
                        Freestyle Fabricator
                        • Dec 2005
                        • 5204

                        #12
                        I am going to revive this thread...

                        I was troubleshooting my brake check light system.. I will try this soon, but I want it to work LIKE IT SHOULD....

                        With that being said, I inspected the circuit board within the 3rd brakelight housing. There was some corrosion, so i cleaned it off and the check light doesn't go out... I may give up and simply connect the wires, but I figure that I would give it a good college shot..

                        How would one test this? What is the proper resistance of the bulb that one should use?
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                        Comment

                        • Kwaaahhh
                          E30 Modder
                          • Apr 2008
                          • 843

                          #13
                          Any chance some have some pics of the wiring done? Got a IS trunk painting right now to swap on my vert. :up:

                          Comment

                          • Kwaaahhh
                            E30 Modder
                            • Apr 2008
                            • 843

                            #14
                            So I jumped the wire OP said. But I was wondering does your guys check brake light still stay on, until you hit the brakes and it goes away?

                            Comment

                            • T.Dot_E30
                              Wrencher
                              • Mar 2004
                              • 286

                              #15
                              Originally posted by Kwaaahhh
                              So I jumped the wire OP said. But I was wondering does your guys check brake light still stay on, until you hit the brakes and it goes away?
                              yes, once you step on the brake the system knows if the brake lights work or not.

                              Hence the "Check" blinking until you do.

                              Comment

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