Lights dim?

Discussion in '3rd & 4th Generation 1990-1997' started by bintings, Feb 24, 2016.

  1. bintings

    bintings New Member

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    Howdy Folks

    I ride with the headlights on at all times of the day. I noticed recently that as more power is needed they dim a tiny bit.
    This happens most noticeably when I press either brake or when the radiator fan turns on.
    It is not just the headlights that dim but all the lights (for example the green neutral light will dim a slight amount if I am waiting at lights and the fan kicks in).


    I am just wondering if this is normal?

    Is the bike telling me something needs upgrading? or cleaning? or replacing?

    or am I over analysing.


    Thanks
     
  2. Knight

    Knight New Member

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    For clarification are you talking solely about idle or have you observed this at speed as well?
     
  3. bintings

    bintings New Member

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    Soley at idle.
     
  4. Terry Smith

    Terry Smith Member

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    A little dimness when an additional drain is applied (the fan motor or brake filaments) would be normal at idle. However to be sure, it would pay to check the voltage across the battery terminals at idle and then at 5000rpm. It may be that your battery is nearing replacement time, or you have a little corrosion on connectors that is reducing the charging rate.
     
  5. Knight

    Knight New Member

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    I leave it to others to report if they have identical behavior with such bike. That said...

    I think all vehicles are taxed at idle. We see this with cars as the AC compressor kicks in and the lights dim, and that is with a huge alternator. However, as this is an important thing, it would not hurt to proactively test the system with a multimeter, then there is no guessing. If we all did this periodically, no one would ever get stranded with a dead charging system. Check this out, and check your generation factory manual for your specs:

    http://vfrworld.com/forums/showthread.php/39277-How-to-fix-common-regulator-Stator-failures
     
  6. slovcan

    slovcan New Member

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    I had this on one of my bikes. I cleaned and redid all my grounds and added one more ground cable from the battery negative directly to a chassis ground point. This practically eliminated the momentary dimming of the lights and totally eliminated the dimming of the neutral light.

    Cheers,
    Glenn
     
  7. squirrelman

    squirrelman Member

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    Everyone here knows already that at idle speed the charging rate is zero, so you're running off the battery, and slight dimming as more accessories switch on is NORMAL. :eagerness:
     
  8. ragincanadian

    ragincanadian New Member

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    Do we? Do we ALL know that? EVERYONE?









    I mean, I do. Just saying.
     
  9. bintings

    bintings New Member

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    I think I heard that somewhere...


    Well its good to know this is normal.

    Voltages check out fine, 12.7 when the bike is off and a good 14.8 when the bike is running.

    Although after a warm up, idle seems a bit up and down when waiting at lights, could be the battery showing its age?
     
  10. slovcan

    slovcan New Member

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    I beg to differ. This was after some electrical testing so battery really needed a top up.

    [video=youtube;bIZkerK-Itk]https://www.youtube.com/watch?v=bIZkerK-Itk[/video]

    Do the basics first. Remove and clean the connections including all the grounds. Get the battery load tested. Per the poster's last entry, his charging system looks fine.

    Cheers,
    Glenn
     
  11. NormK

    NormK New Member

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    So now you have started thinking about the charging system, do yourself a favor and remove the connector between the stator and R/R before it fries itself,( it will, just don't know when) and fit a voltmeter to it so you can monitor the charging all the time. Simple mods but can save you a bucket of money and grief in the future
     
  12. Knight

    Knight New Member

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    I think all of the comments are good. Maybe a misunderstanding?

    At idle a new battery is 12.75V or so, and charge as you've shown will be 13.0+. So the bike is supplying 100% required power to the lights and engine and all with an additional .25V+ charging the system. Then the radiator fan comes on, and will drop that voltage somewhat, so yes, at idle the battery is supplying some juice when additional items are running.

    That said Glenn's point is good that since the system is most strained at idle, it makes sense to bring these components back to a new-like state.

    Bintings, there are a couple checks of a battery. One is after it has been charging when it will show well over 13V. The other is "steady-state". After 24-36 hours of not using it. A voltage of 12.7 would be fine for steady state but worst case scenario if you measure just after the bike was ridden. Next, like Glenn wrote, the one problem is that some batteries will have a good voltage but their ability to supply power is gone. There is a name for that state, bah I wish I could remember it. An automotive shop can test it under load and answer your question of whether the battery is flaky. You cannot do that because you'd have to put a very powerful ammeter in series with the battery and test over repeated starts.
     
  13. Badbilly

    Badbilly Official VFRWorld Troll Of The Year!

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    Sometimes the advice here is flakey.
     
  14. bintings

    bintings New Member

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    Followed this test and everything seems to be as expected!
    I might however opt for a battery loadtest on its next service in a few months.

    Thanks guys
     
  15. NormK

    NormK New Member

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    Seems like another one is happy to ignore the connector issue. They all slip in to "it won't happen to me" syndrome
     
  16. V4toTour

    V4toTour New Member

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    totally normal, as stated. brake lights and rad fan are going to put an extra load on the battery at idle. lights will dim a bit as a result.

    also

    DO AS NORM SAYS.
     
  17. bintings

    bintings New Member

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    Sorry, didn't mean to dismiss your comment Norm,
    I cut off the old stator connector and replaced with a new one, stripped and soldered the wires + updated the whole charging system a few months back. Everything is still clean and shiny since.
    Will fit a voltmeter if I find one that fits with the bike aesthetically although isn't a priority at the moment - It probably should be but hey.
     
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