Taillight / Brake light stays on.... 2007 BMW F800ST - BMW F800 Riders Forum & Registry



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  1. #1
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    I bought a used 2007 BMW F800ST with 20k miles and it was working great. Then at a stop sign it fell over to the right (Had right foot on the brake and left foot down, I'm a new rider and had taken some allergy medicine and boom...) Caused a minor crack on the fairing where it has that hole and flares out at the bottom of the bike, yet other than that great. Well it stayed at my parents house for a week, then when I came to pick it up, while driving it, the lamp light came on after about 20 minutes. Yet my cousin who was following me, came close to me a couple of times, and he said he couldn't tell when I was braking. After we stopped and I tested my brakes, the brake light was on all that time. I tried to remove the bulb and didn't realize that you had to push in and then turn (It was an old bulb and stuck in there), I was pushing, pulling and turning, yet didn't get the combination down correctly. A guy from a store who lended me a screwdriver came out and we tried to get the bulb out, and he used a flat head to push the metal tab that comes out of the little indent on the right side. He actually pushed the metal piece further into the socket. I then was able to get a hold of the parts dept at a BMW dealer, who informed me how to take the bulb out. I got to Oriely's part's store and changed it to a LED bulb and the same thing, no change. Then drove to the BMW dealer, and the parts guy worked on it, putting in the stock required bulb (Incandescent 1157), yet no change. I ordered the Front Brake switch, based on his recommendation, and just plugged it in w/o removing the old one, no change. I reset the battery and, no change.

    A tech said it could be the rear brake switch, yet you hear that click when you activate it, and we weren't hearing the click on front brake, hence why the parts guy rec. ordering the Front brake switch. They also said it could be an ABS issue. Another guy on here from the post of "Brake Light Always On Issue" said he discovered after thorough testing that it was the front brake wire harness being loose. Not sure if he meant the plug or the actual wires coming from underneath.

    I took shots of the light socket are under my profile of motorcycles. I tried submitting the link, but would not allow me.

    I'm wondering if that metal "U' shaped tab on the right could be causing the issue or is it something else. I've researched on this forum and have not come up with any other conclusions. Please share any wisdom and helpful solutions.



    Gary

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  3. #2
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    if it fell over to the right i would be looking at the rear brake pedal and that switch.
    BMW F800ST, 2010, Black, Fuzeblock, Sat Nav, BMW Tank Bag, Givi Touring Screen, Denali Spotlights, Denali CANSmart, Wunderlich Crash Bars, 62K Miles & counting 

  4. #3
    guenner's Avatar
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    If the wire to the break light switch came off, maybe not even completely off, the brake light stays on.
    2017 F700GS - I wish it had a drive shaft 

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  6. #4
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    Hey thanks for the input DJ and Guenther. Do you know how to access the switch w/o taking off the metal cover? Maybe from underneath? I tried to reach from around the metal cover and could barely feel the switch, I'm not sure how to access the plug or where it's located. If you need to take anything off, what would need to be removed? Is there a step by step process available on the forum?

    Also could the metal "U" shaped tab in the light socket be causing an issue?

  7. #5
    Daboo's Avatar
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    You seem to be looking at the right parts, i.e., the front brake lever and switch and the rear brake lever and switch. One of those parts probably was moved and is now making contact with the switch all the time. It wouldn't have to be much.

    A parts fiche will be helpful in seeing what the part looks like and how it fits. Here's one for the front brake switch. Part #18 looks like it is the switch.

    Click image for larger version. 

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    So here's what I could find on the rear brake switch. Part #11 looks like the switch.



    Here's a listing on eBay for the switch. https://www.ebay.com/itm/164937729428 It has three pictures that should give you a fair idea of what it looks like. It also lists the part number, so you can do a search on that part number for more info.

    Chris
    Elnathan - 2014 BMW F800GT
    IBA# 49894 True Rounder = 0-20's - Rounder -- to -- 100's+ Red Hot Rounder

    John 14:6 

  8. #6
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    Hey Chris,

    Thanks for your assist. I'm post 2 links to 2 videos that should also help others who may have this problem. I have not yet tried to sort out the rear brake switch, yet will do so now.

    https://www.youtube.com/watch?v=Xtjj2wNUa9U&t=101s GS 1200 R BMW abs brake repair, fix, problem, motorcycle
    https://www.youtube.com/watch?v=Ze30qVk4oxg BMW F800GS Adventure - Poorly designed brake light switch

    I was hoping to find the plug for the rear brake switch so I could unplug and replug just to ensure that wasn't affected. It appears it may be an issue of not contacting that thin piece of metal. Not sure yet though. And I was not able to find any info on how to access it. On the GS models it looks so easy, but on mine, there is all these barriers to reaching it....

