Blowing Headlight bolbs

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  • 2stroke
    • Feb 2026

    #1

    Blowing Headlight bolbs

    Can an ignition switch being bad cause you to blow headlight bulbs? I recently purchased a use ignition switch for my 1980 GS750E off of EBay and thinking it may be the cause.

    Thanks,

    2Stroke
  • Redman
    Forum LongTimer
    Past Site Supporter
    Super Site Supporter
    • Mar 2004
    • 13747
    • Michigan, west Michigan

    #2
    No

    but faulty regulator rectifier can. Check battery voltage at 5000 rpm and report here.

    Head light bulbs burn out on occassion anywY. YOu having repeat failures??
    Had 650G & 850G. GK since 2005. BOTM GK 2024 June, 850G 2015 Sept
    Bikes

    Comment

    • 2stroke

      #3
      Yes, my low beam blew and then the high beam when I switched it. I then replaced the bulb with an H4 and the same thing happened. It did not even last one day.

      Comment

      • 2stroke

        #4
        Thank you Redman for the reply. I will check the voltage later today when it is light outside. Got to keep the neighbors happy.

        2Stroke

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        • tom203
          Forum Guru
          Past Site Supporter
          • Aug 2010
          • 8925
          • Norway,Maine

          #5
          I doubt it's the switch....too high a charging voltage is more likely to fry bulbs. Measure your charging voltage at idle and as you rev it up
          1981 gs650L

          "We are all born ignorant, but you have to work hard to stay stupid" Ben Franklin

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          • Rich82GS750TZ
            Forum Guru
            Past Site Supporter
            Super Site Supporter
            • Jun 2018
            • 5610
            • Mifflinburg, PA / Land of Tar & Chip

            #6
            I have a theory: If the contacts on the new switch and all the connections are now cleaner than before, could you just now be seeing a pre-existing RR overcharging issue for the first time.
            Links

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            • Steve
              GS Whisperer
              • Jun 2005
              • 35927
              • southwest oHIo

              #7
              Good point, Rich.

              2-stroke, if you find your voltage high, you will obviously have to change your R/R. I highly recommend the SH775 that is discussed widely on the forum.

              Also be sure to check the other electronic stuff on the bike to make sure the over-voltage has not affected them, too.

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

                #8
                Originally posted by Steve
                Good point, Rich.

                2-stroke, if you find your voltage high, you will obviously have to change your R/R. I highly recommend the SH775 that is discussed widely on the forum.

                Also be sure to check the other electronic stuff on the bike to make sure the over-voltage has not affected them, too.

                .
                it is kind of hard to check for accumulated electrical stress, but if the R/R is going to 17 VDC, you certainly have real time stress on most components.

                Comment

                • Redman
                  Forum LongTimer
                  Past Site Supporter
                  Super Site Supporter
                  • Mar 2004
                  • 13747
                  • Michigan, west Michigan

                  #9
                  Yes, do measure the charging voltage.

                  Also tell us if you have a stock R/R...... or, maybe you have a different R/R that has a 6th wire which is a "sense" lead.
                  Reason I ask, is if it is that type of R/R and if the sense lead comes loose or otherwise measures a low voltage, then that R/R will crank up its output. That happened on my GK (about 250 miles from home, in a rain storm) and I saw upper 18 almost 19 volts on my dash voltmeter.
                  (Hint, Hint: Having a dashboard voltmeter helps you notice these situations before causes more problems. But that is a different discussion.)
                  Had 650G & 850G. GK since 2005. BOTM GK 2024 June, 850G 2015 Sept
                  Bikes

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                  • 2stroke

                    #10
                    Thank you all for the information. I am going out to get started on it. One more thing I think I need to add to the equation is I did replace some wiring to the positive and negative leads of the battery that were thicker gauge wire. Could that have anything to do with this issue?

                    2Stroke

                    Comment

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

                      #11
                      Originally posted by 2stroke
                      Thank you all for the information. I am going out to get started on it. One more thing I think I need to add to the equation is I did replace some wiring to the positive and negative leads of the battery that were thicker gauge wire. Could that have anything to do with this issue?

                      2Stroke

                      Not likely

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                      • 2stroke

                        #12
                        I think I found the issue.

                        The negative battery lead bold was too long and causing the wires to be loose even when tighten down all the way. I will still be checking my rectifier voltage.

                        Bolt.jpg

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                        • 2stroke

                          #13
                          RR has 5 wires and is off of a 2005 GS500

                          3 Black for the stater
                          1 black/Red one which I believe is for the positive to the fuse box
                          1 black/white one which I believe is for the negative to the battery

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                          • Redman
                            Forum LongTimer
                            Past Site Supporter
                            Super Site Supporter
                            • Mar 2004
                            • 13747
                            • Michigan, west Michigan

                            #14
                            Originally posted by 2stroke
                            I think I found the issue.

                            The negative battery lead bold was too long ....................... I will still be checking my rectifier voltage.
                            That may be A problem, but not THE problem.
                            Or maybe it is, if the R/R negitive is going to that battery negitive bolt, but not certain.

                            Yes, check battery voltage at mid-rpms, say, 5000 rpm to check for overcharging that can blow out headlights and other things.
                            FOr a more complete check of battery and charging system and various connections, do the "quick check" mentioned elsewhere. But for now, we are trying to determine why you are repeatedly blowing headlights, and fix what ever is the cause of that (before it blows out your ignition).


                            Originally posted by 2stroke
                            RR has 5 wires and is off of a 2005 GS500

                            3 Black for the stater
                            1 black/Red one which I believe is for the positive to the fuse box
                            1 black/white one which I believe is for the negative to the battery
                            So the typical R/R, not the one with a sense wire that can cause the overcharging.

                            Also check to that the blk/wht is well grounded. Check for voltage difference between the blk/wht wire and battery negitive.
                            Last edited by Redman; 12-14-2019, 07:08 PM.
                            Had 650G & 850G. GK since 2005. BOTM GK 2024 June, 850G 2015 Sept
                            Bikes

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                            • 2stroke

                              #15
                              Status update

                              I did not get a chance to the the 5000 RPM test due to my neighbor having an outside wedding at their house and my water heater decided it did not want to cut off.

                              I did do a little rewiring and getting everything ready to test tomorrow. I need to find out if the fuse box is supposed to connect to both battery and the black/red wire of the RR?

                              The RR was going to the that loose battery bolt.


                              Thanks again,

                              2Stroke

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