Blowing headlamps

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  • Jburr
    • Mar 2026

    #1

    Blowing headlamps

    I have blown 2 headlamps in the the last month. When testing my battery with a volt meter, I am getting a reading of nearly 18 volts when I rev the engine. I am guessing that is too high? Need a new regulator?
  • Grimly
    Forum Guru
    Past Site Supporter
    Super Site Supporter
    • Sep 2012
    • 5801
    • Ireland

    #2
    Ooh, yes. Distinctly likely the most probably cause.
    Also, check the headlamp mountings that nothing is causing hard vibes from frame to lamp shell - I had a period where headlight bulbs were lasting a month or two because of vibes.
    Dave
    '79 GS850GN '80 GS850GT
    Only a dog knows why a motorcyclist sticks his head out of a car window

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    • Guest

      #3
      Try running a ground from the R/R ground eye to the frame and battery.
      Clean the stator connections to the R/R or solder directly.
      Clean the red bullet from the positive terminal of the battery.
      Recheck.

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      • posplayr
        Forum LongTimer
        GSResource Superstar
        Past Site Supporter
        • Dec 2007
        • 23673
        • Tucson Az

        #4
        The r/r is toast and so will your other components if you keep ridding it that way

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        • Redman
          Forum LongTimer
          Past Site Supporter
          Super Site Supporter
          • Mar 2004
          • 13762
          • Michigan, west Michigan

          #5
          Originally posted by Jburr
          I have blown 2 headlamps in the the last month. When testing my battery with a volt meter, I am getting a reading of nearly 18 volts when I rev the engine. I am guessing that is too high? Need a new regulator?
          Welcome to GSR.

          And har har har welcome to having an 80s GS.

          Yes 18 volts is way to high.

          Good that you have a volt meter and can use it. (have a lot of folks trying to troubleshoot electrical problems with their eyeballs).

          Need a new regulator? Maybe, or maybe need to check some wiring. Namely the grounding of the R/R.
          You may find the black wire of R/R "grounded" to the solenoid mounting bolt on the battery box, but batterybox isn't a god ground bacuse not really mounted well to frame. And maybe a ground wire (black/white) there also, but sometimes that is not reliable. Hense why the recommendations to add your own ground wire from there to battery neg.
          Bikes
          Had 650G & 850G. GK since 2005. BOTM 850G 6/2024 , GK 9/2015​

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          • Jburr

            #6
            thanks for the input. this confirms my suspicions and gives me some things to try.

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            • tfb

              #7
              Agree with posplayr, the RR is shot. Toss it in the bin and get a newie, lots to choose from when buying online.

              The foregoing is if you have a *combined" reg/rect. unit. If they are separate units (1979 and earlier, I believe), then you could do two things:
              1. Just replace the regulator with an OE or 2nd-hand unit.
              2. Get rid of both the regulator and the rectifier, and replace them with a combined reg/rect. unit. This will require a bit of fiddling around with rewiring, but it's not too hard and there's plenty of info. here on the GSR to help you do the job.

              You will also find that, at a fiesty 18V, your battery will be getting cooked. So fix the problem before you do any more riding, or a new reg/rect. will be the least of your worries.

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              • posplayr
                Forum LongTimer
                GSResource Superstar
                Past Site Supporter
                • Dec 2007
                • 23673
                • Tucson Az

                #8
                Read GS stator in my signature

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                • Guest

                  #9
                  I haven't had to change a headlight bulb since I installed a series R/R. I used to go through them every three or four months until my old shunt type R/R showed obvious signs of over voltage. At that rate it has already paid for itself.

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                  • Redman
                    Forum LongTimer
                    Past Site Supporter
                    Super Site Supporter
                    • Mar 2004
                    • 13762
                    • Michigan, west Michigan

                    #10
                    Originally posted by Jburr
                    thanks for the input. this confirms my suspicions and gives me some things to try.
                    In general, Would be good for you to state what year/model.

                    .
                    Bikes
                    Had 650G & 850G. GK since 2005. BOTM 850G 6/2024 , GK 9/2015​

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                    • tkent02
                      Forum LongTimer
                      Past Site Supporter
                      • Jan 2006
                      • 35571
                      • Near South Park

                      #11
                      Originally posted by OldVet66
                      I haven't had to change a headlight bulb since I installed a series R/R. I used to go through them every three or four months until my old shunt type R/R showed obvious signs of over voltage. At that rate it has already paid for itself.
                      I have never had to replace one on a GS. Not since they were new.
                      http://img.photobucket.com/albums/v5...tatesMap-1.jpg

                      Life is too short to ride an L.

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                      • Guest

                        #12
                        It just shows that my old R/R was bad for a long time until it got bad enough to boil my battery out. At that point I started learning about charging systems. Good voltage regulation, no bulbs burning out. You were lucky with R/R's and probably knew enough to do the proper maintenance. I was totally new to these bikes when I got this one.

                        Comment

                        • posplayr
                          Forum LongTimer
                          GSResource Superstar
                          Past Site Supporter
                          • Dec 2007
                          • 23673
                          • Tucson Az

                          #13
                          Originally posted by OldVet66
                          It just shows that my old R/R was bad for a long time until it got bad enough to boil my battery out. At that point I started learning about charging systems. Good voltage regulation, no bulbs burning out. You were lucky with R/R's and probably knew enough to do the proper maintenance. I was totally new to these bikes when I got this one.
                          From my detailed analysis on the subject, the only way to over charge is either
                          1. you have an old R/R that only controls one leg of the stator.
                          2. the regulator portion of the R/R has to go bad.
                          3. You put a 6 wire Honda R/R sense point in a really bad place(low voltage point WRT battery voltage).


                          Other than 3.) above Dirty connections CAN NOT cause over charging , they always result in UNDER CHARGING.

                          So if Tkent never used a Honda unit, kept his bikes charging in descent order, the regulator section of the R/R may very well have never failed on any of his bikes as temperature is the dominate failure mode for the R/R.

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                          • Guest

                            #14
                            I incorrectly combined the two, my bike is a '78 and had a separate regulator and rectifier. I assume the regulator was going bad. It seemed to be fine except going through a lot of headlight bulbs for the better part of a year until it boiled out the battery and got my attention. That was about the time you were talking about the Compu-Fire. The rest is history.

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                            • posplayr
                              Forum LongTimer
                              GSResource Superstar
                              Past Site Supporter
                              • Dec 2007
                              • 23673
                              • Tucson Az

                              #15
                              I was only trying to explain how tom seems to lead a blessed charging existence.

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