  9. #7
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    Good evening, I just wanted to post an update. Thanks for having a Good Good Father, not only in heaven, but down here as well. Yes me and my Dad worked on it today. We tested the taillight / brake light socket with the LED and Incandescent bulb and no change. Then we moved onto the rear brake switch, and decided to search for the plug, finding it under the right fairing in the corner (I'll post pix in the next few days). We used a meter to test and the rear brake light switch worked properly (I believe) as it showed no resistance when off and resistance when on or visa versa. Either way we noticed a change when it was activated vs being off.

    Then we decided to focus on the taillight / brake light socket again, as I was concerned that maybe that "U" piece of metal was causing it to fault. Well that was a battle to get all that off.... Wheeeewww. Yet finally we got it out and it worked fine w/o any major problems. It appears the green wire I believe, is the one that sends the brake signal. As my Dad concluded that for some reason with no brakes activated, the brake light is HOT / on all the time.

    I have no idea as to what to do next....

    I made an appointment with the BMW 2 weeks ago, after trying the Front brake switch (I just plugged it in w/o changing it out to test) and no change. So my appt is this Friday. Yet still I believe labor is about $110 an hour which is quite costly, (disabled veteran working limited as I try to get back on my feet). The service manager mentioned that it could possibly be a ABS module, yet I never had the ABS light flag, only the lamp light. I'm hoping that someone else on here may have some other options to try, and if nothing else the next plan is to have it diagnosed on Friday by the dealer.

    Lastly, my Dad is recommending changing the taillight assembly due to the socket, he believes is not that good. I was starting to read some on LED taillight assembly's and it didn't look promising. Yet my dad is very good with his hands and with wiring. So he was saying now is the time while we have all these parts off, if we get install an new one or a LED if that'l work. The dealer quoted me $110 for the assembly and about $83 for the rear brake light switch with the wiring harness.

  10. #8
    Daboo's Avatar
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    First, thank you for your service and the sacrifice you made.

    One caution on going with an LED taillight. As far as I know, either you pay the BMW tech an hour's labor to reprogram the computer to accept the lower current of an LED bulb...or you put in a LED bulb that has a resistor to draw the same amount of current. You can get away with the front headlight being LED, but not the other lights.

    Sometimes it is best to bite the bullet and pay for a BMW tech when looking at the amount of time you are spending. I'd ask them to show you why the ABS module was bad, if they change it. That sounds to me like someone changing parts (at your expense) because they don't know what else to do.

    As far as changing the tail light assembly, ...I'm hesitant to recommend that. Electricity isn't that complicated. The switch either opens or closes, let's the light go on, or not. If the light socket looks good and operates as intended...and the switches are good too...you might have a short. So trace the wires and look for a bare wire or loose wire. It's tedious and complicated, but it's where I'd go next.

    Chris
    Elnathan - 2014 BMW F800GT
    IBA# 49894 True Rounder = 0-20's - Rounder -- to -- 100's+ Red Hot Rounder

    John 14:6 

  11. #9
    Daboo's Avatar
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    The BMW tech should have a tester that will help him find the short, if there is one quickly. This might be an excuse to buy one of those testers for yourself.

    eBay has this one for sale. https://www.ebay.com/itm/15404169283...9a8f2365e46779 I don't have one of these, but wish I did.


    Also noted in a DuckDuckGo search that there's lots of resources online both on websites and YouTube videos on how to find electrical shorts.

    Chris
    Elnathan - 2014 BMW F800GT
    IBA# 49894 True Rounder = 0-20's - Rounder -- to -- 100's+ Red Hot Rounder

    John 14:6 

  12. #10
    guenner's Avatar
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    If your brake lever assembly has a wire coming out then the it has a switch built-in. The wire goes to the ZFE (central frame electric unit) and it activates the brake light. If your ST does have wires coming out of the brake lever assembly then the ABS unit is not involved in your problem.

    If there is NO wire then the brake light activation is controlled by the ABS unit when it senses 'pressure' in the brake line. The ABS unit sends a message to the ZFE unit to activate/deactivate the brake light. If the ABS unit's internal switch is ON all the time then the brake light ON problem is in the ABS assembly.

    This can all be tested using a GS911 or Motoscan scanner. Maybe you have someone nearby who has either tool?

    All the diagnostic attempts you did 'physically' could have been done easily with either scanner. There you can tell the ZFE unit to turn on/off the brake light to verify that the ZFE output can indeed control the brake light. You can also verify with the scanner that the switches work.
    2017 F700GS - I wish it had a drive shaft 

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