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Thread: voltage issue

  1. #1
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    voltage issue

    2009 xb12 scg
    6100 miles
    i recently installed a voltmeter, when cruising is have steady 13.9-14.2
    on occasion my headlight dims and the voltmeter will read 10.0-12.9 and throw a yellow check engine light.
    the low voltage episode will last as long as 5 minutes and short as 5 seconds.
    i ride it almost everyday.
    it can happen in any gear or at any speed.
    i do not having any problem starting the bike.
    it does not stall or stutter at low rpm or when stopping.
    i have checked the 4 ground wires behind the headlight and they are solid with no corrosion or wear.(thank you lunaticfringe)
    link: http://www.buellxb.com/forum/showthr...ghlight=ground
    i have LED turn signals front and rear with the relay mod, but this problem existed before i installed them
    what could be the source of my issue?


    *i searched and could not find an answer, if this has covered before please provide the link and i apologize.
    Last edited by bigrig; 12-13-2016 at 08:56 PM.

  2. #2
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    do the following: note that i am seeing voltage regulators on 2009 models failing at an alarming rate....with no rhyme or reason for it:
    1-your stator is an alternator. it is fine. do not mess with it.
    2-remove battery....fully charge it with a quality charger....NOT a tender....and have it load tested. chances are it is also fine but this eliminates any doubt.
    3-install battery...clean both cable ends well....tighten and secure both terminals.
    4-go to front left side of bike and look at the factory air intake cooling scoop. look inside same and you will see 2 wiring loom connectors affixed to the inside of same. pinch the tabs together on each one....remove from scoop...seperate each connector and check for corrosion and cleanliness. spray some kano kroil or similar inside....reconnect...reattach to scoop.
    5-check your negative battery cable where it affixes to frame grounding point. remove the fastener...clean the cable end and attachment point nicely....reattach.
    6-plan on buying a new voltage regulator. yours is headed to VR heaven in short order. your charging system is a SINGLE FIELD system so buy the correct VR for your year. 2008-2010 XB VR's all the same.
    report back with results please. it helps other worldwide board members when you do this.

  3. #3
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    i was hoping you would reply, as usual you nailed it with the response.
    i will do as you listed above and report back.
    thank you sincerely for you help on this board, it is really, really appreciated.

  4. #4
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    Quote Originally Posted by bigrig View Post
    i was hoping you would reply, as usual you nailed it with the response.
    i will do as you listed above and report back.
    thank you sincerely for you help on this board, it is really, really appreciated.
    and i thank YOU for the very kind words my friend. have a very merry Christmas.

  5. #5

  6. #6
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    According the description the item is correct.

    I had similar symptoms on 2009 Buell XB12Scg, in my case it was bad voltage regulator, I just replaced it http://www.buellxb.com/forum/showthr...or-codes/page3 .

    Check all ground spots, check both stator to VR and VR to Battery connectors (connectors 77 and 46), check, clean and tighten battery terminals, check the 30Amp fuse from the fuse box, then check stator and VR using service manual to figure out what is the problem. If you will be able to catch no charging issue you can check AC voltage on the stator plug (plug 46A), if the stator AC voltage is presented and correct according manual (check manual to see which RPM corresponds which stator AC voltage) and if the stator resistance between plug 46A pins correct and there is no shortening between stator and ground, then the stator should be OK. Then check plug 77B DC voltage, if the battery voltage on the plug 77B is presented but there is still no charging or engine RPM voltage response, it means the wiring between the plug 77B and the battery are good and the problem is between the plug 77A and the plug 46B (another words the problem is the VR or the VR wiring).

    Last edited by TPEHAK; 12-14-2016 at 05:49 AM.

  7. #7
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    Hello Bigrig, I just changed my VR on an 09 Uly, I paid the same price through HD in Allen Tx, with about a $10 shipping charge from St. Louis added.
    Testing the wiring and stator is pretty easy if you are good with a Multi-meter. Here is the procedure for the 08 Buells:
    http://www.ukbeg.com/pash/2008%20Bue.../99493-08Y.pdf
    I would look for wiring issues as well before changing the stator, it took about 4 days for my VR to ship in so I took the time to check the wiring.

  8. #8
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    so i did all the steps that lunaticfringe outlined above EXCEPT: fully charging battery and having it load tested.
    i purchased a new voltage regulator and installed it, but the problem still exists-but much less frequent.
    i did a trip a couple of days ago, about 500 miles and this i what i've learned:
    when the voltage drops and the yellow check engine light comes on, if i back the throttle off to "0" (no throttle) the voltage immediately climbs back to the 14.2 and the check engine light goes off.
    so apparently, this is an on-throttle condition that can be remedied by completely closing the throttle application.
    any ideas of what could be causing this?

  9. #9
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    Well, I would now go ahead and finish with the recommendations made earlier by Lunatic, this way you will eliminate the easier steps before going on to the more difficult one's.

  10. #10
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    When voltage drops does it response on engine RPM, at least a little bit?

    Bad connection or damaged wire, somewhere in wiring, or in some unit, or both. When you release throttle it changes vibrations and contact appears. If you cleaned and tightened all contacts with battery and ground spots, checked all connectors in the alternator circuit it is time to start hunting on the bad connection. Once no charging situation has appeared use multimeter and wiring diagram to find the bad circuit or bad unit, see my message above. Once you have figured out the bad circuit double check all connectors in this circuit, wiggle the wires in the bad circuit, shake the units in the circuit and see how it affects the voltage. Once no charge happened I would check the stator first according manual, if the stator is OK but there is still no charge check the circuit between VR and battery, if this circuit has no damage but there is no charge it means the VR is bad, or VR viring is bad, or connector connectors 77 or 46 are bad both or one of them, or everything between the connector 77 and 46 is bad, just use multimeter and common sense. If the circuit and all units between stator and battery are OK it means there are bad circuit between the battery and your motorcycle voltmeter. Again see the wiring diagram where you installed the voltmeter and common sense to figure out where the issue.

    Plug 46, plug 47 and battery terminals are the spots where you can stick your multimeter leads to completely check the circuit paths and units between the battery and the stator. Possibly the 30 Amp fuse has bad contact, check it too.

    If all circuits and units are OK it means the battery might have internal damage or internal bad connection.

    I had weird electric issue and voltage jumping caused rough engine RPM and alarm system ON and OFF when I was riding. The reason was bad battery connection, one battery terminal screw was loosen.


    Last edited by TPEHAK; 01-03-2017 at 01:07 AM.

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