Brake light bulb will not light 2009 990 ADV

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by KMC1, Oct 2, 2013.

  1. KMC1

    KMC1 There is no spoon.

    Joined:
    Sep 13, 2008
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    Ok....I admit it, I suck at electrical stuff...that said, I do know how to align the + & - poles on batteries so I can use the remoter for the TV.....:D

    2009 990 ADV

    My brake light will not light. It's got power at the socket however. Using a multimeter, If I turn the bike on, brakes OFF, I get ~45 milliamperes (it's all up and down though, not really a steady reading, but never into volts).
    Activate the brake, the reading jumps up to ~10 volts.

    Start the bike and activate the brake, and the reading goes up to ~13 volts.

    Ok...so far, so good.

    I tried 3 different single filament bulbs ( not sure if I could have an incorrect bulb? I should mention, bike is brand new to me last week) but I cannot get the bulbs to light?!

    I even tried taking the socket apart and touching the wires directly to the side and base of the bulb to isolate the socket. No luck. Should I be able to light the bulb holding it in my hands touching bare wires to the sides and base? I thought that would definitely work.

    I tried it with bike running, bike off, etc. Got power every time and it cycles with the brake switches, but the bulb will not light up.

    The rest of the circuit does work by the way, (horn beeps) I checked and swapped the fuse as well just to be sure it's not something funky going on with the fuse.

    I'm out of ideas.....anyone got any thoughts on what's wrong??

    :ear :freaky
    #1
  2. markie_wales

    markie_wales Been here awhile

    Joined:
    Nov 12, 2005
    Oddometer:
    947
    Location:
    Hampshire, UK
    Not 100% of sure everything you have tried, but my pressure switch went on my SE. Follow wire from rear MC about 10" - 12" IIRC and there is a connector. Open this up, then with the ignition on, jump with pins with a paper clip or something. This activated my rear light, new pressure switch sorted . Clearly if this does not light the bulb then you can eliminate the pressure switch.

    cheers

    Markie
    #2
  3. KMC1

    KMC1 There is no spoon.

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    Markie, this was really helpful. Thanks for posting it. Started tracing wiring from the switches and was able to isolate the front circuit and get the bulb to light. As I kept tracing I isolated the rear circuit and cannot get he bulb to light.

    I am completely baffled by the switches appearing to switch power correctly as shown on the multimeter..... Bizarre. I can't understand how processing the brake pedal can cause my multimeter to go from millivolts to ~10 volts but not light the bulb. That's a new one for me.

    In either case, it appears the rear circuit is bad and it does seem like it's probably the switch..... I need to find where it's located but ran out of time for right now.


    Thanks man :freaky
    #3
  4. markie_wales

    markie_wales Been here awhile

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    KMC

    Glad it was of some use. The pressure switch is in effect the bolt that goes through the banjo bolt on top of the master cylinder. It has the wire coming out of the m/c as part of it. Easy to replace but (for me) impossible to get a torque wrench on :)

    Did jumping the pins work. If so I'd bet a pint of London Pride it's the pressure switch.

    Cheers

    Markie
    #4
  5. RedRupert

    RedRupert Brit in the Soviet Union

    Joined:
    Jun 12, 2006
    Oddometer:
    633
    Location:
    Riga, Latvia / Bergerac, France / Colchester, UK
    I'm with you. I had the same last year - checked out OK with multimeter, but not with bulb. A new pressure brake switch in the rear master cylinder sorted it. €13.
    #5
  6. KMC1

    KMC1 There is no spoon.

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    Guys, I really appreciate your help - you both helped me greatly! First in isolating the rear switch circuit and then in hearing someone else saw the same phenomenon with the voltage check - that was a makin' me crazeh mon....:D

    I actually found two issues on my bike - the front brake switch wires were disconnected - I spoke with the previous owner and those wires have always been that way.... He must have been riding the bike with only the rear switch activating the brake light and not realized it. Those two little wires ARE pretty short and I can totally understand how they would have come loose. There is some corrosion on the blades and I'll bet they've been that way for quite some time.

    Secondly, I tried your trick of jumping the circuit to by-pass the switch, and that worked... so... off came the switch.... Here's what I found:

    [​IMG]

    [​IMG]


    There's a little rubber boot that covers up the connection - it was hiding the fact that the two wires where they are running into the switch housing, were almost broken completely. Thus this explains getting the 12V reading at the socket upon activating the switch, but not lighting the bulb. The connection was "barely there" and so wouldn't be able to carry any load.

    One thing I do notice is that the way the wires come out of the switch housing, they come very close to the subframe - it looks to me like when the switch was put together, tightening the bolt, caused the wires to get twisted into the subframe and thus caused the wires to have a very sharp bend and be pinched a bit. I would suggest that you make sure that when you replaced yours, you didn't tighten the wires into the frame as well. It looks very easy to do. I called the dealer and they say they do have ONE switch in stock, so I'll go tomorrow to get it and hopefully have this beasty all set by noon or sooner.

    I hope this helps someone else with the same issue someday.

    THANKS GUYS!!!

    :freaky
    #6
  7. markie_wales

    markie_wales Been here awhile

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    Excellent - glad it helped, and agree on the proximity to the sub frame.

    Off to buy myself a London Pride tonight :D

    Cheers

    Markie
    #7
  8. KMC1

    KMC1 There is no spoon.

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    Markie, be sure to put that London pride on my tab for ya! :lol3 :freaky
    #8