Low charge at high RPM

Discussion in 'Electrical' started by Miskatonic, Jan 29, 2015.

  1. Miskatonic

    Miskatonic Account Removed

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    Hi guys,
    Been away for a bit and riding about 1000 miles a week in beautiful sunny Florida!

    On my way across the state last week I noticed that my headlights were going dim and then back to bright. Wen I looked at my voltage gauge I saw that it was fluctuating between 14+ and back down to about 12.

    Last night, however, I was riding home from work when my Battery and Check Engine lights came on, I looked over and saw that the voltage gauge was reading 10v. When I slowed down and dropped my RPM I saw that the voltage went back up to 14+.

    I've had problems the other way around before... low rpm = low voltage, but never this way.

    Any ideas before I take it to a mechanic?

    Thanks in advance!
     
  2. Jeff Klarich

    Jeff Klarich Well-Known Member Contributor

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    The usual questions, how old is your battery? did you clean and tighten all cables? Have you checked the volts at the regulator? Your stator may be going south on you.
     
  3. Miskatonic

    Miskatonic Account Removed

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    The battery itself is only a month old HD battery. I changed it out, not because my diehard died, but because I didn't like the terminals they have. When I replaced it I ensured that all of the connections were clean and tight but I'll have to check on the regulator wiring.

    I was able to recreate the problem reliably by accelerating, seeing the voltage drop and then when I would go back down to below 70-80 mph things were copacetic again. Unfortunately my scoot is my only transportation and I have 2 hour commutes today and tomorrow so I have to keep my fingers crossed and go slow so I can take a better look at everything this weekend.

    Thanks for the pointers, Jack, I forgot my old login but you were helpful in my last posts some time ago as well. You are a great asset to this community.
     
  4. Jack Klarich

    Jack Klarich Expert Member

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    Harley Davidson Forums
    Start here
    Sure sounds like a bad regulator
    Make sure your battery is fully charged @ 12.7 volts before tests
     
  5. Jeff Klarich

    Jeff Klarich Well-Known Member Contributor

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    So if I understand you correctly it drops under load and returns to a more normal state a t cruising. The easiest thing to start with is load test your battery, new does not = good. I'm more leaning towards a bad stator or regulator. JMHO.
     
    Last edited: Jan 29, 2015
  6. tourbox

    tourbox Senior Member

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    If you don't have a manual for your bike you can start here with the charging system checks. Use a volt/ohm meter for these as your dash meter could be bad.
    http://www.hdtalking.com/archive/t-47714.html
    tourbox

    Oh I see Jack beat me to it. Sorry about that.
    tourbox
     
    Last edited by a moderator: Jan 29, 2015
  7. Jack Klarich

    Jack Klarich Expert Member

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    Looks like great minds think alike Ray:D
     
  8. Miskatonic

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    Thanks guys, I do have the full manual. I'll test it out this weekend and just pray that I can limp her along for 4 hours of riding today and tomorrow... If I don't go to work I won't have a job. o job no fix!

    It only happens (so far) when I am going over about 75 mph so 3k ish rpm.
    I'll keep her slow and just keep hoping till I can park her and take a better look. Unfortunately I have to cross some long bridges and slow going is not safe... either is electrical failure in traffic at high speed with someone on your tail, though.
     
  9. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

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    Those are the kind of symptoms I had one of the times the VR failed on my '03 UC. Eventually it just gave up the ghost and quit charging. Luckily I was able to make it home from work though. I was watching the voltage drop on the gauge the whole way home hoping I would make it. Turned off all the electrical draw I could and tried to pick a route with as few stops as possible.

    By the time I got to the house the voltage was just under 9 Vdc on the gauge. That is at the bottom limit of the voltage necessary to power the ECU. Whew!!

    Replaced the VR and recharged the battery to full charge. Ran fine after that, but if memory serves, the Stator and battery went out within the next little while. Not sure of the cause and effect relationship, only giving you a heads up.

    Cheers,

    TQ
     
  10. Miskatonic

    Miskatonic Account Removed

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    UPDATE: Stator seems to be the issue. Possibly combined with some connection issues that happened when I whacked a retread.

    Thanks for the pointers everyone. I got a new VR but found my multimeter before installing it so I recovered that cash.