Dimming headlight

Discussion in 'GS Boxers' started by Yousef, Nov 13, 2012.

  1. Twilight Error

    Twilight Error Going nowhere slowly

    May 18, 2002
    The Submarine Mines
    Oy vey.
    First, check all your connections. Grounds and power to the bus. A problem in either can cause this problem.

    Assuming you've got a non-exotic (i.e. lead acid) battery:

    Go to Napa, pick up a $50 load tester. This is just a big resistor with a volt meter built in. Load testing is the only definitive way to check a battery's health - the battery is shorted through the resistor, which dissipates that energy as heat. The volt meter will show the voltage during this discharge and indicate if the battery voltage is dropping faster than it should.

    If the battery checks out, suspect the Alternator. Check the belt tension, probably not the cause, but its easy to fix. You can check the alternator output with any multimeter, it should read ~14v regardless of throttle. A multimeter with the ability to measure current will tell you what the amp output of the Alternator is.

    If all that checks out, I've got no idea where to go next.
  2. Thunder Pig

    Thunder Pig Been here awhile

    Oct 12, 2011
    Niceville, Fl
    Def I agree with you on the Speedie except for the belly pan, not a fan. But that's why mine doesn't have one. Underseat was available, Wolf made one that was nice but spendy. I also was not a fan, liked the high and tight better, but that's why I don't have one. I had to have the fastest color as yellow is for chickens. Pigs like green as green with envy. Sorry not selling it!

    So what were we talking about again? [​IMG]
  3. def

    def Ginger th wonder dog

    Feb 28, 2004
    The woods and mountains of Alabama
    Ouhhhh....roulette green...my second favorite color.

    I need one....I don't care what color it is...
  4. WindSailor

    WindSailor Been here awhile

    Jan 29, 2008
    Somewhere out West
    Everyone here is pretty much spot on - I would suppose it would depend on what you had electrically running when you were at idle. If you didn't have anything running then I'm with 'Twilight' - except I'm for taking in the battery to a local shop to have it tested.

    Your Gerbings heated gear thermostat is actually cycling at 100% load, the dial on the thermostat is controlling the actual time duration when your heated gear is literally fully on or fully off. It's not a variable resistor anymore - so at idle I would expect to see your headlight dimming in sequence with your heated gear. In fact on my 650 Dakar I could see the headlight varying a little when running down the road at night with my heated gear on at near max.

    For me any battery over 3 years old is suspect and when they go they go all at once - usually after stopping at a service station to fill up. Yep, that last two did just that...
  5. slartidbartfast

    slartidbartfast Love those blue pipes

    Dec 23, 2003
    Southern Louisiana or Southern England or ...
    The electrical experts are all in violent agreement with one another :lol3. Me: - I changed the spark plug leads and caps on The Duchess, my old R80RT, and went for a ride. I have been too busy enjoying the nice weather to play with the other pedants today.

    The Duchess has an HID headlamp, which has a constant-current power supply that will operate quite happily from a supply at anywhere from 9V to 24V DC. The brightness does not change at idle, even though the voltmeter typically drops from around 13.4V to around 12.2V.

    Same thing with my R1100GS. However, on my GTS, which has a different model of HID with higher output, the headlamp will sometimes dim very briefly (more like a flicker) when at idle and the brakes are applied.