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Thread: Tail Light and Peanut light issues

  1. #1
    Coming to your area soon TIGINBNA's Avatar
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    Tail Light and Peanut light issues

    Hi all,.

    We need a little help with her '07 f650.

    Peanut light and tail (running) light are out. They flicker for just a second when the key is turned, so we know they have power and they work. But will not remain functional.

    The brake light works fine, as does the headlight.

    During normal running I get 6.5 volts to the rear light socket, then when applying the brake get 12.7 volts.

    Any help out there???

    Thanks in advance.

    BC/LG

  2. #2
    Registered User lkraus's Avatar
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    Quote Originally Posted by TIGINBNA View Post
    Hi all,.

    We need a little help with her '07 f650.

    Peanut light and tail (running) light are out. They flicker for just a second when the key is turned, so we know they have power and they work. But will not remain functional.

    The brake light works fine, as does the headlight.

    During normal running I get 6.5 volts to the rear light socket, then when applying the brake get 12.7 volts.

    Any help out there???

    Thanks in advance.

    BC/LG
    Stock incandescent bulb or has someone installed an LED? BMW "pulses" the power, rapidly turning it on and off for very short periods to make it appear dimmer for taillight use. Works fine for a filament bulb but it can be a problem for some LEDs.
    Larry
    2006 R1200RT

  3. #3
    Coming to your area soon TIGINBNA's Avatar
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    Quote Originally Posted by lkraus View Post
    Stock incandescent bulb or has someone installed an LED? BMW "pulses" the power, rapidly turning it on and off for very short periods to make it appear dimmer for taillight use. Works fine for a filament bulb but it can be a problem for some LEDs.
    All stock lights. No LED's

  4. #4
    Registered User drneo66's Avatar
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    Have you tried a new bulb? And of the correct type? Constant, stable voltage would generally indicate that the wiring is correct?

    Halogen bulbs are finicky, even if they look good, they can still have a failure when they heat/light up.
    Current: 2007 BMW R1200RT, 2013 F800GS
    Former: 1995 BMW K75S, 2009 BMW G650GS
    MOA Member #:150400, IBA#: 37558

  5. #5
    MOA #24991 Pauls1150's Avatar
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    Just a WAG but I'd guess that the voltage measurements were taken with the bulbs removed...
    Question for the appropriate gurus: Does this bike's computer shut down that circuit if it detects a fault?
    That would explain the flicker at turn-on.

  6. #6
    Registered User drneo66's Avatar
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    Quote Originally Posted by Pauls1150 View Post
    Just a WAG but I'd guess that the voltage measurements were taken with the bulbs removed...
    Question for the appropriate gurus: Does this bike's computer shut down that circuit if it detects a fault?
    That would explain the flicker at turn-on.
    Nope - no CANBUS/ZFE on the single cylinder F650's.
    Current: 2007 BMW R1200RT, 2013 F800GS
    Former: 1995 BMW K75S, 2009 BMW G650GS
    MOA Member #:150400, IBA#: 37558

  7. #7
    MOA #24991 Pauls1150's Avatar
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    Dang.

    Corroded or loose sockets? The little wire leads on those "peanut" bulbs (194/etc.) are pretty fragile.

    ADDED -
    Hey Tig, let's get really picky about the voltage measurements.
    Pull one bulb and connect your voltmeter to the socket. THEN turn on the key while watching the meter; note the voltage and any other reaction. Start the bike and note any new readings, and does it shut off after that "second"?
    Turn the bike off, pull the other bulb, and connect the voltmeter to that socket and repeat the above steps.
    If the voltages are stable and pass the "Reasonability" test, that would indicate that the bulbs are wrong (with all respect to Dr. Neo).
    If any voltage crashes, that points to inside the bike...
    Last edited by Pauls1150; 05-17-2021 at 11:29 PM.

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