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Thread: Stop Light Warning Light Always On

  1. #1
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    Stop Light Warning Light Always On

    I've searched the forum (and the internet) for an answer, but haven't found anything that works.

    I just recently purchased a 1988 BMW 325i convertible with a broken timing belt. Replaced the head, timing belt, water pump, tensioner, V-belts, and other misc. items ... car runs great now ... but ...

    When I first started the car the dash looked like a Christmas tree! ... maintenance light, ABS light, brake pad warning light, coolant light ... and the topic of this post ... brake light warning light.

    I've resolved all the other lights (with the exception of the ABS light - bad RR wheel sensor circuit) ... but I can't get the Brake Light Warning Lamp to go out!

    The trunk-mounted stop light didn't work initially ... put a new bulb in and it worked, I figured that would cure the Brake Light Warning Light ... but ... still on! I've removed ALL the bulbs and cleaned them and the sockets ... I've even tried connecting the two green/black wires to bypass the check system on the center tail light ... still no success ... warning light is still on!

    The warning light is on constantly, not randomly ... I've read where a brake light switch going bad can cause problems randomly, but this is constant. I've checked the brake lights with a mirror, and they work consistently.

    I pulled the Control Unit out of the overhead counsel ... but it looks like there's no way to open it up.

    Any other well-known / common possible reasons for the BLWL to stay on?

  2. #2
    richardodn's Avatar
    richardodn is offline Old Guy BMW CCA Member
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    There's an issue specific to convertibles around the high brake light. I don't remember the specifics, but it had something to do with the circuit board in the light fixture.
    "Howdy, Folks!"

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  3. #3
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    I believe I read about that here ... https://www.bimmerforums.com/forum/s...t-bulb-warning

    He found a bad circuit on the mini-printed circuit board inside the trunk-mounted light ... he said he simply soldered a wire to repair the circuit and it worked for him. I looked and could find no problem with mine. He also said that by connecting the two green/black wires ... it would bypass the check system for the center light ... But the bypass didn't work for me.

    Where are the check relays for the lower brake lights? ... I've heard they're in the left-rear fender ... or possibly under the rear seat in the convertible. Can anyone confirm?

    The way I understand the system, the check relays for all three stop lights are closed when the ignition is on (N.O. with the engine off) ... if a bulb / circuit fails, that particular check relay opens ... causing the check light in the overhead counsel to turn on?

    (Was going to post a wiring diagram here, but apparently I can't?)




  4. #4
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    The Check Relay Unit for all the tail lights, stop lights, license lights, is behind the rear seat side panel on the driver's side (on the convertible) ... I pulled it out, checked all the terminals with a meter and for corrosion ... everything looks good, so that's not the problem.

  5. #5
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    If the check relay is not the cause, I'd try to replace the brake switch above the pedal. I think there are 2 types of these being 4 and 2 wire switches? The brake switch also has the input to the check panel.

  6. #6
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    Hey Geoffzie, here is the picture of the PCB and where I added the new wire (it looks like the picture was finally removed from the original post). If I recall the board didn't really look damaged at first glance but this repair did fix it for good. Good luck!
    Last edited by 87iSee; 11-12-2018 at 11:38 PM.

  7. #7
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    No e30s, again :(
    that's what my gage cluster board looks like, ha ha ha. a few extra soldered wires to fix stuff
    No e30s again.

  8. #8
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    Thanks 87iSee, I wondered where the mentioned picture was.

    I tried the bypass you mentioned, connecting the two green wires together (in my car they're actually Green/Black). The bypass makes sense if you look at the wiring diagrams ... it SHOULD work ... but I still had the warning light.

    And yes Irwie'C ... my brake light switch is 2-wire. I figured since the bake lights are working consistently ... the switch was OK, but maybe not.

    I've spent almost as much time in trying to get this stupid light to go off ... as I did replacing the head, head gasket, timing belt, water pump, and tensioner! I don't mind the Active Check System for other things ... but would really like to bypass the "brake light check" since it seems like an ongoing annoyance for many.

    I removed the Active Check System Module from the overhead counsel to look at it ... but it appears there's NO way to open it up. Anyone ever taken one apart before? Apparently, from the wiring diagrams, those are not bulbs in the unit, but light-emitting diodes.

    I'm going to take a look at it again today. I'm going to ...

    1. Try to get the system to work properly ... or ...
    2. Disable the Brake Light Check function somehow that also eliminates the overhead warning light and "Check" light

    I HATE dash warning / reminder / message lights! I often wonder how many people have ACTUALLY put their seat belts on ... simply because of a LOUD buzzer or big red warning light telling them to?

  9. #9
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    OK, so I finally "resolved" my issue.

    I've replaced all the bulbs with the proper ones, cleaned the sockets, checked all the wiring, checked the tail light "check" relay with a meter, checked the brake light switch, even tried temporarily bypassing the brake light switch ... all to no avail! STILL had the stupid overhead "stop light warning light" and dash "check" light flashing at me!

    This must be an issue primarily with the convertible, which uses a different bulb for the center stop light ... which might be part of the problem.

    With a little help from superj ... I discovered that the face pops off of the overhead Active Check System Module. You've got to pry it out GENTLY ... or you'll break it because it's thin. I removed the outer lens, the inner window, a grid plastic piece ... and there were the light emitting diodes.

    I simply twisted the LED back and forth with needle nose pliers until it came out (soldered onto the board with two wires) ... then I carefully snapped everything back together. I also removed the "Check" light bulb from the dash (you've got to remove the instrument cluster to remove it).

    Put everything back together and ... VOILA! ... no more brake light check light! ... and no more flashing dash "Check" light! The rest of the overhead Active Check System Module is still functional.

    I got to thinking afterwards, that I could have simply put a piece of black tape INSIDE the plastic lens on the overhead console ... but, too late now!

    Now I've just got to repair or replace an ABS wheel sensor wire (RR) ... and ... NO MORE DASH LIGHTS!

    Thanks for all your help!

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